| 1. |
- Apró, William, et al.
(författare)
-
Resistance exercise induced S6K1 kinase activity is not inhibited in human skeletal muscle despite prior activation of AMPK by high intensity interval cycling.
- 2015
-
Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 308:6, s. E470-E481
-
Tidskriftsartikel (refereegranskat)abstract
- Combining endurance and strength training in the same session has been reported to reduce the anabolic response to the latter form of exercise. The underlying mechanism, based primarily on results from rodent muscle, is proposed to involve AMPK-dependent inhibition of mTORC1 signaling. This hypothesis was tested in eight trained male subjects who in a randomized order performed either resistance exercise only (R) or interval cycling followed by resistance exercise (ER). Biopsies taken from the vastus lateralis before and after endurance exercise and repeatedly after resistance exercise were assessed for glycogen content, kinase activity, protein phosphorylation and gene expression. Mixed muscle fractional synthetic rate was measured at rest and during 3h of recovery using the stable isotope technique. In ER, AMPK activity was elevated immediately after both endurance and resistance exercise (~90%, P<0.05) but was unchanged in R. Thr389 phosphorylation of S6K1 was increased several-fold immediately after exercise (P<0.05) in both trials and increased further throughout recovery. After 90 and 180 min recovery, S6K1 activity was elevated (~55% and ~110%, respectively, P<0.05) and eEF2 phosphorylation was reduced (~55%, P<0.05) with no difference between trials. In contrast, markers for protein catabolism were differently influenced by the two modes of exercise; ER induced a significant increase in gene and protein expression of MuRF1 (P<0.05), which was not observed following R exercise only. In conclusion, cycling-induced elevation in AMPK activity does not inhibit mTORC1 signaling after subsequent resistance exercise, but may instead interfere with the hypertrophic response by influencing key components in protein breakdown.
|
|
| 2. |
- Bakkman, L., et al.
(författare)
-
Quantitative and qualitative adaptation of human skeletal muscle mitochondria to hypoxic compared to normoxic training at the same relative work rate
- 2007
-
Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X .- 1748-1708 .- 1748-1716. ; 190:3, s. 243-251
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: To investigate if training during hypoxia (H) improves the adaptation of muscle oxidative function compared with normoxic (N) training performed at the same relative intensity.Method: Eight untrained volunteers performed one-legged cycle training during 4 weeks in a low-pressure chamber. One leg was trained under N conditions and the other leg under hypobaric hypoxia (526 mmHg) at the same relative intensity as during N (65% of maximal power output, Wmax). Muscle biopsies were taken from vastus lateralis before and after the training period. Muscle samples were analysed for the activities of oxidative enzymes [citrate synthase (CS) and cytochrome c oxidase (COX)] and mitochondrial respiratory function.Results: W max increased with more than 30% over the training period during both N and H. CS activity increased significantly after training during N conditions (+20.8%, P < 0.05) but remained unchanged after H training (+4.5%, ns) with a significant difference between conditions (P < 0.05 H vs. N). COX activity was not significantly changed by training and was not different between exercise conditions [+14.6 (N) vs. -2.3% (H), ns]. Maximal ADP stimulated respiration (state 3) expressed per weight of muscle tended to increase after N (+31.2%, P < 0.08) but not after H training (+3.2%, ns). No changes were found in state four respiration, respiratory control index, P/O ratio, mitochondrial Ca2+ resistance and apparent Km for oxygen.Conclusion: The training-induced increase in muscle oxidative function observed during N was abolished during H. Altitude training may thus be disadvantageous for adaptation of muscle oxidative function.
|
|
| 3. |
- Cardinale, Daniele A., 1982-, et al.
(författare)
-
Superior Intrinsic Mitochondrial Respiration in Women Than in Men.
