Irisin seems to play an important role in several chronic diseases, however, the interactions between chronic training and irisin are still unclear. The purpose of this systematic review and meta-analysis was to examine the effect of chronic resistance training on circulating irisin in adults. Literature search was conducted in PubMed, Web of Science and EBSCOhost (Academic Search Complete) until December 2020. Randomized controlled trials researching irisin levels after a resistance training program for at least 8 weeks among an adult population were eligible. Other inclusion criteria comprised recruiting a control group and reporting circulating irisin through ELISA kits. Cohen’s d effect size and subgroup analyses (95% confidence level) were calculated using a random effects analysis model. Data of the seven included studies comprising 282 individuals showed an increasing and non-significant tendency after a resistance training program (d = 0.58, 95% CI: −0.25 to 1.40, p = 0.17). Subgroup analyses showed significant increases for the older adults group (p < 0.001) and when training is demanding and progressive in terms of intensity (p = 0.03). Data suggest that resistance training programs seem to increase circulating irisin, especially in older adults and in demanding and progressive training programs. However, more studies should be conducted using robust measurement methods, such as mass spectrometry, to better understand the interaction between chronic resistance exercise and irisin.

Background: Irisin has been suggested as a helpful hormone for adverse metabolic conditions. However, the interaction between acute endurance exercises and irisin is still unclear. The purpose of this systematic review and meta-analysis was to determine the acute effect of endurance training, either continuous or interval training, on circulating irisin in healthy adults. Methods: Literature search was conducted in Web of Science, PubMed, Scopus and CINAHL until September 2022. Clinical trials measuring irisin levels following a single session of interval or continuous endurance training in healthy adults were eligible. Cohen’s d effect size (95% confidence level), subgroup analyses and univariate meta-regression were calculated using a random-effects model. The procedures described by PRISMA were followed and the protocol was prospectively registered with PROSPERO (CRD 42021240971). Results: Data of the 16 included studies comprising 412 individuals showed a significant increase following one session of continuous endurance training (d = 0.33, 95% CI: 0.20 to 0.46 , p < 0.001), while interval training did not change circulating irisin (d = 0.16, 95% CI: −0.12 to 0.44 , p = 0.202). Both subgroup and univariate meta-regression analyses showed non-significant differences in the change of circulating irisin comparing blood measurement, exercise mode or previous level of physical activity of the participants and circulating irisin at baseline, duration, or intensity of the exercise, respectively. Conclusion: Continuous method for endurance training increases circulating irisin in healthy adults, while studies measuring circulating irisin following interval training in healthy adults are still limited to be conclusive.

The purpose of the study was to analyze hamstrings muscle damage and recovery after a novel Flywheel Russian belt Deadlift (FRBD) exercise using neuromuscular tests and associated biochemical markers of structural damage. Maximal voluntary isometric contraction (MVIC) torque and rate of force development (RFD) over several time-intervals by the 90º_hip:20º_knee test (standing isometric test for the hamstrings) and range of motion (ROM) Jurdan test (combination of active knee extension test and modified Thomas test), together with serum biomarkers of muscle damage and oxidative stress, were tested at baseline and +24h, +48h and +72h in healthy, untrained and physically active 15 females (age= 21.5±3.4 years) and 15 males (age= 21.4±1.9 years). FRBD-induced muscle damage was observed as a reduction in MVIC torque and RFD at all time-intervals until +72h. Also, hamstrings neuromuscular capacity reductions were associated with serum biomarkers of structural and oxidative damage. However, only males showed ROM changes. Overall, the FRBD triggered a decrease in hamstrings neuromuscular capacities, and an upregulation of biochemical markers of structural and oxidative damage until +72h. The 90º_hip:20º_knee test provides an adequate reliability to screen hamstrings recovery in both women and men after flywheel training, through MVIC torque and both early and late RFD.

The relative burden of hamstring strain injuries in professional football has doubled over the last two decades.1 Despite the widespread use of prevention strategies, athletes may be re-exposed to high-speed running, congested match play and eccentric loading before hamstring recovery is complete. Because incomplete hamstring recovery may represent a modifiable risk factor for hamstring strain injuries, monitoring residual fatigue before re-exposure to intense exercise is clinically relevant and helps practitioners balance performance readiness and injury-risk reduction.2