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The Nordic hamstring exercise (NHE) reduces hamstring injury incidence. Compliance to large exercise volumes of the NHE is poor, with exercise related soreness often seen as a contributing factor. We investigated the dose-response of NHE exposure with delayed onset muscle soreness (DOMS) and non-DOMS pain. Forty males were randomized to a 6-week intervention of four different NHE dosages: Group 1: very low volume; Group 2: low volume; Group 3: initial high to low volume; Group 4: low to high volume. Group 4 experienced more DOMS (p < 0.05) and non-DOMS pain (p = 0.030) than other groups. High volumes of NHE increase DOMS and non-DOMS pain while lower volume protocols have lesser DOMS and non-DOMS pain responses., (© 2023 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Objective: To investigate the relationship between repeated clinical measures and the progression of rehabilitation of male athletes with acute adductor injuries., Design: Prospective observational cohort study., Methods: Male athletes with acute adductor injuries received a standardized criteria-based rehabilitation program with 4 repeated clinical measures during rehabilitation: the extent of palpation pain (length and width in centimeters), the bent-knee fall-out test (BKFO; in centimeters), hip abduction range of motion (in degrees), and eccentric hip adduction strength (in Newton meters per kilogram). We analyzed the association between each clinical measure and the percent progression of rehabilitation until return to sport (RTS), divided into 2 RTS milestones: (1) clinically pain free, and (2) completion of controlled sports training., Results: The analyses included 61 male athletes for RTS milestone 1 and 50 athletes for RTS milestone 2, and 381 to 675 tests were performed for each clinical measure. The median time to RTS milestones 1 and 2 was 15 days (interquartile range, 12-29 days) and 24 days (interquartile range, 16-34 days), respectively. Each repeated clinical measure individually explained 13% to 36% of the variance in rehabilitation progression to the RTS milestones. The extent of palpation pain explained the highest variance of the progression of rehabilitation ( R 2 = 0.26-0.27 for length and R 2 = 0.36 for width, P <.001). Eccentric adduction strength ( R 2 = 0.19-0.27, P <.001) improved throughout rehabilitation, whereas the flexibility tests (BKFO, R 2 = 0.13-0.15; P <.001 and hip abduction range of motion, R 2 = 0.19-0.21; P <.001) returned to normal values early in rehabilitation., Conclusion: Repeated measures of adductor strength, flexibility, and palpation pain provided only a rough impression of rehabilitation progress following acute adductor injuries in male athletes. These clinical measures cannot define a precise recovery point during rehabilitation. J Orthop Sports Phys Ther 2021;51(3):126-134. Epub 28 Oct 2020. doi:10.2519/jospt.2021.9951 .

New approaches that promise more for less rarely pan out despite the hopes of physical therapists. In this Viewpoint, the author discusses blood flow restriction training, an intervention claiming that some low-intensity exercise performed while wearing a blood pressure cuff will result in strength gains, improved performance, shorter postexercise recovery, and pain reduction. J Orthop Sports Phys Ther 2019;49(5):294-298. doi:10.2519/jospt.2019.0608 .

