Expression of VO2peak in Children and Youth, with Special Reference to Allometric Scaling.

The aim of this review was to highlight research that has focused on examining expressions of peak oxygen uptake (VO2peak) in children and youth, with special reference to allometric scaling. VO2peak is considered the highest VO2 during an increasing workload treadmill or bicycle ergometer test until volitional termination. We have reviewed scholarly works identified from PubMed, One Search, EBSCOhost and Google Scholar that examined VO2peak in absolute units (L·min(-1)), relative units [body mass, fat-free mass (FFM)], and allometric expressions [mass, height, lean body mass (LBM) or LBM of the legs raised to a power function] through July 2015. Often, the objective of measuring VO2peak is to evaluate cardiorespiratory function and fitness level. Since body size (body mass and height) frequently vary greatly in children and youth, expressing VO2peak in dimensionless units is often inappropriate for comparative or explanatory purposes. Consequently, expressing VO2peak in allometric units has gained increased research attention over the past 2 decades. In our review, scaling mass was the most frequent variable employed, with coefficients ranging from approximately 0.30 to over 1.0. The wide variance is probably due to several factors, including mass, height, LBM, sex, age, physical training, and small sample size. In summary, we recommend that since skeletal muscle is paramount for human locomotion, an allometric expression of VO2peak relative to LBM is the best expression of VO2peak in children and youth.

Improving physical activity in daycare interventions.

BACKGROUND: The aim of the study was to objectively determine whether the Nutrition and Physical Activity Self-Assessment for Child Care (NAP SACC) program improved physical activity levels during the school day. METHODS: The study compared the physical activity levels of subjects from 26 daycare centers, randomized into treatment (N=13) and control (N=13) groups. The subjects were 3 to 5 year olds (N=209, 104 males and 105 females; age [years]=3.85±0.8 [mean±standard deviation]), and accelerometry was used to determine the subjects' physical activity levels. Accelerometers were attached to each subject for 2 days before and immediately after a 6-month intervention. Height, mass, and waist were also measured. RESULTS: Regression analyses indicated that the treatment group demonstrated significant increases in moderate and vigorous physical activity, as compared to the control group (F(1, 207)=6.3, p<0.05, Cohen's d=0.30; F(1, 207)=4.7, p<0.05, Cohen's d=0.25, respectively). The treatment group also showed significant increases in total physical activity (F(1, 218)=12.4; p<0.05) from pre- to post-test with significant increases in moderate and vigorous intensity physical activity (F(1, 218)=18.6, p<0.05; F(1, 218)=23.3, p<0.05, respectively). Regression analyses revealed significant increases in height for both groups from pre- to post-tests, but no differences were noted between groups. CONCLUSIONS: Implementation of the NAP SACC program in treatment daycare facilities resulted in significant increases in objectively measured physical activity levels, compared to the control group, demonstrating physical activity improvement in the treatment daycare centers.

Gender comparison of physiologic and perceptual responses in recreational marathon runners.

PURPOSE: The aim of this investigation was to compare gender differences in physiologic and perceptual responses during a 1-h run at recent marathon pace and running economy at three speeds in recreational marathon runners. METHODS: In a counterbalanced design, 10 men and 10 women completed a 1-h treadmill run and a running economy test. Treadmill speed for the 1-h run ranged from 141 to 241 mmin(-1) and 134, 168, and 188 m x min(-1) for running economy. Physiologic parameters (oxygen uptake, carbon dioxide production, pulmonary ventilation, and heart rate) and perceived exertion were measured. Repeated-measures ANOVA was used to compare any gender differences (P < .05) during the 1-h run and a two-way ANOVA was used to compare running economy. With this sample, estimated marathon energy expenditure, body composition, and maximal physiologic function was reported. RESULTS: With the exception of an allometric expression of VO2 (mL x min(-1) kg BW(-0.75)), similar gender physiologic and perceptual responses were found during the 1-h run. Although not significant, the females exercised at a higher percent VO2(max) (8% to 9%) during the run. Similar gender differences were also noted during the running economy tests. CONCLUSIONS: Although the male runners completed a recent marathon significantly faster than the females, similar gender physiologic and perceptual responses were generally found during the 1-h treadmill run and the running economy tests.

Body composition of elite, eumenorrheic and amenorrheic, adolescent cross-country runners.

