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| 2. |
- Hébert-Losier, Kim
(författare)
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An Investigation of the Influence of Knee Flexion Angle on the Activity of the Triceps Surae Muscles during the Heel-Raise Test
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The heel-raise test (HRT) is used in clinical practice and research to assess the triceps suare (TS) muscles. The test involves repetitive unilateral heel-raises in upright stance. The test is administered with the knee straight for gastrocnemius medialis (GM) and lateralis (GL), and with the knee bent for soleus (SOL). The maximum number of heel-raises which can be performed is utilised as a clinical outcome measure and informs clinical decisions. The use of knee flexion (KF) to direct HRT assessment towards SOL or GAST currently relies on fundamental principles and has a limited evidence-base. Aims: The primary aim of this research was to investigate the influence of KF angle on SOL, GM, and GL activity and fatigue during the HRT. Secondary aims were to explore the total number of heel-raises completed, and the influence of age group on TS muscle activity and fatigue. Methods: Specific literature reviews were undertaken to contextualise the HRT within a comprehensive anatomical and biomechanical framework, and the experimental research involved a sequence of biomechanical studies. Seventeen subjects participated in a preliminary study that involved heel-raise testing to fatigue in two KF positions and generalised estimation equations were used to determine whether select KF angles were maintained. Forty-eight subjects, stratified by age and gender, participated in the main experimental study. Surface electromyography (EMG) activity of SOL, GM, and GL during maximum voluntary isometric contractions (MVIC) was collected in 0°KF, 45°KF, and 90°KF to inform EMG normalisation. Subjects then completed 10 unilateral heel-raises in 0°KF and 45°KF to investigate EMG amplitudes (% of MVIC) and heel-raises to fatigue for power spectrum analysis (median frequency and normalised slope). Mixed-effects models and stepwise regressions were used for the main analysis. Results: The preliminary study identified that select KF angles were reasonably well maintained during testing and subjects completed an average of 40 heel-raises in the two KF positions. The investigation of (EMG) muscle activity during MVIC developed a normalisation protocol specific to capturing SOL, GM, and GL peak activity. Data collected from heel-raises demonstrated higher SOL (p=.005) and lower GM (p<.001) and GL (p<.001) amplitudes in 45°KF rather than 0°KF; however, KF did not influence fatigue of the individual TS muscles. GM and GL fatigued at the same rate (p=.088), to the same extent (p=.385), and faster than SOL (p<.001) in both angles. GM (p=.008), but not GL (p=.118), fatigued more than SOL. Similar maximum numbers of heel-raises were performed in 0°KF (n=45) and 45°KF (n=48). Age did not influence any of the variables analysed. Conclusion: The research results question the common utilisation of KF to direct the HRT towards SOL or GAST assessment. Although influences of KF on EMG amplitudes were statistically significant, they may not be clinically meaningful. KF did not influence TS fatigue or the total number of heel-raises. While these findings do not imply the absence of clinical or rehabilitative benefits from HRT procedures in select KF positions, the evidence challenges the common perceptions and definitions that the test assesses SOL with the knee bent and GAST with the knee straight.
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- Hébert-Losier, Kim, et al.
(författare)
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Analysis of knee flexion angles during 2 clinical versions of the heel raise test to assess soleus and gastrocnemius function.
- 2011
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Ingår i: Journal of Orthopaedic and Sports Physical Therapy. - : Journal of Orthopaedic & Sports Physical Therapy (JOSPT). - 0190-6011 .- 1938-1344. ; 41:7, s. 505-13
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: Controlled laboratory study, using a repeated-measures, counterbalanced design. OBJECTIVES: To provide estimates on the average knee angle maintained, absolute knee angle error, and total repetitions performed during 2 versions of the heel raise test. BACKGROUND: The heel raise test is performed in knee extension (EHRT) to assess gastrocnemius and knee flexion (FHRT) for soleus. However, it has not yet been determined whether select knee angles are maintained or whether total repetitions differ between the clinical versions of the heel raise test. METHODS: Seventeen healthy males and females performed maximal heel raise repetitions in 0° (EHRT) and 30° (FHRT) of desired knee flexion. The average angle maintained and absolute error at the knee during the 2 versions, and total heel raise repetitions, were measured using motion analysis. Participants' kinematic measures were fitted into a generalized estimation equation model to provide estimates on EHRT and FHRT performance applicable to the general population. RESULTS: The model estimates that average angles of 2.2° and 30.7° will be maintained at the knee by the general population during the EHRT and the FHRT, with an absolute angle error of 3.4° and 2.5°, respectively. In both versions, 40 repetitions should be completed. However, the average angles maintained by participants ranged from -6.3° to 21.6° during the EHRT and from 22.0° to 43.0° during the FHRT, with the highest absolute errors in knee position being 25.9° and 33.5°, respectively. CONCLUSION: On average, select knee angles will be maintained by the general population during the select heel raise test versions, but individualized performance is variable and total repetitions do not distinguish between versions. Clinicians should, therefore, interpret select heel raise test outcomes with caution when used to respectively assess and rehabilitate soleus and gastrocnemius function.
