time of day on the different fields to minimize the influence of temperature and humidity on performance and metabolic response. Instrumentation Six digital (120 frames/s @ 1080 p) cameras (GoPro Hero4, San Mateo, CA) were positioned to record the 30-m sprint and agility course. The cameras were
Michael E. Hales and John D. Johnson II
Samuel N. Cheuvront, Robert J. Moffatt, Kyle D. Biggerstaff, Shawn Bearden and Paul McDonough
Claims that ENDUROX™ enhances performance by altering metabolic responses to exercise were tested. In a double-blind crossover design, 10 male subjects were randomly assigned to consume 400 mg of placebo or 800 mg ENDUROX™ for 7 days. Cycle ergometry was performed for 30 minutes at 25%, followed by 10 min at 65% of peak oxygen consumption. After a 1-week washout period, subjects performed the identical exercise protocol following 7 days of reciprocal supplemental conditions. Expired gases were collected and analyzed continuously for oxygen consumption, minute ventilation, and respiratory exchange ratio. Heart rate, blood pressure, rating of perceived exertion, blood lactate, and serum glycerol data were also collected at regular intervals. A two-way ANOVA with repeated measures revealed no significant main or interaction effects involving group differences (p > 0.05) between trials for any variable during rest, 25% or 65% (VO2 peak), or recovery. Our findings do not support the ergogenic claims for ENDUROX™.
Ya Jun Chen, Stephen H. Wong, Chun Kwok Wong, Ching Wan Lam, Ya Jun Huang and Parco M. Siu
This study examined the effect of ingesting 3 isocaloric meals with different glycemic indices (GI) and glycemic loads (GL) 2 hr before exercise on metabolic responses and endurance running performance. Eight male runners completed 3 trials in a randomized order, separated by at least 7 days. Carbohydrate (CHO) content (%), GI, and GL were, respectively, 65%, 79, and 82 for the high-GI/high-GL meal (H-H); 65%, 40, and 42 for the low-GI/low-GL meal (L-L); and 36%, 78, and 44 for the high-GI/low-GL meal (H-L). Each trial consisted of a 1-hr run at 70% VO2max, followed by a 10-km performance run. Low-GL diets (H-L and L-L) were found to induce smaller metabolic changes during the postprandial period and during exercise, which were characterized by a lower CHO oxidation in the 2 trials (p < .05) and a concomitant, higher glycerol and free-fatty-acid concentration in the H-L trial (p < .05). There was no difference, however, in time to complete the preloaded 10-km performance run between trials. This suggests that the GL of the preexercise meal has an important role in determining subsequent metabolic responses.
Manuel Lugo, William M. Sherman, Gregory S. Wimer and Keith Garleb
This study examined the effects of consuming the same amount of carbohydrate in solid form, liquid form, or both on metabolic responses during 2 hrs of cycling at 70% peak VO2 and on cycling time-trial performance. Subjects consumed 0.4 g carbohydrate/kg body mass before and every 30 min during exercise. The liquid was a 7% carbohydrate-electrolyte beverage and the solid was a sports bar (1171 kJ) in which 76%, 18%, and 6% of total energy was derived from carbohydrate, fat, and protein, respectively. Blood obtained at baseline, before exercise, and every 30 min was analyzed for glucose, insulin, lactate, hemoglobin, hematocrit, and plasma volume. There were no differences among the treatments for the blood parameters. Total carbohydrate oxidation and time-trial performance were also similar among treatments. Under thermoneutral conditions with equal liquid inges-tion, the metabolic and performance responses are similar when consuming carbohydrate as a liquid, solid, or in combination during prolonged, moderate intensity cycling.
Andrea Nicolò, Ilenia Bazzucchi, Mauro Lenti, Jonida Haxhi, Alessandro Scotto di Palumbo and Massimo Sacchetti
To investigate the effects of work-to-rest-ratio manipulation on neuromuscular and metabolic responses during 2 high-intensity intermittent training (HIT) protocols to exhaustion. Since different exercise durations were expected, the authors hypothesized that the protocol registering a longer duration would have a more pronounced effect on neuromuscular responses, while the other would challenge the cardiopulmonary system more.
Thirteen competitive cyclists (age 19 ± 2 y) performed a preliminary incremental test to identify their maximal power output and 2 intermittent protocols to exhaustion (40:20s and 30:30s) at a fixed work rate of 135%Pmax interspersed by passive recovery. Surface electromyographic (sEMG) parameters (including muscle-fiber conduction velocity), cardiopulmonary parameters, and blood lactate concentration [La−] were recorded.
Time to exhaustion and total work were significantly higher for the 30:30s (38 ± 13 min, 495 ± 161 kJ) than for the 40:20s (10 ± 3 min, 180 ± 51 kJ). No differences were found in sEMG parameters for the 2 protocols. Mean and peak values of VO2, heart rate, ventilatory parameters (except for the peak value of respiratory frequency), and [La−] were significantly higher in the 40:20s than in the 30:30s.
These results do not support the hypothesis that a longer time spent at high intensity has a more pronounced effect on neuromuscular responses, as no differences in EMG parameters were found in the 2 HIT protocols. Regarding metabolic responses, while the 40:20s led to maximal values of VO2, [La−], and ventilatory parameters within a few minutes, the 30:30s allowed maintenance of moderately high values for a considerably longer period, especially for [La−] and ventilatory parameters.
Amy L. Nikolai, Brittany A. Novotny, Cortney L. Bohnen, Kathryn M. Schleis and Lance C. Dalleck
The purposes of this study were (1) to assess the cardiovascular and metabolic responses to water aerobic exercise and (2) to determine if water aerobics exercise meets the American College of Sports Medicine (ACSM) guidelines for improving and maintaining car-diorespiratory fitness.