Objectives: This study examines neuromuscular firing patterns in overhead athletes and non-athletes of the periscapular, prime-moving, and rotator cuff muscles during "clinical" cardinal plane physiological movements., Design: Cohort prospective study., Setting: EMG recordings were taken of the periscapular, prime-moving, and rotator cuff muscles during flexion, scaption, and abduction performed at fast, medium, and slow speeds with a loaded (3 kg) and unloaded arm., Participants: 14 Handball players and 20 non-athletes. Differences in firing patterns between groups were analyzed by fitting mixed linear models with random intercepts per subject, and fixed factors for group, muscle, movement type, speed, and load., Main Outcome Measures: No difference in timing of activation was seen between the professional athletes and non-athletes., Results: Speed and load appear to independently vary muscle activation timing in a non-intuitive manner in both athletes and non-athletes. Onset timing of periscapular, prime movers and rotator cuff muscles are prior to movement in all scenarios studied, with rotator cuff muscles firing last., Conclusions: Onset activation patterns in overhead athletes are not different to non-athletes during cardinal plane movements., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Rehabilitation after injury and reconstruction to the anterior cruciate ligament is thought to require a gradual reintroduction of loading, particularly during resumption of running. One strategy to achieve this is via the use of a reduced-gravity treadmill but it is unknown, if and how muscle activity varies in the reduced gravity conditions compared to regular treadmill running. Nineteen healthy participants and 18 male patients at the end of their rehabilitation (8 with a bone-patellar-bone graft, 10 with a hamstring graft) participated in this multi-muscle surface electromyography (sEMG) running study. The hamstrings and triceps surae were evaluated during a 16km/h running while at 6 different relative bodyweight conditions from 50% (half weight-bearing) to 100% (full weight-bearing). Muscle activation was examined individually as well as normalized to a composite "entire" activation and considered across the entire gait cycle using Statistical Parametric Mapping. The healthy participants showed differences between the 50-100% BW and 60-100% conditions and in the hamstring graft group for 60-100% and 80-100% conditions. No differences were seen comparing all loading conditions in the bone-patellar-bone graft group. For the hamstrings, from 70% BW and above, there appear to be no difference in activation patterns for any of the groups. The activation patterns of the hamstrings was essentially the same from 70% indicated bodyweight through to full weight bearing when running at 16km/h. Accordingly, when running at this relatively high speed, we do not expect any adverse effects in terms of altered motor patterns during rehabilitation of these muscles., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: The optimal timing of MRI following acute hamstring injury is not known and is mainly based on expert opinions., Aims: To describe the day-to-day changes in the extent of oedema and investigate the optimal timing for detection of fibre disruption on MRI following acute hamstring injuries., Study Design: Prospective, descriptive study., Methods: We performed standardised MRI (1.5T) ≤1 day after injury in male athletes with acute hamstring injury. If initial MRI revealed positive signs of injury (increased signal intensity on fluid sensitive sequences), consecutive MRIs were obtained daily throughout the subsequent week (ie, 7 times). The MRI parameters (day 1-7) were scored by a single radiologist using a standardised scoring form. The day-to-day changes in the extent of oedema (distance from tuber, craniocaudal length, mediolateral width and anteroposterior depth) and the presence and extent of fibre disruption (tear) were assessed with descriptive statistics and repeated measures using analysis of variance of log-transformed data. The overall main effect for time was reported with a significance level set at p<0.05., Results: 13 out of 132 male athletes assessed for eligibility between January 2014 and December 2015 were included. 1 dropped out, while 12 (31 years, range 20-49) completed the study; 11 had 7 MRI scans each and one had 5 MRI scans performed. There were no significant day-to-day changes for any of the extent of oedema measures (p values ranging from 0.12 to 0.81). Fibre disruption (tear), present in 5 of the athletes, was detectable from day 1, with small and insignificant day-to-day changes (p values ranging from 0.45 to 0.95)., Conclusions: We observed insignificant day-to-day changes in the extent of oedema throughout the first week following acute hamstring injury. Fibre disruption (tear) was detectable from the first day after injury. These findings indicate that MRI can be performed on any day during the first week following an acute (hamstring) muscle injury., Competing Interests: Competing interests: None declared., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Background: MRI is frequently used in addition to clinical evaluation for predicting time to return to sport (RTS) after acute hamstring