| 1. |
- Liebermann, Dario G., et al.
(författare)
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Spatiotemporal lower-limb asymmetries during stair descent in athletes following anterior cruciate ligament reconstruction
- 2024
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Ingår i: Journal of Electromyography & Kinesiology. - : Elsevier. - 1050-6411 .- 1873-5711. ; 75
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study evaluated motor control recovery at different times following anterior cruciate ligament reconstruction (ACLR) by investigating lower-limb spatiotemporal symmetry during stair descent performances.Methods: We used a cross-sectional design to compare asymptomatic athletes (Controls, n = 18) with a group of people with ACLR (n = 49) divided into three time-from-ACLR subgroups (Early: <6 months, n = 17; Mid: 6–18 months, n = 16; Late: ≥18 months, n = 16). We evaluated: “temporal symmetry” during the stance subphases (single-support, first and second double-support) and “spatial symmetry” for hip-knee-ankle intra-joint angular displacements during the stance phase using a dissimilarity index applied on superimposed 3D phase plots.Results: We found significant between-group differences in temporal variables (p ≤ 0.001). Compared to Controls, both Early and Mid (p ≤ 0.05) showed asymmetry in the first double-support time (longer for their injured vs. non-injured leg), while Early generally also showed longer durations in all other phases, regardless of stepping leg. No statistically significant differences were found for spatial intra-joint symmetry between groups.Conclusion: Temporal but not spatial asymmetry in stair descent is often present early after ACLR; it may remain for up to 18 months and may underlie subtle intra- and inter-joint compensations. Spatial asymmetry may need further exploration.
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| 2. |
- Arumugam, Ashokan, 1981-, et al.
(författare)
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A novel test reliably captures hip and knee kinematics and kinetics during unanticipated/anticipated diagonal hops in individuals with anterior cruciate ligament reconstruction
- 2020
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Ingår i: Journal of Biomechanics. - : Elsevier. - 0021-9290 .- 1873-2380. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- Unanticipated land-and-cut maneuvers might emulate lower limb mechanics associated with anterior cruciate ligament (ACL) injury. Reliability studies on landing mechanics of such maneuvers are however lacking. This study investigated feasibility and within-session reliability of landing mechanics of a novel one-leg double-hop test, mimicking a land-and-cut maneuver, in individuals with ACL reconstruction (ACLR). Our test comprised a forward hop followed by a diagonal hop in either of two directions (medial/lateral) under anticipated and unanticipated conditions. Twenty individuals with a unilateral ACLR (aged 24.2 ± 4.2 years, 0.7-10.8 years post-surgery) performed three successful hops/direction per leg. We determined reliability (intraclass correlation coefficient [ICC]) and agreement (standard error of measurement [SEM]) of 3-dimensional hip and knee angles and moments during the deceleration phase of the land-and-cut maneuver (vulnerable for non-contact ACL injuries). Mean success rate for unanticipated hops was 71-77% and for anticipated hops 91-95%. Both limbs demonstrated moderate-excellent reliability (ICC 95% confidence intervals: 0.50-0.99) for almost all hip and knee peak angles and moments in all planes and conditions, with a few exceptions: poor-good reliability for hip and knee frontal and/or transverse plane variables, especially for lateral diagonal hops. The SEMs were ≤5° and ≤0.23 N·m/kg·m for most peak angles and moments, respectively. Our test seems feasible and showed satisfactory reliability for most hip and knee angles and moments; however, low knee abduction and internal rotation angles and moments, and moderate reliability of these moments deserve consideration. The test appears to challenge dynamic knee control and may prove valuable in evaluation during knee rehabilitation.
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| 3. |
- Arumugam, Ashokan, 1981-, et al.
(författare)
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Introducing a novel test with unanticipated medial/lateral diagonal hops that reliably captures hip and knee kinematics in healthy women
- 2019
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Ingår i: Journal of Biomechanics. - : Elsevier. - 0021-9290 .- 1873-2380. ; 82, s. 70-79
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Tidskriftsartikel (refereegranskat)abstract
- Despite a vast literature on one-leg hops and cutting maneuvers assessing knee control pre/post-injury of the anterior cruciate ligament (ACL), comprehensive and reliable tests performed under unpredictable conditions are lacking. This study aimed to: (1) assess the feasibility of an innovative, knee-challenging, one-leg double-hop test consisting of a forward hop followed by a diagonal hop (45°) performed medially (UMDH) or laterally (ULDH) in an unanticipated manner; and (2) determine within- and between-session reliability for 3-dimensional hip and knee kinematics and kinetics of these tests. Twenty-two healthy women (22.3 ± 3.3 years) performed three successful UMDH and ULDH, twice 1–4 weeks apart. Hop success rate was 69–84%. Peak hip and knee angles demonstrated moderate to excellent within-session reliability (intraclass correlation coefficient [ICC] 95% confidence interval [CI]: 0.67–0.99, standard error of measurement [SEM] ≤ 3°) and poor to excellent between-session reliability (ICC CI: 0.22–0.94, SEM ≤ 3°) for UMDH and ULDH. The smallest real difference (SRD) was low (≤ 5°) for nearly all peak angles. Peak hip and knee moments demonstrated poor to excellent reliability (ICC CI: 0–0.97) and, in general, moments were more reliable within-session (SEM ≤ 0.14 N.m/kg.m, both directions) than between-session (SRD ≤ 0.43 N.m/kg.m). Our novel test was feasible and, in most but not all cases, provided reliable angle estimates (within-session > between-session, both directions) albeit less reliable moments (within-session > between-session, both directions). The relatively large hip and knee movements in the frontal and transverse planes during the unanticipated hops suggest substantial challenge of dynamic knee control. Thus, the test seems appropriate for evaluating knee function during ACL injury rehabilitation.
