Heart rate variability (HRV) is often modulated by pain; therefore, the objective of this study was to assess whether the induction of delayed-onset muscle soreness (DOMS) is already affected by HRV alterations during exercise, in spite of the fact that pain evolves only post-exercise. An isokinetic dynamometer was used to induce DOMS in this study on 19 young male elite handball players who were subjected to HRV measurements throughout a DOMS-inducing exercise session. The result of this study indicated that the heart rate (HR) dependence of time–frequency domain parameters could be described by an exponential-like function, while entropy showed a V-shaped function, with a minimum “turning point” separated by descending and ascending intervals. The DOMS protocol upshifted the time–frequency domain HRV parameters in the entire HR range, contrary to the sample entropy values that were systematically downshifted, indicative of an upregulated sympathetic tone. The group-averaged HR-dependent sample entropy function showed a nonlinear character under exercise, with lower values for higher DOMS than for the group with lower DOMS below the turning-point HR, and vice versa above it. The differences between the respective HRV(HR) point sets representing the low-DOMS and high-DOMS groups were quantified using a statistical method and found to be significant at the current sample size for all the HRV parameters used. Since oxidative stress is implicated in DOMS, we are the first to report that nonlinear alterations may impact HRV in a HR-dependent manner in DOMS using a Piezo2 interpretation. This finding provides further indirect evidence for an initiating neural microdamage that prevails under DOMS-inducing exercise, and the diagnostic detection of this point may provide control for avoiding further injury risk in sports and exercise activities.

The aim of the study was to develop and assess the reliability of a functional agility test containing offensive elements for water polo players. Eighteen young male (15.3 ± 0.5 years, 178.3 ± 4.7 cm, 69.4 ± 10.0 kg) water polo players with a minimum of 5 years of sport-specific experience participated in this study. The test contained reactive high-intensity short-term swimming with changes in direction and manoeuvres after perceiving unknown stimuli given by tester players, and also included a shooting task at a goal, first from 7 m and then from 5 m. Execution time and shooting efficiency were measured by two experienced water polo coaches (Evaluators A and B). All statistical analyses were calculated using SPSS. The intrarater reliability between attempts showed good reliability for both evaluators (Evaluator A: ICC: 0.87; 95% CI: 0.66–0.95 and Evaluator B: ICC: 0.88; 95% CI: 0.68–0.96). Interrater reliability between Evaluators A and B was excellent at both attempts (Attempt 1: ICC: 0.97; 95% CI: 0.93–0.99 and Attempt 2: ICC: 0.98; 95% CI: 0.91–0.99). A lack of correlation between shooting performance from 7 m and 5 m distances and execution time was observed in the protocol. The test we presented in this study was found to be a reliable measurement tool for testing offensive agility performance based on open skill nature among water polo players.

Heart rate variability (HRV) is often modulated by pain therefore the object of the study was to assess whether delayed-onset mescle soreness (DOMS) inducing exercise bout is affected by HRV alterations already during exercise in spite of the fact that pain evolves only post-exercise. Isokinetic dynamometer was used to induce DOMS in the study on 19 young male elite handball players who were exposed to HRV measurements for the time being. The result of the study found that heart rate (HR)-dependence of time- and frequency-domain parameters could be described by an exponential-like function, while entropy showed a V-shaped function, with a minimum "turning point" seperated by descending and ascending intervals. The DOMS protocol upshifted the time- and frequency-domain parameters in the entire HR range, contrary to sample entropy values that were systematically down-shifted, indicative of an upregulated sympathetic tone. The gourp-averaged HR dependent sample entropy function showed a non-linear character under exercise, with values lower for higher DOMS than for the group with lower DOMS below the turning point HR, and vice versa above it. The differences between the respective HRV(HR)point sets representing the Low-DOMS and High-DOMS groups were quantified by a statistical method, and found to be significant at the current sample size for all the HRV parameters used. Since oxidative stress is implicated in DOMS, therefore we are the first to report that after all non-linear alterations may impact HRV in a HR dependent manner in DOMS with a Piezo2 interpretation. This finding provides further indirect evidence for an initiating neural microdamage that prevails already under DOMS-inducing exercise and the diagnostic detection of this point empowers control over avoiding further injury risk in sport and exercise activities.