Rebuilding strength capacity is of crucial importance in rehabilitation since significant atrophy due to immobilization after injury and/or surgery can be assumed. To increase maximal strength (MSt), strength training is commonly used. The literature regarding animal studies show that long-lasting static stretching (LStr) interventions can also produce significant improvements in MSt with a dose–response relationship, with stretching times ranging from 30 min to 24 h per day; however, there is limited evidence in human studies. Consequently, the aim of this study is to investigate the dose–response relationship of long-lasting static stretching on MSt. A total of 70 active participants (f = 30, m = 39; age: 27.4 ± 4.4 years; height: 175.8 ± 2.1 cm; and weight: 79.5 ± 5.9 kg) were divided into three groups: IG1 and IG2 both performed unilateral stretching continuously for one (IG1) or two hours (IG2), respectively, per day for six weeks, while the CG served as the non-intervened control. MSt was determined in the plantar flexors in the intervened as well as in the non-intervened control leg to investigate the contralateral force transfer. Two-way ANOVA showed significant interaction effects for MSt in the intervened leg (ƞ² = 0.325, p < 0.001) and in the contralateral control leg (ƞ² = 0.123, p = 0.009), dependent upon stretching time. From this, it can be hypothesized that stretching duration had an influence on MSt increases, but both durations were sufficient to induce significant enhancements in MSt. Thus, possible applications in rehabilitation can be assumed, e.g., if no strength training can be performed, atrophy could instead be reduced by performing long-lasting static stretch training.

There are many reasons for reduced physical activity leading to reduced maximal strength and sport-specific performance, such as jumping performance. These include pandemic lockdowns, serious injury, or prolonged sitting in daily work life. Consequently, such circumstances can contribute to increased morbidity and reduced physical performance. Therefore, a demand for space-saving and home-based training routines to counteract decreases in physical performance is suggested in the literature. This study aimed to investigate the possibility of using daily static stretching using a stretching board to counteract inactivity-related decreases in performance. Thirty-five (35) participants were either allocated to an intervention group (IG), performing a daily ten-minute stretch training combined with reduced physical activity or a reduced physical activity-only group (rPA). The effects on maximal voluntary contraction, range of motion using the knee-to-wall test, countermovement jump height (CMJ_height), squat jump height (SJ_height), drop jump height (DJ_height), contact time (DJ_ct) and the reactive strength index (DJ_RSI) were evaluated using a pre-test-post-test design. The rPA group reported reduced physical activity because of lockdown. Results showed significant decreases in flexibility and jump performance (d = −0.11–−0.36, p = 0.004–0.046) within the six weeks intervention period with the rPA group. In contrast, the IG showed significant increases in MVC90 (d = 0.3, p < 0.001) and ROM (d = 0.44, p < 0.001) with significant improvements in SJ_height (d = 0.14, p = 0.002), while no change was measured for CMJ_height and DJ performance. Hence, 10 min of daily stretching seems to be sufficient to counteract inactivity-related performance decreases in young and healthy participants.

Recent research showed significant stretch-mediated maximum strength increases when performing stretching between 5 to 120 minutes per day with the calf muscle. However, since the practical applicability of these long stretching durations was questioned and studies exploring the transferability to the upper body are scarce, the aim of this study was to investigate the possibility of using a home-based stretching program to induce significant increases in maximum strength and flexibility. Therefore, 31 recreationally active participants (intervention group: 18, control group: 13) stretched the pectoralis major for 15min/day for eight weeks, incorporating three different stretching exercises. The maximum strength was tested isometrically and dynamically in the bench press (one-repetition maximum: 1RM) as well as shoulder range of motion (ROM) performing bilateral shoulder rotation with a scaled bar. Using a two-way analysis of variance (ANOVA) with repeated measures, the results showed high magnitude Time effects (η2 = 0.388-0.582, p < 0.001) and Group*Time interaction (η2 = 0.281-0.53, p < 0.001-0.002), with increases of 7.4 ± 5.6% in 1RM and of 9.8 ± 5.0% in ROM test in the intervention group. In the isometric testing, there was a high-magnitude Time effect (η2 = 0.271, p = 0.003), however, the Group*Time interaction failed to reach significance (p = 0.75). The results are in line with previous results that showed stretch-mediated maximum strength increases in the lower extremity. Future research should address the underlying physiological mechanisms such as muscle hypertrophy, contraction conditions as well as pointing out the relevance of intensity, training frequency and stretching duration.