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| 4. |
- Brinkmann, Gunnar, et al.
(författare)
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Generation and properties of snarks
- 2013
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Ingår i: Journal of combinatorial theory. Series B (Print). - : Elsevier BV. - 0095-8956 .- 1096-0902. ; 103:4, s. 468-488
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Tidskriftsartikel (refereegranskat)abstract
- For many of the unsolved problems concerning cycles and matchings in graphs it is known that it is sufficient to prove them for snarks, the class of non-trivial 3-regular graphs which cannot be 3-edge coloured.In the first part of this paper we present a. new algorithm for generating all non-isomorphic snarks of a given order. Our implementation of the new algorithm is 14 times faster than previous programs for generating snarks, and 29 times faster for generating weak snarks. Using this program we have generated all non-isomorphic snarks on n <= 36 vertices. Previously lists up to n = 28 vertices have been published.In the second part of the paper we analyze the sets of generated snarks with respect to a number of properties and conjectures. We find that some of the strongest versions of the cycle double cover conjecture hold for all snarks of these orders, as does Jaeger's Petersen colouring conjecture, which in turn implies that Fulkerson's conjecture has no small counterexamples. In contrast to these positive results we also find counterexamples to eight previously published conjectures concerning cycle coverings and the general cycle structure of cubic graphs.(C) 2013 Published by Elsevier Inc.
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| 5. |
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| 6. |
- Hägglund, Jonas, 1982-, et al.
(författare)
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On stable cycles and cycle double covers of graphs with large circumference
- 2012
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Ingår i: Discrete Mathematics. - : Elsevier. - 0012-365X .- 1872-681X. ; 312:17, s. 2540-2544
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Tidskriftsartikel (refereegranskat)abstract
- A cycle C in a graph is called stable if there exists no other cycle D in the same graph such that V(C)⊆V(D). In this paper, we study stable cycles in snarks and we show that if a cubic graph G has a cycle of length at least |V(G)|−9 then it has a cycle double cover. We also give a construction for an infinite snark family with stable cycles of constant length and answer a question by Kochol by giving examples of cyclically 5-edge connected snarks with stable cycles.
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| 7. |
- Hägglund, Jonas, et al.
(författare)
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Shortest cycle covers and cycle double covers with large 2-regular subgraphs
- 2013
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Ingår i: Journal of Combinatorics. - 2156-3527 .- 2150-959X. ; 4:4, s. 457-468
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we show that many snarks have a shortest cycle cover of length 4/3 m + c for a constant c, where m is the number of edges in the graph, in agreement with the conjecture that all snarks have shortest cycle covers of length 4/3 m + o(m). In particular, we prove that graphs with perfect matching index at most 4 have cycle covers of length 4/3 m and satisfy the (1,2)-covering conjecture of Zhang, and that graphs with large circumference have cycle covers of length close to 4/3 m. We also prove some results for graphs with low oddness and discuss the connection with Jaeger’s Petersen colouring conjecture.
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| 8. |
- Hägglund, Jonas, 1982-
(författare)
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Snarks : Generation, coverings and colourings
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For a number of unsolved problems in graph theory such as the cycle double cover conjecture, Fulkerson's conjecture and Tutte's 5-flow conjecture it is sufficient to prove them for a family of graphs called snarks. Named after the mysterious creature in Lewis Carroll's poem, a \emph{snark} is a cyclically 4-edge connected 3-regular graph of girth at least 5 which cannot be properly edge coloured using three colours. Snarks and problems for which an edge minimal counterexample must be a snark are the central topics of this thesis. The first part of this thesis is intended as a short introduction to the area. The second part is an introduction to the appended papers and the third part consists of the four papers presented in a chronological order.In Paper I we study the strong cycle double cover conjecture and stable cycles for small snarks. We prove that if a bridgeless cubic graph $G$ has a cycle of length at least $|V(G)|-9$ then it also has a cycle double cover. Furthermore we show that there exist cyclically 5-edge connected snarks with stable cycles and that there exists an infinite family of snarks with stable cycles of length 24.In Paper II we present a new algorithm for generating all non-isomorphic snarks with a given number of vertices. We generate all snarks on 36 vertices and less and study these with respect to various properties. We find that a number of conjectures on cycle covers and colourings holds for all graphs of these orders. Furthermore we present counterexamples to no less than eight published conjectures on cycle coverings, cycle decompositions and the general structure of regular graphs. In Paper III we show that Jaeger's Petersen colouring conjecture holds for three infinite families of snarks and that a minimum counterexample to this conjecture cannot contain a certain subdivision of $K_{3,3}$ as a subgraph. Furthermore, it is shown that one infinite family of snarks have strong Petersen colourings while another does not have any such colourings.Two simple constructions for snarks with arbitrary high oddness and resistance is given in Paper IV. It is observed that some snarks obtained from this construction have the property that they require at least five perfect matchings to cover the edges. This disproves a suggested strengthening of Fulkerson's conjecture.
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| 9. |
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| 10. |
- Markström, Jonas, 1985-, et al.