- 2018
-
Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Sexual dimorphism is apparent in humans, however, to date no studies have investigated mitochondrial function focusing on intrinsic mitochondrial respiration (i.e., mitochondrial respiration for a given amount of mitochondrial protein) and mitochondrial oxygen affinity (p50mito) in relation to biological sex in human. A skeletal muscle biopsy was donated by nine active women, and ten men matched for maximal oxygen consumption (VO2max) and by nine endurance trained men. Intrinsic mitochondrial respiration, assessed in isolated mitochondria, was higher in women compared to men when activating complex I (CIP) and complex I+II (CI+IIP) (p < 0.05), and was similar to trained men (CIP, p = 0.053; CI+IIP, p = 0.066). Proton leak and p50mito were higher in women compared to men independent of VO2max. In conclusion, significant novel differences in mitochondrial oxidative function, intrinsic mitochondrial respiration and p50mito exist between women and men. These findings may represent an adaptation in the oxygen cascade in women to optimize muscle oxygen uptake to compensate for a lower oxygen delivery during exercise.
|
|
| 4. |
- Kazior, Zuzanna, et al.
(författare)
-
Endurance Exercise Enhances the Effect of Strength Training on Muscle Fiber Size and Protein Expression of Akt and mTOR.
- 2016
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- Reports concerning the effect of endurance exercise on the anabolic response to strength training have been contradictory. This study re-investigated this issue, focusing on training effects on indicators of protein synthesis and degradation. Two groups of male subjects performed 7 weeks of resistance exercise alone (R; n = 7) or in combination with preceding endurance exercise, including both continuous and interval cycling (ER; n = 9). Muscle biopsies were taken before and after the training period. Similar increases in leg-press 1 repetition maximum (30%; P<0.05) were observed in both groups, whereas maximal oxygen uptake was elevated (8%; P<0.05) only in the ER group. The ER training enlarged the areas of both type I and type II fibers, whereas the R protocol increased only the type II fibers. The mean fiber area increased by 28% (P<0.05) in the ER group, whereas no significant increase was observed in the R group. Moreover, expression of Akt and mTOR protein was enhanced in the ER group, whereas only the level of mTOR was elevated following R training. Training-induced alterations in the levels of both Akt and mTOR protein were correlated to changes in type I fiber area (r = 0.55-0.61, P<0.05), as well as mean fiber area (r = 0.55-0.61, P<0.05), reflecting the important role played by these proteins in connection with muscle hypertrophy. Both training regimes reduced the level of MAFbx protein (P<0.05) and tended to elevate that of MuRF-1. The present findings indicate that the larger hypertrophy observed in the ER group is due more to pronounced stimulation of anabolic rather than inhibition of catabolic processes.
|
|
| 5. |
- Larsen, Filip J, 1977-, et al.
(författare)
-
Mitochondrial oxygen affinity increases after sprint interval training and is related to the improvement in peak oxygen uptake.
- 2020
-
Ingår i: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 229:3
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: The body responds to exercise training by profound adaptations throughout the cardiorespiratory and muscular systems, which may result in improvements in maximal oxygen consumption (VO2 peak) and mitochondrial capacity. By convenience, mitochondrial respiration is often measured at supra-physiological oxygen levels, an approach that ignores any potential regulatory role of mitochondrial affinity for oxygen (p50mito ) at physiological oxygen levels.METHODS: In this study, we examined the p50mito of mitochondria isolated from the Vastus lateralis and Triceps brachii in 12 healthy volunteers before and after a training intervention with 7 sessions of sprint interval training using both leg cycling and arm cranking. The changes in p50mito were compared to changes in whole-body VO2 peak.RESULTS: We here show that p50mito is similar in isolated mitochondria from the Vastus (40 ± 3.8 Pa) compared to Triceps (39 ± 3.3) but decreases (mitochondrial oxygen affinity increases) after 7 sessions of sprint interval training (to 26 ± 2.2 Pa in Vastus and 22 ± 2.7 Pa in Triceps, both p<0.01). The change in VO2 peak modeled from changes in p50mito was correlated to actual measured changes in VO2 peak (R2 =0.41, p=0.002).CONCLUSION: Together with mitochondrial respiratory capacity, p50mito is a critical factor when measuring mitochondrial function, it can decrease with sprint interval training and should be considered in the integrative analysis of the oxygen cascade from lung to mitochondria.
