Effects of muscle fatigue on exercise-induced hamstring muscle damage: a three-armed randomized controlled trial.

PURPOSE: Hamstring injuries in soccer reportedly increase towards the end of the matches' halves as well as with increased match frequency in combination with short rest periods, possibly due to acute or residual fatigue. Therefore, this study aimed to investigate the effects of acute and residual muscle fatigue on exercise-induced hamstring muscle damage. METHODS: A three-armed randomized-controlled trial, including 24 resistance-trained males, was performed allocating subjects to either a training group with acute muscle fatigue + eccentric exercise (AF/ECC); residual muscle fatigue + eccentric exercise (RF/ECC) or a control group with only eccentric exercise (ECC). Muscle stiffness, thickness, contractility, peak torque, range of motion, pain perception, and creatine kinase were assessed as muscle damage markers pre, post, 1 h post, and on the consecutive three days. RESULTS: Significant group × time interactions were revealed for muscle thickness (p = 0.02) and muscle contractility parameters radial displacement (Dm) and contraction velocity (Vc) (both p = 0.01), with larger changes in the ECC group (partial η2 = 0.4). Peak torque dropped by an average of 22% in all groups; stiffness only changed in the RF/ECC group (p = 0.04). Muscle work during the damage protocol was lower for AF/ECC than for ECC and RF/ECC (p = 0.005). CONCLUSION: Hamstring muscle damage was comparable between the three groups. However, the AF/ECC group resulted in the same amount of muscle damage while accumulating significantly less muscle work during the protocol of the damage exercise. TRIAL REGISTRATION: This study was preregistered in the international trial registration platform (WHO; registration number: DRKS00025243).

Comparative Effectiveness of Upper Limb Exercise Interventions in Individuals With Stroke: A Network Meta-Analysis.

BACKGROUND: Although numerous effective exercise interventions can treat upper limb motor impairments after stroke, it remains unknown as to which are the most effective. The objective of the present study was to investigate the comparative effectiveness of various exercise interventions of the upper limb for individuals with an acute or subacute stroke. METHODS: For this systematic review with network meta-analysis, we searched PubMed/MEDLINE, Cochrane Library CENTRAL and Web of Science from database inception to September 2021 for randomized controlled trials examining individuals within 6 months of stroke onset, active upper limb exercise interventions, and any kind of control intervention. The primary outcome was upper limb motor function, secondary outcomes were activities of daily living and social participation, both assessed at post-intervention and follow-up. Nonspecific/multimodal active upper limb therapy was the standard comparator. Standardized mean differences, that is, Hedge's g, were the effect size estimators. We calculated Frequentist-based network meta-analysis for the comparative effectiveness calculations using the R package netmeta. Main analyses were network plotting to display the geometry of the network and P-scores to summarize the intervention hierarchy. Results were derived from direct within-study and indirect between-study evidence comparisons. The Cochrane risk-of-bias tool II assessed all risk of bias domains. RESULTS: This review involved 145 randomized controlled trial on 6432 participants and 45 different treatment categories. The network meta-analysis analyzed 119 randomized controlled trials on 5553 participants and 41 different treatment categories. Electrical stimulation combined with task-specific training (standardized mean difference, 1.03 [95% CI, 0.51-1.55]; P<0.0001, P-score=0.11), high-volume constraint-induced movement therapy (0.86 [0.4-1.32]; P=0.0003, P-score=0.18), and strength training (0.65 [0.17-1.13]; P=0.01, P-score=0.28) were the most effective interventions (each k=107). CONCLUSIONS: Electrical stimulation combined with task-specific training (low evidence), high-volume constraint-induced movement therapy (moderate evidence), and strength training (low evidence) were the most effective interventions in improving upper limb motor function in individuals with a stroke. As the results were sensitive against a high risk of bias, likewise, these interventions should receive more attention in research and practice. Due to the heterogeneous use, electrical stimulation in combination with task-specific training should be further investigated in well-designed studies alongside other successful interventions (eg, constraint-induced movement therapy). REGISTRATION: URL: https://www.crd.york.ac.uk/prospero/; Unique identifier: CRD42021284064.

The evaluation of strength imbalances as risk factor for contactless injuries of the knee and thigh: a critical review.