(författare)
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A minority of athletes pass symmetry criteria in a series of hop and strength tests irrespective of having an ACL reconstructed knee or being noninjured
- 2023
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Ingår i: Sports Health. - : Sage Publications. - 1941-7381 .- 1941-0921. ; 15:1, s. 45-51
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Tidskriftsartikel (refereegranskat)abstract
- Background: Between-leg symmetry in 1-leg hop and knee strength performances is considered important after anterior cruciate ligament reconstruction (ACLR) to facilitate a safer return to sport. While few athletes with ACLR demonstrate symmetry in test batteries, reference data for noninjured athletes are lacking, thus questioning how ACLR-specific poor symmetry is.Hypothesis: Athletes with ACLR (hamstring autograft) show lower symmetry and have a lower proportion of symmetric individuals than noninjured athletes for knee flexion strength but not for hop for distance, vertical hop, and knee extension strength.Study design: Cross-sectional.Level of Evidence: Level 3.Methods: A total of 47 athletes with ACLR (median 13.0 months post-ACLR) who had returned to their sport, and 46 noninjured athletes participated. Symmetry was calculated between the worse and better legs for each test and combinations of them using the limb symmetry index (LSIWORSE-BETTER, ranging from 0% to 100%). The 2 groups were compared for these values and the proportions of individuals classified as symmetric (LSIWORSE-BETTER ≥90%) using independent t-tests and Fisher’s exact tests, respectively.Results: Athletes with ACLR were less symmetric than noninjured athletes for knee flexion strength with a lower LSIWORSE-BETTER (83% vs 91%, P < 0.01) and a lower proportion of symmetric individuals (39% vs 63%, P = 0.04). No differences between groups were revealed for the hop tests, knee extension strength, or combinations of tests (P > 0.05). Only 17% of the athletes with ACLR and 24% of the noninjured athletes demonstrated symmetric performances for all 4 tests.Conclusion: Athletes with ACLR (hamstring autograft) showed poorer symmetry in knee flexion strength than noninjured athletes, although both groups had few individuals who passed the test battery’s symmetry criteria.Clinical relevance: Symmetry is uncommon among athletes irrespective of ACLR and should be considered regarding expected rehabilitation outcomes and return-to-sport decisions post-ACLR.
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| 11. |
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| 12. |
- Markström, Jonas, 1985-, et al.
(författare)
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Atypical lower limb mechanics during weight acceptance of stair descent at different time frames after anterior cruciate ligament reconstruction
- 2022
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Ingår i: American Journal of Sports Medicine. - : Sage Publications. - 0363-5465 .- 1552-3365. ; 50:8, s. 2125-2133
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Tidskriftsartikel (refereegranskat)abstract
- Background: An anterior cruciate ligament (ACL) rupture may result in poor sensorimotor knee control and, consequentially, adapted movement strategies to help maintain knee stability. Whether patients display atypical lower limb mechanics during weight acceptance of stair descent at different time frames after ACL reconstruction (ACLR) is unknown.Purpose:To compare the presence of atypical lower limb mechanics during the weight acceptance phase of stair descent among athletes at early, middle, and late time frames after unilateral ACLR.Study Design:Controlled laboratory study.Methods:A total of 49 athletes with ACLR were classified into 3 groups according to time after ACLR—early (<6 months; n = 17), middle (6-18 months; n = 16), and late (>18 months; n = 16)—and compared with asymptomatic athletes (control; n = 18). Sagittal plane hip, knee, and ankle angles; angular velocities; moments; and powers were compared between the ACLR groups’ injured and noninjured legs and the control group as well as between legs within groups using functional data analysis methods.Results:All 3 ACLR groups showed greater knee flexion angles and moments than the control group for injured and noninjured legs. For the other outcomes, the early group had, compared with the control group, less hip power absorption, more knee power absorption, lower ankle plantarflexion angle, lower ankle dorsiflexion moment, and less ankle power absorption for the injured leg and more knee power absorption and higher vertical ground reaction force for the noninjured leg. In addition, the late group showed differences from the control group for the injured leg revealing more knee power absorption and lower ankle plantarflexion angle. Only the early group took a longer time than the control group to complete weight acceptance and demonstrated asymmetry for multiple outcomes.Conclusion:Athletes with different time frames after ACLR revealed atypically large knee angles and moments during weight acceptance of stair descent for both the injured and the noninjured legs. These findings may express a chronically adapted strategy to increase knee control. In contrast, atypical hip and ankle mechanics seem restricted to an early time frame after ACLR.Clinical Relevance:Rehabilitation after ACLR should include early training in controlling weight acceptance. Including a control group is essential when evaluating movement patterns after ACLR because both legs may be affected.
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| 13. |
- Markström, Jonas, et al.
(författare)
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Countermovement jump peak force relative to body weight and jump height as predictors for sprint running performances : (in)homogeneity of track and field athletes?
- 2013
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Ingår i: Journal of Strength and Conditioning Research. - Philadelphia : Lippincott Williams & Wilkins. - 1064-8011 .- 1533-4287. ; 27:4, s. 944-953
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate: (1) If variables from one-leg drop jump (DJ), DJ, squat jump (SJ), and counter movement jump (CMJ) tests can predict sprint performances for sprinters. (2) If sprinters and jumpers can be distinguished based on variables from one-leg DJ, DJ, SJ, and CMJ tests, also if sprinters and throwers can be distinguished based on variables from stiff leg jump (SLJ), SJ, and CMJ tests. A single linear regression and multiple linear regression analysis approach with models including two or three variables were used when predicting sprint performances. Five elite sprinters (1 female) participated in the first subexamination and five sprinters (1 female) vs five jumpers and six sprinters vs. six throwers (4 females) participated in the second. The force variable CMJ peak force relative to body weight significantly predicted the sprint performances maximal running velocity through 10 m (Vmax10m) and 60 m time. Vmax10m was also predicted by CMJ height. Jump heights from SJ and DJ did not predict sprint performances. The between group analysis of the athletes showed a non-significant group difference with respect to the jump variables. However, planned comparisons between sprinters and throwers showed significant differences on a number of SLJ variables. When constructing training programs for sprinters, aim should be to improve CMJ peak force and CMJ height because of the prediction of Vmax10m and 60 m time, presumably due to velocity specificity components.
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| 14. |
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| 15. |
- Markström, Jonas, 1985-, et al.
