| 1. |
- Shekka Espinosa, Aaron, et al.
(författare)
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Differences between cardiac troponin I vs. T according to the duration of myocardial ischaemia
- 2023
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Ingår i: European Heart Journal-Acute Cardiovascular Care. - : Oxford University Press (OUP). - 2048-8726 .- 2048-8734. ; 12:6, s. 355-363
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Tidskriftsartikel (refereegranskat)abstract
- Aims Cardiac troponin T (cTnT) and troponin I (cTnI) are expressed as an obligate 1:1 complex in the myocardium. However, blood levels of cTnI often rise much higher than that of cTnT in myocardial infarction (MI), whereas cTnT is often higher in patients with stable conditions such as atrial fibrillation. Here we examine high-sensitive (hs) cTnI and hs-cTnT after different durations of experimental cardiac ischaemia. Methods and results hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were measured in plasma samples from rats before and at 30 and 120 min after 5, 10, 15, and 30 min of myocardial ischaemia. The animals were killed after 120 min of reperfusion, and the infarct volume and volume at risk were measured. hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were also measured in plasma samples collected from patients with ST-elevation myocardial infarction (STEMI). hs-cTnT and hs-cTnI increased over 10-fold in all rats subjected to ischaemia. The increase of hs-cTnI and hs-cTnT after 30 min was similar, resulting in a hs-cTnI/hs-cTnT ratio around 1. The hs-cTnI/hs-cTnT ratio was also around 1 in blood samples collected at 120 min in rats subjected to 5 or 10 min of ischaemia where no localized necrosis was observed. In contrast, the hs-cTnI/hs-cTnT ratio at 2 h was 3.6-5.5 after longer ischaemia that induced cardiac necrosis. The large hs-cTnI/hs-cTnT ratio was confirmed in patients with anterior STEMI. Conclusion Both hs-cTnI and hs-cTnT increased similarly after brief periods of ischaemia that did not cause overt necrosis, whereas the hs-cTnI/hs-cTnT ratio tended to increase following longer ischaemia that induced substantial necrosis. A low hs-cTnI/hs-cTnT ratio around 1 may signify non-necrotic cTn release.
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| 2. |
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| 3. |
- Bjornsen, T., et al.
(författare)
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Frequent blood flow restricted training not to failure and to failure induces similar gains in myonuclei and muscle mass
- 2021
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Ingår i: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 31:7, s. 1420-1439
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to compare the effects of short-term high-frequency failure vs non-failure blood flow-restricted resistance exercise (BFRRE) on changes in satellite cells (SCs), myonuclei, muscle size, and strength. Seventeen untrained men performed four sets of BFRRE to failure (Failure) with one leg and not to failure (Non-failure; 30-15-15-15 repetitions) with the other leg using knee-extensions at 20% of one repetition maximum (1RM). Fourteen sessions were distributed over two 5-day blocks, separated by a 10-day rest period. Muscle samples obtained before, at mid-training, and 10-day post-intervention (Post10) were analyzed for muscle fiber area (MFA), myonuclei, and SC. Muscle size and echo intensity of m.rectus femoris (RF) and m.vastus lateralis (VL) were measured by ultrasonography, and knee extension strength with 1RM and maximal isometric contraction (MVC) up until Post24. Both protocols increased myonuclear numbers in type-1 (12%-17%) and type-2 fibers (20%-23%), and SC in type-1 (92%-134%) and type-2 fibers (23%-48%) at Post10 (p < 0.05). RF and VL size increased by 5%-10% in both legs at Post10 to Post24, whereas the MFA of type-1 fibers in Failure was decreased at Post10 (-10 +/- 16%; p = 0.02). Echo intensity increased by similar to 20% in both legs during Block1 (p < 0.001) and was similar to 8 to 11% below baseline at Post24 (p = 0.001-0.002). MVC and 1RM decreased by 5%-10% after Block1, but increased in both legs by 6%-11% at Post24 (p < 0.05). In conclusion, both short-term high-frequency failure and non-failure BFRRE induced increases in SCs, in myonuclei content, muscle size, and strength, concomitant with decreased echo intensity. Intriguingly, the responses were delayed and peaked 10-24 days after the training intervention. Our findings may shed light on the mechanisms involved in resistance exercise-induced overreaching and supercompensation.
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| 4. |
- Bjornsen, T., et al.
(författare)
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High-frequency blood flow-restricted resistance exercise results in acute and prolonged cellular stress more pronounced in type I than in type II fibers
- 2021
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Ingår i: Journal of Applied Physiology. - Rockville : American Physiological Society. - 8750-7587 .- 1522-1601. ; 131:2, s. 643-660
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Tidskriftsartikel (refereegranskat)abstract
- Myocellular stress with high-frequency blood flow-restricted resistance exercise (BFRRE) was investigated by measures of heat shock protein (HSP) responses, glycogen content, and inflammatory markers. Thirteen participants [age: 24 +/- 2 yr (means +/- SD), 9 males] completed two 5-day blocks of seven BFRRE sessions, separated by 10 days. Four sets of unilateral knee extensions to failure at 20% of one-repetition maximum (1RM) were performed. Muscle samples obtained before, 1 h after the first session in the first and second block (acute 1 and acute 2), after three sessions (day 4), during the "rest week," and at 3 (post 3) and 10 days postintervention (post 10) were analyzed for HSP70, alpha beta-crystallin, glycogen [periodic acid-Schiff (PAS) staining], mRNAs, miRNAs, and CD68(+) (macrophages) and CD661D(+) (neutrophils) cell numbers. alpha beta-crystallin translocated from the cytosolic to the cytoskeletal fraction after acute 1 and acute 2 (P < 0.05) and immunostaining revealed larger responses in type I than in type II fibers (acute 1, 225 +/- 184% vs. 92 +/- 81%, respectively, P = 0.001). HSP70 was increased in the cytoskeletal fraction at day 4 and post 3, and immunostaining intensities were more elevated in type I than in type II fibers at day 4 (206 +/- 84% vs. 72 +/- 112%, respectively, P <0.001), during the rest week (98 +/- 66% vs. 42 +/- 79%, P < 0.001), and at post 3 (115 +/- 82% vs. 28 +/- 78%, P = 0.003). Glycogen content was reduced in both fiber types, but most pronounced in type I, which did not recover until the rest week (-15% to 29%, P <= 0.001). Intramuscular macrophage numbers were increased by similar to 65% postintervention, but no changes were observed in muscle neutrophils. We conclude that high-frequency BFRRE with sets performed till failure stresses both fiber types, with type I fibers being most affected. NEW & NOTEWORTHY BFRRE has been reported to preferentially stress type I muscle fibers, as evidenced by HSP responses. We extend these findings by showing that the HSP responses occur in both fiber types but more so in type I fibers and that they can still be induced after a short-term training period. Furthermore, the reductions in glycogen content of type I fibers after strenuous frequent BFRRE in unaccustomed subjects can be prolonged (>= 5 days), probably due to microdamage.
