Zhaowei Kong

Comparison of High-Intensity Interval Training and Moderate-to-Vigorous Continuous Training for Cardiometabolic Health and Exercise Enjoyment in Obese Young Women: A Randomized Controlled Trial.

Objective The aim of this study was to compare the effects of 5-week high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (MVCT) on cardiometabolic health outcomes and enjoyment of exercise in obese young women. Methods A randomized controlled experiment was conducted that involved thirty-one obese females (age range of 18–30) randomly assigned to either HIIT or MVCT five-week training programs. Participants in HIIT condition performed 20 min of repeated 8 s cycling interspersed with 12 s rest intervals, and those in MVCT condition cycled continuously for 40 min at 60–80% of peak oxygen consumption (V˙O2peak), both for four days in a week. Outcomes such as V˙O2peak, body composition estimated by bioimpedance analysis, blood lipids, and serum sexual hormones were measured at pre-and post-training. The scores of Physical Activity Enjoyment Scale (PAES) were collected during the intervention. Results After training, V˙O2peak increased significantly for both training programs (9.1% in HIIT and 10.3% in MVCT) (p = 0.010, η2 = 0.41). Although MVCT group had a significant reduction in total body weight (TBW, −1.8%, p = 0.034), fat mass (FM, - 4.7%, p = 0.002) and percentage body fat (PBF, −2.9%, p = 0.016), there were no significant between-group differences in the change of the pre- and post-measures of these variables. The HIIT group had a higher score on PAES than the MVCT group during the intervention. For both conditions, exercise training led to a decline in resting testosterone and estradiol levels, but had no significant effect on blood lipids. Conclusion Both HIIT and MVCT are effective in improving cardiorespiratory fitness and in reducing sexual hormones in obese young women; however, HIIT is a more enjoyable and time-efficient strategy. The mild-HIIT protocol seems to be useful for at least maintaining the body weight among sedentary individuals.

Effects of short-term resistance training on serum leptin levels in obese adolescents

The purpose of this study was to examine the effects of a short-term resistance training program on serum leptin concentrations in obese adolescents. Eighteen Chinese obese adolescents participated in the supervised weight management program. Resistance training was conducted three times a week on alternate days for 6 weeks. Body composition [body fat mass (FM) and body lean mass (LM)] determined by dual-energy X-ray absorptiometry, muscle strength and leptin, insulin and glucose were measured before and after training. Subjects demonstrated significantly improved strength of leg, chest and bicep under conditions of stability in weight, FM and LM. There were positive correlations between leptin and body mass index, FM, %FM, waist girth and hip girth, and negative correlations between leptin and %L M at the resting state before and after 6 weeks of resistance training. No significant relationship was found between leptin concentration and the parameters of muscular strength or concentrations of insulin and glucose. Compared to pre-training values, serum leptin levels were not significantly altered, while relative leptin (leptin/FM) decreased significantly after the short-term resistance training. These results indicate that short-term resistance training enhances muscle strength but does not alter leptin levels in obese adolescents with weight and FM stability. The results also suggest that 6 weeks of resistance training decreases the requirement of leptin per unit of FM and improves leptin sensitivity in obese adolescents.

Sex differences in release of cardiac troponin T after endurance exercise

Abstract Context: Post-exercise cardiac troponin release has been extensively described in athletic groups but little attention has been given to any role of sex in mediating this phenomenon. Objective: We compared the release of cardiac troponin T (cTnT) after endurance running in training-experience, biological-age and maturity-matched young male and female runners. Materials and methods: Nineteen male (training history: 2.3 ± 1.0 years; mean age: 16.1 ± 1.2 years; Tanner stage: 3.7 ± 0.6) and 19 female (training history: 2.2 ± 1.0 years; mean age: 15.9 ± 1.4 years; Tanner stage: 4.0 ± 0.4) runners performed a 21 km run with “all-out” effort. Serum cTnT levels were assessed at pre-exercise (Pre-ex) and at 4 h post-exercise (Post-ex). Results: At Pre-ex, cTnT concentrations were below the 99th percentile value (10 ng.l−1) in 32/38 runners. Post-ex cTnT increased in all subjects but the response was substantially higher (p < 0.05) in males [median (range): 210 (20–1360) ng.l−1] than females [median (range): 80 (10–550) ng.l−1]. At Post-ex, 95% (95% confidence interval: 75–99%) of males and 63% (95% confidence interval: 41–81%) of females (p < 0.05) had cTnT concentrations above the cut-off for acute myocardial infarction. Conclusions: The present data suggest that post-exercise cTnT elevation occurs in all runners but is augmented in young male compared to female athletes.