Contact injuries are difficult to prevent in sports because of the influence of many uncontrollable factors. Non-contact injuries, on the other hand, appear to be controllable and therefore predictable due to their exclusively internal nature. Nevertheless, the scientific community is still searching in vain for indicators to reliably predict the likelihood of injuries to athletes in order to prevent them. Therefore, a critical review of published data was conducted to discuss the current evaluation of strength imbalances as risk factors for contactless knee and thigh injuries. Different approaches to measure muscle strength, detect asymmetries, and methodological issues with the final goal of evaluating their relationship with injury rates was considered as well. All common strength tests on the basis of which an injury risk assessment is calculated had high to excellent ICC values. However, we found that all these tests have their respective limitations and problems. The HQ Ratio can be determined using different contraction forms or calculation methods. This variance in procedures in use makes uniform interpretation enormously difficult. Regardless, we found moderate or strong evidence of no association with future hamstring injury for half of all variables. For lateral differences, we were unable to find any relevant data directly indicating an influence on injury probability. Thus, to date, no significant relationship between asymmetries and non-contact injuries has been detected for either inter- or intra-limb differences. Therefore, the assessment of strength imbalances can only be considered as one component in a multifactorial approach to assess potential injury risks.

Sensor location affects skeletal muscle contractility parameters measured by tensiomyography.

Tensiomyography (TMG) is a non-invasive method for measuring contractile properties of skeletal muscle that is increasingly being used in research and practice. However, the lack of standardization in measurement protocols mitigates the systematic use in sports medical settings. Therefore, this study aimed to investigate the effects of lower leg fixation and sensor location on TMG-derived parameters. Twenty-two male participants underwent TMG measurements on the m. biceps femoris (BF) in randomized order with and without lower leg fixation (fixed vs. non-fixed). Measurements were conducted at 50% of the muscle's length (BF-mid) and 10 cm distal to this (BF-distal). The sensor location affected the contractile properties significantly, both with and without fixation. Delay time (Td) was greater at BF-mid compared to BF-distal (fixed: 23.2 ± 3.2 ms vs. 21.2 ± 2.7 ms, p = 0.002; non-fixed: 24.03 ± 4.2 ms vs. 21.8 ± 2.7 ms, p = 0.008), as were maximum displacement (Dm) (fixed: 5.3 ± 2.7 mm vs. 3.5 ± 1.7 mm, p = 0.005; non-fixed: 5.4 ± 2.5 mm vs. 4.0 ± 2.0 mm, p = 0.03), and contraction velocity (Vc) (fixed: 76.7 ± 25.1 mm/s vs. 57.2 ± 24.3 mm/s, p = 0.02). No significant differences were revealed for lower leg fixation (all p > 0.05). In summary, sensor location affects the TMG-derived parameters on the BF. Our findings help researchers to create tailored measurement procedures in compliance with the individual goals of the TMG measurements and allow adequate interpretation of TMG parameters.

The course of knee extensor strength after total knee arthroplasty: a systematic review with meta-analysis and -regression.

PURPOSE: Muscular strength loss and atrophy are postoperative complications. This systematic review with meta-analysis investigated the course of on knee extensor mass and strength from pre-surgery over total knee arthroplasty to rehabilitation and recovery. METHODS: A systematic literature search was conducted in PubMed (Medline), Cochrane Library (CINAHL, Embase) and Web of Science (until 29th of June 2022). Main inclusion criteria were ≥ 1 preoperative and ≥ 1 measurement ≥ 3-months post-operation and ≥ 1 objective assessment of quadriceps strength, muscle mass or neuromuscular activity, measured at both legs. Studies were excluded if they met the following criteria: further impairment of treated extremity or of the contralateral extremity; further muscle affecting disease, or muscle- or rehabilitation-specific intervention. The Robins-I tool for non-randomized studies, and the Cochrane Rob 2 tool for randomized controlled studies were used for risk of bias rating. Pre-surgery, 3 months, 6 months and 1 year after surgery data were pooled using random effects meta-analyses (standardized mean differences, SMD, Hedge's g) in contrast to the pre-injury values. RESULTS: 1417 studies were screened, 21 studies on 647 participants were included. Thereof, 13 were non-randomized controlled trails (moderate overall risk of bias in most studies) and 7 were randomized controlled trials (high risk of bias in at least one domain in most studies). Three (k = 12 studies; SMD = - 0.21 [95% confidence interval = - 0.36 to - 0.05], I2 = 4.75%) and six (k = 9; SMD = - 0.10 [- 0.28 to - 0.08]; I2 = 0%) months after total knee arthroplasty, a deterioration in the strength of the operated leg compared with the strength of the non-operated leg was observed. One year after surgery, the operated leg was stronger in all studies compared to the preoperative values. However, this increase in strength was not significant compared to the non-operated leg (k = 6, SMD = 0.18 [- 0.18 to 0.54], I2 = 77.56%). CONCLUSION: We found moderate certainty evidence that deficits in muscle strength of the knee extensors persist and progress until 3 months post-total knee arthroplasty in patients with end-stage knee osteoarthritis. Very low certainty evidence exists that preoperatively existing imbalance of muscle strength and mass in favor of the leg not undergoing surgery is not recovered within 1 year after surgery.