(författare)
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Dynamic knee control and movement strategies in athletes and non‐athletes in side hops : implications for knee injury
- 2019
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 29:8, s. 1181-1189
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Tidskriftsartikel (refereegranskat)abstract
- Athletes exposed to rapid maneuvers need a high level of dynamic knee stability and robustness, while also controlling whole body movement, to decrease the risk of non‐contact knee injury. The effects of high‐level athletic training on such measures of movement control have not, however, been thoroughly evaluated. This study investigated whether elite athletes (who regularly perform knee‐specific neuromuscular training) show greater dynamic knee robustness and/or different movement strategies than non‐athletic controls, in relation to overall knee function. Thirty‐nine women (19 athletes, 20 controls) performed standardized rebound side hops (SRSH) while a motion capture system synchronized with two force plates registered three‐dimensional trunk, hip, and knee joint angles and moments. Dynamic knee robustness was evaluated using finite helical axis (FHA) inclination angles extracted from knee rotation intervals of 10°, analyzed with independent t tests. Angle and moment curves were analyzed with inferential methods for functional data. Athletes had superior knee function (less laxity, greater hop performances, and strength) but presented similar FHA inclination angles to controls. Movement strategies during the landing phase differed; athletes presented larger (a) hip flexion angles (during 9%‐29% of the phase), (b) hip adduction moments (59%‐99%), (c) hip internal rotation moments (83%‐89%), and (d) knee flexion moments (79%‐93%). Thus, elite athletes may have a greater ability than non‐athletes to keep the knee robust while performing SRSH more efficiently through increased engagement of the hip. However, dynamic knee robustness associated with lower FHA inclination angles still show room for improvement, thus possibly decreasing knee injury risk.
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| 16. |
- Markström, Jonas, 1985-, et al.
(författare)
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Elite women athletes with superior knee function present similar dynamic knee stability, although different movement strategies, when compared to controls
- 2018
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Ingår i: 23rd annual Congress of the European College of Sport Science: Sport Science at the cutting edge, Dublin, Ireland, July 4-7, 2018. - : European College of Sport Sciences. - 9783981841411 ; , s. 555-555
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: Neuromuscular training (NMT) of the lower limb is vital for athletes in learning correct movement technique to avoid risk of injury to the anterior cruciate ligament (ACL). The NMT aims for improved knee control while maintaining dynamic knee stability (DKS; resistance to linear/angular accelerations) during knee-challenging tasks. Assessing DKS is commonly attempted by evaluating discrete values of kinematic and kinetic variables during one-leg hops, but these measures may not sufficiently capture knee dynamics. We aimed to evaluate if elite women athletes who regularly perform NMT have greater DKS and/or different landing technique than normally active women who do not perform NMT, and if there are any correlations of DKS to peak knee extensor or flexor strength.METHODS: A motion capture system (Qualisys) synchronized with two force plates (Kistler) registered hip and knee 3D joint angles and moments during one-leg standardized lateral side hop landings for 39 women (19 athletes, 20 controls). Ten trials were performed for the dominant leg with hands behind their back holding a rope (25 cm), deemed successful following 3 s of single leg stance after landing without putting the contralateral foot on the ground or making major adjustments with the ipsilateral foot. DKS was evaluated using the inclination angle of the knee’s helical axis relative to the flexion-extension axis calculated for rotation intervals of 10 degrees, as has been proven useful (Grip and Häger, 2013), to quantify how much knee joint motion deviated from pure flexion-extension at landing. Hip and knee joint angles were analysed at initial contact (IC), and peak angles and peak moments were analysed during the deceleration phase of landing from IC to peak knee flexion (ind. t-tests, p < 0.05).RESULTS: Athletes had more successful hops, faster task execution, greater knee extension strength, greater hip flexion angle at IC, and higher peak moments of hip adduction and knee flexion than controls. There were however, no group differences in DKS or any significant correlations between DKS and knee extensor or flexor strength for any of the groups (r < absolute values of 0.41).CONCLUSION: Elite women athletes that perform NMT on a regular basis had superior knee function but similar DKS to controls when performing a sport-specific one-leg side hop maneuver. The greater hip flexion at IC for athletes shows a different movement strategy for landing preparation. Potential benefits of NMT in sports contexts, e.g. less ACL injuries (Sugimoto et al., 2016), may be due to movement alterations of the hip to increase landing control to avoid positions that strain the ACL rather than improving DKS. Further emphasis on knee-specific landing control may be important to also improve DKS, which seems unrelated to strength.
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| 17. |
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| 18. |
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| 19. |
- Markström, Jonas L., 1985-, et al.
(författare)
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A novel standardised side hop test reliably evaluates landing mechanics for anterior cruciate ligament reconstructed persons and controls
- 2021
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Ingår i: Sports Biomechanics. - : Routledge. - 1476-3141 .- 1752-6116. ; 20:2, s. 213-229
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Tidskriftsartikel (refereegranskat)abstract
- We propose a novel one-leg standardised rebound side-hop test (SRSH) specifically designed for detailed analysis of landing mechanics. Anterior cruciate ligament reconstructed persons (ACLR, n = 30) and healthy-knee controls (CTRL, n = 30) were tested for within-session and test-retest (CTRL only, n = 25) reliability and agreement. Trunk, hip and knee angles and moments in sagittal, frontal, and transversal planes during landing, including time to stabilisation (TTS), were evaluated using intra-class correlations (ICCs), average within-person standard deviations (SW) and minimal differences. Excellent within-session reliability were found for angles in both groups (most ICCs > 0.90, SW ≤ 5°), and excellent to good for moments (most ICCs > 0.80, SW ≤ 0.34 Nm/kg). Only knee internal rotation moment showed poor reliability (ICC < 0.4). Test-retest results were excellent to fair for all angles and moments (ICCs 0.47–0.91, SW < 5° and ≤ 0.25 Nm/kg), except for peak trunk lateral bending angle and knee internal rotation moment. TTS showed excellent to fair within-session reliability but poor test-retest results. These results, with a few exceptions, suggest promising potential of evaluating landing mechanics during the SRSH for ACLR and CTRL, and emphasise the importance of joint-specific movement control variables in standardised tasks.
