Background: In animal studies long-term stretching interventions up to several hours per day have shown large increases in muscle mass as well as maximal strength. The aim of this study was to investigate the effects of a long-term stretching on maximal strength, muscle cross sectional area (MCSA) and range of motion (ROM) in humans.Methods: 52 subjects were divided into an Intervention group (IG, n = 27) and a control group (CG, n = 25). IG stretched the plantar flexors for one hour per day for six weeks using an orthosis. Stretching was performed on one leg only to investigate the contralateral force transfer. Maximal isometric strength (MIS) and 1RM were both measured in extended knee joint. Furthermore, we investigated the MCSA of IG in the lateral head of the gastrocnemius (LG) using sonography. Additionally, ROM in the upper ankle was investigated via the functional “knee to wall stretch” test (KtW) and a goniometer device on the orthosis. A two-way ANOVA was performed in data analysis, using the Scheffé Test as post-hoc test.Results: There were high time-effects (p = 0.003, ƞ² = 0.090) and high interaction-effect (p < 0.001, ƞ²=0.387) for MIS and also high time-effects (p < 0.001, ƞ²=0.193) and interaction-effects (p < 0.001, ƞ²=0,362) for 1RM testing. Furthermore, we measured a significant increase of 15.2% in MCSA of LG with high time-effect (p < 0.001, ƞ²=0.545) and high interaction-effect (p=0.015, ƞ²=0.406). In ROM we found in both tests significant increases up to 27.3% with moderate time-effect (p < 0.001, ƞ²=0.129) and high interaction-effect (p < 0.001, ƞ²=0.199). Additionally, we measured significant contralateral force transfers in maximal strength tests of 11.4% (p < 0.001) in 1RM test and 1.4% (p=0.462) in MIS test. Overall, there we no significant effects in control situations for any parameter (CG and non-intervened leg of IG).Discussion: We hypothesize stretching-induced muscle damage comparable to effects of mechanical load of strength training, that led to hypertrophy and thus to an increase in maximal strength. Increases in ROM could be attributed to longitudinal hypertrophy effects, e.g., increase in serial sarcomeres. Measured cross-education effects could be explained by central neural adaptations due to stimulation of the stretched muscles.

BackgroundWorldwide, one third of the adult population is insufficiently physically active. This fact has led to a strong demand for public health initiatives. Given the mixed evidence on the effectiveness of worksite interventions promoting physical activity (PA), a pedometer-based and gamified intervention, Healingo Fit, was developed and evaluated over a period of six weeks.MethodsThe effectiveness of Healingo Fit was evaluated as part of a randomized controlled trial (RCT) with two measurement points involving employees of an automobile manufacturer. Direct health promotion outcomes were assessed using self-developed items on PA knowledge, the HAPA brief scales and the exercise self-efficacy scale. IPAQ short version was used to assess different forms of PA behavior. Intervention effects were identified using a two-way analysis of variance (ANOVA) with repeated measurements.ResultsA total of 144 participants took part in the study (intervention group = 80, control group = 64). The results of the ANOVA show significant interaction effects (group x time) for health promotion outcomes (knowledge, intention, and self-efficacy), with medium to high effect sizes. In the health behavior related outcomes, there were significant improvements, with large effect sizes for low levels of PA, but not for moderate and high PA. Walking time increased by 125 min/week in the intervention group, corresponding to a percentage increase of 30% compared to baseline.ConclusionsPedometer-based interventions using gamification elements can have positive effects not only on health promotion parameters but can also lead to an increase in PA behavior. The online format of Healingo Fit is suitable for reaching large numbers of people and achieving population effects.Trial registrationGerman Clinical Trials Register (DRKS): DRKS00006105, date of registration: 2017–03-24.Electronic supplementary materialThe online version of this article (10.1186/s12889-017-4697-6) contains supplementary material, which is available to authorized users.

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 (ƞ 2 = 0.325, p < 0.001) and in the contralateral control leg (ƞ 2 = 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.

Muscular hypertrophy depends on metabolic exhaustion as well as mechanical load on the muscle. Mechanical tension seems to be the crucial factor to stimulate protein synthesis. The present meta-analysis was conducted to determine whether stretching can generate adequate mechanical tension to induce muscle hypertrophy. We used PubMed, Web of Science, and Scopus to search for literature examining the effects of long-term stretching on muscle mass, muscle cross-sectional area, fiber cross-sectional area, and fiber number. Since there was no sufficient number of studies investigating long-lasting stretching in humans, we only included original animal studies in the current meta-analysis. Precisely, we identified 16 studies meeting the inclusion criteria (e. g. stretching of at least 15 min per day). The 16 studies yielded 39 data points for muscle mass, 11 data points for muscle cross-sectional area, 20 data points for fiber cross-sectional area, and 10 data points for fiber number. Across all designs and categories, statistically significant increases were found for muscle mass (d = 8.51; 95% CI 7.11–9.91), muscle cross-sectional area (d = 7.91; 95% CI 5.75–10.08), fiber cross-sectional area (d = 5.81; 95% CI 4.32–7.31), and fiber number (d = 4.62; 95% CI 2.54–6.71). The findings show an (almost) continuous positive effect of long-term stretching on the listed parameters, so that it can be assumed that stretch training with adequate intensity and duration leads to hypertrophy and hyperplasia, at least in animal studies. A general transferability to humans—certainly with limited effectiveness—can be hypothesized but requires further research and training studies.

Background Strength and speed are two major factors that determine performance in basketball players especially sprinting, jumping and change of direction. This study examined relationships of maximal strength in the front squat and the deadlift with basketball-specific sprint and jump performance tests that are commonly used in test batteries of athletic diagnostics. Materials and methods In all, 42 youth male elite basketball players (age: 14.7 ± 2.4 years, age range: 13–18 years, height: 179.1 ± 15.3 cm, weight: 69.8 ± 19.2 kg) volunteered to take part in the present study. The one repetition maximum (1 RM) in the front squat and deadlift were used to determine maximum strength. Countermovement jump (CMJ) and standing long jump were evaluated to determine jump performance and 5, 10, and 20 m linear sprint as well as agility T‑test were performed to determine sprint performance. Pearson correlation analysis was used to assess the relationships between strength and jump and sprint performance. Results Strong positive correlations were found between maximal strength and jump heights (r = 0.85–0.91, p < 0.001) and strong negative correlations were determined between maximal strength and measured sprint times r = (−0.71 to −0.85, p < 0.001). Conclusion The measured maximal strength in the front squat and deadlift seem to be good predictors for basketball-specific jump and sprint performance. From this, it seems to be beneficial to include training of maximal strength via front squat and deadlift into training routines as well as performance diagnostics.