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| 5. |
- Bjørnsen, Thomas, et al.
(författare)
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Delayed myonuclear addition, myofiber hypertrophy and increases in strength with high-frequency low-load blood flow restricted training to volitional failure.
- 2019
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 126:3, s. 578-592
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Tidskriftsartikel (refereegranskat)abstract
- To investigate muscle hypertrophy, strength, myonuclear and satellite cell (SC) responses to high-frequency blood flow restricted resistance exercise (BFRRE).Thirteen individuals (24±2 years [mean ± SD], 9 males) completed two 5-day-blocks of 7 BFRRE sessions, separated by a 10-day rest period. Four sets of unilateral knee extensions to voluntary failure at 20% of 1RM were conducted with partial blood flow restriction (90-100 mmHg). Muscle samples obtained before-, during, 3- and 10 days after training were analyzed for muscle fiber area (MFA), myonuclei, SC, and mRNA and miRNA expression. Muscle size was measured by ultrasonography and magnetic resonance imaging, and strength with 1RM knee-extension.With the first block of BFRRE, SC number increased in both fiber types (70-80%, p<0.05), while type I and II MFA decreased by 6±7% and 15±11% (p<0.05), respectively. With the second block of training, muscle size increased by 6-8%, while the number of SC (type I: 80±63%, type II 147±95%), myonuclei (type I: 30±24%, type II: 31±28%) and MFA (type I: 19±19%, type II: 11±19%) peaked 10 days after the second block of BFRRE, whereas strength peaked after 20 days of detraining (6±6%, p<0.05). Pax7- and p21 mRNA expression were elevated during the intervention, while myostatin, IGF1R, MyoD, myogenin, cyclinD1 and -D2 mRNA did not change until 3-10 days post intervention.High frequency low-load BFRRE induced robust increases in SC, myonuclei and muscle size, but modest strength gains. Intriguingly, the responses were delayed and peaked 10-20 days after the training intervention, indicating overreaching.
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| 6. |
- Bjørnsen, Thomas, et al.
(författare)
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Type 1 Muscle Fiber Hypertrophy after Blood Flow-restricted Training in Powerlifters.
- 2019
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Ingår i: Medicine and science in sports and exercise. - 1530-0315. ; 51:2, s. 288-298
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the effects of blood flow restricted resistance exercise (BFRRE) on myofiber areas (MFA), number of myonuclei and satellite cells (SC), muscle size and strength in powerlifters. METHODSSeventeen national level powerlifters (25±6 yrs [mean±SD], 15 men) were randomly assigned to either a BFRRE group (n=9) performing two blocks (week 1 and 3) of five BFRRE front squat sessions within a 6.5-week training period, or a conventional training group (Con; n=8) performing front squats at ~70% of one-repetition maximum (1RM). The BFRRE consisted of four sets (first and last set to voluntary failure) at ~30% of 1RM. Muscle biopsies were obtained from m. vastus lateralis (VL) and analyzed for MFA, myonuclei, SC and capillaries. Cross sectional areas (CSA) of VL and m. rectus femoris (RF) were measured by ultrasonography. Strength was evaluated by maximal voluntary isokinetic torque (MVIT) in knee extension and 1RM in front squat.BFRRE induced selective type I fiber increases in MFA (BFRRE: 12% vs. Con: 0%, p<0.01) and myonuclear number (BFRRE: 17% vs. Con: 0%, p=0.02). Type II MFA was unaltered in both groups. BFRRE induced greater changes in VL CSA (7.7% vs. 0.5%, p=0.04), which correlated with the increases in MFA of type I fibers (r=0.81, p=0.02). No group differences were observed in SC and strength changes, although MVIT increased with BFRRE (p=0.04), whereas 1RM increased in Con (p=0.02).Two blocks of low-load BFRRE in the front squat exercise resulted in increased quadriceps CSA associated with preferential hypertrophy and myonuclear addition in type 1 fibres of national level powerlifters.
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| 7. |
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| 8. |
- Ellefsen, S., et al.
(författare)
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Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training
- 2015
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Ingår i: American Journal of Physiology-Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 309:7
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Tidskriftsartikel (refereegranskat)abstract
- Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 +/- 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSA(peak), potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women.
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| 9. |
- Hammarsten, Ola, et al.
(författare)
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How is cardiac troponin released from cardiomyocytes?
- 2022
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Ingår i: European heart journal. Acute cardiovascular care. - : Oxford University Press (OUP). - 2048-8726 .- 2048-8734. ; 11:9, s. 718-720
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Holm, Paetur M., et al.