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| 20. |
- Markström, Jonas L., 1985-, et al.
(författare)
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ACL-reconstructed and ACL-deficient individuals show differentiated trunk, hip, and knee kinematics during vertical hops more than 20 years post-injury
- 2018
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Ingår i: Knee Surgery, Sports Traumatology, Arthroscopy. - : Springer Science and Business Media LLC. - 0942-2056 .- 1433-7347. ; 26:2, s. 358-367
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Little is known regarding movement strategies in the long term following injury of the anterior cruciate ligament (ACL), and even less about comparisons of reconstructed and deficient knees in relation to healthy controls. The present purpose was to compare trunk, hip, and knee kinematics during a one-leg vertical hop (VH) ~20 years post-ACL injury between persons treated with surgery and physiotherapy (ACLR), solely physiotherapy (ACLPT), and controls (CTRL). Between-leg kinematic differences within groups were also investigated.METHODS: Sixty-six persons who suffered unilateral ACL injury on average 23 ± 2 years ago (32 ACLR, 34 ACLPT) and 33 controls performed the VH. Peak trunk, hip, and knee angles during Take-off and Landing phases recorded with a 3D motion capture system were analysed with multivariate statistics.RESULTS: Significant group effects during both Take-off and Landing were found, with ACLPT differing from CTRL in Take-off with a combination of less knee flexion and knee internal rotation, and from both ACLR and CTRL in Landing with less hip and knee flexion, knee internal rotation, and greater hip adduction. ACLR also presented different kinematics to ACLPT and CTRL in Take-off with a combination of greater trunk flexion, hip flexion, hip internal rotation, and less knee abduction, and in Landing with greater trunk flexion and hip internal rotation. Further, different kinematics and hop height were found between legs within groups in both Take-off and Landing for both ACL groups, but not for CTRL.CONCLUSION: Different kinematics for the injured leg for both ACL groups compared to CTRL and between treatment groups, as well as between legs within treatment groups, indicate long-term consequences of injury. Compensatory mechanisms for knee protection seem to prevail over time irrespective of initial treatment, possibly increasing the risk of re-injury and triggering the development of osteoarthritis. Detailed investigation of movement strategies during the VH provides important information and a more comprehensive evaluation of knee function than merely hop height. More attention should also be given to the trunk and hip in clinics when evaluating movement strategies after ACL injury.LEVEL OF EVIDENCE: Prospective cohort study, Level II.
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| 21. |
- Markström, Jonas L., 1985-, et al.
(författare)
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Individuals With an Anterior Cruciate Ligament-Reconstructed Knee Display Atypical Whole Body Movement Strategies but Normal Knee Robustness During Side-Hop Landings: A Finite Helical Axis Analysis
- 2020
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Ingår i: American Journal of Sports Medicine. - : Sage Publications. - 0363-5465 .- 1552-3365. ; 48:5, s. 1117-1126
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Atypical knee joint biomechanics after anterior cruciate ligament reconstruction (ACLR) are common. It is, however, unclear whether knee robustness (ability to tolerate perturbation and maintain joint configuration) and whole body movement strategies are compromised after ACLR.PURPOSE: To investigate landing control after ACLR with regard to dynamic knee robustness and whole body movement strategies during sports-mimicking side hops, and to evaluate functional performance of hop tests and knee strength.STUDY DESIGN: Controlled laboratory study.METHODS: An 8-camera motion capture system and 2 synchronized force plates were used to calculate joint angles and moments during standardized rebound side-hop landings performed by 32 individuals with an ACL-reconstructed knee (ACLR group; median, 16.0 months after reconstruction with hamstring tendon graft [interquartile range, 35.2 months]) and 32 matched asymptomatic controls (CTRL). Dynamic knee robustness was quantified using a finite helical axis approach, providing discrete values quantifying divergence of knee joint movements from flexion-extension (higher relative frontal and/or transverse plane motion equaled lower robustness) during momentary helical rotation intervals of 10°. Multivariate analyses of movement strategies included trunk, hip, and knee angles at initial contact and during landing and hip and knee peak moments during landing, comparing ACLR and CTRL, as well as legs within groups.RESULTS: Knee robustness was lower for the first 10° motion interval after initial contact and then successively stabilized for both groups and legs. When landing with the injured leg, the ACLR group, as compared with the contralateral leg and/or CTRL, demonstrated significantly greater flexion of the trunk, hip, and knee; greater hip flexion moment; less knee flexion moment; and smaller angle but greater moment of knee internal rotation. The ACLR group also had lower but acceptable hop and strength performances (ratios to noninjured leg >90%) except for knee flexion strength (12% deficit).CONCLUSION: Knee robustness was not affected by ACLR during side-hop landings, but alterations in movement strategies were seen for the trunk, hip, and knee, as well as long-term deficits in knee flexion strength.CLINICAL RELEVANCE: Knee robustness is lowest immediately after landing for both the ACLR group and the CTRL and should be targeted in training to reduce knee injury risk. Assessment of movement strategies during side-hop landings after ACLR should consider a whole body approach.
