Neuromuscular function and fatigue resistance of the plantar flexors following short-term cycling endurance training

Previously published studies on the effect of short-term endurance training on the neuromuscular function of the plantar flexors have shown that the H-reflex elicited at rest and during weak voluntary contractions was increased following the training regime. However, these studies did not test H-reflex modulation during isometric maximum voluntary contraction (iMVC) and did not incorporate a control group in their study design to compare the results of the endurance training group to individuals without the endurance training stimulus. Therefore, this randomized controlled study was directed to investigate the neuromuscular function of the plantar flexors at rest and during iMVC before and after eight weeks of cycling endurance training. Twenty-two young adults were randomly assigned to an intervention group and a control group. During neuromuscular testing, rate of torque development, isometric maximum voluntary torque and muscle activation were measured. Triceps surae muscle activation and tibialis anterior muscle co-activation were assessed by normalized root mean square of the EMG signal during the initial phase of contraction (0-100, 100-200 ms) and isometric maximum voluntary contraction of the plantar flexors. Furthermore, evoked spinal reflex responses of the soleus muscle (H-reflex evoked at rest and during iMVC, V-wave), peak twitch torques induced by electrical stimulation of the posterior tibial nerve at rest and fatigue resistance were evaluated. The results indicate that the endurance training did not lead to a significant change in any variable of interest. Data of the present study conflict with the outcome of previously published studies that have found an increase in H-reflex excitability after endurance training. However, these studies had not included a control group in their study design as was the case here. It is concluded that short-term cycling endurance training does not necessarily enhance H-reflex responses and fatigue resistance

Cardiac troponin T and echocardiographic dimensions after repeated sprint vs. moderate intensity continuous exercise in healthy young males

Regular physical exercise can positively influence cardiac function; however, investigations have shown an increase of myocardial damage biomarkers after acute prolonged endurance exercises. We investigated the effect of repeated sprint vs. moderate long duration exercise on markers of myocardial necrosis, as well as cardiac dimensions and functions. Thirteen healthy males performed two different running sessions (randomized, single blinded cross-over design): 60 minutes moderate intensity continuous training (MCT, at 70% of peak heart rate (HRpeak)) and two series of 12 × 30-second sprints with set recovery periods in-between (RST, at 90% HRpeak). Venous blood samples for cardiac troponin T (cTnT), creatine kinase (CK) and MB isoenzyme (CK-MB) were taken 1 and 4 hours after exercise sessions. After each session electrocardiographic (ECG) and transthoracic echocardiographic (TTE) data were recorded. Results showed that all variables - average heart rate, serum lactate concentration during RST, subjective exertion and cTnT after RST - were significantly higher compared to MCT. CK and CK-MB significantly increased regardless of exercise protocol, while ECG and TTE indicated normal cardiac function. Our results provide evidence that RST contributes significantly to cTnT and CK release. This biomarker increase seems to reflect a physiological rather than a pathological phenomenon in healthy, exercising subjects

Drafting, pacing, winning: Why the fastest 1,500-meter runner did not become the Paris 2024 Olympic champion

Introduction: Considering the season bests before the Olympics as well as individual critical velocities, the question arose, why the obviously fastest runner of the 2024 season, Ingebrigtsen, did not became Olympic champion over the 1,500 m despite being in a top form in Paris. Beside the fact that the winner of the race improved his personal best by 2.9 s in the, the answer may lie in the tactical decision making during the race. Methods: To answer this question a race and performance analysis of Hocker (winner), Kerr (2nd place) and Ingebrigtsen (4th place, world lead 2024) as well as a literature search was carried out to narratively review potential factors of middle-distance race performance in elite athletes that may be modulated by tactical decisions. Results: Based on the data of  Kyle (1979) and assuming a distance of 2 m to the front runner at a running velocity of 7.2 m*s-1 an approximately 3% higher energy consumption can be assumed for the front runner Ingebrigtsen compared to the drafting runners. This corresponds to a theoretical time loss of 1.0 to 1.7 s per 400 m for the front runner. Further, empirical data and models of fatigue support the view of a negative effect of a very fast start, as realized by Ingebrigtsen, on middle-distance performance. Conclusion: On the home straight Hocker outpaced Ingebrigtsen (13.84 s) by almost a second in the last 100 m with 13.05 s, probably because of his well-preserved anaerobic capacity through drafting and running the curves on the inner bend