(författare)
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Effects of neuromuscular control and strengthening exercises on MRI-measured thigh tissue composition and muscle properties in people with knee osteoarthritis - an exploratory secondary analysis from a randomized controlled trial
- 2024
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Ingår i: SEMINARS IN ARTHRITIS AND RHEUMATISM. - 0049-0172 .- 1532-866X. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the effects of adding strength training to neuromuscular control exercises on thigh tissue composition and muscle properties in people with radiographic -symptomatic knee osteoarthritis (KOA). Methods: In this exploratory secondary analysis of a randomized controlled trial, using a complete -case approach, participants performed 12 weeks of twice -weekly neuromuscular control exercise and patient education (NEMEX, n = 34) or NEMEX plus quadriceps strength training (NEMEX+ST, n = 29). Outcomes were MRImeasured inter- and intramuscular adipose tissue (InterMAT, IntraMAT), quadriceps muscle cross-sectional area (CSA), knee -extensor strength, specific strength (strength/lean CSA) and 30 s chair -stands. Betweengroup effects were compared using a mixed model analysis of variance. Results: At 12 weeks, responses to NEMEX+ST overlapped with NEMEX for all outcomes. Both groups reduced InterMAT (NEMEX+ST=25 %, NEMEX=21 %); between -group difference: 0.8cm2 (95 % CI: -0.1, 1.7). NEMEX+ST decreased IntraMAT (2 %) and NEMEX increased IntraMAT (4 %); between -group difference 0.1 %-points (-0.3, 0.5). Both groups increased quadriceps CSA and lean CSA (CSA minus IntraMAT), improved knee -extensor strength and specific strength, and improved chair -stand performance with a trend towards greater effects in NEMEX+ST. Conclusion: Adding strength training to 12 weeks of neuromuscular control exercises provided largely similar effects to neuromuscular control exercises alone in decreasing InterMAT and IntraMAT, in improving kneeextensor strength, CSA and in improving performance -based function in KOA persons, with a trend towards greater effects with additional strength training. Notably, both groups substantially reduced InterMAT and improved specific strength (an index of muscle quality). Our hypothesis -generating work warrants exploration of the roles played by InterMAT and IntraMAT in exercise effects in KOA.
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| 11. |
- Holm, Pætur Mikal, et al.
(författare)
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Intrarater Reliability and Agreement of Recommended Performance-Based Tests and Common Muscle Function Tests in Knee Osteoarthritis.
- 2021
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Ingår i: Journal of geriatric physical therapy (2001). - 2152-0895. ; 44:3, s. 144-152
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Tidskriftsartikel (refereegranskat)abstract
- Some uncertainty persists regarding the reproducibility of the recommended core set of performance-based tests, as well as common muscle function tests, when applied in individuals with knee osteoarthritis (KOA). The purpose of this study was to investigate the intrarater reliability and agreement of the recommended core set of performance-based tests and common muscle function tests in KOA.Participants (N=40) with radiographic and/or symptomatic KOA were evaluated twice with a 3-day interval between test sessions using the following tests: Leg extensor (LE) maximal muscle power measured in a Nottingham Power Rig; knee extensor (KE) peak isometric strength measured with a handheld dynamometer; 40-m walk test; 30-second chair-stand test; and 9-step stair climb test. Reliability was assessed using a 2-way, mixed-effects, single-measures model (3,1), absolute agreement-type intraclass correlation coefficient (ICC). Agreement was assessed using 95% limits of agreement (LOA) and LOA relative to the mean score from test and retest (LOA-%).Reliability for all tests was very high (ICC ≥ 0.97). LOA (LOA-%) was ±32.3 watt (W) (±22%) for LE power; ±22.7 N·m (±24%) for KE strength; ±0.2 m/s (±10%) for 40-m walk test; ±2.4 repetitions (±14%) for 30-second chair-stand test; and ±2 second (±20%) for stair climb test. A potential participant learning effect was found for all 3 performance-based tests, indicated by the significantly better scores at retest.The very high reliability found for the performance-based tests supports findings from previous studies and confirms discriminate reliability of these tests on a group level. Also, very high reliability estimates were demonstrated for both muscle function tests. This study also provided estimates of agreement for both performance-based and muscle function tests, which are important to consider when using these tests on an individual level in clinical practice.When using these tests to monitor changes over time in the clinic, depending on the test, improvements of less than 10% to 24% could be a result of measurement error alone and therefore may not be considered an actual improvement after treatment.
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| 12. |
- Holm, P. M., et al.
(författare)
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Low-dose strength training in addition to neuromuscular exercise and education in patients with knee osteoarthritis in secondary care – a randomized controlled trial
- 2020
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Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 28:6, s. 744-754
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To investigate the effects of lower limb strength training in addition to neuromuscular exercise and education (ST + NEMEX-EDU) compared to neuromuscular exercise and education alone (NEMEX-EDU) on self-reported physical function in patients with knee osteoarthritis (KOA). Design: Patient-blinded, parallel-group randomized controlled trial (RCT). Methods: The trial included 90 patients in secondary care with radiographic and symptomatic KOA, ineligible for knee replacement. Both groups exercised twice weekly for 12 weeks. Additional strength training consisted of a single, fatiguing knee extension set (30-60RM) before four sets of leg-press (8-12RM). Primary outcome was the between-group difference on the subscale activities of daily living from the Knee Injury and Osteoarthritis Outcome Score (KOOSADL) at 12 weeks. Secondary outcomes included KOOS symptoms, pain, function in sport and recreation, and quality of life, 40 m walk, stair climb, leg extension power, EuroQol-5D-5L, pain medication usage, and adverse events. Results: There was no statistically significant between-group difference in KOOSADL at 12-weeks; adjusted mean difference −1.15 (−6.78 to 4.48). Except for the stair climb test, which demonstrated an adjusted mean difference of 1.15 (0.09–2.21) in favor of ST + NEMEX-EDU, all other outcomes showed no statistically significant between-group differences. Neither group improved leg extension power. Conclusion: The addition of lower-limb strength training, using a low-dose approach, to neuromuscular exercise and education carried no additional benefits on self-reported physical function or on most secondary outcomes. Both groups displayed similar improvements at 12-week follow-up. Hence, the current low-dose strength training approach provided no additional clinical value in this group of KOA patients. Trial identifier (ClinicalTrials.gov): NCT03215602. © 2020 Osteoarthritis Research Society International
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| 13. |
- Holm, P. M., et al.
