Autonomic response to tactical pistol performance measured by heart rate variability.

This study evaluated changes in autonomic tone during a tactical pistol competition. At rest and during a match, heart rate variability (HRV) was examined in 28 healthy subjects. Heart rate variability time-domain variables (including interbeat interval [IBI]) and frequency-domain variables (low frequency [LF], high frequency [HF], total power [TP]) measured during shooting were subtracted from those measured during rest to produce Δs. The shooting task involved several, rapid tactical maneuvers. Raw time to completion and inaccurate shots (points down [PDs]) were recorded and combined to form a match score where lower values indicated superior shooting performance. Mean (±SD) raw time was 135.9 ± 34.1 seconds, PDs were 78 ± 34, and match score was 175.3 ± 39.8. Shooting decreased IBI (i.e., increased heart rate) and LF. ΔLF, ΔHF, and ΔTP were independent of ΔIBI. Raw time was significantly (p ≤ 0.05) correlated to shooting IBI (r = 0.404) and ΔIBI (r = -0.426). Points down were significantly correlated to ΔTP (r = 0.416) and ΔLF (r = 0.376). Match score was significantly correlated to ΔIBI (r = -0.458), ΔHF (r = 0.467), ΔLF (r = 0.377), and ΔTP (r = 0.451). In conclusion, individuals with a greater decrease in IBI (and thus heart rate) performed better by accomplishing the match faster. Individuals with less change in stress-related HRV measures (LF, HF, and TP) performed better through improved accuracy. Thus, HRV-derived sympathetic response is significantly related to shooting performance and should be used to assess marksmanship effectiveness under duress.

Acute effect of breathing exercises on heart rate variability in type 2 diabetes: a pilot study.

BACKGROUND: Type 2 diabetes (T2D) is associated with autonomic nervous system damage resulting in reduced heart rate variability (HRV). Limited evidence suggests yogic breathing exercises may improve indices of HRV. PURPOSE: The purpose of this study was to evaluate the effect of two commonly used yogic breathing exercises on HRV in T2D versus an age-matched, normoglycemic (CON) population. METHODS: Twelve (12) subjects with T2D (7 female, 5 male; 54.9±7.4 years) and 14 CON subjects (12 female, 2 male; 54.7±6.8 years) participated in a breathing protocol consisting of two 10-min bouts of randomly assigned uni-nostril breathing (UNB). UNB bouts were preceded and followed by 5-min periods of dual-nostril paced breathing (PB). HRV was measured by standard deviation of normal-to-normal consecutive heartbeats (SDNN), square root of the mean squared differences in successive normal heartbeats (RMSSD), and total spectral power (TP). All data (except instantaneous heart rate) were log transformed to improve normality. Within-group comparisons were analyzed using analysis of variance with repeated measures, whereas between-group comparisons were analyzed using independent-samples t-test. RESULTS: Between-groups comparisons revealed significant reductions in all measures of HRV at nearly all time points in T2D compared to CON. Within-group comparison demonstrated no significant effect of UNB or PB on HRV in CON. In the T2D group, however, left UNB significantly reduced mean HR (-1.2 bpm, p<0.05) as well as TP (p<0.05). CONCLUSIONS: In summary, neither UNB nor PB had an impact upon HRV in a healthy older population and had a minimal impact in T2D.

Exercise effects on postprandial glycemia, mood, and sympathovagal balance in type 2 diabetes.

OBJECTIVES: To compare the impact of walking with a recreational activity on postprandial glycemia, heart rate variability, and mood state following the dinner meal. DESIGN: Participants with type 2 diabetes (T2D) participated in 3 trials on different days in random order after ingestion of a standardized dinner meal (300 ± 6 kcals). SETTING: University clinical testing laboratory. PARTICIPANTS: Twelve participants (9 female, 3 male; 58.7 ± 2.4 years) with uncomplicated T2D not taking insulin or beta-blocker medications. INTERVENTION: Thirty minutes of self-paced walking on a treadmill (TM), 30 minutes of table tennis played continuously against the iPong robot (TT), and 30 minutes of rest (CON) undertaken 30 minutes after the start of ingestion of the same dinner meal on three occasions within a week. MEASUREMENTS: Blood glucose was measured at 30-minute intervals through 180 minutes starting immediately prior to the dinner meal. Profile of Mood States was completed before and immediately following exercise or rest. Sympathovagal balance (heart rate variability) was measured prior to eating and 30 minutes after trial completion. RESULTS: Compared with TT or CON, TM resulted in significantly lower postprandial blood glucose (P < .05), as well as a greater quantity of physical activity than TT (+72%) or rest (+91%; P < .01). Mean heart rate during TM was significantly greater than during TT (+25.9 beats per minute; P < .01). However, neither mood state nor HRV were significantly different among trials. CONCLUSIONS: Thirty minutes of self-paced walking following the dinner meal may be more effective at lowering postprandial glycemia in T2D than a similar duration of table tennis played continuously against a robot.