injury. However, the additional value of MRI to patient history taking and clinical examination remains unknown and is debated., Aim: To prospectively investigate the predictive value of patient history and clinical examination at baseline alone and the additional predictive value of MRI findings for time to RTS using multivariate analysis while controlling for treatment confounders., Methods: Male athletes (N=180) with acute onset posterior thigh pain underwent standardised patient history, clinical and MRI examinations within 5 days, and time to RTS was registered. A general linear model was constructed to assess the associations between RTS and the potential baseline predictors. A manual backward stepwise technique was used to keep treatment variables fixed., Results: In the first multiple regression model including only patient history and clinical examination, maximum pain score (visual analogue scale, VAS), forced to stop within 5 min, length of hamstring tenderness and painful resisted knee flexion (90°), showed independent associations with RTS and the final model explained 29% of the total variance in time to RTS. By adding MRI variables in the second multiple regression model, maximum pain score (VAS), forced to stop within 5 min, length of hamstring tenderness and overall radiological grading, showed independent associations and the adjusted R(2) increased from 0.290 to 0.318. Thus, additional MRI explained 2.8% of the variance in RTS., Summary: There was a wide variation in time to RTS and the additional predictive value of MRI was negligible compared with baseline patient history taking and clinical examinations alone. Thus, clinicians cannot provide an accurate time to RTS just after an acute hamstring injury. This study provides no rationale for routine MRI after acute hamstring injury., Trial Registration Number: ClinicalTrials.gov Identifier: NCT01812564., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Study Design: Cross-sectional., Context: Gluteus medius (GM) muscle dysfunction is associated with overuse injury. The GM is functionally composed of 3 separate subdivisions: anterior, middle, and posterior. Clinical assessment of the GM subdivisions is relevant to detect strength and activation deficits and guide specific rehabilitation programs. However, the optimal positions for assessing the strength and activation of these subdivisions are unknown., Objective: The first aim was to establish which strength-testing positions produce the highest surface electromyography (sEMG) activation levels of the individual GM subdivisions. The second aim was to evaluate differences in sEMG activation levels between the tested and contralateral (stabilizing) leg., Method: Twenty healthy physically active male subjects participated in this study. Muscle activity using sEMG was recorded for the GM subdivisions in 8 different strength-testing positions and analyzed using repeated-measures analysis of variance., Results: Significant differences between testing positions for all 3 GM subdivisions were found. There were significant differences between the tested and the contralateral anterior and middle GM subdivisions (P < .01). The posterior GM subdivision showed no significant difference (P = .154)., Conclusion: Side-lying in neutral and side-lying with hip internal rotation are the 2 positions recommended to evaluate GM function and guide specific GM rehabilitation.

Background: Acute groin injuries are common in high-intensity sports, but there are insufficient data on injury characteristics such as injury mechanisms and clinical and radiological findings., Purpose: To describe these characteristics in a cohort of athletes., Study Design: Cross-sectional study; Level of evidence, 3., Methods: A total of 110 male athletes (mean age, 25.6 ± 4.7 years) with sports-related acute groin pain were prospectively included within 7 days of injury from August 2012 to April 2014. Standardized history taking, a clinical examination, magnetic resonance imaging (MRI), and/or ultrasound (US) were performed., Results: The most frequent injury mechanism in soccer was kicking (40%), and change of direction was most frequent in other sports (31%). Clinically, adductor injuries accounted for 66% of all injuries and primarily involved the adductor longus on imaging (91% US, 93% MRI). The iliopsoas and proximal rectus femoris were also frequently injured according to all examination modalities (15%-25%). Acute injury findings were negative in 22% of the MRI and 25% of the US examinations. Of the clinically diagnosed adductor injuries, 3% (US) and 6% (MRI) showed a radiological injury in a different location compared with 35% to 46% for clinically diagnosed iliopsoas and proximal rectus femoris injuries., Conclusion: Adductor injuries account for the majority of acute groin injuries. Iliopsoas and proximal rectus femoris injuries are also common. More than 1 in 5 injuries showed no imaging signs of an acute injury. Clinically diagnosed adductor injuries were often confirmed on imaging, whereas iliopsoas and rectus femoris injuries showed a different radiological injury location in more than one-third of the cases. The discrepancy between clinical and radiological findings should be considered when diagnosing acute groin injuries., (© 2015 The Author(s).)