The purpose of the study was to investigate the seasonal relationship of athletic amenorrhea and body composition in elite, adolescent, cross-country runners. The participants consisted of 28 female adolescent cross-country runners (mean age +/- SD = 15.4 +/- 1.5 years); 17 eumenorrheics and 11 amenorrheics. The participants' body composition was measured pre- and postseason using dual-energy X-ray Absorptiometer (DXA). The eumenorrheics' postseason BMD was significantly greater than the amenorrheics' postseason BMD (F(1,54) = 16.22, p < .05, partial eta2 = .231). The eumenorrheics' postseason bodyweight (F(1,54) = 7.65, p < .05, partial eta2 = .124), BF (F(1,54) = 8.56, p < .05, partial eta2 = .137), and BMC (F(1,54) = 8.52, p < .05, partial eta2 = .136) were significantly greater than the amenorrheic subgroup. There was also a significant seasonal increase in BMD (t(27) = -4.01, p < .05) for the overall group and the eumenorrheic subgroup (t(16) = -3.90, p < .05). Bodyweight best predicted BMD (F(1,26) = 46.434, p < .05, R2 = .641). In the study, athletic amenorrhea was highly associated with lower levels of BMD in the participants, and cross-country running was highly associated with increased BMD.

Energy expenditure and influence of physiologic factors during marathon running.

This study examined energy expenditure and physiologic determinants for marathon performance in recreational runners. Twenty recreational marathon runners participated (10 males aged 41 +/- 11.3 years, 10 females aged 42.7 +/- 11.7 years). Each subject completed a V(.-)O2max and a 1-hour treadmill run at recent marathon pace, and body composition was indirectly determined via dual energy X-ray absorptiometry. The male runners exhibited higher V(.-)O2max (ml x kg(-1) x min(-1)) values (52.6 +/- 5.5) than their female counterparts (41.9 +/- 6.6), although ventilatory threshold (T-vent) values were similar between groups (males: 76.2 +/- 6.1 % of V(.-)O2max, females: 75.1 +/- 5.1%). The male runners expended more energy (2,792 +/- 235 kcal) for their most recent marathon as calculated from the 1-hour treadmill run at marathon pace than the female runners (2,436 +/- 297 kcal). Body composition parameters correlated moderately to highly (r ranging from 0.50 to 0.87) with marathon run time. Also, V(.-)O2max (r = -0.73) and ventilatory threshold (r = -0.73) moderately correlated with marathon run time. As a group, the participants ran near their ventilatory threshold for their most recent marathon (r = 0.74). These results indicate the influence of body size on marathon run performance. In general, the larger male and female runners ran slower and expended more kilocalories than smaller runners. Regardless of marathon finishing time, the runners maintained a pace near their T-vent, and as T-vent or V(.-)O2max increased, marathon performance time decreased.

Comparison of oxygen uptake kinetics and oxygen deficit in severely overweight and normal weight adolescent females.

The purpose of this study was to determine if differences in oxygen uptake kinetics and oxygen deficit existed between normal weight and severely overweight adolescent girls. Subjects included 10 normal weight and 8 severely overweight girls. The participants performed a leg cycling VO2 peak test and a constant load leg cycling test at 80% of the ventilatory threshold (T-vent). In the constant workload test O2 kinetics as indicated by Phase I (VO2 L at 20 sec) and Phase II time constants (t) were determined. Also, the O2 deficit (VO2 L) was measured. As expected significant differences were noted in body composition and VO2 peak relative to mass with normal weight body mass averaging 55.3 ± 7.0 kg, severely overweight 90.5 ± 18.0 kg, % fat normal weight 27.3 ± 3.9%, severely overweight 49.7 ± 4.9% and VO2 peak (ml·kg(-1)·min(-1)) normal weight 32.0 ± 2.7 and severely overweight 22.0 ± 5.3. VO2 peak (l·min(-1)) and T-vent (%VO2 max) were similar between groups. Results revealed similar O2 kinetic responses between groups; phase I kinetics normal weight 0.72 ± 0.15 L; severely overweight 0.75 ± 0.13L, phase II (t) normal weight 41.5 ± 21.3 sec; severely overweight 33.9 ± 22.7 sec. However, the O2 deficit was significantly higher in the severely overweight (0.75 ± 0.15L) when compared to the normal weight group (0.34 ± 0.13L). Correlations ranged from r = -0.15 to 0.51 between VO2 peak (L·min(-1)) or fat weight and phase I, t and O2 deficit. These data generally support previous research concerning the independence of O2 uptake response and body size. Key PointsVO2 (L·min(-1) ) similar between the severely overweight and normal weight female youthPhase I and II O2 kinetic responses similar between severely overweight and normal weight female youthO2 deficit was significantly greater in the severely overweight participants.