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- Hébert-Losier, Kim, et al.
(författare)
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Biomechanical Factors Influencing the Performance of Elite Alpine Ski Racers
- 2014
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Ingår i: Sports Medicine. - : IADIS Press. - 0112-1642 .- 1179-2035. ; 44:4, s. 519-533
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Forskningsöversikt (refereegranskat)abstract
- BackgroundAlpine ski racing is a popular international winter sport that is complex and challenging from physical, technical, and tactical perspectives. Despite the vast amount of scientific literature focusing on this sport, including topical reviews on physiology, ski-snow friction, and injuries, no review has yet addressed the biomechanics of elite alpine ski racers and which factors influence performance. In World Cup events, winning margins are often mere fractions of a second and biomechanics may well be a determining factor in podium place finishes.Objective The aim of this paper was to systematically review the scientific literature to identify the biomechanical factors that influence the performance of elite alpine ski racers, with an emphasis on slalom, giant slalom, super-G, and downhill events.Methods Four electronic databases were searched using relevant medical subject headings and key words, with an additional manual search of reference lists, relevant journals, and key authors in the field. Articles were included if they addressed human biomechanics, elite alpine skiing, and performance. Only original research articles published in peer-reviewed journals and in the English language were reviewed. Articles that focused on skiing disciplines other than the four of primary interest were excluded (e.g., mogul, ski-cross and freestyle skiing). The articles subsequently included for review were quality assessed using a modified version of a validated quality assessment checklist. Data on the study population, design, location, and findings relating biomechanics to performance in alpine ski racers were extracted from each article using a standard data extraction form.Results A total of 12 articles met the inclusion criteria, were reviewed, and scored an average of 69 ± 13 % (range 40–89 %) upon quality assessment. Five of the studies focused on giant slalom, four on slalom, and three on downhill disciplines, although these latter three articles were also relevant to super-G events. Investigations on speed skiing (i.e., downhill and super-G) primarily examined the effect of aerodynamic drag on performance, whereas the others examined turn characteristics, energetic principles, technical and tactical skills, and individual traits of high-performing skiers. The range of biomechanical factors reported to influence performance included energy dissipation and conservation, aerodynamic drag and frictional forces, ground reaction force, turn radius, and trajectory of the skis and/or centre of mass. The biomechanical differences between turn techniques, inter-dependency of turns, and abilities of individuals were also identified as influential factors in skiing performance. In the case of slalom and giant slalom events, performance could be enhanced by steering the skis in such a manner to reduce the ski-snow friction and thereby energy dissipated. This was accomplished by earlier initiation of turns, longer path length and trajectory, earlier and smoother application of ground reaction forces, and carving (rather than skidding). During speed skiing, minimizing the exposed frontal area and positioning the arms close to the body were shown to reduce the energy loss due to aerodynamic drag and thereby decrease run times. In actual races, a consistently good performance (i.e., fast time) on different sections of the course, terrains, and snow conditions was a characteristic feature of winners during technical events because these skiers could maximize gains from their individual strengths and minimize losses from their respective weaknesses.Limitations Most of the articles reviewed were limited to investigating a relatively small sample size, which is a usual limitation in research on elite athletes. Of further concern was the low number of females studied, representing less than 4 % of all the subjects examined in the articles reviewed. In addition, although overall run time is the ultimate measure of performance in alpine ski racing, several other measures of instantaneous performance were also employed to compare skiers, including the aerodynamic drag coefficient, velocity, section time, time lost per change in elevation, and mechanical energy behaviours, which makes cross-study inferences problematic. Moreover, most studies examined performance through a limited number of gates (i.e., 2–4 gates), presumably because the most commonly used measurement systems can only capture small volumes on a ski field with a reasonable accuracy for positional data. Whether the biomechanical measures defining high instantaneous performance can be maintained throughout an entire race course remains to be determined for both male and female skiers.Conclusions Effective alpine skiing performance involves the efficient use of potential energy, the ability to minimize ski-snow friction and aerodynamic drag, maintain high velocities, and choose the optimal trajectory. Individual tactics and techniques should also be considered in both training and competition. To achieve better run times, consistency in performance across numerous sections and varied terrains should be emphasized over excellence in individual sections and specific conditions.
