RETRACTED ARTICLE: Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-Analysis

Inflated effect estimates for vitamin D supplementation are driven by common meta-analytical errors

PURPOSE

Han et al. (J Int Soc Sports Nutr 16:55, 2019) sought to quantify the effects of vitamin D supplementation on strength outcomes among athletes in a meta-analysis. The authors reported a pooled effect size (standardized mean difference; SMD) of -0.75 (95% CI: -1.82 to 0.32, p = 0.17) in favor of supplementation, but the analytical approach was not appropriate for a pooled analysis of randomized controlled trials and the effect sizes were calculated incorrectly. This letter discusses how these issues impact the results and interpretation of the paper, then provides an update on the estimated average effect of vitamin D on strength outcomes in athletes.

METHODS

Identified errors included the use of within-group rather than between-group effect size metrics, the use of standard error values in place of standard deviations, and failure to account for correlated observations within the model. The data were reanalyzed after correcting for these common meta-analytic errors.

RESULTS

The results of this reanalysis reflect a dramatically smaller and statistically nonsignificant pooled effect estimate of SMD = 0.16 (-0.24 to 0.56, p = 0.43) in favor of supplementation. Further, the model from this reanalysis has more favorable statistical characteristics than the original analysis, as evidenced by a fairly symmetrical funnel plot and a nonsignificant result for Cochrane's Q test (Q = 5.02, p = 0.41).

CONCLUSION

In order to disseminate robust information to sports nutrition practitioners and researchers, it is critically important for meta-analyses to produce valid effect estimates that are appropriate for the underlying study designs and calculated without error. This letter highlights common errors to inform the calculation and interpretation of future meta-analyses in sports nutrition.

Mat Pilates improves lower and upper body strength and flexibility in breast cancer survivors undergoing hormone therapy: a randomized controlled trial (HAPiMat study)

PURPOSE

To evaluate the effects of 24 weeks of Mat Pilates in breast cancer survivors (BCS) undergoing hormone therapy on lower and upper body muscle strength parameters and flexibility.

MATERIALS AND METHODS

Forty-three BCS (≥40 years) with confirmed breast cancer stage 0-III undergoing hormone therapy were included. Participants were randomized into Mat Pilates (three times/week, 60 min session) or control group (relaxation activities every two weeks). The difficulty and number of exercise repetitions were increased over the weeks. Assessments were performed at three times points (baseline, 12 weeks, and 24 weeks). The generalized estimating equations (GEE) model was used to compare each outcome measure during the analysis of intention to treat (ITT) and "Per protocol analysis" (PPA).

RESULTS

The Pilates group presented significantly increased (p < 0.05) isometric flexor-extensor PT, and concentric and eccentric flexor PT and mechanical work (MW) after the intervention. Most of the upper body strength parameters, time to achieve maximal force (TF_max), maximal force (F_max), and rapid force index (RFI) and right-left upper and lower body flexibility (p < 0.05) also improved.

CONCLUSIONS

From our findings, we conclude that 24 and 12-weeks of Mat Pilates induced strength and flexibility gains for lower and upper body, respectively.Implications for rehabilitationMat Pilates can be adapted to the fitness level of breast cancer survivors, with a great variety of exercises that can be performed using a mat only or a few pieces of equipment.Patients can practice at home to gain different health benefits (i.e., increasing strength, flexibility, and functional capacity level), which could positively impact on quality of life.Mat Pilates performed three times per week with systematized increments in exercise level, load, and volume throughout the intervention was effective to improve hip extensor-flexor muscles peak torque and mechanical work at different muscle contractions, as well as upper and lower body flexibility.Mat Pilates was also able to improve right-left shoulder abductor and trunk extensor muscles strength parameters after 12 weeks of intervention, as well as both surgery and non-surgery sides of the upper body.

Functional relevance of resistance training-induced neuroplasticity in health and disease

Repetitive, monotonic, and effortful voluntary muscle contractions performed for just a few weeks, i.e., resistance training, can substantially increase maximal voluntary force in the practiced task and can also increase gross motor performance. The increase in motor performance is often accompanied by neuroplastic adaptations in the central nervous system. While historical data assigned functional relevance to such adaptations induced by resistance training, this claim has not yet been systematically and critically examined in the context of motor performance across the lifespan in health and disease. A review of muscle activation, brain and peripheral nerve stimulation, and imaging data revealed that increases in motor performance and neuroplasticity tend to be uncoupled, making a mechanistic link between neuroplasticity and motor performance inconclusive. We recommend new approaches, including causal mediation analytical and hypothesis-driven models to substantiate the functional relevance of resistance training-induced neuroplasticity in the improvements of gross motor function across the lifespan in health and disease.

A Systematic Review and Meta-Analysis on Neural Adaptations Following Blood Flow Restriction Training: What We Know and What We Don't Know

Objective: To summarize the existing evidence on the long-term effects of low-load (LL) blood flow restricted (BFR) exercise on neural markers including both central and peripheral adaptations. Methods: A systematic review and meta-analysis was conducted according to the PRISMA guidelines. The literature search was performed independently by two reviewers in the following electronic databases: PubMed, Web of Science, Scopus and CENTRAL. The systematic review included long-term trials investigating the effects of LL-BFR training in healthy subjects and compared theses effects to either LL or high-load (HL) training without blood flow restriction. Results: From a total of N = 4499 studies, N = 10 studies were included in the qualitative synthesis and N = 4 studies in a meta-analysis. The findings indicated that LL-BFR resulted in enhanced levels of muscle excitation compared to LL training with pooled effect sizes of 0.87 (95% CI: 0.38-1.36). Compared to HL training, muscle excitation following LL-BFR was reported as either similar or slightly lower. Differences between central activation between LL-BFR and LL or HL are less clear. Conclusion: The summarized effects in this systematic review and meta-analysis highlight that BFR training facilitates neural adaptations following LL training, although differences to conventional HL training are less evident. Future research is urgently needed to identify neural alterations following long-term blood flow restricted exercise.