Parasympathetic baroreflexes and heart rate variability during acute stage of sport concussion recovery.

PRIMARY OBJECTIVE: To assess and compare the parasympathetic state of individuals in healthy vs concussion groups, by measuring cardiovascular metrics under resting and baroreflex conditions using a squat-stand manoeuvre. RESEARCH DESIGN: This was a retrospective mixed-method study, with participants who sustained a medically diagnosed sport concussion (n = 12), being tested within 72-hours post-injury. METHODS AND PROCEDURES: Participant's heart rate (Electrocardiogram, ECG) and blood pressure (finger plethysmography) data was collected during rest and during 10-second squat-stands (10SS, 0.05 Hz). Blood pressure and heart rate standard deviation data was analysed in the 0-5 seconds and 6-10 seconds periods of squatting and standing. Resting and baroreflex ECG data were analysed via Fourier Transformations for %Low Frequency and %High Frequency (%LF and %HF). RESULTS: The control group alleviated more pressure and had a significantly higher standard deviation of heart rate during the 6-10 seconds of squatting (p < 0.05). Overall heart rate standard deviation in the concussion group was significantly lower than healthy controls when standing (p < 0.05). There were no differences in %LF and % HF between groups or between rest and 10SS. CONCLUSION: This study provides preliminary evidence that autonomic function is dysregulated following mTBI within the initial 72 hours of injury.

Effect of Preexercise Creatine Ingestion on Muscle Performance in Healthy Aging Males.

Preexercise creatine supplementation may have a beneficial effect on aging muscle performance. Using a double-blind, repeated measures, crossover design, healthy males (N = 9, 54.8 ± 4.3 years; 92.9 ± 11.5 kg; 179.2 ± 11.1 cm) were randomized to consume creatine (20 g) and placebo (20 g corn starch maltodextrin), on 2 separate occasions (7 days apart), 3 hours before performing leg press and chest press repetitions to muscle fatigue (3 sets at 70% 1-repetition maximum; 1 minute rest between sets). There was a set main effect (p ≤ 0.05) for the leg press and chest press with the number of repetitions performed decreasing similarly for creatine and placebo. These results suggest that a bolus ingestion of creatine consumed 3 hours before resistance exercise has no effect on upper or lower-body muscle performance in healthy aging males.