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Purpose: To evaluate the effectiveness of heart-rate variability (HRV) biofeedback in improving autonomic function, mood, and sleep in elite bobsleigh athletes. Methods: Eight Chinese Winter Olympic bobsleigh athletes (age: 24 [2] y, body mass: 89 [15] kg, and height: 184 [5] cm) completed a randomized crossover study with and without HRV biofeedback before a single night’s sleep. HRV biofeedback was provided 35 minutes prior to bedtime in the experimental condition. The assessment of HRV took place 45 and 10 minutes before bedtime. The Profile of Mood States questionnaire was completed 50 and 15 minutes prior to bedtime. Sleep duration and quality were measured through an air-mattress sleep-monitoring system. Results: Sleep efficiency (P = .020; F = 7.831; CI, 0.008 to 0.072) and the percentage of deep sleep duration increased (P = .013; F = 10.875; CI, 0.006 to 0.035), while the percentage of light sleep decreased (P = .034; F = 6.893; CI, −0.038 to −0.002). Presleep HRV biofeedback increased parasympathetic and decreased sympathetic activity. Mood states of anger (P = .006, F = 7.573), panic (P = .031, F = 4.288), tension (P = .011, F = 6.284), depression (P = .010, F = 6.016), fatigue (P = .000, F = 16.901), and total mood disturbance (P = .001, F = 11.225) were reduced before sleep. Conclusion: Presleep HRV biofeedback improved some measures of autonomic function, mood, and sleep quality in Chinese Olympic bobsleigh athletes. Presleep HRV biofeedback provides a practical strategy that may help reduce sleep disturbances during periods of training and competition.

Magnesium supplementation modulates glucose metabolism and inflammation, which could influence exercise performance and recovery. This study investigated the effect of magnesium intake on physiological responses and performance during eccentric exercise and recovery. Nine male recreational runners completed a counterbalanced, double-blind, placebo-controlled, cross-over study, registered at ClinicalTrial.gov. Participants consumed low magnesium diets and were supplemented with 500 mg/day of magnesium (SUP) or placebo (CON) for 7 days prior to a 10 km downhill (− 10%) running time trial (TT), separated by a 2-week washout period. At baseline and 24 h post-TT, maximal muscle force was measured. Interleukin-6 (IL-6), soluble interleukin-6 receptor (sIL-6R) and creatine kinase (CK) were measured at rest, 0 h, 1 h and 24 h post-TT. Muscle soreness was measured at the previous times plus 48 h and 72 h post. Glucose and lactate were measured during the TT. The main effect of condition was detected for IL-6 (SUP: 1.36 ± 0.66 vs CON: 2.06 ± 1.14 pg/ml) (P