(författare)
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Muscle Function Tests as Supportive Outcome Measures for Performance-Based and Self-Reported Physical Function in Patients With Knee Osteoarthritis: Exploratory Analysis of Baseline Data From a Randomized Trial
- 2022
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Ingår i: Journal of Strength and Conditioning Research. - 1064-8011. ; 36:9, s. 2635-2642
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainty on the role of muscle function in relation to physical function in knee osteoarthritis (KOA) persists. This study aimed to assess the associations between muscle function and performance-based and self-reported physical function in patients with KOA. Physical function in 80 subjects with symptomatic and radiographic KOA was assessed using 40-m fast-paced walk, 30-second chair stand, 9-step stair climb tests, and the subscale activities of daily living from the Knee injury and Osteoarthritis Outcome Score (KOOS-ADL). Measurements of muscle function included leg extension (LE) power, knee extension (KE) torque, and estimated leg press one repetition maximum (LP RM). Associations were investigated using multivariable hierarchical linear regressions adjusted for age, sex, body mass index, self-reported physical activity, and thigh muscle lean area. Leg extension power was significantly associated with 40-m walk, stair climb, and 30-second chair stand, explaining 18, 8, and 3% of additional variance, respectively. Knee extension torque explained 13, 7, 17, and 7% of additional variance in the 40-m walk, stair climb, 30-second chair stand, and KOOS-ADL, respectively. Leg press one repetition maximum explained 11% of additional variance in the 30-second chair stand. In conclusion, LE power was the best explanatory variable for performance on the 40-m walk and stair climb tests, whereas KE torque best explained chair stand performance. Only KE torque was associated with KOOS-ADL. Our results highlight the importance of selecting supportive muscle function tests based on the specific physical function and suggest that other factors may be more important for certain physical function outcomes.
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| 14. |
- Holm, P. M., et al.
(författare)
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Strength training in addition to neuromuscular exercise and education in individuals with knee osteoarthritis—the effects on pain and sensitization
- 2021
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Ingår i: European Journal of Pain (United Kingdom). - : Wiley. - 1090-3801 .- 1532-2149. ; 25:9, s. 1898-1911
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is a lack of evidence of the relative effects of different exercise modes on pain sensitization and pain intensity in individuals with knee osteoarthritis (KOA). Methods: Ninety individuals with radiographic and symptomatic KOA, ineligible for knee replacement surgery, were randomized to 12weeks of twice-weekly strength training in addition to neuromuscular exercise and education (ST+NEMEX-EDU) or neuromuscular exercise and education alone (NEMEX-EDU). Outcomes were bilateral, lower-leg, cuff pressure pain- and tolerance thresholds (PPT, PTT), temporal summation (TS), conditioned pain modulation (CPM), self-reported knee pain intensity and number of painful body sites. Results: After 12weeks of exercise, we found significant differences in increases in PPT (−5.01kPa (−8.29 to −1.73, p=.0028)) and PTT (−8.02kPa (−12.22 to −3.82, p=.0002)) in the KOA leg in favour of ST+NEMEX-EDU. We found no difference in effects between groups on TS, CPM or number of painful body sites. In contrast, there were significantly greater pain-relieving effects on VAS mean knee pain during the last week (−8.4mm (−16.2 to −0.5, p=.0364) and during function (−16.0mm (−24.8 to −7.3, p=.0004)) in favour of NEMEX-EDU after 12weeks of exercise. Conclusion: Additional strength training reduced pain sensitization compared to neuromuscular exercise and education alone, but also attenuated the reduction in pain intensity compared to neuromuscular exercise and education alone. The study provides the first dose- and type-specific insight into the effects of a sustained exercise period on pain sensitization in KOA. Future studies are needed to elucidate the role of different exercise modes. Significance: This study is an important step towards better understanding the effects of exercise in pain management of chronic musculoskeletal conditions. We found that strength training in addition to neuromuscular exercise and education compared with neuromuscular exercise and education only had a differential impact on pain sensitization and pain intensity, but also that regardless of the exercise mode, the positive effects on pain sensitization and pain intensity were comparable to the effects of other therapeutic interventions for individuals with knee osteoarthritis. © 2021 European Pain Federation - EFIC®
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| 15. |
- Högberg, Johan, et al.
(författare)
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No Association Between Hamstrings-to-Quadriceps Strength Ratio and Second ACL Injuries After Accounting for Prognostic Factors : A Cohort Study of 574 Patients After ACL-Reconstruction
- 2024
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Ingår i: Sports Medicine - Open. - Heidelberg : Springer. - 2199-1170 .- 2198-9761. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Background: The stress on the anterior cruciate ligament (ACL) induced by the quadriceps can be attenuated by activation of the hamstrings by exerting an opposing torque to the anterior translation of tibia. Consequently, considering the ratio between strength of the hamstrings-to-quadriceps (HQ-ratio) may be of value to reduce the odds of second ACL injuries. The objective was therefore to evaluate (1) the association between HQ-ratio and the occurrence of a second ACL injury in patients after ACL-reconstruction within 2 years of return to preinjury sport level and (2) to compare the HQ-ratio between males and females after ACL reconstruction. Methods: Patients who had undergone primary ACL reconstruction and participated in knee-strenuous activity preinjury were included. Demographics, the occurrence of a second ACL injury, and muscle strength test results before returning to preinjury sport level were extracted from a rehabilitation registry. The endpoint was set at a second ACL injury or 2 years after return to preinjury sport level. A multivariable logistic regression was used to analyze the association between the HQ-ratio and a second ACL injury. Results: A total of 574 patients (50.0% female) with a mean age of 24.0 ± 9.4 years at primary ACL reconstruction were included. In the univariable logistic regression analysis, the odds of sustaining a second ACL injury decreased by 3% for every 1% increase in the HQ-ratio (OR 0.97 [95% CI 0.95–1.00], p = 0.025). After adjusting for the time from reconstruction to return to preinjury sport level, sex, preinjury sport level, graft choice, age, and body mass index, the results were no longer significant (OR 0.98 [95% CI 0.95–1.01], p = 0.16). Females had a higher HQ-ratio compared with males for both the ACL-reconstructed and uninjured side (3.7% [95% CI 5.7; 1.8%], p = 0.0002 and 3.3% [95% CI 4.6; 2.1], p < 0.001, respectively). Conclusion: The HQ-ratio did not significantly affect the odds for sustaining a second ACL injury upon return to preinjury sports level after primary ACL reconstruction. Females had a significant higher HQ-ratio than males for both the ACL reconstructed and uninjured side. © 2024, The Author(s).
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| 16. |
- Högberg, Johan, et al.
