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Nancy L. Keim, Amy Z. Belko and Teresa F. Barbieri

Energy expenditure (EE) was measured at specific steady-state work rates to determine if body fat percentage or gender was associated with exercise EE, substrate oxidation, or work efficiency. Body fat percentage (leaner vs. fatter men, 9-15% vs. 20-25% fat; leaner vs. fatter women, 16-24% vs. 32-48% fat) was not related to work efficiency or submaximal EE. Fatness affected substrate oxidation in men but not in women. Compared to fatter men, leaner men had higher fat oxidation (6.7 ± 1.6 vs. 1.4 ± 2.0 mg · kg fat-free mass [FFM]1 · min1; p < .01) and lower carbohydrate oxidation (26.6 ± 4.2 vs. 39.3 ± 5.0 mg ⋅ kg FFM1min1; p< .01) at 60% V˙O2max. When men and women of similar fatness and relative aerobic capacity were compared, men had higher EE measured as kilojoules per minute but similar rates of EE and substrate oxidation per kilogram of FFM at 40-60% V˙O2max. It was concluded that body FFM, not fatness, is a determinant of exercise EE, whereas fatness is associated with differences in exercise substrate oxidation in men. Along with aerobic fitness, gender and fatness should be considered in future studies of exercise substrate oxidation.

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Anni Vanhatalo, Andrew M. Jones and Mark Burnley

The critical power (CP) is mathematically defined as the power-asymptote of the hyperbolic relationship between power output and time-to-exhaustion. Physiologically, the CP represents the boundary between the steady-state and nonsteady state exercise intensity domains and therefore may provide a more meaningful index of performance than other well-known landmarks of aerobic fitness such as the lactate threshold and the maximal O2 uptake. Despite the potential importance to sports performance, the CP is often misinterpreted as a purely mathematical construct which lacks physiological meaning and only in recent years has this concept begun to emerge as valid and useful technique for monitoring endurance fitness. This commentary defines the basic principles of the CP concept, outlines its importance to high-intensity exercise performance, and provides an overview of the current methods available for its assessment. Interventions including training, pacing and prior exercise can be used to alter the parameters of the power-time relationship. A future challenge lies in optimizing such interventions in order to positively affect the parameters of the power-time relationship and thereby enhance sports performance in specific events.

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Abderraouf Ben Abderrahman, Jacques Prioux, Karim Chamari, Omar Ben Ounis, Zouhair Tabka and Hassane Zouhal

The effect of endurance interval training (IT) on hematocrit (Ht), hemoglobin (Hb), and estimated plasma-volume variation (PVV) in response to maximal exercise was studied in 15 male subjects (21.1 ± 1.1 y; control group n = 6, and training group, n = 9). The training group participated in interval training 3 times a week for 7 wk. A maximal graded test (GXT) was performed to determine maximal aerobic power (MAP) and maximal aerobic speed (MAS) both before and after the training program. To determine Ht, Hb concentration, and lactate concentrations, blood was collected at rest, at the end of GXT, and after 10 and 30 min of recovery. MAP and MAS increased significantly (P < .05) after training only in training group. Hematocrit determined at rest was significantly lower in the training group than in the control group after the training period (P < .05). IT induced a significant increase of estimated PVV at rest for training group (P < .05), whereas there were no changes for control group. Hence, significant relationships were observed after training between PVV determined at the end of the maximal test and MAS (r = .60, P < .05) and MAP (r = .76, P < .05) only for training group. In conclusion, 7 wk of IT led to a significant increase in plasma volume that possibly contributed to the observed increase of aerobic fitness (MAP and MAS).

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Timothy A. Brusseau, James Hannon and Ryan Burns

Background:

The purpose of this study was to examine the effect of a Comprehensive School Physical Activity Program (CSPAP) on physical activity and health-related fitness (HRF) in children from low-income families.

Methods:

Participants included 1390 children recruited from kindergarten through sixth grade (mean age = 8.4 ± 1.8 years). Physical activity measures were collected at baseline and at 6 weeks and 12 weeks after program implementation, and HRF measures were collected at baseline and at 12 weeks after program implementation.