Resistance training volume does not influence lean mass preservation during energy restriction in trained males.

This study investigated the effects of a relatively high- versus moderate-volume resistance training program on changes in lean mass during caloric restriction. Thirty-eight resistance-trained males were randomized to perform either a high-volume (HVG; 5 sets/exercise) or a moderate-volume (MVG; 3 sets/exercise) resistance training program. Both groups were supervised during lower body training. Participants consumed 30 kcal/kg for 6 weeks after 1 week of weight maintenance (45 kcal/kg), with protein intake fixed at 2.8 g/kg fat-free mass. Muscle thickness of the m. rectus femoris, body composition, contractile properties, stiffness, mood, and sleep status were assessed at pre-, mid-, and post-study. No significant group × time interaction was observed for muscle thickness of the m. rectus femoris at 50% (∆ [post-pre] 0.36 ± 0.93 mm vs. ∆ -0.01 ± 1.59 mm; p = 0.226) and 75% length (∆ -0.32 ± 1.12 mm vs. ∆ 0.08 ± 1.14 mm; p = 0.151), contractility, sleep, and mood in the HVG and MVG, respectively. Body mass (HVG: ∆ -1.69 ± 1.12 kg vs. MVG: ∆ -1.76 ± 1.76 kg) and lean mass (∆ -0.51 ± 2.30 kg vs. ∆ -0.92 ± 1.59 kg) decreased significantly in both groups (p = 0.022), with no between-group difference detected (p = 0.966). High-volume resistance training appears to have neither an advantage nor disadvantage over moderate-volume resistance training in terms of maintaining lean mass or muscle thickness. Given that both groups increased volume load and maintained muscle contractility, sleep quality, and mood, either moderate or higher training volumes conceivably can be employed by resistance-trained individuals to preserve muscle during periods of moderate caloric restriction.

Neuromuscular Electrical Stimulation Training vs. Conventional Strength Training: A Systematic Review and Meta-Analysis of the Effect on Strength Development.

ABSTRACT: Happ, KA, and Behringer, M. Neuromuscular electrical stimulation Training vs. conventional strength training: a systematic review and meta-analysis of the effect on strength development. J Strength Cond Res 36(12): 3527-3540, 2022-A systematic review of the current state of literature and a meta-analysis were conducted to compare the strength development between neuromuscular electrical stimulation (NMES) and conventional strength training when training volume is matched. Searches of PubMed and several other databases were conducted for studies that met the following primary inclusion criteria: randomized studies of >20 days duration with a sample size of >4 subjects in each group ("voluntary contraction" [VC] and "electrically stimulated" [ES]) conducted with percutaneous stimulation only in healthy individuals at equal training volume. Finally, a total of 19 studies were included in the analysis. When comparing strength gains between groups (ES-VC), no favorable effect toward a training method could be observed (0.023 hg [95% CI: -0.198 to 0.246, p = 0.836]). Subgroup analyses were performed based on the application type (NMES evoked and NMES onto voluntary contractions) and stimulation frequency. Both analyses revealed no favorable effect and significant difference of groups (significance level set at 0.05). A meta-regression evaluated the relationship between stimulation frequency and effect size difference. The regression showed a tendency of higher stimulation frequencies being associated with higher study effect size differences (predicted effect size = -0.599 + 0.008 (Hz) ( p = 0.176)). The findings indicate that training with NMES results in virtually identical strength gains compared with conventional strength training when training volume is matched. If training with NMES is preferred, the stimulation frequency type (regular or Burst Mode Alternating Current) can be chosen according to preference without loss of effectiveness.