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The purpose of this study was to investigate the effects of carbohydrate substrate availability on ratings of perceived exertion (RPE) during prolonged submaximal running. Thirty marathon runners were recruited as subjects. A double-blind study design was used in which subjects performed an experimental trial that consisted of a 2.5-hr treadmill run at 75–80% $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ . During the experimenal trial, the subjects in the carbohydrate feeding group ingested a 6% glucose and fructose solution at a rate of approximately 60 g · hr^-1, wheras subjects in the placebo group consumed an equal volume of artificially flavored placebo. Statistical analysis of RPE, respitory exchange ratio, fat at carbohydrate oxidation rate, and blood glucose concentrations indicated that increased carbohydrate substrate availability attenuated the intensity of exertional perceptions during the later stages of prolonged running at 75–80% $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ in marathon runners.

The effects of creatine and creatine plus β-alanine on strength, power, body composition, and endocrine changes were examined during a 10-wk resistance training program in collegiate football players. Thirty-three male subjects were randomly assigned to either a placebo (P), creatine (C), or creatine plus β-alanine (CA) group. During each testing session subjects were assessed for strength (maximum bench press and squat), power (Wingate anaerobic power test, 20-jump test), and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, IGF-1, and sex hormone binding globulin. Changes in lean body mass and percent body fat were greater (P < 0.05) in CA compared to C or P. Significantly greater strength improvements were seen in CA and C compared to P. Resting testosterone concentrations were elevated in C, however, no other significant endocrine changes were noted. Results of this study demonstrate the efficacy of creatine and creatine plus β-alanine on strength performance. Creatine plus β-alanine supplementation appeared to have the greatest effect on lean tissue accruement and body fat composition.

The effect of 10 wk of protein-supplement timing on strength, power, and body composition was examined in 33 resistance-trained men. Participants were randomly assigned to a protein supplement either provided in the morning and evening (n = 13) or provided immediately before and immediately after workouts (n = 13). In addition, 7 participants agreed to serve as a control group and did not use any protein or other nutritional supplement. During each testing session participants were assessed for strength (one-repetition-maximum [1RM] bench press and squat), power (5 repetitions performed at 80% of 1RM in both the bench press and the squat), and body composition. A significant main effect for all 3 groups in strength improvement was seen in 1RM bench press (120.6 ± 20.5 kg vs. 125.4 ± 16.7 at Week 0 and Week 10 testing, respectively) and 1RM squat (154.5 ± 28.4 kg vs. 169.0 ± 25.5 at Week 0 and Week 10 testing, respectively). However, no significant between-groups interactions were seen in 1RM squat or 1RM bench press. Significant main effects were also seen in both upper and lower body peak and mean power, but no significant differences were seen between groups. No changes in body mass or percent body fat were seen in any of the groups. Results indicate that the time of protein-supplement ingestion in resistance-trained athletes during a 10-wk training program does not provide any added benefit to strength, power, or body-composition changes.

Sixteen men completed four trials at random as follows: (Trial A) performance of a single bout of resistance exercise preceded by placebo ingestion (vitamin C); (Trial B) ingestion of 1,500 mg L-arginine and 1,500 mg L-lysine, immediately followed by exercise as in Trial A; (Trial C) ingestion of amino acids as in Trial B and no exercise; (Trial D) placebo ingestion and no exercise. Growth hormone (GH) concentrations were higher at 30,60, and 90 min during the exercise trials (A and B) compared with the resting trials (C and D) (p < .05). No differences were noted in [GH] between the exercise trials. [GH] was significantly elevated during resting conditions 60 min after amino acid ingestion compared with the placebo trial. It was concluded that ingestion of 1,500 mg arginine and 1,500 mg ly sine immediately before resistance exercise does not alter exercise-induced changes in [GH] in young men. However, when the same amino acid mixture is ingested under basal conditions, the acute secretion of GH is increased.

The purpose of this study was to assess the lifting performance of boys (N = 12; age 11.3 ± 0.8 yr), teens (N = 13; age 13.6 ± 0.6 yr), and men (N = 17; age 21.4 ± 2.1 yr) to various rest interval (RI) lengths on the bench press exercise. Each subject performed 3 sets with a 10 repetition maximum load and a 1, 2, and 3 min RI between sets. Significant differences in lifting performance between age groups were observed within each RI for selected sets with boys and teens performing significantly more total repetitions than adults following protocols with 1 min (27.9 ± 3.1, 26.9 ± 3.9, and 18.2 ± 4.1, respectively), 2 min (29.6 ± 1.0, 27.8 ± 3.5, and 21.4 ± 4.1, respectively) and 3 min (30.0 ± 0.0, 28.8 ± 2.4, and 23.9 ± 5.3, respectively) RIs. Significant differences in average velocity and average power between age groups were also observed. These findings indicate that boys and teens are better able to maintain muscle performance during intermittent moderate-intensity resistance exercise as compared with men.