Results:

There were significant but weak-to-moderate increases in step counts (mean difference = 603.1 steps, P < .001, d = 0.39) and moderate-to-vigorous physical activity (mean difference = 4.9 minutes, P < .001, d = 0.39) at 12 weeks compared with baseline. There were also significant but moderate increases in Progressive Aerobic Cardiovascular Endurance Run laps (mean difference = 6.5 laps, P < .001, d = 0.47) at 12 weeks compared with baseline. Generalized mixed models respectively yielded 3.02 and 2.34 greater odds that a child would achieve step count and moderate-to-vigorous physical activity standards and 2.26 greater odds that a child would achieve aerobic fitness standards at 12 weeks compared with baseline (P < .001).

Conclusions:

The 12-week CSPAP improved physical activity and HRF in children from low-income families; however, the magnitude of the effects was weak to moderate.

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Marina L. McCready and Bonita C. Long

The purpose of this investigation was to examine the relationship between exercise adherence and the combined effects of locus of control and attitudes toward physical activity. The primary instruments used were the Internal, Powerful Others, and Chance Scales (Levenson, 1974); the Exercise Objectives Locus of Control Scales (developed by the first author); and the Revised Children's Attitudes Toward Physical Activity Inventory (Schutz, Smell, & Wood, 1981a). The subjects were 61 females, ages 15-57 (M = 28), voluntarily participating in 8- to 12-week aerobic fitness programs. Findings indicated only a weak relationship between adherence and the combination of locus of control and attitudes. Results of stepwise regression analysis revealed that two attitude measures were the best predictors of exercise adherence. In general, those subjects who at the outset of the programs had a less positive attitude toward participating in physical activity for continuing social relations and a more positive attitude toward participating in order to reduce stress and tension tended to have a higher percent attendance.

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Fabien Deruelle, Cédric Nourry, Patrick Mucci, Frédéric Bart, Jean-Marie Grosbois, Ghislaine Lensel and Claudine Fabre

This study aimed to analyze the impact of step-duration protocols, 1-min vs. 3-min, on cardiorespiratory responses to exercise, whatever the aerobic-fitness level of sedentary (65.5 ± 2.3 years, n = 8) or highly fit (63.1 ± 3.2 years, n = 19) participants. Heart rate and VO2 at the first and second ventilatory thresholds (VT1, VT2) and maximal exercise were not significantly different between the two protocols. In master athletes, the 3-min protocol elicited significantly lower ventilation at VT2 and maximal exercise (p < .01). In the latter, breathlessness was also lower at maximal exercise (p < .05) than in sedentary participants. In trained or sedentary older adults, VT1, VT2, and VO2max were not influenced by stage duration. According to the lower breathlessness and ventilation, however, the 3-min step protocol could be more appropriate in master athletes. In untrained participants, because the cardiorespiratory responses were similar with the two incremental exercise tests, either of them could be used.

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Jennifer L. Gay, Sara W. Robb, Kelsey M. Benson and Alice White

Background:

The Social Vulnerability Index (SVI), a publicly available dataset, is used in emergency preparedness to identify communities in greatest need of resources. The SVI includes multiple socioeconomic, demographic, and geographic indicators that also are associated with physical fitness and physical activity. This study examined the utility of using the SVI to explain variation in youth fitness, including aerobic capacity and body mass index.

Methods:

FITNESSGRAM data from 2,126 Georgia schools were matched at the census tract level with SVI themes of socioeconomic, household composition, minority status and language, and housing and transportation. Multivariate multiple regression models were used to test whether SVI factors explained fitness outcomes, controlling for grade level (ie, elementary, middle, high school) and stratified by gender.

Results:

SVI themes explained the most variation in aerobic fitness and body mass index for both boys and girls (R 2 values 11.5% to 26.6%). Socioeconomic, Minority Status and Language, and Housing and Transportation themes were salient predictors of fitness outcomes.