|
|
| 6. |
- Lund Ohlsson, Marie
(författare)
-
Double Poling Incross-Country Skiing : Biomechanical and Physiological Analysis of Sitting and Standing Positions
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Double poling (DP) is a sub-technique in cross-country skiing that has increased in interest over the last decades, e.g. athletes in cross-country skiing have increased their utilisation of double poling during competitions. In cross-country sit-skiing athletes with impairments in legs and/or trunk sit in a sledge and utilise DP to propel themselves. Technique (i.e. movement pattern) is one key factor determining performance but also a factor that may affect the risk of overuse injuries in sports.Therefore, the overall aim of the thesis was to improve the understanding of the human movement technique in cross-country skiing DP, in both standing (paper I-II) and sitting positions (paper III-IV, Thesis A-B) using biomechanical and physiological measurements and inverse dynamics simulations. All studies were carried out on a double poling ergometer in laboratory. Three experimental studies were performed with able-bodied participants (papers I-II, IV-VI), one study with one participant with growth defect in the legs (paper III), and one study (Thesis B) with one participant with complete spinal cord injury at thoracic vertebra 4.In paper I the first full-body simulation of DP was performed and results were comparable to results found in literature when the kinematics and external kinetics were similar. Paper II showed how increased leg utilisation increased performance (forward impulse) but reduced skiing efficiency (output work divided by metabolic muscle work). These results indicate that both high performance (power output) and efficiency may not be achieved in the same technique.In sitting DP many different sitting positions are utilised. Athletes with full muscle control in hip and trunk mainly sit with their knees lower than their hips (KLnoS). Athletes with paralysis in lower trunk and legs need trunk stability from the sit-ski. Most often, this is achieved by adopting a knees higher than hips (KH) position together with a support for the lower back. However, this position might induce large flexion in the spine, which is hypothesised to affect injury risk in the shoulders and lower back. This thesis has enabled the knees low sitting position for athletes with paralysis in the lower trunk and legs by supporting the anterior trunk with the sledge (KL). In sitting DP in athletes with full hip and trunk muscle control, high performance was achieved through proximal-distal sequencing from the hips through the trunk to the arms, and large muscle work in spine and legs (IV, V, Thesis A). In order of performance, KLnoS utilised muscles in the hips-spine-arms, compared with utilisation of spine-arms in KH, and mainly arms in KL. Higher amount of activated muscle mass resulted in lower relative anaerobic metabolism during submaximal exercise (IV).The lower back joint reactions were higher for the sitting position with larger spinal flexion, KH compared to KL (VI). These results suggest that there is an increased risk of injury in the lower back for the sitting position KH. Athletes with paraplegia generally have a high risk of injuries in the shoulders. The results of this thesis showed higher shoulder joint reactions in the sitting position with larger shoulder-arm muscle work, in KL compared to KH.For the case study with one participant with thoracic spinal cord injury (Thesis B) highest performance was achieved in the KH sitting position where spinal flexion occurred at the beginning of the poling phase. When comparing the fixed trunk positions KL and KHS, higher performance was achieved in KHS. It was speculated that the difference between KL and KHS was due to the impairment of the vasoconstriction in paralysed muscles. The effect of gravity on venous pooling is probably larger when the legs are lower down as in KL. This effect was not present for individuals without paralysis (III), where KL was more economical than KHS.Parasport classification needs evidence of how impairment affects sporting performance (Tweedy et al., 2014, Tweedy and Vanlandewijck, 2011). Classification might benefit from simulations as performed in this thesis. The musculoskeletal simulations of seated DP in paper V and the KLnoS position presented in the thesis have showed the relative contribution of different muscle groups on performance. These results are novel and might contribute to improvement of the classification system.
|
|
| 7. |
- Lund Ohlsson, Marie, et al.