Effect of intensity of aerobic training on insulin sensitivity/resistance in recreationally active adults.

Previous research demonstrates that moderate-intensity aerobic exercise improves insulin effectiveness. Whether higher exercise intensities improve insulin action more so is unclear. The purpose of this study was to evaluate the effect of various levels of aerobic intensity on insulin action in young adult men and women. Forty-five healthy subjects (22.2 ± 3.9 years; 169 ± 9 cm; 74.5 ± 17.8 kg) were matched for age, gender, and VO2max and randomly assigned to moderate-intensity (50% heart rate reserve [HRR]), vigorous-intensity (75% HRR), maximal-intensity intervals (95/50% HRR) or a non-exercising control group. Subjects completed a 6-week training protocol on a stationary bicycle ergometer. Weekly duration and frequency of training varied to ensure equivalent energy expenditure across groups. The homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) were used to assess insulin effectiveness. Significant increases occurred after training in VO2max in the vigorous-intensity(15.4%) and maximal-intensity(14.2%) groups (p < 0.01) but not the moderate-intensity or control group. There were no significant changes in insulin effectiveness in any exercise group. Training intensity did not significantly affect insulin effectiveness in a young adult population as assessed by HOMA or QUICKI; it did, however, significantly affect VO2max.

Effects of a combined resistance-plyometric training program on muscular strength, running economy, and Vo2peak in division I female soccer players.

Resistance and plyometric training programs have demonstrated consistent improvements in running economy (RE) in trained and untrained adults in the absence of improvements in maximal oxygen consumption. The purpose of this study was to investigate the effect of a 10-week combined resistance-plyometric training program on the RE and V[Combining Dot Above]O2max in female soccer players. Fifteen Division 1A female soccer players (age 19.0 ± 0.7 years; height 1.67 ± 0.1 m; weight 61.7 ± 8.1 kg) performed a treadmill test for V[Combining Dot Above]O2max and RE at the end of a competitive season (PRE) and after a 10-week training program (POST). Isometric strength was measured in knee flexion and extension. Resistance training was conducted 2 d·wk on nonconsecutive days; plyometric training was conducted separately on different nonconsecutive days. Eleven subjects were included in the PRE-POST analysis (age 19.0 ± 0.8 years; height 1.67 ± 0.5 m; weight 59.9 ± 6.7 kg). Descriptive statistics were compared using analysis of variance with repeated measures with a Bonferroni adjustment, and significance was set at p < 0.05. A significant increase occurred after training in the V[Combining Dot Above]O2peak (10.5%; p = 0.008), time to fatigue (6.9%; p = 0.017), and interpolated maximal speed (3.6%; p = 0.016), despite there being a decrease in the maximal respiratory exchange ratio (2.9%; p = 0.001). There was no significant change in the RE at 9 km·h; however, there was a significant decrease in the percentage of the V[Combining Dot Above]O2peak at 9 km·h (-5.6%; p = 0.02). Maximal isometric strength of knee flexors and extensors did not change. The results suggest a plyometric-agility training program may increase the V[Combining Dot Above]O2peak in female soccer players; however, the effect on RE was equivocal.

Exercise in the treatment and prevention of diabetes.

The inclusion of regular physical activity is critical for optimal insulin action and glycemic control in individuals with diabetes. Current research suggests that Type II diabetes mellitus can be prevented and that all types of diabetes can be controlled with physical activity, largely through improvements in muscular sensitivity to insulin. This article discusses diabetes prevention and the acute and chronic benefits of exercise for individuals with diabetes, along with the importance and impact of aerobic, resistance, or combined training upon glycemic control. To undertake physical activity safely, individuals also must learn optimal management of glycemia.