Conclusions:

Youth fitness in Georgia was related to socioeconomic, demographic, and geographic themes. The SVI may be a useful needs assessment tool for health officials and researchers examining multilevel influences on health behaviors or identifying communities for prevention efforts.

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Michael J. Davies, Gail P. Dalsky and Paul M. Vanderburgh

This study employed allometry to scale maximal oxygen uptake (V̇O2 max) by body mass (BM) and lean body mass (LBM) in healthy older men. Ratio standards (ml · kg−1 · min−1) derived by dividing absolute V̇O2 max (L · min−1) by BM or LBM often fail to control for the body size variable. The subjects were 73 older men (mean ± SD: age = 69.7 ± 4.3 yrs, BM = 80.2 ± 9.6 kg, height = 174.1 ± 6.9 cm). V̇O2 max was assessed on a treadmill with the modified Balke protocol (V̇O2 max = 2.2 ± 0.4 L · min−1). Body fat (27.7 ± 6.4%) was assessed with dual energy x-ray absorptiometry. Allometry applied to BM and V̇O2 max determined the BM exponent to be 0.43, suggesting that heavier older men are being penalized when ratio standards are used. Allometric scaling applied to LBM revealed the LBM exponent to be 1.05 (not different from the ratio standard exponent of 1.0). These data suggest that the use of ratio standards to evaluate aerobic fitness in older men penalized fatter older men but not those with higher LBM.

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Homero Gustavo Ferrari, Leonardo H.D. Messias, Ivan G.M. Reis, Claudio A. Gobatto, Filipe A.B. Sousa, Camila C.S. Serra and Fúlvia B. Manchado-Gobatto

Background:

Among other aspects, aerobic fitness is indispensable for performance in slalom canoe.

Purpose:

To propose the maximal-lactate steady-state (MLSS) and critical-force (CF) tests using a tethered canoe system as new strategies for aerobic evaluation in elite slalom kayakers. In addition, the relationship between the aerobic parameters from these tests and the kayakers’ performances was studied.

Methods:

Twelve male elite slalom kayakers from the Brazilian national team participated in this study. All tests were conducted using a tethered canoe system to obtain the force records. The CF test was applied on 4 d and analyzed by hyperbolic (CFhyper) and linear (CFlin) mathematical models. The MLSS intensity (MLSSint) was obtained by three 30-min continuous tests. The time of a simulated race was considered the performance index.

Results:

No difference (P < .05) between CFhyper (65.9 ± 1.6 N) and MLSSint (60.3 ± 2.5 N) was observed; however, CFlin (71.1 ± 1.7 N) was higher than MLSSint. An inverse and significant correlation was obtained between MLSSint and performance (r = –.67, P < .05).

Conclusion:

In summary, MLSS and CF tests on a tethered canoe system may be used for aerobic assessment of elite slalom kayakers. In addition, CFhyper may be used as an alternative low-cost and noninvasive method to estimate MLSSint, which is related with slalom kayakers’ performance.

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Carla Cox, Steven Gaskill, Brent Ruby and Sharon Uhlig

The purpose of the present case study was threefold: (a) to estimate intake and expenditure of a dog driver (musher) while participating in the Iditarod, (b) to determine the hydration status of the musher at the completion of the event, and (c) to evaluate training related changes in aerobic capacity and body composition of a long-distance dog sled driver in preparation for and following completion of a 1049-mile (1692-km) sled dog race. Actual energy intake during the Iditarod Sled Dog Race was estimated at 8,921 kilojoules (kJ) per day. Nutrient intake expressed as percentage kJ of total energy (14%, 44% and 42% for protein, carbohydrates, and fat, respectively). Weight loss of .72 kg of body weight indicated an energy deficit of 1819 kJ per day during the race. Total energy needs per day were calculated to be 10,740 kJ/day. An increase in hematocrit and hemoglobin during the race may indicate dehydration during the event. There was an improvement in aerobic fitness during on-snow training as determined by ventilatory threshold and VO2peak data. Fat-free mass was maintained during training (46.4 kg), with a concomitant decrease in fat (2.4 kg). Fat-free mass was also maintained during the 12-day race.