(författare)
-
Estimation of muscle work in cross-country sit-skiing
- 2019
-
Konferensbidrag (refereegranskat)abstract
- Introduction: In Nordic skiing all sitting athletes compete in the same event competition. The sitting positions differ between athletes. Most of the athletes sit knee-seated, or with their thighs tilted downward (KL) and free to move their trunk. Some athletes do not have the possibility to sit in that position and therefore adjust their sitting position. For example, athletes with reduced muscle control in hips and lower trunk sit with their knees higher than their hips (KH) to increase stability.Purpose: The purpose of this study was to examine how sitting position KL and KH affects the muscular power.Methods: One female able-bodied athlete performed one test session in each sitting position (KL and KH) comprising five times 3 minutes sub-maximal exercise and a maximal time-trial in a double-poling ergometer (ThoraxTrainer A/S, Denmark). During the tests 3D kinematics (Qualisys AB, Sweden), pole forces and power output were measured. From the measured data, participant and test specific musculo-skeletal inverse-dynamics simulation models were created using the AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). From the simulations of submaximal exercise power output 37 W, 52 W and maximal time-trial the muscular metabolic power (mMP) was computed according to Holmberg (2013).Results: The power output in maximal exercise was higher in KL (90.1 W) compared to KH (74.7 W). During both submaximal and maximal exercise, the total muscular metabolic power was larger in KL compared to KH (KL mean 861 W and KH mean 682 W). The muscular metabolic power also showed larger relative involvement of legs in KL (KL mean 18 % and KH mean 4 %) and larger relative involvement of arms and trunk in KH.Conclusion: That sitting position KL compared to KH is related to higher performance for athletes without impairment in hips and trunk is known before (Gastaldi, 2012). However, the results from this study explains why performance is higher in KL, i.e. that larger muscular metabolic power are produced in the legs. This study also shows the size of the involvement of legs, which could be interesting for development of classification rules.
|
|
| 8. |
- Lund Ohlsson, Marie, et al.
(författare)
-
Estimation of muscular metabolic power in two different cross-country sit-skiing sledges using inverse-dynamics simulation
- 2022
-
Ingår i: Journal of Rehabilitation and Assistive Technologies Engineering. - : SAGE Publications. - 2055-6683 .- 2055-6683. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to estimate and compare the muscular metabolic power produced in the human body using musculoskeletal inverse-dynamics during cross-country sit-skiing. Two sitting positions were adapted for athletes with reduced trunk and hip muscle control, knee low with frontal trunk support (KL-fix), and knee high (KH). Five female national class able-bodied cross-country skiers performed submaximal and maximal exercise in both sitting positions, while recording 3-D kinematics, pole forces, electromyography and respiratory variables. Simulations were performed from these experimental results and muscular metabolic power was computed. The main part of the muscle metabolic power was produced in the upper limbs for both sitting positions, but KH produced more muscle metabolic power in lower limbs and trunk during maximal intensity. KH was also more efficient, utilizing less muscular metabolic power during submaximal intensities, relatively less power in the upper limbs and more power in the trunk, hip and lower limb muscles. This implies that sitting position KH is preferable for high power output when using able-bodied simulation models. This study showed the potential of using musculoskeletal simulations to improve the understanding of how different equipment design and muscles contribute to performance.
|
|
| 9. |
- Lund Ohlsson, Marie, et al.
(författare)
-
LUMBAR SPINE REACTION FORCES IN SEATED PARA-SPORT: CROSS-COUNTRY SIT-SKIING
- 2017
-
Ingår i: Brisbane 2017.