(författare)
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Persistent knee flexor strength deficits identified through the NordBord eccentric test not seen with “gold standard” isokinetic concentric testing during the first year after anterior cruciate ligament reconstruction with a hamstring tendon autograft
- 2022
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Ingår i: Physical Therapy in Sport. - Oxford : Elsevier. - 1466-853X .- 1873-1600. ; 55, s. 119-124
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the recovery of knee flexor muscle strength evaluated with a Nordic hamstring eccentric test (NordBord) compared with an isokinetic concentric test (Biodex) during the first year after anterior cruciate ligament (ACL) reconstruction using a hamstring tendon autograft.Design: Prospective observational registry study; level of evidence, 3.Setting: Primary care.Participants: Cross-sectional data of 127 patients (45% women, mean age 24.9 ± 8.1 years) were extracted from a rehabilitation outcome registry at 10 weeks and 4, 8 and 12 months after ACL reconstruction with hamstring tendon autograft.Main outcome measures: All patients performed a concentric Biodex test, and an eccentric NordBord test on the same occasion or within seven days of the concentric test. The primary outcome was the limb symmetry index between the respective tests.Results: A greater knee flexor symmetry deficit was observed with the eccentric test compared with the concentric test at all follow-ups with clinically relevant differences at 4 (11.8% ± 12.7% [CI 7.8–15.8%]) and 8 months (13.4 ± 11.9 [CI 9.7–17.2%].Conclusion: The eccentric NordBord test was able to identify clinically relevant deficits in knee flexor strength symmetry that were not identified by gold standard isokinetic concentric testing during the first year among patients treated with an ACL reconstruction using a hamstring tendon autograft. © 2022 The Authors
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| 17. |
- Högberg, Johan, et al.
(författare)
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Restoring Knee Flexor Strength Symmetry Requires 2 Years After ACL Reconstruction, But Does It Matter for Second ACL Injuries? A Systematic Review and Meta-analysis
- 2024
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Ingår i: Sports Medicine – Open. - Heidelberg : SpringerOpen. - 2199-1170 .- 2198-9761. ; 10
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Forskningsöversikt (refereegranskat)abstract
- Background: It is unknown whether knee flexor strength recovers after anterior cruciate ligament (ACL) reconstruction with a hamstring tendon (HT) autograft and whether persistent knee flexor strength asymmetry is associated to a second ACL injury. Objective: We aimed to systematically review (1) whether knee flexor strength recovers after ACL reconstruction with HT autografts, and (2) whether it influences the association with a second ACL injury. A third aim was to summarize the methodology used to assess knee flexor strength. Design: Systematic review and meta-analysis reported according to PRISMA. Methods: A systematic search was performed using the Cochrane Library, Embase, Medline, PEDRo, and AMED databases from inception to December 2021 and until completion in January 2023. Human clinical trials written in English and conducted as randomized controlled trials, longitudinal cohort, cross-sectional, and case–control studies on patients with index ACL reconstructions with HT autografts harvested from the ipsilateral side were considered. Knee flexor strength was measured isokinetically in both the reconstructed and uninjured limb to enable the calculation of the limb symmetry index (LSI). The Risk of Bias Assessment Tool for Non-Randomized Studies was used to assess risk of bias for non-randomized studies and the revised Cochrane Risk of Bias tool was used for randomized controlled trials. For the meta-analysis, the LSI (mean ± standard error) for concentric knee flexor strength at angular velocities of 60°/second (s) and 180°/s preoperatively and at 3 months, 6 months, 12 months, and 24 months were pooled as weighted means with standard errors. Results: The search yielded 64 studies with a total of 8378 patients, which were included for the assessment of recovery of knee flexor strength LSI, and a total of 610 patients from four studies that investigated the association between knee flexor strength and second ACL injuries. At 1 year after ACL reconstruction, the knee flexor strength LSI had recovered to 89.0% (95% CI 87.3; 90.7%) and 88.3% (95% CI 85.5; 91.1%) for the velocities of 60°/s and 180°/s, respectively. At 2 years, the LSI was 91.7% (95% CI 90.8; 92.6%) and 91.2% (95% CI 88.1; 94.2%), for velocities of 60°/s and 180°/s, respectively. For the association between knee flexor strength and second ACL injuries, there was insufficient and contradictory data. Conclusions: There was low to very low certainty of evidence indicating that the recovery of knee flexor strength LSI, defined as ≥ 90% of the uninjured side, takes up to 2 years after ACL reconstruction with HT autografts. Whether knee flexor strength deficits influence the association of second ACL injuries is still uncertain. There was considerable heterogeneity in the methodology used for knee flexor strength assessment, which together with the low to very low certainty of evidence, warrants further caution in the interpretation of our results. Registration number: CRD42022286773. © 2024, The Author(s).
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| 18. |
- Högberg, Johan, 1994, et al.
(författare)
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The NordBord test reveals persistent knee flexor strength asymmetry when assessed two and five years after ACL reconstruction withhamstring tendon autograft
- 2024
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Ingår i: Physical Therapy in Sport. - 1466-853X .- 1873-1600. ; 66, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Comparison of knee flexor strength limb symmetry index (LSI) between the NordBord-test and the Biodex-test, and to determine the relationship between knee flexor strength and function in patients 2 and 5 years after anterior cruciate ligament reconstruction (ACL-R) with hamstring tendon (HT) autografts. Design: Observational registry study. Setting: Primary care. Patients: Cross-sectional data from 96 patients (55% women) participating in a rehabilitation-registry after ACL-R with HT autografts. Main outcome measures: Comparison of knee flexor strength symmetry between the Biodex-test and the NordBord-test. Secondly, the relationship between knee flexor strength test and perceived knee function, activity level, and hop performance. Results: The NordBord-test demonstrated greater strength deficits compared to the Biodex-test with a mean difference of 12.5% ± 15.1% 95 % CI [8.1; 16.9%] at 2 years, and 11.1% ± 11.9% 95 % CI [7.7; 14.6 %] at 5 years after ACL-R. Relative concentric knee flexor strength (Nm/kg) in the Biodex demonstrated significant weak-to-moderate correlations with activity level and hop performance (r = 0.33–0.67) at 2 and 5 years. Conclusion: The NordBord-test identified deficits in knee flexor strength LSI not seen with the Biodex-test at 2 and 5 years after ACL-R. No significant correlations were found between the persistent knee flexor strength asymmetry and perceived function, activity level or hop performance.
