Effects of prior muscle glycogen depletion level on metabolic response during endurance exercise / 体力科学

Recent studies indicate that exercise with a low muscle glycogen state enhances exercise-induced metabolic adaptation. However, it is unclear whether metabolic adaptation is involved with muscle glycogen depletion level. In this study, we investigated the effects of prior muscle glycogen depletion level on metabolic response during acute continuous exercise. Seven men completed two experimental trials consisting of two exercise sessions per day. During the first session, participants performed either intermittent exercise (IE) at VO₂max (the IE-CE trial) or continuous exercise (CE) at lactate threshold (the CE-CE trial). During the second session, participants performed 60 minutes of CE at lactate threshold. During this second session, fatty acid oxidation (FAO) was calculated. To determine muscle glycogen content and PGC-1α and PDK-4 mRNA abundance, muscle biopsies were taken at rest after the first session and 2 hours after the second session. After the first session, muscle glycogen content was significantly lower in the IE-CE trial (38.1±5.0 mmol/kg w.w.) than in the CE-CE trial (56.7±10.2 mmol/kg w.w.), <i>P</i><0.05. FAO was higher in the IE-CE trial than the CE-CE trial at baseline and 15 minutes after the second session (both <i>P</i><0.05). PGC-1α mRNA abundance increased after exercise (IE-CE, 5.9±2.5; CE-CE, 2.6±1.3-fold; <i>P</i><0.1). PDK-4 mRNA abundance increased significantly after exercise (IE-CE, 22.2±8.8; CE-CE, 31.5±10.6-fold; <i>P</i><0.05). PGC-1α and PDK-4 mRNA were not significantly different between the trials. In conclusion, continuous exercise with a slightly muscle glycogen-depleted state induced similar level of PGC-1α and PDK-4 mRNA expression, but attenuated FAO, compared to exercise with a moderate muscle glycogen-depleted state.

AN EFFECTIVE HIGH-INTENSITY INTERMITTENT EXERCISE PROTOCOL FOR DECREASING SKELETAL MUSCLE GLYCOGEN / 体力科学

The decrease of muscle glycogen may be useful for the improvement of endurance performance. Intense anaerobic exercise requires a high rate of glycogen utilization, but consecutive intense anaerobic exercises induce a pronounced decline of external power and muscle glycogen consumption. We hypothesized that a long rest period between consecutive intense anaerobic exercises may aid in sustaining external power and glycogen consumption. Secondly, we hypothesized that active rest (AR) during the long resting period may be more effective than passive rest (PR).Six subjects performed four 30-second Wingate tests (WAnT) with a 4-minute recovery between each bout (Consecutive method). The subjects also performed a similar exercise procedure, but with a 30-minute seated resting period after the second bout (PR method).The other six male subjects performed four 30-second WAnTs with a 4-minute recovery between each bout, with 30-minutes of cycling at 40% VO₂max after the second bout (AR method). The subjects also performed PR method.The total work during the third and fourth bouts was greatest under the AR condition, followed by the PR condition, and finally the Consecutive method (p<0.05 for all comparisons). Blood lactate concentration during resting period was significantly lower, while muscle glycogen consumption was greater AR method than PR method (p<0.05 for both).A long resting period between consecutive intense anaerobic exercises may prevent the decline in external power and work. Additionally, AR has more favorable effects on muscle glycogen consumption, resulting in very low muscle glycogen levels, even with a small total amount of exercise.

HOME BASED EXERCISE EFFECTS ON COGNITION IN THE SEMI-INDEPENDENT ELDERLY / 体力科学

This study sought to determine whether aerobic exercise training affects cognitive functioning among semi-independent (> 75 years) and independent elderly people. Seventy-six semi-independent and independent elderly subjects were divided into the following groups: semi-independent control (n = 16); semi-independent training (n = 13); independent control (n = 22); independent training (n = 25). During the 12-week intervention, subjects in both training groups performed a bench-stepping exercise at the intensity of the lactate threshold. Subjects were assessed at baseline and post-intervention using the Frontal Assessment Battery test (FAB), the Modified Mini-Mental State Exam (3MS), and a bench-stepping test of aerobic capacity. During the intervention, FAB scores improved only in the semi-independent training group (<i>p</i> = .002), while 3MS and MMSE scores improved in both the semi-independent training (<i>p</i> = .032 and <i>p</i> = .004) and independent training groups (<i>p</i> = .001 and <i>p</i> = .013). FAB and 3MS scores were higher in the semi-independent training (<i>p</i> = .001 and <i>p</i> = .002) compared with the semi-independent control group after the intervention. Finally, post-intervention scores for FAB, and 3MS in the semi-independent training group almost reached the baseline levels of the independent control and independent training groups. These results indicate that moderate intensity bench-stepping exercise training can improve cognitive and frontal lobe functioning in semi-independent elderly people, almost to the level exhibited by independent elderly people.

ANGIOTENSIN I CONVERTING ENZYME GENE INSERTION/DELETION POLYMORPHISM AND HUMAN PHYSICAL PERFORMANCE / 体力科学

Angiotensin I converting enzyme (ACE) gene Insertion/Deletion (I/D) polymorphism was first shown as a genetic factor which influences human physical performance in 1998. Since then, various gene polymorphisms which influence physical performance and trainability have been reported. ACE is a key enzyme which produces angiotensin II in the renin-angiotensin system, and its activity was determined by I/D polymorphism. Many studies indicate that the I/I genotype is frequently found in elite endurance athletes, while the D/D genotype is frequently found in power-oriented elite athletes. Longitudinal studies show that the D/D genotype may contribute to enhanced strength trainability. However, it is still unclear whether the I/I genotype enhances endurance trainability. Therefore, the ACE gene I/D polymorphism can be a genetic factor which influences human physical performance.