Physiological characteristics of the elite adolescent athlete : effect of age and maturity
thesisposted on 12.11.2013 by Stephanie Hemmings
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This thesis examined the physiological characteristics of elite adolescent male and female sports perfonners compared to non-elite adolescents in relation to age and maturity. The determinants of endurance perfonnance in adolescent males was also investigated. In Chapter 3a the reliability of the laboratory tests employed in the thesis were examined. Seven male and 11 female adolescents (age: 13.6 ± 0.7 and 13.3 ± 0.5 years, respectively) perfonned a submaximal oxygen uptake CV02)-blood lactate test and a peak V 02 test on a treadmill, and a maximal 30 s cycle ergometer sprint, on 2 days, 6 weeks apart. Pearson correlation coefficients for male and female data combined were: peak V 02, r = 0.93 (p < 0.01); submaximal V02 at 8.8 km.h-l,r = 0.91 (p < 0.01); and peak power output, r = 0.90 (p < 0.01). T-tests revealed a difference between submaximal V02 of males (t = 8.51; p < 0.01). Mean difference and limits of agreement for peak V 02, submaxima1 V O2 and peak power output, were -0_03 ± 6.4 rnl.kg-l_min-l, -0.8 ± 2.7 rnl.kg-l.min-l, and -11 ± 91 W, respectively_ The laboratory tests employed within this thesis were deemed suitably reliable for use in detecting any physiological differences between elite and non-elite adolescents. In Chapter 4 the physical characteristics and sexual maturity of 109 elite (67 male, 42 female) and 123 non-elite (65 male, 58 female) adolescents (aged 12 to 16 years) were examined. Height, body mass, sum of 4 skinfolds and sexual maturity were compared. Sexual maturity was more advanced in the elite males (main effect group: p < 0.05; main effect group: p = 0.08, n.s.; genital and pubic hair developmerIt, respectively)_ Elite females were older at stages of pubic hair (main effect group:p < 0_01) and breast development (main effect group: p < 0.05) and age at menarche (13.2 ± 0.9 vs. 12.3 ± 0.9 yrs; p < 0.01). The results suggest that elite males were more advanced in sexual maturity with elite females characteristic of late maturers. Chapter 5 examined peak V Oz in 101 elite (65 male, 36 female) and 114 non-elite (62 male, 52 female) adolescents, aged 12 to 16 years. Absolute (A) and relative (R) peak V O2 were higher in elite males and females when compared by age (main effect group: p < 0.01). Also, when compared by sexual maturity absolute and relative peakV02 were higher in elite males (A - main effect group: p < 0.05; genital development; R - main effect group: p < 0.01; pubic hair / genital development) and elite females (A - main effect group: p < 0.01; pubic hair / breast development; R - main effect group: p < 0.01; pubic hair / breast development). Differences in peak V02 between elite and non-elite adolescent males and females cannot be wholly attributed to differences in maturity. Chapter 6 examined submaximal V 02 and blood lactate concentration in 108 elite (66 male, 42 female) and 120 non-elite (64 males, 56 females) adolescents, aged 12 to 16 years. Running at 7, 8.8 and 10.6 km_h-l, non-elite males were more economical (lower submaximal V02; rnl.kg-l.min-l) than elite males when compared by age (main effect group: p < 0.05) and maturity (main effect group: p < 0.01; pubic hair development). In contrast non-elite females were less economical than elite females at equivalent ages (main effect group: p < 0.01) and stages of sexual maturity (main effect group: p < 0.05; p < 0.01; pubic hair and breast development, respectively). Submaxima1 blood lactate concentration was lower in elite males and females when compared by age (main effect group: p < 0.01) and by stage of pubic hair (main effect group: p < 0.01) and genital (main effect group: p < 0.05) and breast development (main effect group: p < 0.01). Superior running economy in the non-elite males may be due to a greater body fatness improving economy, or be due to an uneconomical running gait in the elite males. Superior running economy in the elite girls may have been related to biomechanical factors or the relative contribution from aerobic and anaerobic energy sources. Lower submaximal blood lactate concentration in both elite males and females may be related to the lower relative exercise intensities at each work rate. Chapter 7 examined the determinants of 3 km run performance in 13 active adolescent males aged 15.3 ± 0.4 yrs. Peak V02 (59.8 ± 4.1 m1.kg-1.min-1; range: 52.9 - 67.1) was most highly associated with running performance (13:02 ± 01:27 min:s; range: 10:35- 16:07; r = - 0.90; P < 0.01). Running velocity at peak V02 (16.9 ± 2.2 km.h-1; range: 13.4 - 21.0) also demonstrated a high correlation (r = -0.77; P < 0.01) with performance. Endurance capacity run time (running at a treadmill speed which elicited 83 ± 2 % (range: 81 - 87 %) of peak V~) was the only other variable examined to relate to 3 km performance time (r = -0.77; P < 0.01). Stepwise multiple regression analysis revealed the best predictor of 3 km running time (s) to be a combination of peak V02 (ml.kg-1.min-1) and body mass (kg). Chapter 8 investigated the short-term maximal power output in 63 elite and 39 non-elite males and 39 elite and 57 non-elite females aged 12 to 16 years. Absolute (W) and ratio scaled (W.kg-1) peak power were higher in elite males (p = 0.063, n.s.; p < 0.05; absolute and ratio scaled, respectively) when compared by age. Absolute peak power was lower at age 13 years in elite females, yet higher at subsequent ages compared to non-elite (age x group interaction: p < 0.01). Elite females demonstrated a lower fatigue index (%) when compared by sexual maturity (main effect group: p < 0.05). Superior short-term power output of elite males may be related to advanced sexual maturity and possibly differences in body composition. The [mal chapter examined the longitudinal development of peak V O2, submaximal V O2 (ml.kg-1.min-1), and power output in 11 elite and 5 non-elite males over 2 or 3 consecutive years. Linear additive multilevel regression modeling revealed that sum of skinfolds remained the same in the elite group yet increased in the non-elite. Peak V O2 was greater in the elite males by 9.1 ml.kg-1.min-1, with no change in age. Oxygen uptake at 10.6 km.h-1 declined by 1.2 ml.kg-1.min-1 per yr in each group. Percentage peak V O2 at the same running speed was 12 % lower in the elite and declined by 1.3 % each year in both groups. Also at the same treadmill speed, blood lactate concentration was 1.5 mmoU1 lower in the elite males compared to the non-elite, however there was no decline with age. Optimum running economy and that at 65 and 85 % peak V O2 declined by 8.0, 9.2 and 6.6 ml.kg-1.km-1, respectively, each year, yet was not different between groups. Both peak and mean power output increased disproportionately in the elite group, with percentage fatigue increasing similarly in both groups. Blood lactate 2 min post-sprint increased by 0.94 mmol.r1 per year in both groups, yet increased by - 3.0 mmor at Tanner (1962) pubic hair stage 3. The athletic superiority of young elite male and female performers may be related to advanced maturity in males but later maturity in females. A high peak V 02 is an important characteristic of young elite athletes, and also an important determinant of endurance performance. The influence of running economy upon performance remains to be elucidated, however, young elite athletes are characterised by lower blood lactate concentrations during submaximal exercise. The role of power output to performance appears to be influenced by a maturity-related factor, in addition to training.
- Sport, Exercise and Health Sciences