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| 19. |
- Matteucci, Angelo, et al.
(författare)
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Comparison of knee flexor strength recovery between semitendinosus alone versus semitendinosus with gracilis autograft for ACL reconstruction: a systematic review and meta-analysis
- 2024
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Ingår i: BMC MUSCULOSKELETAL DISORDERS. - 1471-2474. ; 25:1
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Forskningsöversikt (refereegranskat)abstract
- BackgroundWhether there is a difference in harvesting the semitendinosus tendon alone (S) or in combination with the gracilis tendon (SG) for the recovery of knee flexor strength after anterior cruciate ligament (ACL) reconstruction remains inconclusive. Therefore, this study aimed to assess the recovery of knee flexor strength based on the autograft composition, S or SG autograft at 6, 12, and >= 24 months after ACL reconstruction.MethodsA systematic review and meta-analysis was conducted following the PRISMA guidelines. A comprehensive search was performed encompassing the Cochrane Library, Embase, Medline, PEDRo and AMED databases from inception to January 2023. Inclusion criteria were human clinical trials published in English, comprised of randomized controlled trials (RCTs), longitudinal cohort-, cross-sectional and case-control studies that compared knee flexor strength recovery between S and SG autografts in patients undergoing primary ACL reconstruction. Isokinetic peak torques were summarized for angular velocities of 60 degrees/s, 180 degrees/s, and across all angular velocities, assessed at 6, 12, and >= 24 months after ACL reconstruction. A random-effects model was used with standardized mean differences and 95% confidence intervals. Risk of bias was assessed with the RoBANS for non-randomized studies and the Cochrane RoB 2 tool for RCTs. Certainty of evidence was appraised using the GRADE working group methodology.ResultsAmong the 1,227 patients from the 15 included studies, 604 patients received treatment with S autograft (49%), and 623 received SG autograft (51%). Patients treated with S autograft displayed lesser strength deficits at 6 months across all angular velocities d = -0.25, (95% CI -0.40; -0.10, p = 0.001). Beyond 6 months after ACL reconstruction, no significant difference was observed between autograft compositions.ConclusionThe harvest of S autograft for ACL reconstruction yields superior knee flexor strength recovery compared to SG autograft 6 months after ACL reconstruction, irrespective of angular velocity at isokinetic testing. However, the clinical significance of the observed difference in knee flexor strength between autograft compositions at 6 months is questionable, given the very low certainty of evidence and small effect size. There was no significant difference in knee flexor strength recovery between autograft compositions beyond 6 months after ACL reconstruction.
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| 20. |
- Psilander, Niklas, et al.
(författare)
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Effects of training, detraining, and retraining on strength, hypertrophy, and myonuclear number in human skeletal muscle
- 2019
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 126:6, s. 1636-1645
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Tidskriftsartikel (refereegranskat)abstract
- Previously trained mouse muscles acquire strength and volume faster than naive muscles; it has been suggested that this is related to increased myonuclear density. The present study aimed to determine whether a previously strength-trained leg (mem-leg) would respond better to a period of strength training than a previously untrained leg (con-leg). Nine men and 10 women performed unilateral strength training (T1) for 10 wk, followed by 20 wk of detraining (DT) and a 5-wk bilateral retraining period (T2). Muscle biopsies were taken before and after each training period and analyzed for myonuclear number, fiber volume, and cross-sectional area (CSA). Ultrasound and one repetition of maximum leg extension were performed to determine muscle thickness (MT) and strength. CSA (similar to 17%), MT (similar to 10%), and strength (similar to 20%) increased during T1 in the mem-leg. However, the myonuclear number and fiber volume did not change. MT and CSA returned to baseline values during DT, but strength remained elevated (similar to 60%), supporting previous findings of a long-lasting motor learning effect. MT and strength increased similarly in the mem-leg and con-leg during T2, whereas CSA, fiber volume, and myonuclear number remained unaffected. In conclusion, training response during T2 did not differ between the mem-leg and con-leg. However, this does not discount the existence of human muscle memory. since no increase in the number of myonuclei was detected during T1 and no clear detraining effect was observed for cell size during DT; thus, the present data did not allow for a rigorous test of the muscle memory hypothesis. NEW & NOTEWORTHY If a long-lasting intramuscular memory exists in humans. this will affect strength-training advice for both athletes and the public. Based on animal experiments, we hypothesized that such a memory exists and that it is related to the myonuclear number. However, a period of unilateral strength training, followed by detraining, did not increase the myonuclear number. The training response, during a subsequent bilateral retraining period, was not enhanced in the previously trained leg.
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| 21. |
- Sieljacks, Peter, et al.
(författare)
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Body position influences arterial occlusion pressure: implications for the standardization of pressure during blood flow restricted exercise
- 2018
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 118:2, s. 303-312
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Springer-Verlag GmbH Germany, part of Springer Nature Purpose: Arterial occlusion pressure (AOP) measured in a supine position is often used to set cuff pressures for blood flow restricted exercise (BFRE). However, supine AOP may not reflect seated or standing AOP, thus potentially influencing the degree of occlusion. The primary aim of the study was to investigate the effect of body position on AOP. A secondary aim was to investigate predictors of AOP using wide and narrow cuffs. Methods: Twenty-four subjects underwent measurements of thigh circumference, skinfold and blood pressure, followed by assessments of thigh AOP in supine and seated positions with a wide and a narrow cuff, respectively, using Doppler ultrasound. Results: In the supine position, AOP was 148 ± 19 and 348 ± 94 mmHg with the wide and narrow cuff, respectively. This increased to 177 ± 20 and 409 ± 101 mmHg in the seated position, with correlations between supine and seated AOP of R 2 = 0.81 and R 2 = 0.50 for the wide and narrow cuff, respectively. For both cuff widths, thigh circumference constituted the strongest predictor of AOP, with diastolic blood pressure explaining additional variance with the wide cuff. The predictive strength of these variables did not differ between body positions. Conclusion: Our results indicate that body position strongly influences lower limb AOP, especially with narrow cuffs, yielding very high AOP (≥ 500–600 mmHg) in some subjects. This should be taken into account in the standardization of cuff pressures used during BFRE to better control the physiological effects of BFRE.