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| 22. |
- Markström, Jonas L., 1985-
(författare)
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Movement strategies and dynamic knee control after anterior cruciate ligament injury : a three-dimensional biomechanical analysis
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Rupture of the anterior cruciate ligament (ACL) is common and mainly occurs in non-contact situations in sports, often due to momentarily poor movement control. Assessment of movement quality during sport-like tasks iscrucial to understand how to decrease the high risk of reinjury for ACL-injured persons, but also how to prevent primary injury. This thesis addresses movement quality after ACL injury and includes development and evaluation of a novel standardized rebound side hop test (SRSH) for reliability and agreement of landing mechanics, and compares these outcomes between asymptomatic persons with different athletic levels, and between different hop tests.Methods: This thesis involves five papers based on two separate data collections performed in a motion analysis laboratory. Paper I is a long-term follow up of ACL-injured persons treated with or without ACL reconstruction (ACLR) compared to asymptomatic persons (total N = 99, age 35-63), while papers II-V included ACLR persons, and asymptomatic elite athletes and non-athletes (total N = 79, age 17-34). A motion capture system synchronized with force plates and surface electromyography (EMG) registered trunk, hip and knee angles and moments and knee muscle activity during the hop for distance, vertical hop, and SRSH. Novel measures of dynamic knee robustness were also evaluated using finite helical axis inclination angles extracted from knee rotation intervals of 10˚.Results: On average 23 years after injury, ACL injured persons performed the vertical hop with diverse angles compared to controls and their non-injured leg.The younger groups of ACLR persons and controls generally displayed excellent reliability and agreement for SRSH landing mechanics. These outcomes differed between the groups, and between legs for ACLR persons, despite similar dynamic knee robustness and acceptable knee function outcomes. Curve analyses further displayed differences between athletes and non-athletes, mainly with greater hip moments for athletes, although with similar values for dynamic knee robustness. Finally, greater knee angles and moments considered strenuous for the ACL were evident during the first rebound landing in SRSH compared to the other landings.Conclusions: Persons who have suffered an ACL injury, regardless of whether treated with ACLR or not, appear to use task-coping strategies in preparation for and during landings to decrease knee joint loading, probably to preserve dynamic knee robustness. More attention should be given to the trunk and hip in clinics when evaluating movement quality after ACL injury to reduce the risk of future injuries due to movement compensation. High-level athletic training may also improve the ability to maintain dynamic knee robustness whilst performing a sport-like side-to-side task more efficiently through increased engagement of the hip. Finally, side hop landings should be assessed when evaluating and correcting for erroneous landing mechanics to improve knee landing control.
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| 23. |
- Markström, Jonas, 1985-, et al.
(författare)
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Side-hops challenge knee control in the frontal and transversal plane more than hops for distance or height among ACL-reconstructed individuals
- 2023
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Ingår i: Sports Biomechanics. - : Taylor & Francis Group. - 1476-3141 .- 1752-6116. ; 22:1, s. 142-159
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Tidskriftsartikel (refereegranskat)abstract
- We compared knee landing mechanics with presumed relation to risk of anterior cruciate ligament (ACL) injury among three single-leg hop tests and between legs in individuals with unilateral ACL reconstruction. Thirty-four participants (>10 months' post-surgery, 23 females) performed the standardised rebound side hop (SRSH), maximal hop for distance (OLHD) and maximal vertical hop (OLVH). We calculated the following knee outcomes from motion capture and force plate data: finite helical axis inclination angles (approximates knee robustness), frontal and transversal plane angles at initial contact, peak angles of abduction and internal rotation during landing, and peak external moments of flexion, abduction and internal rotation during landing. Repeated-measures MANOVA analysis ('sex' as covariate) confirmed that SRSH induced greater angles and moments, particularly in the frontal plane, compared to OLHD and OLVH. There was between-leg asymmetry for peak knee flexion moment for males during OLHD and OLVH, and for females during SRSH. Our results advocate the SRSH over OLHD and OLVH for assessment of knee landing control to screen for movement patterns potentially related to ACL injury risk. However, clear differences in both knee kinematics and kinetics between OLHD and SRSH motivate the use of both tests to evaluate different aspects of landing control.
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| 24. |
- Markström, Jonas, 1985-, et al.
(författare)
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Similar dynamic knee stability but different movement strategies and between-leg asymmetries for hip and knee joints for ACL-reconstructed persons relative to knee-healthy controls
- 2018
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Ingår i: 8th World Congress of Biomechanics, Dublin, July 8-12, 2018.
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Konferensbidrag (refereegranskat)abstract
- Introduction: Jumping involves complex control processes of sensory input and feedback with coordination of multiple joints. Following anterior cruciate ligament reconstruction (ACLR), altered movement strategies identified by kinematics and/or kinetics unload the injured leg and increase demands on nearby joints. Dynamic knee stability (DKS; resistance to linear/angular accelerations) has not been evaluated for ACLR persons during sport-similar tasks. It is therefore unknown if there is true instability or altered task execution, e.g. due to fear. We hypothesized that DKS following rehabilitation after ACLR would be similar to that of knee-healthy controls, but with prevailing protective movement strategies.Methods: A motion capture system synchronized with two force plates registered hip and knee 3D angles and moments during a one-leg standardized side hop for 30 ACLR persons (7-129 months post-reconstruction) and 30 controls. EMG provided mean knee extensor and flexor muscle activation patterns and co-contraction ratios and indexes before (50ms window) and during landing. DKS was evaluated using a helical axis rotation interval of 10˚ to describe how much knee kinematics diverges from flexion-extension. DKS and muscle activation variables were analysed with t-tests. Hip and knee movement strategies were analysed for angles at initial contact, peak angles during landing, and peak moments during landing with MANOVAs between and within groups (p<0.05).Results: No significant differences in DKS was found between groups. A significant main effect of group was however observed for angles at initial contact (p=0.028) with ACLR showing greater hip and knee flexion than controls. A significant main effect of group was also found during landing for peak angles (p=0.001) and moments (p=0.017) with ACLR displaying greater hip flexion and knee internal rotation moment, and also greater mean knee flexor activation than controls (p=0.049). No group differences in muscle activation patterns were shown before landing. ACLR had between-leg asymmetries at initial contact (p=0.010) with greater hip flexion, and asymmetries for peak angles (p=0.008) and moments (p=0.030) during landing with greater hip flexion angle, greater hip flexion moment and less knee flexion moment in the injured leg.Discussion: Despite similar DKS, ACLR displayed different movement strategies and asymmetries relative to controls, which indicates a task-coping strategy in preparation for and during landing. The greater hip and knee flexion angles at initial contact in relation to the greater hip flexion moment and knee flexor activation that followed may have increased knee joint stiffness, which could explain the similar DKS relative to controls. The between-leg asymmetry with greater reliance on the hip and simultaneous unloading of the knee further supports a coping strategy for ACLR. Further attention should be given to the hip during rehabilitation for ACLR persons to avoid future injuries due to movement compensation.