In recent years, the EnodePro^® device has been one of the most frequently used velocity sensors to track the bar velocity in resistance training, with the aim of providing load–velocity profiles. However, recent articles highlight a lack of reliability and validity in the estimated maximal strength, which can cause a serious health risk due to the overestimation of the bar velocity. With this study, we aimed to investigate whether imprecision in the measurement could explain the variance in this measurement error. Methods: The research question was evaluated by comparing the integrated velocities from the EnodePro^® with the velocities from a high-resolution displacement sensor for the squat and bench press. The velocity was measured with loads corresponding to 30%, 50%, and 70% of the one-repetition maximum (1RM) in moderately trained participants (n = 53, f = 16, m = 37). Intraclass correlation coefficients (ICC) for agreement were supplemented by an exploration of the systematic bias and the random error (mean absolute error (MAE), mean absolute percentage error (MAPE)). Results: The results indicated movement specificity, with the ICC values for the squat ranging from 0.204 to 0.991 and with ICC = 0.678–0.991 for the bench press. Systematically higher velocities were reported by the EnodePro^® sensor (p < 0.001–0.176), with an MAE = 0.036–0.198 m/s, which corresponds to an MAPE of 4.09–42.15%. Discussion: The EnodePro^® seems to provide overly high velocities, which could result in the previously reported overestimation of the 1RM. Despite the validity problems of force/load–velocity profiles, we suggest evaluating the bar velocity with accurate measurement devices, which is, contrary to previous reports, not the case with the EnodePro^®.

Purpose: Stretch-induced force deficit suggests an acute stretch-specific strength capacity loss, which is commonly attributed to EMG reductions. Since those deficits could also be attributed to general fatigue induced by overloading the muscle, this study aimed to compare stretching with an exhausting calf raise programme to compare strength and stretching responses. Method: This study included 16 participants with different, high-duration calf muscle stretching effects (10, 20, 30 min of stretching) with resistance training (RT) (3 × 12 repetitions) performed until muscle failure, by using a cross-over study design with pre-post comparisons. Strength was tested via isometric plantar flexor diagnostics, while flexibility was assessed using the knee-to-wall test (KtW) and an isolated goniometer test. Results: Using a three-way ANOVA, RT strength decreases were greater compared to 10 and 20 min of stretching (p = 0.01–0.02), but similar to those of 30 min of stretching. ROM in the KtW showed no specific stretch-induced increases, while only the stretching conditions enhanced isolated tested ROM (p < 0.001–0.008). No RT-related isolated ROM increases were observed. Conclusions: The results showed both interventions had similar effects on strength and ROM in the calf muscles. More holistic explanatory approaches such as fatigue and warm-up are discussed in the manuscript and call for further research.

Background: Drop jumps (DJs) are common tests for determining stretch-shortening cycle efficiency. Despite their wide implementation, numerous studies did not adhere to validity guidelines, and participants reached ground contact times (GCTs) of > 250ms. The DJ is a coordinatively-demanding task and it could be hypothesized that a lack of adherence to GCT thresholds could be attributed to insufficient test familiarization. Accordingly, this study evaluated the impact of extensive task habituation on test-retest reliability and GCT adherence. Methods: Eighty-nine healthy participants were allocated to an experienced and inexperienced subgroup. All subjects performed DJs on five days from three different drop heights, with three trials per height (5 × 3 × 3 DJs = 45 jumps). Reliability coefficients and test-retest systematic and random errors were quantified between testing days. Results: The inexperienced subgroup showed systematic performance increases between test day 1 and the subsequent days in most evaluated parameters with largest effects obtained for GCTs (up to d = 0.83, p < 0.001). With up to 30%, the MAPEs peaked for reactive strength index (RSI) in the day 1 to day 5 comparison. No systematic test-retest increases occurred in the experienced group, and the random percentage error was meaningfully smaller (16–17% for the RSI). Conclusion: The systematic bias observed in the inexperienced subgroup might indicate significant task habituation, while the experienced group was already familiar with the testing procedure and showed no test-retest improvements. Since subgroup measurement errors differed meaningfully (e.g. 16% versus 30% RSI MAPE), future DJ research should provide their own reliability quantifications and sufficient habituation.