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| 22. |
- Sieljacks, Peter, et al.
(författare)
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Muscle damage and repeated bout effect following blood flow restricted exercise
- 2016
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 116:3, s. 513-525
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Blood-flow restricted resistance exercise training (BFRE) is suggested to be effective in rehabilitation training, but more knowledge is required about its potential muscle damaging effects. Therefore, we investigated muscle-damaging effects of BFRE performed to failure and possible protective effects of previous bouts of BFRE or maximal eccentric exercise (ECC). Methods Seventeen healthy young men were allocated into two groups completing two exercise bouts separated by 14 days. One group performed BFRE in both exercise bouts (BB). The other group performed ECC in the first and BFRE in the second bout. BFRE was performed to failure. Indicators of muscle damage were evaluated before and after exercise. Results The first bout in the BB group led to decrements in maximum isometric torque, and increases in muscle soreness, muscle water retention, and serum muscle protein concentrations after exercise. These changes were comparable in magnitude and time course to what was observed after first bout ECC. An attenuated response was observed in the repeated exercise bout in both groups. Conclusion We conclude that unaccustomed single-bout BFRE performed to failure induces significant muscle damage. Additionally, both ECC and BFRE can precondition against muscle damage induced by a subsequent bout of BFRE.
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| 23. |
- Sieljacks, Peter, et al.
(författare)
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Non-failure blood flow restricted exercise induces similar muscle adaptations and less discomfort than failure protocols.
- 2019
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Ingår i: Scandinavian journal of medicine & science in sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 29:3, s. 336-347
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Tidskriftsartikel (refereegranskat)abstract
- Low-load blood flow restricted resistance exercise (BFRE) performed to volitional failure is suggested to constitute an effective method for producing increases in muscle size and function. However, failure BFRE may entail high levels of perceived exertion, discomfort and/or delayed onset of muscle soreness (DOMS). The aim of the study was to compare BFRE performed to volitional failure (F-BFRE) vs non-failure BFRE (NF-BFRE) on changes in muscle size, function and perceptual responses. Fourteen young untrained males had one leg randomized to knee-extension F-BFRE while the contralateral leg performed NF-BFRE. The training consisted of 22 training bouts over an 8-week period. Whole-muscle cross-sectional area (CSA) of quadriceps components, muscle function, and DOMS were assessed before and after the training period. Perceived exertion and discomfort were registered during each training bout. Both F-BFRE and NF-BFRE produced regional increases in muscle CSA in the range of; quadriceps (2.5-3.8%), vastus lateralis (8.1-8.5%), and rectus femoris (7.9-25.0%). All without differences between leg. Muscle strength (6.8-11.5%) and strength-endurance capacity (13.9-18.6%) also increased to a similar degree in both legs. Less perceived exertion, discomfort and DOMS were reported with NF-BFRE compared to F-BFRE. In conclusion, non-failure BFRE enable increases in muscle size and muscle function, while involving reduced perceptions of exertion, discomfort and DOMS. Non-failure BFRE may be a more feasible approach in clinical settings. This article is protected by copyright. All rights reserved.
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| 24. |
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| 25. |
- Vissing, K., et al.
(författare)
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Myocellular Adaptations to Low-Load Blood Flow Restricted Resistance Training
- 2020
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Ingår i: Exercise and sport sciences reviews. - : Ovid Technologies (Wolters Kluwer Health). - 0091-6331 .- 1538-3008. ; 48:4, s. 180-187
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Tidskriftsartikel (refereegranskat)abstract
- Low-load blood flow restricted resistance exercise (BFRRE) can stimulate whole-muscle growth and improve muscle function. However, limited knowledge exists on the effects at the myocellular level. We hypothesize that BFRRE has the ability to produce concurrent skeletal muscle myofibrillar, mitochondrial, and microvascular adaptations, thus offering an alternative strategy to counteract decay in skeletal muscle health and function in clinical populations.
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| 26. |
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| 27. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Acute low-load resistance exercise with and without blood flow restriction increased protein signalling and number of satellite cells in human skeletal muscle.
- 2013
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Ingår i: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 113:12, s. 2953-2965
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To investigate hypertrophic signalling after a single bout of low-load resistance exercise with and without blood flow restriction (BFR). Methods Seven subjects performed unilateral knee extensions at 30 % of their one repetition maximum. The subjects performed five sets to failure with BFR on one leg, and then repeated the same amount of work with the other leg without BFR. Biopsies were obtained from m. vastus lateralis before and 1, 24 and 48 h after exercise. Results At 1-h post-exercise, phosphorylation of p70S6KThr389 and p38MAPKThr180/Tyr182 was elevated in the BFR leg, but not in the free-flow leg. Phospho-p70S6KThr389 was elevated three- to fourfold in both legs at 24-h post-exercise, but back to baseline at 48 h. The number of visible satellite cells (SCs) per muscle fibre was increased for all post-exercise time points and in both legs (33–53 %). The proportion of SCs with cytoplasmic extensions was elevated at 1-h post in the BFR leg and the number of SCs positive for myogenin and/or MyoD was increased at 1- and 24-h post-exercise for both legs combined. Conclusion Acute low-load resistance exercise with BFR resulted in early (1 h) and late (24 h) enhancement of phospho-p70S6KThr389, an early response of p38MAPK, and an increased number of SCs per muscle fibre. Enhanced phospho-p70S6KThr389 at 24-h post-exercise and increases in SC numbers were seen also in the free-flow leg. Implications of these findings for the hypertrophic effects of fatiguing low-load resistance exercise with and without BFR are discussed.