-
Konferensbidrag (refereegranskat)abstract
- INTRODUCTIONFor wheel-chair users shoulder injuries [1] and lower back injuries [2] are common. Lower back kyphosis of the spine, increases the anterior shear force in the lower back [3] and increases the risk of shoulder injuries [4]. Cross-country sit-skiing (CCSS) is an endurance sport where the athlete is seated in a sledge mounted on a pair of skis and propel themselves by poling with a pair of sticks. This sport creates more equal loading on the muscles around the shoulder than wheel-chair rolling [5] which is positive in an injury perspective for the gleno-humeral joint [1]. Athletes in CCSS with reduced trunk muscle control often sits in a sledge with their knees higher than their hips (KH) and a backrest. This position is hypothesized to be associated with spinal kyphosis and hence an increased risk of injuries. Therefore we have created a new sitting position with knees lower than hips (KL) with the trunk restrained on a frontal support. The aim of this study was to compute the L4/L5 joint reactions and compare the results between the positions KH and KL.METHODSFive female abled-bodied cross-country skiing athletes (62.6 ± 8.1kg, 1.67 ± 0.05m) performed one exercise test session in each sitting position; The sessions included a sub-maximal incremental test, including 4-6 exercise levels of 3 min (exercise intensity nr 4, 37W, reflected race-pace) and a maximal time-trial (MAX) of 3 min on a commercial skiing ergometer (ThoraxTrainer A/S, Denmark). Full-body kinematics (Qualisys AB, Sweden) and pole forces (Biovision, Germany) were measured in 200 Hz. These data served as input to inverse dynamic simulations in The AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). For each participant and sitting position, simulations were made for exercise intensity 37W and MAX over four poling cycles using a 5th order polynomial muscle recruitment criteria. Compression forces and anterior shear forces between L4 and L5 were computed and normalized to each participant’s standing joint reactions. Data were compared pair-wise between the two sitting positions. Statistical significance (p ≤ 0.05) were marked with asterisk (*). Tendency of difference (0.05 ≤ p < 0.10) were marked (ǂ). RESULTS AND DISCUSSIONPerformance was higher in position KH (KL: 0.77±0.08 W/kg, KH: 1.00±0.14 W/kg, p < 0.01). No difference were observed in cycle length or cycle time. Kinematics results showed that KL had less spine flexion and range of motion in flexion. KH showed higher mean pole force in 37W and tendency of higher peak pole force in MAX. In standing, L4/L5 compression and anterior shear forces were 354 ± 45N and 32 ± 11N respectively. The normalized L4/L5 reaction forces (fig. 1) were larger in KH, especially during MAX intensity due to higher power. For equal power output, 37W, the mean anterior shear force was larger in KH and the mean compression force showed tendency of larger in KH (p=0.077). Figure 1: Normalized joint reaction forces, compression and anterior shear forces, between vertebrae L4/L5 for the two sitting positions KH and KL with trunk restraint. Min – minimal force, Maximal force and Mean – mean force over the four poling cycles. CONCLUSIONSBased on inverse-dynamics musculo-skeletal simulations of 5 abled-bodied athletes, the sitting position KL with frontal restraint reduced the compression and shear force between the L4/L5 vertebrae but impeded performance. This study shows the difficulty of comparing performance and safety in the same piece of equipment. ACKNOWLEDGEMENTSThe authors acknowledge the Rolf & Gunilla Enström foundation and the Promobilia foundation, Sweden, for financial support, and the Ableway AB (Sweden) for construction of the sledges. REFERENCESBurnham RS, et al., Am J Sports Med, 21: 238-242, 1993.Thyberg M, et al., Disabil rehabil. 23:677-682, 2001.McGill SM, et al., Clin Biomech, 15: 777-780, 2000.Samuelsson KA, et al., J Rehabil Res Dev, 41: 65-74, 2004.Bjerkefors A, et al., Int J Sports Med, 34: 176-182, 2013.
|
|
| 10. |
- Moberg, Marcus, 1986-, et al.
(författare)
-
High-intensity leg cycling alters the molecular response to resistance exercise in the arm muscles.
- 2021
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- This study examined acute molecular responses to concurrent exercise involving different muscles. Eight men participated in a randomized crossover-trial with two sessions, one where they performed interval cycling followed by upper body resistance exercise (ER-Arm), and one with upper body resistance exercise only (R-Arm). Biopsies were taken from the triceps prior to and immediately, 90- and 180-min following exercise. Immediately after resistance exercise, the elevation in S6K1 activity was smaller and the 4E-BP1:eIF4E interaction greater in ER-Arm, but this acute attenuation disappeared during recovery. The protein synthetic rate in triceps was greater following exercise than at rest, with no difference between trials. The level of PGC-1α1 mRNA increased to greater extent in ER-Arm than R-Arm after 90 min of recovery, as was PGC-1α4 mRNA after both 90 and 180 min. Levels of MuRF-1 mRNA was unchanged in R-Arm, but elevated during recovery in ER-Arm, whereas MAFbx mRNA levels increased slightly in both trials. RNA sequencing in a subgroup of subjects revealed 862 differently expressed genes with ER-Arm versus R-Arm during recovery. These findings suggest that leg cycling prior to arm resistance exercise causes systemic changes that potentiate induction of specific genes in the triceps, without compromising the anabolic response.
|
|