Fourteen men and women—mean ± SD age 57.4 ± 7.6 y, height 171.3 ± 7.8 cm, weight 89.9 ± 13.9 kg, body-fat percentage 32.5% ± 5.8%, and maximal oxygen uptake (VO2max) 31.0 ± 8.3 mL · kg−1 · min−1—completed a maximal treadmill exercise test and a 50-min water aerobics session. Cardiovascular and metabolic data were collected via a portable calorimetric measurement system.
Mean exercise intensity was 43.4% of heart-rate reserve and 42.2% of maximal oxygen uptake reserve. Training intensity in metabolic equivalents was 4.26 ± 0.96. Total net energy expenditure for the exercise session was 249.1 ± 94.5 kcal/session.
Results indicate that water aerobics is a feasible alternative to land-based exercise for middle-aged and older adults that fulfills the ACSM guidelines for improving and maintaining cardiorespiratory fitness.
Santiago Lopez, Jan G. Bourgois, Enrico Tam, Paolo Bruseghini and Carlo Capelli
To explore the cardiovascular and metabolic responses of 9 Optimist sailors (12.7 ± 0.8 y, 153 ± 9 cm, 41 ± 6 kg, sailing career 6.2 ± 1 y, peak oxygen uptake [V̇O2peak] 50.5 ± 4.5 mL · min−1 · kg−1) during on-water upwind sailing with various wind intensities (W).
In a laboratory session, peak V̇O2, beat-by-beat cardiac output (Q̇), mean arterial blood pressure (MAP), and heart rate (f H) were measured using a progressive cycle ramp protocol. Steady-state V̇O2, Q̇, MAP, and f H at 4 submaximal workloads were also determined. During 2 on-water upwind sailing tests (constant course and with tacks), W, Q̇, MAP, and f H were measured for 15 min. On-water V̇O2 was estimated on the basis of steady-state f H measured on water and of the individual ΔV̇O2/Δf H relationship obtained in the laboratory.
V̇O2, f H, and Q̇ expressed as percentage of the corresponding peak values were linearly related with W; exercise intensity during on-water sailing corresponded to 46–48% of V̇O2peak. MAP and total vascular peripheral resistance (TPR = MAP/Q̇) were larger (P < .005) during on-water tests (+39% and +50%, respectively) than during cycling, and they were correlated with W. These responses were responsible for larger values of the double (DP) and triple (TP) products of the heart during sailing than during cycling (P < .005) (+37% and +32%, respectively).
These data indicate that the cardiovascular system was particularly stressed during upwind sailing even though the exercise intensity of this activity was not particularly high.
Heather K. Vincent, Laura A. Zdziarski, Kyle Fallgatter, Giorgio Negron, Cong Chen, Trevor Leavitt, MaryBeth Horodyski, Joseph G. Wasser and Kevin R. Vincent
energy expenditure and oxygen use (relative and per unit distance) were considered negligible to large ( d range = 0.05–0.80). Table 2 Average Metabolic Responses During the 4 Running Conditions Control Full bottle Half-full bottle Hydration belt P Effect-size range, d HR, bpm 157 (12) 162 (12) 163 (16
Emma Stevenson, Clyde Williams and Helen Biscoe
This study investigated the metabolic responses to high glycemic index (HGI) or low glycemic index (LGI) meals consumed during recovery from prolonged exercise. Eight male, trained athletes undertook 2 trials. Following an overnight fast, subjects completed a 90-min run at 70% VO2max. Meals were provided 30 min and 2 h following cessation of exercise. The plasma glucose responses to both meals were greater in the HGI trial compared to the LGI trial (P < 0.05). Following breakfast, there were no differences in the serum insulin concentrations between the trials; however, following lunch, concentrations were higher in the HGI trial compared to the LGI trial (P < 0.05). This suggests that the glycemic index of the carbohydrates consumed during the immediate post-exercise period might not be important as long as sufficient carbohydrate is consumed. The high insulin concentrations following a HGI meal later in the recovery period could facilitate further muscle glycogen resynthesis.
Daniela A. Rubin, Diobel M. Castner, Hoang Pham, Jason Ng, Eric Adams and Daniel A. Judelson
During childhood, varying exercise modalities are recommended to stimulate normal growth, development, and health. This project investigated hormonal and metabolic responses triggered by a resistance exercise protocol in lean children (age: 9.3 ± 1.4 y, body fat: 18.3 ± 4.9%), obese children (age: 9.6 ± 1.3 y, body fat: 40.3 ± 5.2%) and lean adults (age: 23.3 ± 2.4 y, body fat: 12.7 ± 2.9%). The protocol consisted of stepping onto a raised platform (height = 20% of stature) while wearing a weighted vest (resistance = 50% of lean body mass). Participants completed 6 sets of 10 repetitions per leg with a 1-min rest period between sets. Blood samples were obtained at rest preexercise, immediately postexercise and 2 times throughout the 1-hr recovery to analyze possible changes in hormones and metabolites. Children-adult differences included a larger exercise-induced norepinephrine increase in adults vs. children and a decrease in glucagon in children but not adults. Similarities between adults and children were observed for GH-IGF-1 axis responses. Metabolically, children presented with lower glycolytic and increased fat metabolism after exercise than adults did. Obesity in childhood negatively influenced GH, insulin, and glucose concentrations. While adults occasionally differed from children, amount of activated lean mass, not maturation, likely drove these dissimilarities.