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| 25. |
- Markström, Jonas, 1985-, et al.
(författare)
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Strategies for knee stabilising and pivot-shift avoidance in a step-down and cross-over task observed sub-acutely after anterior cruciate ligament reconstruction
- 2024
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Ingår i: Clinical Biomechanics. - : Elsevier. - 0268-0033 .- 1879-1271. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- Background: Individuals with a recent anterior cruciate ligament reconstruction may demonstrate an altered movement strategy for protecting the knee and maintaining stability. Altered knee movement might lead to abnormal intra-articular load, potentially contributing to early knee osteoarthritis onset. A protective strategy may be particularly evident during active tasks that induce a pivot-shift manoeuvre, such as a step-down and cross-over task. In this study, we investigated whether knee joint mechanics and muscle activity differed between participants early (∼3 months) following reconstruction (n = 35) to uninjured controls (n = 35) during a step-down and cross-over task with a 45° change-of-direction.Methods: We used motion capture, force plates and surface electromyography to compare time-normalised curves of sagittal and transverse-plane knee mechanics and muscle activity during the cross-over phase between groups using functional t-tests. We also compared knee mechanics between sides within the injured group and compared discrete outcomes describing the cross-over phase between groups.Findings: Compared to controls, the injured participants had greater knee flexion angle and moment, lower internal rotation moment, more preparatory foot rotation of the pivoting leg, a smaller cross-over angle, and a longer cross-over phase for both the injured and uninjured sides. The injured leg also had greater biceps femoris and vastus medialis muscle activity compared to controls and different knee mechanics than the uninjured leg.Interpretation: Individuals with anterior cruciate ligament reconstruction showed a knee-stabilising and pivot-shift avoidance strategy for both legs early in rehabilitation. These results may reflect an altered motor representation and motivate considerations early in rehabilitation.
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| 26. |
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| 27. |
- Naili, Josefine E., et al.
(författare)
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A longitudinal case-control study of a female athlete preinjury and after ACL reconstruction : hop performance, knee muscle strength, and knee landing mechanics
- 2023
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Ingår i: Sports Health. - : Sage Publications. - 1941-7381 .- 1941-0921. ; 15:3, s. 357-360
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Tidskriftsartikel (refereegranskat)abstract
- Athletes with an anterior cruciate ligament (ACL) injury followed by ACL reconstruction (ACLR) often perform various testing to guide return to sport, but preinjury data are rarely available for comparison. This longitudinal case-control study reports absolute value and between-leg symmetry data on maximal performances for single-leg hop height and distance, muscle strength, and side hop landing mechanics of an 18-year-old female soccer athlete collected 5 months before sustaining an ACL injury and again at 10, 13, and 29 months post-ACLR. Her data were compared across test sessions and to cross-sectional data of 15 asymptomatic female athletes.
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| 28. |
- Pini, Alessia, 1985-, et al.
(författare)
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Test-retest reliability measures for curve data : an overview with recommendations and supplementary code.
- 2022
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Ingår i: Sports Biomechanics. - : Routledge. - 1476-3141 .- 1752-6116. ; 21:2, s. 179-200
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to provide an overview of available methods for reliability investigations when the outcome of interest is a curve. Curve data, or functional data, is commonly collected in biomechanical research in order to better understand different aspects of human movement. Using recent statistical developments, curve data can be analysed in its most detailed form, as functions. However, an overview of appropriate statistical methods for assessing reliability of curve data is lacking. A review of contemporary literature of reliability measures for curve data within the fields of biomechanics and statistics identified the following methods: coefficient of multiple correlation, functional limits of agreement, measures of distance and similarity, and integrated pointwise indices (an extension of univariate reliability measures to curve data, inclusive of Pearson correlation, intraclass correlation, and standard error of measurement). These methods are briefly presented, implemented (R-code available as supplementary material) and evaluated on simulated data to highlight advantages and disadvantages of the methods. Among the identified methods, the integrated intraclass correlation and standard error of measurement are recommended. These methods are straightforward to implement, enable results over the domain, and consider variation between individuals, which the other methods partly neglect.
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| 29. |
- Schelin, Lina, et al.
(författare)
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Test-retest reliability of entire time-series data from hip, knee and ankle kinematics and kinetics during one-leg hops for distance: Analyses using integrated pointwise indices
- 2021
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Ingår i: Journal of Biomechanics. - : Elsevier BV. - 0021-9290 .- 1873-2380. ; 124
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Tidskriftsartikel (refereegranskat)abstract
- Motion capture systems enable in-depth interpretations of human movements based on data from three-dimensional joint angles and moments. Such analyses carry important bearings for evaluation of movement control during for instance hop landings among sports-active individuals from a performance perspective but also in rehabilitation. Recent statistical development allows analysis of entire time-series of angle and moment during hops using functional data analysis, but the reliability of such multifaceted data is not established. We used integrated pointwise indices (intra-class correlation, ICC; standard error of measurement, SEM) to establish the test–retest reliability of three-dimensional hip, knee and ankle angle and moment curves during landings of one-leg hop for distance (OLHD) in 23 asymptomatic individuals aged 18–28. We contrasted these findings to reliability of discrete variables extracted at specific events (initial contact, peak value). We extended the calculations of ICC and SEM to handle unbalanced situations (varying number of repetitions) to include all available data. Hip and knee angle curves proved reliable with stable ICC curves throughout the landing, with integrated ICCs ≥ 0.71 for all planes except for knee internal/external rotation (ICC = 0.57). Hip and knee moment curves and ankle angle and moments were less reliable and less stable, particularly in the first ~ 10–25% of the landing (integrated ICCs 0.44–0.57). Curve data were generally not in agreement with the results for discrete event data, thus advocating analysis of curve data which contains more information. To conclude, hip and knee angle curve data during OLHD landings can reliably be evaluated, while moment curves necessitate careful consideration.
