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Near-infrared spectroscopy (NIRS) is a common tool used to study oxygen availability and utilization during repeated-sprint exercise. However, there are inconsistent methods of smoothing and determining peaks and nadirs from the NIRS signal, which make interpretation and comparisons between studies difficult. To examine the effects of averaging method on deoxyhaemoglobin concentration ([HHb]) trends, nine males performed ten 10-s sprints, with 30 seconds of recovery, and six analysis methods were used for determining peaks and nadirs in the [HHb] signal. First, means were calculated over predetermined windows in the last 5 and 2 seconds of each sprint and recovery period. Second, moving 5-seconds and 2-seconds averages were also applied, and peaks/nadirs were determined for each 40-seconds sprint/recovery cycle. Third, a Butterworth filter was used to smooth the signal, and the resulting signal output was used to determine peaks and nadirs from predetermined time points and a rolling approach. Correlation and residual analysis showed that the Butterworth filter attenuated the "noise" in the signal, while maintaining the integrity of the raw data (r = .9892; mean standardized residual -9.71 × 103 ± 3.80). Means derived from predetermined windows, irrespective of length and data smoothing, underestimated the magnitude of peak and nadir [HHb] compared to a rolling mean approach. Consequently, sprint-induced metabolic changes (inferred from Δ[HHb]) were underestimated. Based on these results, we suggest using a digital filter to smooth NIRS data, rather than an arithmetic mean, and a rolling approach to determine peaks and nadirs for accurate interpretation of muscle oxygenation trends.

Introduction: Magnetic stimulation can be used to assess muscle function by calculating voluntary activation using an interpolated twitch during maximal voluntary contractions (MVCs) and control twitches to potentiated muscle. In this study we assessed the reliability of torque, electromyography (EMG), and voluntary activation variables. Methods: Fifteen men completed 5 testing sessions (2 familiarization and 3 reliability trials) to assess quadriceps femoris muscle function. Intra- and interday reliability levels of torque and EMG variables were estimated using typical error ± 90% confidence limits, expressed as percentage [coefficient of variation (CV)] and intraclass correlation coefficient. The smallest worthwhile change was calculated as 0.2 × between-participant standard deviation. Results: Intra- and interday torque variables for MVC were reliable (CV < 4%, ICC 0.98, and CV < 5%, ICC 0.99, respectively). EMG variables were less reliable than torque variables, with CVs ranging from 7% to 18%. Conclusion: Magnetic stimulation of the femoral nerve is a reliable method for assessing muscle function.

The cerebral blood flow response to high‐intensity interval training (HIIT) remains unclear. HIIT induces surges in mean arterial pressure (MAP), which could be transmitted to the brain, especially early after exercise onset. The aim of this study was to describe regional cerebral blood velocity changes during and following 30 s of high‐intensity exercise. Ten women (age: 27 ± 6 years; VO2max: 48.6 ± 3.8 ml·kg·min−1) cycled for 30 s at the workload reached at V˙O2max followed by 3min of passive recovery. Middle (MCAvmean) and posterior cerebral artery mean blood velocities (PCAvmean; transcranial Doppler ultrasound), MAP (finger photoplethysmography), and end‐tidal carbon dioxide partial pressure (PETCO2; gaz analyzer) were measured. MCAvmean (+19 ± 10%) and PCAvmean (+21 ± 14%) increased early after exercise onset, returning toward baseline values afterward. MAP increased throughout exercise (p, The novel findings of this study are that in young fit women, the acute cerebral blood velocity response to a high‐intensity exercise bout is biphasic and characterized by a rapid increase followed by a return toward baseline values. The subsequent recovery period is also characterized by large cerebral blood velocity elevations.

This study examined the effects of post-exercise cooling on recovery of neuromuscular, physiological, and cerebral hemodynamic responses after intermittent-sprint exercise in the heat. Nine participants underwent three post-exercise recovery trials, including a control (CONT), mixed-method cooling (MIX), and cold-water immersion (10 °C; CWI). Voluntary force and activation were assessed simultaneously with cerebral oxygenation (near-infrared spectroscopy) pre- and post-exercise, post-intervention, and 1-h and 24-h post-exercise. Measures of heart rate, core temperature, skin temperature, muscle damage, and inflammation were also collected. Both cooling interventions reduced heart rate, core, and skin temperature post-intervention (P 0.05). CWI reduced cerebral oxygenation compared to MIX and CONT post-intervention (P

This study aimed to determine the impact of short-term normobaric hypoxia on physiology and performance in highly trained athletes. Twelve (7 male and 5 female) athletes were randomly assigned into two groups and spent 8 h per night for two consecutive nights a week over 3 weeks under either short-term normobaric hypoxia (simulating 3636 m altitude, inspired O2= 13%) or in normobaric normoxia in a single-blind study. Following a 3 week washout period, athletes were then exposed to the other condition. Athletes were tested for maximal oxygen consumption and time to exhaustion on an electromagnetically braked cycle ergometer before and after each treatment in addition to being tested for anaerobic performance (Wingate test) on a modified Monark cycle ergometer. Blood samples were taken throughout the experiment and vastus lateralis muscle biopsies were taken before and after each treatment. Increases in red blood cell count, haematocrit, haemoglobin, platelet number and erythropoietin concentration were observed following short-term normobaric hypoxia. Except for a modest decrease in phosphofructokinase activity following short-term normobaric hypoxia, no changes were observed in muscle enzyme activities, buffer capacity, capillary density or morphology. No performance measures were changed following short-term normobaric hypoxia or normobaric normoxia. Although short-term normobaric hypoxia exposure increased levels of a number of haematological parameters, this was not associated with improved aerobic or anaerobic performance in highly trained athletes.