Blood glucose following training sessions in runners

Different amount of training affects body composition and performance in High-Intensity Functional Training participants

The effects of High-Intensity Functional Training (HIFT) on body composition and the relationship of the latter with performance are not well defined. In this work we investigated, by means of Dual-energy X-ray Absorptiometry, the relative proportions of fat-, lean soft tissue-, and mineral mass in CrossFit^® (CF, a popular mode of HIFT) participants (n = 24; age, 28.2 ± 3.39 y; BMI, 25.3 ± 2.04 kg/m²) with at least 1 year of CF training experience and weekly amount of training > 10 h/w (n = 13; Higher Training, HT) or < 10 h/w (n = 11; Lower Training, LT) as well as age- matched and BMI-matched physically active controls (CHT, CLT). Performance was assessed in the “Fran” workout. Data were analyzed by one-way or repeated measures ANOVA where needed. Association between variables was assessed with the Pearson’s correlation coefficient r. Partial correlation was used where needed. Results showed that HT performed better than LT in the “Fran” (P < 0.001) and they had higher whole-body bone mineral density (P = 0.026) and higher lean soft mass (P = 0.002), and borderline lower percent fat mass (P = 0.050). The main difference between CF participants (HT, LT) and their respective controls (CHT, CLT) was a lower adiposity in the former. In CF participants, performance positively correlated with appendicular lean soft tissue mass (P = 0.030). It can be concluded that, in CF participants, a higher amount of weekly training improves most notably lean body mass and increases performance in association with increased skeletal muscle mass. CF participation is especially effective in reducing fat mass vs. age- and BMI-matched physically active controls.

Acute effect of a brief bout of exercise on alcohol urges

AIM

To examine whether a brief bout of moderate intensity exercise reduces alcohol urges and mood disturbance in those with alcohol dependence.

DESIGN

A counterbalanced cross-over design (within-subjects).

SETTING

A hospital-based alcohol rehabilitation clinic.

PARTICIPANTS

Twenty males and females [mean (SD) age = 40.1 (8.2) years, mean (SD) Severity of Alcohol Dependence Questionnaire score = 34.2 (13.4)] who had recently completed alcohol detoxification [mean (SD) days since completing detoxification = 3.5 (2.3)].

INTERVENTION

On the first day of experimentation all participants (N = 20) were randomized to undergo one of two conditions, either: (i) a single bout of 10 minutes of moderate intensity cycling (experimental), or (ii) a single bout of 10 minutes of very light intensity cycling (control). On the following day they underwent the remaining condition.

MEASUREMENTS

All participants completed the Alcohol Urge Questionnaire and a six-item measure of mood disturbance at the following times: (i) immediately before exercise (baseline), (ii) during exercise (at 5 minutes), (iii) immediately following exercise, (iv) 5 minutes following exercise and (v) 10 minutes after exercise.

FINDINGS

Relative to baseline, there was a significant decline in alcohol urges for the experimental condition versus control during exercise (P = 0.02) but not at any measurement point following exercise. At baseline, by chance, there was a non-significant tendency for there to be higher ratings of alcohol urges for the experimental condition versus the control. For mood, there was no evidence for significant differences between treatment conditions for baseline versus any subsequent measurement point.

CONCLUSIONS

A brief bout of moderate intensity exercise may provide some short-term relief from alcohol urges during exercise. Further studies are required to replicate the present findings and to confirm whether any moderating effect of exercise on alcohol urges is sustained following exercise.

Fuel kinetics during intense running and cycling when fed carbohydrate

On two occasions, six well-trained, male competitive triathletes performed, in random order, two experimental trials consisting of either a timed ride to exhaustion on a cycle ergometer or a run to exhaustion on a motor-driven treadmill at 80% of their respective peak cycling and peak running oxygen (VO2 max) uptakes. At the start of exercise, subjects drank 250 ml of a 15 g.100 ml-1 w/v [U-14C]glucose solution and, thereafter, 150 ml of the same solution every 15 min. Despite identical metabolic rates [VO2 3.51 (0.06) vs 3.51 (0.10) 1.min-1; values are mean (SEM) for the cycling and running trials, respectively], exercise times to exhaustion were significantly longer during cycling than running [96 (14) vs 63 (11) min; P < 0.05]. The superior cycling than running endurance was not associated with any differences in either the rate of blood glucose oxidation [3.8 (0.1) vs 3.9 (0.4) mmol.min-1], or the rate of ingested glucose oxidation [2.0 (0.1) vs 1.7 (0.2) mmol.min-1] at the last common time point (40 min) before exhaustion, despite higher blood glucose concentrations at exhaustion during running than cycling [7.0 (0.9) vs 5.8 (0.5) mmol.l-1; P < 0.05]. However, the final rate of total carbohydrate (CHO) oxidation was significantly greater during cycling than running [24.0 (0.8) vs 21.7 (1.4) mmol C6.min-1; P < 0.01]. At exhaustion, the estimated contribution to energy production from muscle glycogen had declined to similar extents in both cycling and running [68 (3) vs 65 (5)%]. These differences between the rates of total CHO oxidation and blood glucose oxidation suggest that the direct and/or indirect (via lactate) oxidation of muscle glycogen was greater in cycling than running.