The purpose of the present study was to define the optimal loads (OL) for eliciting maximal power-outputs (PO) in the leg and arm modes of the 30s Wingate Anaerobic Test (WAnT). Eighteen female and seventeen male physical education students, respectively 20.6 +/- 1.6 and 24.1 +/- 2.5 years old, volunteered to participate. In each of the total five sessions, the test was administered twice on a convertible, mechanically braked cycle-ergometer, once for the legs and once for the arms. The five randomized, evenly-spaced resistance loads ranged from 2.43 to 5.39 Joule per pedal revolution per kg body weight (B. W.) for the legs, and from 1.96 to 3.92 for the arms. The measured variables were mean (MP x kg-1) and peak PO as well as absolute and relative measures of fatigue. A parabola-fitting technique was employed to define the optimal loads from the MP x kg-1 data. The resulting OL were 5.04 and 5.13 Joule x Rev-1 x kg B.W.-1 in the leg and 2.82 and 3.52 in the arm tests for the women and men, respectively. OL were shown to depend on PO magnitude. However, within a two-load span (0.98 Joule x Rev-1 x kg B.W.-1) about the OL, MP x kg-1 did not vary by more than 1.4% in the leg and 2.2% in the arm tests. It is suggested that although the WAnT is rather insensitive to moderate variation in load assignment, improved results could be obtained by using the stated OL as guidelines that may be modified according to individual body build, composition, and, particularly, anaerobic fitness level.

Children differ from adults in many muscular performance attributes such as size-normalized strength and power, endurance, fatigability and the recovery from exhaustive exercise, to name just a few. Metabolic attributes, such as glycolytic capacity, substrate utilization, and VO2 kinetics also differ markedly between children and adults. Various factors, such as dimensionality, intramuscular synchronization, agonist-antagonist coactivation, level of volitional activation, or muscle composition, can explain some, but not all of the observed differences. It is hypothesized that, compared with adults, children are substantially less capable of recruiting or fully employing their higher-threshold, type-II motor units. The review presents and evaluates the wealth of information and possible alternative factors in explaining the observations. Although conclusive evidence is still lacking, only this hypothesis of differential motor-unit activation in children and adults, appears capable of accounting for all observed child-adult differences, whether on its own or in conjunction with other factors.

The purpose of this study was to evaluate the extent of anaerobic glycogenolysis, as indicated by intramuscular lactate concentration, after 10 and 30 s of supramaximal exercise and to compare male and female subjects in this regard. Fifteen males and seven females performed two cycle exercise bouts against a resistance which was standardized so that one pedal revolution resulted in 4.90 J work X kg body wt-1. A muscle biopsy was obtained after 10- and 30-s exercise bouts and analyzed for lactate concentration. The lactate concentrations averaged 36 and 61 mmol X kg dry wt-1 after the 10- and 30-s exercise bouts, respectively. The male subjects had higher (P less than 0.005) lactate concentrations and generated higher (P less than 0.001) power outputs for both exercise bouts. When the mean lactate concentrations were statistically adjusted after controlling for between-group variation in power output, no difference was evident between groups for the 10- or the 30-s lactate value. The results are evidence that pronounced lactate accumulation occurs during supramaximal exercise of a 10-s duration, suggesting that glycolysis can occur within this time frame. This is in contrast to the theory that glycolysis does not occur until endogenous phosphagen levels reach some critically low value, not thought to be obtainable within the first 10 s of supramaximal exercise.

Children recover from physical exertion faster than adults, especially, from high-intensity exercise. It is argued that, qualitatively, this is due mainly to dimensional differences but that, predominantly, it is a quantitative difference, stemming from the lower relative power children can generate and from which they need to recover. Children's lesser power capacity is, in turn, likely due to maturation-dependent neuromotor differences.

The review revisits some child-adult differences relevant to thermoregulation and offers alternatives to accepted interpretations. Morphologically, children have a higher body surface area to mass ratio -- a major factor in "dry" heat dissipation and effective sweat evaporation. Locomotion-wise, children are less economical than adults, producing more heat per unit body mass. Additionally, children need to divert a greater proportion of their cardiac output to the skin under heat stress. Thus, a larger proportion of their cardiac output is shunted away from the body's core and working muscles -- particularly in hot conditions. Finally, under all environmental conditions and allometric comparisons, children's sweating rates are lower than those of adults. The differences appear to suggest thermoregulatory inferiority, but no epidemiological data show higher heat-injury rates in children, even during heat waves. We suggest that children employ a different thermoregulatory strategy. In extreme temperatures, they may indeed be more vulnerable, but under most ambient conditions they are not necessarily inferior to adults. Children rely more on dry heat dissipation by their larger relative skin surface area than on evaporative heat loss. This also enables them to evaporate sweat more efficiently with the added bonus of conserving water better than adults.