Short sprints (30 s) attenuate post-prandial blood glucose in young healthy males

AIMS Low-volume, high-intensity exercise is a time-efficient method of inducing physiological responses and may also improve glucose homeostasis. Therefore, effects of two different volumes of sprint-interval cycling on post-prandial blood glucose were assessed. METHODS Twenty healthy young males undertook two Wingate anaerobic tests (2WAT), four Wingate anaerobic (4WAT) and without-exercise (CON) 90 min after eating a standard meal. Blood glucose was examined at 60, 90, 105, 120, 135 and 150 min post-prandially. RESULTS 2WAT and 4WAT both accelerated the decrease of blood glucose compared with CON (P<0.05). There were significant reductions at 120 (4.45 ± 0.64 vs. 4.93 ± 0.9 vs. 5.68 ± 0.69), 135 (4.28 ± 0.50 vs. 4.48 ± 0.75 vs. 5.54 ± 0.6) and 150 min (4.64 ± 0.71 vs. 4.71 ± 0.73 vs. 5.36 ± 0.48, all P<0.05). Blood glucose at 120 min was lower after 2WAT than 4WAT (4.45 ± 0.64 vs. 4.93 ± 0.9, P<0.05), this producing a significant statistical interaction between groups and post-exercise time (P<0.005). CONCLUSIONS 2WAT and 4WAT tests both accelerate the post-prandial decrease in blood glucose in young healthy males, 2WAT being superior to 4WAT in producing this response, even though 2WAT is easier to perform and less time consuming.

High-Intensity Interval Training in Normobaric Hypoxia Improves Cardiorespiratory Fitness in Overweight Chinese Young Women

Previous studies have investigated the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness and body composition in overweight populations. However, the additive effect of HIIT and hypoxia on health parameters is not clear. This study compared the effects of HIIT under hypoxic conditions on cardiometabolic function with that under normoxia in overweight Chinese young women. Methods: A double-blind randomized controlled experimental design was applied. Twenty-four sedentary overweight Chinese young women (weight: 68.8 ± 7.0 kg, BMI: 25.8 ± 2.3 kg·m−2) participated in the HIIT under either normoxia (NORM, n = 13, PIO2: 150 mmHg, FIO2: 0.21) or normobaric hypoxia (HYP, n = 11, PIO2: 117 mmHg, FIO2: 0.15) for 5 weeks. HIIT was composed of 60 repetitions of 8 s maximal cycling effort interspersed with 12-s recovery per day, for 4 days per week. Cardiorespiratory fitness [peak oxygen uptake (V·O2peak), and peak oxygen pulse (peak O2 pulse)], serum lipid profile [triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)], and body composition (regional and whole-body), were assessed at pre- and post-intervention during the days beyond the self-reported menstrual phase of the participants. Habitual physical activity and diary behavior were maintained during the intervention period. Results: With similar daily energy intake and physical activity, the increases in V·O2peak [NORM: 0.26 ± 0.37 L·min−1 (+11.8%) vs. HYP: 0.54 ± 0.34 L·min−1 (+26.1%)] and peak O2 pulse (NORM: +13.4% vs. HYP: +25.9%) for HYP were twice-larger than for NORM (p < 0.05). Although the 5-wk HIIT led to significant improvements in the ratios of TC/HDL-C (p = 0.035) and TG/HDL-C (p = 0.027), no significant group effects were found on the serum variables. Further, no significant changes in body composition or serum fasting leptin were observed in either group. Conclusion: 5-wk of HIIT improved cardiorespiratory fitness and blood lipids in overweight Chinese young females, while the additive effect of the HIIT under normobaric hypoxia solely enhanced cardiorespiratory fitness, but not body composition or serum lipid profile.

Effects of 12-Week Endurance Training at Natural Low Altitude on the Blood Redox Homeostasis of Professional Adolescent Athletes: A Quasi-Experimental Field Trial

This field study investigated the influences of exposure to natural low altitude on endurance training-induced alterations of redox homeostasis in professional adolescent runners undergoing 12-week off-season conditioning program at an altitude of 1700 m (Alt), by comparison with that of their counterparts completing the program at sea-level (SL). For age-, gender-, and Tanner-stage-matched comparison, 26 runners (n = 13 in each group) were selected and studied. Following the conditioning program, unaltered serum levels of thiobarbituric acid reactive substances (TBARS), total antioxidant capacity (T-AOC), and superoxide dismutase accompanied with an increase in oxidized glutathione (GSSG) and decreases of xanthine oxidase, reduced glutathione (GSH), and GSH/GSSG ratio were observed in both Alt and SL groups. Serum glutathione peroxidase and catalase did not change in SL, whereas these enzymes, respectively, decreased and increased in Alt. Uric acid (UA) decreased in SL and increased in Alt. Moreover, the decreases in GSH and GSH/GSSG ratio in Alt were relatively lower compared to those in SL. Further, significant interindividual correlations were found between changes in catalase and TBARS, as well as between UA and T-AOC. These findings suggest that long-term training at natural low altitude is unlikely to cause retained oxidative stress in professional adolescent runners.

