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.

Background: Biomechanical factors behind non-contact anterior cruciate ligament (ACL) injury in soccer and handball are still not fully understood. Unfortunately, ACL injuries more frequently appear in game situations. Aim: To describe a possible ACL injury mechanism in male professional handball players using MRI images and our own biomechanical model. Hypothesis: The friction parameters of the surface have extreme importance in the non-contact ACL injury mechanism. If the surface is more slippery, the horizontal component of the ground reaction force (GRF) will be smaller, consequently the torque originating from the GRF acting on the knee will be greater during the landing phase of a vertical jump, resulting in greater abduction effect on the knee. Consequently, the risk of knee injury increases. Methods: We have collected MRI images and anthropometric data of 15 healthy male individuals (age 19–23) to create a biomechanical model to calculate the torques in the knee to obtain more knowledge about ACL injury mechanism. Results: The lower extremity lean angle during the landing phase of a jump and friction parameters substantially affect abduction torques in the knee and consequently the risk of ACL injury occurrence. Conclusions: The landing posture when the knee is fully extended during landing is highly unfortunate for the ACL, compared to when the knee is partially flexed. If the knee is fully extended, greater hip abduction will increase the risk of an ACL injury, and if the surface is more slippery, e.g., the surface is wet, the possibility of ACL injury is even greater. In addition, we also applied a molecular working hypothesis through acquired Piezo2 channelopathy theory, as the proposed preceding neuromuscular disruptor prior to non-contact ACL injury.

Background: Biomechanical factors behind non-contact Anterior Cruciate Ligament (ACL) injury in soccer are still not fully understood. Unfortunately, ACL injuries almost always appear in game situations. Aim: To describe a possible ACL injury mechanism in male professional soccer players using MRI images and our own biomechanical model. Hypothesis: The friction parameters of the surface have extreme importance in the ACL injury mechanism. If the surface is more slippery, the horizontal component of the ground reaction force (GRF) will be smaller, consequently the torque originated from the GRF acting on the knee will be greater during the landing phase of a vertical jump, resulting in greater abduction effect on the knee. Consequently, the risk of knee injury increases. Methods: We have collected Magnetic Resonance Image images and anthropometric data of 15 healthy male individuals (age 19-23) to create a biomechanical model to calculate the torques in the knee to obtain more knowledge about ACL injury mechanism. Results: Lower extremity lean angle during the landing phase of a jump and friction parameters substantially affect abduction torques in the knee and consequently the risk of ACL injury occurrence. Conclusions: The landing posture when the knee is fully extended during landing is highly unfortunate for the ACL, compared to when the knee is partially flexed. If the knee is fully extended, greater hip abduction will increase the risk of an ACL injury, and if the surface is more slippery e.g. the surface is wet, the possibility of ACL injury is even greater. In addition, we also applied a molecular interpretation through acquired Piezo2 channelopathy, as the proposed preceding neuromuscular disruptor prior to non-contact ACL injury.

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.