Sprint Interval Training: Recovery Format, Enjoyment and Blood Pressure in Inactive Men

ABSTRACT Background: While the efficacy of sprint interval training (SIT) to provide positive health effects in inactive populations is established, feasibility is associated with enjoyment and safety, which are dependent on the acute physiological and perceptual responses. The recovery format likely influences physiological and perceptual responses that occur during and immediately after SIT. It was hypothesized that during SIT interspersed with active recovery periods, enjoyment and blood pressure (BP) values would be higher compared with passive recovery periods, in inactive participants. Methods: Twelve males (mean ± SD; age 23 ± 3 y) completed 3 exercise sessions on a cycle ergometer in a randomized order on separate days: (a) SIT with passive recovery periods between 4 bouts (SITPASS), (b) SIT with active recovery periods between 4 bouts (SITACT), and (c) SITACT with the 4 SIT bouts replaced with passive periods. BP was measured immediately after each bout and every 2 min during a 6 min recovery. Physical activity enjoyment was measured during postexercise recovery. Results: There were no significant differences in physical activity enjoyment or systolic BP between SITPASS and SITACT. Diastolic BP was lower during recovery in SITACT (P = 0.025) and SITPASS (P = 0.027), compared with resting BP. Furthermore, diastolic BP was lower after 6 min of recovery following SITPASS, compared with SITACT (P = 0.01). Conclusion: Exercise enjoyment and acute systolic BP responses were independent of SIT recovery format in inactive men. Reductions in diastolic BP were greater and more prolonged after SIT protocols that included passive recovery periods.

Impact of Moderate Exercise Training on Heart Rate Variability in Obese Adults

ABSTRACT Background: Exercise has been shown to improve heart rate variability (HRV) at rest in healthy subjects. HRV response during and immediately after acute exercise in obese individuals following aerobic exercise training has not been evaluated. The purpose of this study was to examine the effect of 12 weeks of moderate intensity aerobic exercise training on HRV during acute exercise and active postexercise recovery in obese individuals. Methods: Eleven obese individuals (5 men, 6 women; body mass index = 39.2 ± 6.3 kg·m−2] underwent 12 weeks of exercise training at 60% of predicted VO2max, determined via a submaximal treadmill test. Body composition was assessed with dual-energy x-ray absorptiometry. HRV was measured during the final minute in each exercise stage and in recovery and analyzed with Kubios HRV software. Results: Predicted VO2max (baseline: 28.2 ± 3.5 mL·kg−1·min−1 and posttraining: 27.4 mL·kg−1·min−1, P > 0.05) was unchanged and body fat % decreased (46.2% ± 2.2 vs 45.5% ± 7.2, respectively). Initial stage heart rate and postexercise recovery heart rate was lower after training. The high frequency component was greater during the initial exercise stage after training. The low frequency component and the standard deviation of instantaneous beat-to-beat variability were greater during the final exercise stage after training. During cooldown, the root-mean-square of differences between adjacent RR intervals and high frequency normalized units were greater after training. Conclusion: HRV markers were improved during acute exercise stage and active recovery in obese individuals following 12 weeks of moderate intensity exercise training. These results suggest improvements in autonomic function can be seen with reductions in adiposity, independent of cardiorespiratory fitness changes in obese adults.

Combining cooling or heating applications with exercise training to enhance performance and muscle adaptations

Athletes use cold water immersion, cryotherapy chambers, or icing in the belief that these strategies improve postexercise recovery and promote greater adaptations to training. A number of studies have systematically investigated how regular cold water immersion influences long-term performance and muscle adaptations. The effects of regular cold water immersion after endurance or high-intensity interval training on aerobic capacity, lactate threshold, power output, and time trial performance are equivocal. Evidence for changes in angiogenesis and mitochondrial biogenesis in muscle in response to regular cold water immersion is also mixed. More consistent evidence is available that regular cold water immersion after strength training attenuates gains in muscle mass and strength. These effects are attributable to reduced activation of satellite cells, ribosomal biogenesis, anabolic signaling, and muscle protein synthesis. Athletes use passive heating to warm up before competition or improve postexercise recovery. Emerging evidence indicates that regular exposure to ambient heat, wearing garments perfused with hot water, or microwave diathermy can mimic the effects of endurance training by stimulating angiogenesis and mitochondrial biogenesis in muscle. Some passive heating applications may also mitigate muscle atrophy through their effects on mitochondrial biogenesis and muscle fiber hypertrophy. More research is needed to consolidate these findings, however. Future research in this field should focus on 1) the optimal modality, temperature, duration, and frequency of cooling and heating to enhance long-term performance and muscle adaptations and 2) whether molecular and morphological changes in muscle in response to cooling and heating applications translate to improvements in exercise performance.