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- Hébert-Losier, Kim, et al.
(författare)
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Biomechanics of the heel-raise test performed on an incline in two knee flexion positions
- 2013
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Ingår i: Clinical Biomechanics. - : Elsevier BV. - 0268-0033 .- 1879-1271. ; 28:6, s. 664-671
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Although single-legged heel-raise cycles are often performed on an incline in different knee flexion positions to discriminate the relative contribution of the triceps surae muscles, detailed kinematic and kinetic analyses of this procedure are not available. Our study characterizes and compares the biomechanics and clinical outcomes of single-legged heel-raise cycles performed to volitional exhaustion on an incline with the knee straight (0°) and bent (45°), considering the effect of sex and age.METHODS:Fifty-six male and female volunteers, with equal numbers of younger (20 to 40 years of age) and older (40 to 60 years of age) individuals, completed a maximal number of heel-raise cycles on an incline at both nominal knee angles. Kinematic and kinetic data were acquired during testing using a 3D motion capturing system and multi-axial force plate. The impact of fatigue on performance was quantified using changes in maximal voluntary isometric contraction force and biomechanical performance of cycles.FINDINGS:Overall, participants completed three more cycles and maintained better biomechanical performance with 45° than 0° of knee flexion. More precisely, the decreases in maximal heel-raise heights, plantar-flexion angles at maximal height and ranges of ankle motion per cycle were all smaller with the knee bent. However, several outcomes indicated similar plantar-flexion fatigue at both knee angles. Males demonstrated a more rapid decline in peak ground reaction forces during testing; but otherwise, neither sex nor age significantly impacted outcomes.INTERPRETATION:It is concluded that the differences discerned here in the biomechanics of single-legged heel-raise cycles performed at 0° and 45° of knee flexion to volitional exhaustion on an incline may be too small to identify in clinical settings or reflect substantial alterations in the relative contribution of the triceps surae muscles.
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| 7. |
- Hébert-Losier, Kim, et al.
(författare)
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Curve analyses reveal altered knee, hip, and trunk kinematics during drop-jumps long after anterior cruciate ligament rupture
- 2018
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Ingår i: Knee (Oxford). - : Elsevier. - 0968-0160 .- 1873-5800. ; 25:2, s. 226-239
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Tidskriftsartikel (refereegranskat)abstract
- Background: Anterior cruciate ligament (ACL) ruptures may lead to knee dysfunctions later in life. Single-leg tasks are often evaluated, but bilateral movements may also be compromised. Our aim was to use curve analyses to examine double-leg drop–jump kinematics in ACL-reconstructed, ACL-deficient, and healthy-knee cohorts.Methods: Subjects with unilateral ACL ruptures treated more than two decades ago (17–28 years) conservatively with physiotherapy (ACLPT, n = 26) or in combination with reconstructive surgery (ACLR, n = 28) and healthy-knee controls (n = 25) performed 40-cm drop–jumps. Three-dimensional knee, hip, and trunk kinematics were analyzed during Rebound, Flight, and Landing phases. Curves were time-normalized and compared between groups (injured and non-injured legs of ACLPT and ACLR vs. non-dominant and dominant legs of controls) and within groups (between legs) using functional analysis of variance methods.Results: Compared to controls, ACL groups exhibited less knee and hip flexion on both legs during Rebound and greater knee external rotation on their injured leg at the start of Rebound and Landing. ACLR also showed less trunk flexion during Rebound. Between-leg differences were observed in ACLR only, with the injured leg more internally rotated at the hip. Overall, kinematic curves were similar between ACLR and ACLPT. However, compared to controls, deviations spanned a greater proportion of the drop–jump movement at the hip in ACLR and at the knee in ACLPT.Conclusions: Trunk and bilateral leg kinematics during double-leg drop–jumps are still compromised long after ACL-rupture care, independent of treatment. Curve analyses indicate the presence of distinct compensatory mechanisms in ACLPT and ACLR compared to controls.