Influence of recovery duration during 6-s sprint interval exercise on time spent at high rates of oxygen uptake

Background/Objective This study examined whether time spent at high rates of oxygen consumption (VO2) during 6-s sprint interval exercises (SIE) is a function of recovery interval duration. Methods In a randomised crossover study, thirteen male endurance runners performed 40 × 6-s all-out sprints interspersed with 15-s, 30-s and 60-s passive recovery intervals (SIE15, SIE30, and SIE60 trials respectively), and a work duration-matched Wingate-SIE (8 × 30-s all-out sprints with 4-min passive recovery, SIEWin trial). The accumulated exercise time at ≥ 80%, 85%, 90%, 95% and 100% of VO2max, and maximum heart rate (HRmax) in the four trials were compared. Results During the 6-s SIEs, accumulated time spent at all selected high rates of VO2max increased as recovery time decreased, whilst the SIE work rate decreased (p < .05). In SIEWin, although the exercise lasted longer, the time spent at ≥90% VO2max (74 ± 16 s) was significant less than that in SIE15 (368 ± 63 s, p < .05), yet comparable to that in SIE30 (118 ± 30 s, p > .05), and longer than that in SIE60 (20 ± 14 s, p < .05). The differences between the four trials in accumulated time at high percentages of HRmax were similar to those for VO2, although the temporal characteristics of the increases in HR and VO2 during the SIEs were different. Conclusion In conclusion, the duration of the recovery interval in 6-s SIE protocols appears to be a crucial parameter when sprint interval training is prescribed to enhance aerobic capacity. Further, the SIE15 protocol may represent a potential alternative to 30-s SIEWin in the development of time-efficient aerobic training intervention.

Comparing Time Efficiency of Sprint vs. High-Intensity Interval Training in Reducing Abdominal Visceral Fat in Obese Young Women: A Randomized, Controlled Trial

Introduction: High-intensity interval training (HIIT) is an emerging lifestyle intervention strategy for controlling obesity. HIIT consisted of brief all-out supramaximal sprint intervals was termed as sprint interval training (SIT). This study was designed to examine the time-efficient characteristics of SIT in reducing abdominal visceral fat. Methods: A randomized controlled trial was conducted to compare the specific adaptations of SIT (80 × 6 s all-out cycle sprints interspersed with 9 s passive recovery) with those resulting from a HIIT regimen with training volume relatively higher (repeated 4 min bouts of cycling at 90% V˙O2max alternated with 3 min rest, until the work of 400KJ was achieved), and with those of nonexercising control counterparts (CON). Forty-six obese young women (body fat percentage ≥30) received either SIT (n = 16), HIIT (n = 16), or no training (n = 14), 3–4 sessions per week, for 12 weeks. The abdominal visceral fat area (AVFA) and abdominal subcutaneous fat area (ASFA) of the participants were measured through computed tomography scans pre-intervention and post-intervention. Total fat mass and the fat mass of the android, gynoid, and trunk regions were assessed through dual-energy X-ray absorptiometry. Results: Following the intervention, abdominal visceral and subcutaneous fat were reduced markedly (p < 0.05). The reduction in AVFA (−6.31, −9.7 cm2) was not different between SIT and HIIT (p > 0.05), while the reduction in ASFA (−17.4, −40.7 cm2) in SIT was less than that in HIIT (p < 0.05). Less reduction in the fat mass of the trunk (−1.2, −2.0 kg) region was also found in SIT, while the reductions in fat percentage (−1.9%, −2.0%), total fat mass (−2.0, −2.8 kg), and fat mass of the android (−0.2, −0.2 kg), and gynoid (−0.4, −0.3 kg) regions did not differ between the two regimes (p > 0.05). In contrast, the increase in V˙O2max was significant greater following the SIT than HIIT (p < 0.01). No variable changed in CON. Conclusion: Such findings suggest that the lower training load and exercise time commitments of the SIT regime could optimize the time-efficiency advantage of the traditional HIIT, facilitating the abdominal visceral fat reduction in obese young women.

Impact of high‐intensity interval training and moderate‐intensity continuous training on resting and postexercise cardiac troponin T concentration

What is the central question of this study? Does exercise training impact resting and postexercise cardiac troponin T (cTnT) concentration? What is the main finding and its importance? This randomized controlled intervention study demonstrated that 12 weeks of either high‐intensity interval training or moderate‐intensity continuous training largely abolished the exercise‐induced elevation in cTnT when exercise was performed at the same absolute intensity. There was no impact of training on resting cTnT or postexercise appearance of cTnT when exercise was performed at the same relative intensity. These findings provide new information that might help clinicians with decision‐making in relationship to basal and postexercise values of cTnT in individuals with different training status.