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| 28. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Contractile function and sarcolemmal permeability after acute low-load resistance exercise with blood flow restriction
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:6, s. 2051-2063
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Tidskriftsartikel (refereegranskat)abstract
- Conflicting findings have been reported regarding muscle damage with low-intensity resistance exercise with blood flow restriction (BFR) by pressure cuffs. This study investigated muscle function and muscle fibre morphology after a single bout of low-intensity resistance exercise with and without BFR. Twelve physically active subjects performed unilateral knee extensions at 30% of their one repetition maximum (1RM), with partial BFR on one leg and the other leg without occlusion. With the BFR leg, five sets were performed to concentric torque failure, and the free-flow leg repeated the exact same number of repetitions and sets. Biopsies were obtained from vastus lateralis before and 1, 24 and 48 h after exercise. Maximum isometric torque (MVC) and resting tension were measured before and after exercise and at 4, 24, 48, 72, 96 and 168 h post-exercise. The results demonstrated significant decrements in MVC (lasting a parts per thousand yen48 h) and delayed onset muscle soreness in both legs, and increased resting tension for the occluded leg both acutely and at 24 h post-exercise. The percentage of muscle fibres showing elevated intracellular staining of the plasma protein tetranectin, a marker for sarcolemmal permeability, was significantly increased from 9% before exercise to 27-38% at 1, 24 and 48 h post-exercise for the BFR leg. The changes in the free-flow leg were significant only at 24 h (19%). We conclude that an acute bout of low-load resistance exercise with BFR resulted in changes suggesting muscle damage, which may have implications both for safety aspects and for the training stimulus with BFR exercise.
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| 29. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Effects of vascular occlusion on muscular endurance in dynamic knee extension exercise at different submaximal loads
- 2006
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Ingår i: Journal of Strength and Conditioning Research. - 1064-8011. ; 20:2, s. 372-7
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Tidskriftsartikel (refereegranskat)abstract
- Strength training with low load under conditions of vascular occlusion has been proposed as an alternative to heavy-resistance exercise in the rehabilitation setting, when large forces acting upon the musculoskeletal system are unwanted. Little is known, however, about the relative intensity at which occlusion of blood flow significantly reduces dynamic muscular endurance and, hence, when it may increase the training effect. The purpose of this study was to investigate endurance during dynamic knee extension at different loads with and without cuff occlusion. Sixteen subjects (20-45 years of age) with strength-training experience were recruited. At 4 test sessions, the subjects performed unilateral knee extensions to failure with and without a pressure cuff around the thigh at 20, 30, 40, and 50% of their 1 repetition maximum (1RM). The pressure cuff was inflated to 200 mm Hg during exercise with occlusion. Significant differences in the number of repetitions performed were found between occluded and nonoccluded conditions for loads of 20, 30, and 40% of 1RM (p < 0.01) but not for the 50% load (p = 0.465). Thus, the application of a pressure cuff around the thigh appears to reduce dynamic knee extension endurance more at a low load than at a moderate load. These results may have implications regarding when it could be useful to apply a tourniquet in order to increase the rate of fatigue and perhaps also the resulting training effect. However, the short- and long-term safety of training under ischemic conditions needs to be addressed in both healthy and less healthy populations. Furthermore, the high acute pain ratings and the delayed-onset muscle soreness associated with this type of training may limit its potential use to highly motivated individuals.
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| 30. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Ischemic strength training: a low-load alternative to heavy resistance exercise?
- 2008
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Ingår i: Scandinavian Journal of Medicine & Science in Sports. - 1600-0838. ; 18:4, s. 401-16
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Tidskriftsartikel (refereegranskat)abstract
- Strength training with low loads in combination with vascular occlusion has been proposed as an alternative to heavy resistance exercise in the rehabilitation setting, especially when high forces acting upon the musculo-skeletal system are contraindicated. Several studies on low-to-moderate intensity resistance exercise combined with cuff occlusion have demonstrated increases in muscle strength and size that are comparable to those typically seen after conventional high-load strength training. However, the physiological mechanisms by which occlusion training induces increased muscle mass and strength are currently unclear, although several candidate stimuli have been proposed. Also, the long-term safety, practicality, and efficacy of this training method are still controversial. Furthermore, recent studies have demonstrated that in some instances, tourniquet cuffs may not be necessary for relative ischemia and significant training effects to occur with resistance exercise at low-to-moderate loads. The aims of the present review are to summarize current opinion and knowledge regarding the physiology of ischemic strength training and to discuss some of the training and health aspects of this type of exercise. In addition, suggestions for further research are given.
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| 31. |
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| 32. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Muscle fibre activation and fatigue with low-load blood flow restricted resistance exercise—An integrative physiology review
- 2020
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 228:1
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Forskningsöversikt (refereegranskat)abstract
- Blood flow-restricted resistance exercise (BFRRE) has been shown to induce increases in muscle size and strength, and continues to generate interest from both clinical and basic research points of view. The low loads employed, typically 20%-50% of the one repetition maximum, make BFRRE an attractive training modality for individuals who may not tolerate high musculoskeletal forces (eg, selected clinical patient groups such as frail old adults and patients recovering from sports injury) and/or for highly trained athletes who have reached a plateau in muscle mass and strength. It has been proposed that achieving a high degree of muscle fibre recruitment is important for inducing muscle hypertrophy with BFRRE, and the available evidence suggest that fatiguing low-load exercise during ischemic conditions can recruit both slow (type I) and fast (type II) muscle fibres. Nevertheless, closer scrutiny reveals that type II fibre activation in BFRRE has to date largely been inferred using indirect methods such as electromyography and magnetic resonance spectroscopy, while only rarely addressed using more direct methods such as measurements of glycogen stores and phosphocreatine levels in muscle fibres. Hence, considerable uncertainity exists about the specific pattern of muscle fibre activation during BFRRE. Therefore, the purpose of this narrative review was (1) to summarize the evidence on muscle fibre recruitment during BFRRE as revealed by various methods employed for determining muscle fibre usage during exercise, and (2) to discuss reported findings in light of the specific advantages and limitations associated with these methods. © 2019 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd
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| 33. |
- Wernbom, Mathias, 1968, et al.
(författare)
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Reply
- 2021
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Ingår i: Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. - 1536-3724. ; 31:6
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Tidskriftsartikel (refereegranskat)
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| 34. |
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| 35. |
- Wernbom, Mathias, 1968
(författare)
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Styrketräning
- 2018
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Ingår i: Idrottsskada - Från prevention till säker återgång till idrott. - Stockholm : Studentlitteratur. - 9789144103600 ; , s. 101-109
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 36. |
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| 37. |
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