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| 30. |
- Strong, Andrew, et al.
(författare)
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Asymmetric loading strategies during squats following anterior cruciate ligament reconstruction : a longitudinal investigation with curve analyses throughout and after rehabilitation
- 2024
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 34:1
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of kinetic asymmetries during bilateral squats following anterior cruciate ligament reconstruction (ACLR) are limited to mainly cross-sectional studies and discrete value data extracted at specific knee angles. We assessed loading asymmetries during squats longitudinally throughout rehabilitation using curve analysis and compared patient-reported outcome measures (PROMs) between those with and without asymmetry. Bodyweight squats were performed by 24 individuals (13 females) post-ACLR on three occasions: (1) Early 2.9 (1.1) months; (2) Mid 8.8 (3.1) months; (3) at Return to Sport (RTS) 13.1 (3.6) months; and 29 asymptomatic controls (22 females) once. Time-normalized between-leg asymmetry curves of sagittal plane hip, knee, and ankle moments and vertical ground reaction forces were compared using functional data analysis methods. Individual asymmetrical loading for ACLR was classified when exceeding the 95% confidence interval of controls during ≥50% of the squat. At Early, ACLR had greater asymmetry than controls for knee (15%–100% eccentric phase; 0%–100% concentric) and ankle flexion moments (56%–65% concentric). At Mid, ACLR had greater asymmetry for knee (41%–72% eccentric) and ankle flexion moments (56%–69% concentric). No between-group differences were found at RTS. From Early to RTS, ACLR reduced asymmetry for hip (21%–46% eccentric), knee (27%–58% concentric), and ankle flexion moments (21%–57% eccentric). At Early, 11/24 underloaded their ACLR knee and 1 overloaded compared with controls. At RTS, 4 underloaded and 6 overloaded. No differences in PROMs were found based on loading asymmetry. Beyond the early phase of rehabilitation from ACLR, individual-level analyses are required to reveal differing loading strategies during bilateral squats.
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| 31. |
- Strong, Andrew, et al.
(författare)
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Asymmetric loading strategies during squats following anterior cruciate ligament reconstruction : a longitudinal investigation throughout rehabilitation with curve analyses
- 2022
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Ingår i: 27th annual congress of the European college of sport science. - : European College of Sport Science. - 9783981841459 ; , s. 483-483
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: Kinetic loading asymmetries during bilateral squats have been reported following anterior cruciate ligament reconstruction (ACLR). Evidence is however limited to discrete value data extracted at specific knee angles from cross-sectional studies where side-toside strategies are presented only at group level. It is therefore unclear whether loading asymmetries occur throughout the entire squat, whether they change during rehabilitation and how they are distributed between sides.METHODS: Bilateral bodyweight squats were performed by 24 individuals (13 females) post-ACLR on three occasions: 1) Early rehab - 2.9(1.1) months; 2) Mid-rehab - 8.8 (3.1) months; 3) Return to sport (RTS) - 13.1 (3.6) months; and 29 asymptomatic controls (22 females) on one occasion. Motion capture and two force plates were used to calculate time-normalized curves of vertical ground reaction forces andhip, knee, and ankle moments. Outcomes were compared between sides and groups, and over time, using functional t-tests with p-values adjusted by the interval-wise testing procedure. Individual knee loading strategies, i.e., under-/overloading of the ACLR side, were classified when asymmetry in favour of the respective side exceeded the 95% pointwise confidence interval of controls during at least 50% of the squat.RESULTS: At Early rehab, ACLR had significantly greater (adjusted P < .05) asymmetry in knee flexion moment than controls during thetime-normalized interval of 15-100% of the eccentric phase and the entire concentric phase, as well as ankle flexion moment during 56-65% of the concentric phase. At Mid-rehab, ACLR had significantly greater asymmetry than controls for knee flexion moment during 41-72% of the eccentric phase and for ankle flexion moment during 56-69% of the concentric phase. No significant between-group differences were found at RTS. At RTS compared with Early rehab, ACLR significantly reduced asymmetry for hip (21-46%, eccentric phase), knee (27-58%, concentric phase), and ankle flexion moment (21-57%, eccentric phase). Individual asymmetry strategies for knee flexion moment atEarly rehab were mainly due to individuals underloading the ACLR side (46%) rather than overloading (4%). At RTS, however, more individuals overloaded (25%) than underloaded (17%) the ACLR side.CONCLUSION: Curve analyses revealed significant kinetic loading asymmetries throughout bilateral bodyweight squats for our ACLR group compared with controls at Early rehab and Mid-rehab, but not at RTS. Significant reductions in hip, knee and ankle flexion moment asymmetry from Early rehab to RTS showed modifications during rehabilitation. An expected underloading strategy was evident for almost half of the ACLR participants at Early rehab, but an overloading strategy was the main reason for knee flexion moment asymmetry at RTS.Loading asymmetries during bilateral tasks should thus not be assumed due to underloading of the ACLR side, but may depend on anoverloading strategy, particularly late in rehabilitation.
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