Postexercise Glucose–Fructose Coingestion Augments Cycling Capacity During Short-Term and Overnight Recovery From Exhaustive Exercise, Compared With Isocaloric Glucose

During short-term recovery, postexercise glucose–fructose coingestion can accelerate total glycogen repletion and augment recovery of running capacity. It is unknown if this advantage translates to cycling, or to a longer (e.g., overnight) recovery. Using two experiments, the present research investigated if postexercise glucose–fructose coingestion augments exercise capacity following 4-hr (short experiment; n = 8) and 15-hr (overnight experiment; n = 8) recoveries from exhaustive exercise in trained cyclists, compared with isocaloric glucose alone. In each experiment, a glycogen depleting exercise protocol was followed by a 4-hr recovery, with ingestion of 1.5 or 1.2 g·kg−1·hr−1 carbohydrate in the short experiment (double blind) and the overnight experiment (single blind), respectively. Treatments were provided in a randomized order using a crossover design. Four or fifteen hours after the glycogen depletion protocol, participants cycled to exhaustion at 70% Wmax or 65% Wmax in the short experiment and the overnight experiment, respectively. In both experiments there was no difference in substrate oxidation or blood glucose and lactate concentrations between treatments during the exercise capacity test (trial effect, p > .05). Nevertheless, cycling capacity was greater in glucose + fructose versus glucose only in the short experiment (28.0 ± 8.4 vs. 22.8 ± 7.3 min, d = 0.65, p = .039) and the overnight experiment (35.9 ± 10.7 vs. 30.6 ± 9.2 min, d = 0.53, p = .026). This is the first study to demonstrate that postexercise glucose–fructose coingestion enhances cycling capacity following short-term (4 hr) and overnight (15 hr) recovery durations. Therefore, if multistage endurance athletes are ingesting glucose for rapid postexercise recovery then fructose containing carbohydrates may be advisable.

Age- and Sex-Related Differences in Recovery From High-Intensity and Endurance Exercise: A Brief Review

Postexercise recovery is a fundamental component for continuous performance enhancement. Due to physiological and morphological changes in aging and alterations in performance capacity, athletes of different ages may recover at different rates from physical exercise. Differences in body composition, physiological function, and exercise performance between men and women may also have a direct influence on restoration processes. Purpose: This brief review examines current research to indicate possible differences in recovery processes between male and female athletes of different age groups. The paper focuses on postexercise recovery following sprint and endurance tests and tries to identify determinants that modulate possible differences in recovery between male and female subjects of different age groups. Results: The literature analysis indicates age- and sex-dependent differences in short- and long-term recovery. Short-term recovery differs among children, adults, and masters. Children have shorter lactate half-life and a faster cardiac and respiratory recovery compared to adults. Additionally, children and masters require shorter recovery periods during interval bouts than trained adults. Trained women show a slower cardiac and respiratory recovery compared to trained men. Long-term recovery is strongly determined by the extent of muscle damage. Trained adults tend to have more extensive muscle damage compared to masters and children. Conclusion: The influence of age and sex on the recovery process varies among the different functional systems and depends on the time of the recovery processes. Irrespective of age and sex, the performance capacity of the individual determines the recovery process after high-intensity and endurance exercise.

Effects of β-hydroxybutyrate treatment on glycogen repletion and its related signaling cascades in epitrochlearis muscle during 120 min of postexercise recovery

We investigated the effects of β-hydroxybutyrate (β-HB), the most abundant type of ketone body in mammals, on postexercise glycogen recovery in skeletal muscle by using an in vitro experimental model. Male ICR mice swam for 60 min and then their epitrochlearis muscles were removed and incubated with either physiological levels of glucose (8 mmol/L) and insulin (60 μU/mL) or glucose and insulin plus 1, 2, or 4 mmol/L of sodium β-HB. Four millimoles per liter β-HB had a significant positive effect on glycogen repletion in epitrochlearis muscle at 120 min after exercise (p < 0.01), while 2 mmol/L of β-HB showed a tendency to increase the glycogen level (p < 0.09), and 1 mmol/L of β-HB had no significant effect. We further investigated the effect of 4 mmol/L β-HB treatment on the signaling cascade related to glycogen repletion in the epitrochlearis muscles throughout a 120-min recovery period. After incubating the muscles in 4 mmol/L of β-HB for 15 min postexercise, the Akt substrate of 160 kDa Thr642 (p < 0.05) and Akt Thr308 (p < 0.05) phosphorylations were significantly increased compared with the control treatment. At the same time point, 5′-AMP–activated protein kinase and acetyl-coenzyme A carboxylase phosphorylations were significantly lower (p < 0.05) in the epitrochlearis muscle incubated with 4 mmol/L of β-HB than in the control muscle. Our results demonstrate that postexercise 4 mmol/L β-HB administration enhanced glycogen repletion in epitrochlearis muscle. Four millimoles per liter β-HB treatment was associated with alternation of the phosphorylated status of several proteins involved in glucose uptake and metabolic/energy homeostasis at the early stage of postexercise.