Background: To evaluate the efficacy of a single platelet-rich plasma (PRP) injection in reducing the return to sport duration in male athletes, following an acute hamstring injury., Methods: A randomised, three-arm (double-blind for the injection arms), parallel-group trial, in which 90 professional athletes with MRI positive hamstring injuries were randomised to injection with PRP-intervention, platelet-poor plasma (PPP-control) or no injection. All received an intensive standardised rehabilitation programme. The primary outcome measure was time to return to play, with secondary measures including reinjury rate after 2 and 6 months., Results: The adjusted HR for the PRP group compared with the PPP group was 2.29 (95% CI 1.30 to 4.04) p=0.004; for the PRP group compared with the no injection group 1.48 (95% CI 0.869 to 2.520) p=0.15, and for the PPP group compared with the no injection group 1.57 (95% CI 0.88 to -2.80) p=0.13. The adjusted difference for time to return to sports between the PRP and PPP groups was -5.7 days (95% CI -10.1 to -1.4) p=0.01; between the PRP and no injection groups -2.9 days (95% CI -7.2 to 1.4) p=0.189 and between the PPP and no injection groups 2.8 days (95% CI -1.6 to 7.2) p=0.210. There was no significant difference for the secondary outcome measures. No adverse effects were reported., Conclusions: Our findings indicate that there is no benefit of a single PRP injection over intensive rehabilitation in athletes who have sustained acute, MRI positive hamstring injuries. Intensive physiotherapy led rehabilitation remains the primary means of ensuring an optimal return to sport following muscle injury., Trial Registration Number: ClinicalTrials.gov Identifier: NCT01812564., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

The human foot is characterized by a pronounced longitudinal arch (LA) that compresses and recoils in response to external load during locomotion, allowing for storage and return of elastic energy within the passive structures of the arch and contributing to metabolic energy savings. Here, we examine the potential for active muscular contribution to the biomechanics of arch deformation and recoil. We test the hypotheses that activation of the three largest plantar intrinsic foot muscles, abductor hallucis, flexor digitorum and quadratus plantae is associated with muscle stretch in response to external load on the foot and that activation of these muscles (via electrical stimulation) will generate sufficient force to counter the deformation of LA caused by the external load. We found that recruitment of the intrinsic foot muscles increased with increasing load, beyond specific load thresholds. Interestingly, LA deformation and muscle stretch plateaued towards the maximum load of 150% body weight, when muscle activity was greatest. Electrical stimulation of the plantar intrinsic muscles countered the deformation that occurred owing to the application of external load by reducing the length and increasing the height of the LA. These findings demonstrate that these muscles have the capacity to control foot posture and LA stiffness and may provide a buttressing effect during foot loading. This active arch stiffening mechanism may have important implications for how forces are transmitted during locomotion and postural activities as well as consequences for metabolic energy saving.

Objectives: Describe inter-rater reliability of, and correlations between a novel method of isometric knee extension and flexion and eccentric knee flexion strength using hand-held dynamometry and isokinetic testing for flexion/extension in the knees of athletic participants. Document strength data normalized to the individual's limb muscle mass., Design: Observational and reliability study., Methods: Inter-rater reliability for each of the hand-held dynamometry measures was established in both legs of 10 volunteers (6 male). During routine annual screening, 216 male professional football (soccer) players were examined using these same measures in addition to performing an isokinetic evaluation of knee flexion and extension strength. Intra-class correlation coefficients for inter-rater reliability, Pearson r correlations between hand-held dynamometry and isokinetic dynamometry were calculated. Peak torque, peak torque normalized to: body weight; lean body mass; and lean limb mass were documented., Results: Excellent inter-rater reliability was demonstrated with intra-class correlation₂,₁ values of 0.90, 0.91, and 0.96, for the eccentric hamstrings, isometric hamstrings, and isometric quadriceps measures respectively. Medium to high correlations (r=0.322-0.617) which were all significant (p<0.001) were found for the comparisons between the hand-held dynamometry and isokinetic measures., Conclusions: We present 3 novel and reliable methods of examining knee flexion and extension strength using hand-held dynamometry which require less skill and strength on the part of the examiner than previous measures. Correlations between these measures and isokinetic dynamometry are documented. The hand-held dynamometry examinations took less than 4 min per player to conduct and may be useful in clinical practice where isokinetic examination can be difficult to implement., (Copyright © 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)