Frequenzanalyse der Herzratenvariabilität in der Präventivmedizin

Aim was to test the ability of the parameter heart rate variability (HRV) to give insight into different stress-strain relations in the field of preventive medicine. Based on an overview of HRV`s physiology and potential, methodological aspects of HRV-analysis and HRV in the applied setting were explored. Results lead to the assumption that precise and valid measurements of inter-heartbeat-intervals are essential for HRV-analysis. Considering these criteria, HRV can complete the picture drawn by other physiological measures with respect to stress, strain and health risks of an individual

Sex-Specific Relationships Between Interoceptive Accuracy and Emotion Regulation

Over the last years, there has been a resurge in the interest to study the relationship between interoception and emotion. By now, it is well established that interoception contributes to the experience of emotions. However, it may also be possible that interoception contributes to the regulation of emotions. To test this possibility, we studied the relationship between interoception and emotion regulation in a sample of healthy individuals (n = 84). We used a similar heartbeat detection task and a similar self-report questionnaire for the assessment of interoceptive accuracy and emotion regulation as in previous studies. In contrast to previous studies, we differentiated between male and female individuals in our analyses and controlled our analyses for individual characteristics that may affect the relationship between interoceptive accuracy and emotion regulation. We found sex-differences in interoceptive accuracy and emotion regulation that amounted to a sex-specific relationship between interoceptive accuracy and emotion regulation: Whereas interoceptive accuracy was related to reappraisal but not to suppression in male individuals, interoceptive accuracy was unrelated to reappraisal and suppression in female individuals. These findings indicate that the relationship between interoception and emotion regulation is far more complex than has been suggested by previous findings. However, these findings nonetheless support the view that interoception is essential for both, the regulation and experience of emotions

It's Harder to Push, When I Have to Push Hard—Physical Exertion and Fatigue Changes Reasoning and Decision-Making on Hypothetical Moral Dilemmas in Males

Despite the prevalence of physical exertion and fatigue during military, firefighting and disaster medicine operations, sports or even daily life, their acute effects on moral reasoning and moral decision-making have never been systematically investigated. To test the effects of physical exertion on moral reasoning and moral decision-making, we administered a moral dilemma task to 32 male participants during a moderate or high intensity cycling intervention. Participants in the high intensity cycling group tended to show more non-utilitarian reasoning and more non-utilitarian decision-making on impersonal but not on personal dilemmas than participants in the moderate intensity cycling group. Exercise-induced exertion and fatigue, thus, shifted moral reasoning and moral decision-making in a non-utilitarian rather than utilitarian direction, presumably due to an exercise-induced limitation of prefrontally mediated executive resources that are more relevant for utilitarian than non-utilitarian reasoning and decision-making

Oxyhemoglobin Concentration and Oxygen Uptake Signal During Recovery From Exhaustive Exercise in Healthy Subjects—Relationship With Aerobic Capacity

This proof of concept study is dedicated to the quantification of the short-term recovery phase of the muscle oxygenation and whole-body oxygen uptake kinetics following an exhaustive cycling protocol. Data of 15 healthy young participants (age 26.1 ± 2.8 years, peak oxygen uptake 54.1 ± 5.1 mL∗min-1∗kg-1) were recorded during 5 min cool down-cycling with a power output of 50 W on an electro-magnetically braked cycle ergometer. The oxygen uptake (VO2) signal during recovery was modeled by exponential function. Using the model parameters, the time (T1/2) needed to return VO2 to 50% of VO2peak was determined. The Hill’s model was used to analyze the kinetics of oxyhemoglobin concentration (Sm, %), non-invasively recorded by near-infrared spectroscopy (NIRS) over the M. vastus lateralis. Analysis of the Pearson correlation results in statistically significant negative relationships between T1/2 and relative VO2peak (r = −0.7). Relevant significant correlations were determined between constant defining the slope of VO2 decrease (parameter B) and the duration of the anaerobic phase (r = −0.59), as well as between Hill’s coefficient and average median Smmax for the final 2 min of recovery. The high correlation between traditional variables commonly used to represent the cardio-metabolic capacity and the parameters of fits from exponential and Hill models attests the validity of our approach. Thus, proposed descriptors, derived from non-invasive NIRS monitoring during recovery, seem to reflect aerobic capacity. However, the practical usefulness of such modeling for clinical or other vulnerable populations has to be explored in studies using alternative testing protocols.</jats:p