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| 8. |
- Hébert-Losier, Kim, et al.
(författare)
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December 2011 Letters to the Editor-in-Chief : Differentiating the Soleus From the Gastrocnemius With the Heel Raise Test
- 2011
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Ingår i: Journal of Orthopaedic and Sports Physical Therapy. - 0190-6011 .- 1938-1344. ; 41:12, s. 983-7
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Tidskriftsartikel (refereegranskat)abstract
- Letters to the Editor-in-Chief of JOSPT as follows:"Early Prognostic Factors in Patients With Whiplash" and Author's Response "Staying Current in the Use of Ultrasound Imaging" and Author's Response"Differentiating the Soleus From the Gastrocnemius With the Heel Raise Test" and Author's ResponseJ Orthop Sports Phys Ther 2011;41(12):983-987. doi:10.2519/jospt.2011.0202.
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| 9. |
- Hébert-Losier, Kim, et al.
(författare)
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December 2011 Letters to the Editor-in-Chief.
- 2011
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Ingår i: Journal of Orthopaedic and Sports Physical Therapy. - : Journal of Orthopaedic & Sports Physical Therapy (JOSPT). - 0190-6011 .- 1938-1344. ; 41:12, s. 983-7
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Tidskriftsartikel (refereegranskat)abstract
- Letters to the Editor-in-Chief of JOSPT as follows:"Early Prognostic Factors in Patients With Whiplash" and Author's Response "Staying Current in the Use of Ultrasound Imaging" and Author's Response"Differentiating the Soleus From the Gastrocnemius With the Heel Raise Test" and Author's ResponseJ Orthop Sports Phys Ther 2011;41(12):983-987. doi:10.2519/jospt.2011.0202.
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| 10. |
- Hébert-Losier, Kim, et al.
(författare)
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Dynamometric indicators of fatigue from repeated maximal concentric isokinetic plantar-flexion contractions are independent of knee flexion angles and age, but differ for males and females.
- 2014
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Ingår i: Journal of Strength and Conditioning Research. - 1064-8011 .- 1533-4287. ; 28:3, s. 843-855
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Tidskriftsartikel (refereegranskat)abstract
- Sex and age are reported to influence the maximal dynamometric performance of major muscle groups, inclusive of ankle plantar-flexors. Knee flexion (KF) also impacts plantar-flexion function from where stems utilization of 0[degrees] and 45[degrees] of KF for clinical assessment of gastrocnemius and soleus, respectively. The influence of KF, sex and age on dynamometric indicators of plantar-flexion fatigue was examined in 28 males and 28 females recruited in two different age groups (above and below 40 years). Each subject performed 50 maximal concentric isokinetic plantar-flexions at 60 deg[middle dot]s-1 with 0[degrees] and 45[degrees] of KF. Maximal voluntary isometric contractions were determined before and after isokinetic trials; and maximal, minimal and normalized linear slopes of peak power during testing. Main effects of and two-way interactions between KF, sex, age and order of testing were explored using mixed-effect models and stepwise regressions. At 0[degrees] and 45[degrees], the fatigue indicators in younger and older individuals were similar and not influenced by testing order. However, peak isokinetic power and isometric torque declined to greater extents in males than females and, moreover, KF exerted greater impacts on the absolute plantar-flexion performance and maximal-to-minimal reduction in isokinetic power in males. Because KF wielded no pronounced effect on fatigue indicators, this test may perhaps be used over time with no major concern regarding the exact knee angle. Our findings indicate that sex, rather than age, should be considered when interpreting dynamometric indicators of fatigue from repeated maximal concentric isokinetic plantar-flexions, e.g., when establishing normative values or comparing outcomes.
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