The purpose of this study was to examine the influence of recovery time following a dynamic warm-up (DY) and a static stretch warm-up (SS) on power performance in adolescent athletes. Following baseline measures, 19 males (16.5 ± 1.1 yrs) performed the vertical jump (VJ) and seated medicine ball toss (MB) at the following time points after DY and SS: 2, 6, 10, 14, 18, 22 min. Analysis of variance revealed that VJ was significantly greater following DY than SS at 2, 6, 10, 14 and 18 min. Main effects indicated a significant increase in VJ from baseline at 2 and 6 min following DY (2.6–3.9%) and a significant decrease in VJ from baseline at 2, 6, 10, 14 and 18 min following SS (–3.2% to –7.0%). No significant interaction effects between DY and SS were observed for MB. These findings indicate that lower body power performance in male adolescent athletes can be enhanced following DY as compared with SS during the first 18 min of the post warm-up period.

The aim of this study was to evaluate the effects of integrative neuromuscular training (INT) during physical education (PE) class on selected measures of health- and skill-related fitness in children. Forty children from two 2nd grade PE classes were cluster randomized into either an INT group (n = 21) or a control (CON) group (n = 19). INT was performed 2x/wk during the first ~15 min of each PE class and consisted of body weight exercises. INT and CON participants were assessed for health- and skill-related fitness before and after 8 wks of PE with or without INT, respectively. A significant interaction of group by time was observed in INT participants with improvements noted in push-ups, curl-ups, long jump, single leg hop, and 0.5 mile (0.8 km) run performance (p < .05). These data indicate that INT is an effective and time-efficient addition to PE as evidenced by improvements in health- and skill-related fitness measures in children.

Although pre-event static stretching (SS) is an accepted practice in most youth programs, pre-event dynamic exercise (DY) is becoming popular. The purpose of this study was to examine the acute effects of pre-event SS, DY, and combined SS and DY (SDY) on vertical jump (VJ), medicine-ball toss (MB), 10-yard sprint (SP), and pro-agility shuttle run (AG) in teenage athletes (15.5 ± 0.9 years). Thirty athletes participated in three testing sessions in random order on three nonconsecutive days. Before testing, participants performed 5 min of walking/jogging followed by one of the following 10 min warm-up protocols: a) five static stretches (2 × 30 s), b) nine moderate-to-high-intensity dynamic movements (2 × 10 yards), or c) five static stretches (1 × 30 s) followed by the same nine dynamic movements (1 × 10 yards). Statistical analysis of the data revealed that performance on the VJ, MB, and SP were significantly (p < .05) improved after DY and SDY as compared with SS. There were no significant differences in AG after the 3 warm-up treatments. The results of this study indicate that pre-event dynamic exercise or static stretching followed by dynamic exercise might be more beneficial than pre-event static stretching alone in teenage athletes who perform power activities.

This investigation determined whether carbohydrate ingestion during prolonged moderate-intensity exercise enhanced endurance performance when the exercise was preceded by carbohydrate supercompensation. Seven male trained cyclists performed two trials at an initial power output corresponding to 71 ± 1 % of their peak oxygen consumption. During the trials, subjects ingested either a 6% glucose/sucrose (C) solution or an equal volume of artificially flavored and sweetened placebo (P) every 20 min throughout exercise. Both C and P were preceded by a 6-day carbohydrate supercompensation procedure in which subjects undertook a depletion-taper exercise sequence in conjunction with a moderate- and high-carbohydrate diet regimen. Statistical analysis of time to exhaustion, plasma glucose concentration, carbohydrate oxidation rate, fat oxidation rate, and plasma glycerol concentration indicated that in spite of a carbohydrate supercompensation procedure administered prior to exercise, carbohydrate ingestion during exercise can exert an additional ergogenic effect by preventing a decline in blood glucose levels and maintaining carbohydrate oxidation during the later stages of moderate-intensity exercise.