Older individuals, regardless of how one classifies 'old', are the most rapidly growing portion of the population. Statistics from heat waves and other morbidity-mortality data strongly suggest that older persons are at greater risk of developing life-threatening manifestations of heat stress such as heat stroke. Most laboratory studies have found that ageing is associated with decreased heat tolerance and alterations in thermoregulatory effector responses. What is not so clear is the role of ageing per se in this decreased heat tolerance (as opposed to some concomitant functional decline, e.g. decreasing VO2max, which accompanies ageing across a population). Studies have shown decrements in resting heat tolerance and responses to thermal transients in older adults. With exercise in warm environments, most research has focused on the sweating response and it appears that whether or not sweating rate declines in the elderly is dependent upon the environment studied. In hot dry environments, older persons (of both sexes) consistently secrete sweat at a lower rate than their younger counterparts. However, as humidity of the environment increases, this difference tends to disappear. A key issue which deserves further attention is that of hydration in the elderly, both in terms of body water content and compartmentalisation, and of skin water content. Finally, ageing is often accompanied by other conditions (e.g. hypertension, diabetes, cardiovascular insufficiencies, long term therapeutic drug modalities) which further affect heat tolerance and thermoregulation.

A cross-sectional relationship of fat-free mass to height expressed as a ratio (FFM:ht) is presented for 1103 people aged 6-86 y. Data are presented for 13 specific age groups by gender. By providing information for normal, healthy individuals, these data may be of comparative value for nutritionists and clinicians concerned with body composition of patients with wasting diseases. The data were collected over 20 y in our laboratory by using the same densitometric procedure. A significant increase in FFM:ht occurs during the preadolescent and adolescent years. The adolescent spurt continues for a longer period for boys than for girls, resulting in a significant gender difference beginning at approximately age 16 y and continuing throughout adulthood. A decline in FFM:ht, not statistically significant, appears to occur in men greater than 60 y of age, and a significant decline occurs among women greater than 50 y of age (alpha less than 0.01). Thus, both gender- and age-related trends that have implications for the interpretation of comparative body-composition status are suggested.

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This study compared the oxygen uptake (VO2) and running velocity at which the lactate threshold (LT), the ventilatory threshold (VT), and the maximal lactate steady state (MSSLA), and the maximal VO2 steady state (MSSVO2) occurred in 11 trained male runners (mean age = 22.4 years, range 18-28 years). Each underwent an incremental treadmill test to exhaustion. The LT was defined by a systematic, continuous increase in arterialised venous blood lactate; the VT was determined by an abrupt rise in VE.VO2(-1) without an increase in VE.VCO2(-1). Each subject also completed a series of steady state treadmill runs of 20 minutes duration. The MSSLA was determined as the highest velocity and VO2 at which lactate concentration increased by less than 0.2 mmol.l-1 from minute 10 to minute 20. The MSSVO2 was determined as the highest velocity or VO2 at which a steady state in VO2 was not delayed for more than 3 minutes (with a steady state defined as VO2 within 0.2 l.min-1 of the average VO2 over the last 10 minutes of each test). Each subject also completed a 5 km time trial run to assess performance. No significant differences were found among the four variables expressed either as VO2 or velocity. Significant correlations were found between MSSLA and MSSVO2 (r = 0.74) expressed as VO2, and between MSSLA and MSSVO2 (r = 0.90), MSSVO2 and VT (r = 0.70) and MSSLA and VT (r = 0.67) expressed as velocity. A stepwise regression analysis found MSSLA (expressed as velocity) to be the best predictor of 5 km performance (r = 0.87). It was concluded that (a) MSSLA and MSSVO2 are closely related, and (b) MSSLA is a good predictor of performance and may be an important, objective measure of cardiorespiratory endurance capacity.

The purpose of this study was to investigate possible factors which may account for differences in performance times within a closely-matched group (in terms of performance) of elite distance runners. The runners were training for competition in the 1984 Olympic Games in either the 5000 m or the 3000 m steeplechase events. Each runner's best performance time (BPT) was obtained and a stepwise regression analysis was performed with the following independent variables: age, weight, % body fat, V02 max, aerobic threshold (AerT), and anaerobic threshold (AnT). For the 5000 m-runners, a multiple correlation of age and AnT accounted for 77% of the variance (p < 0.02); for the 3000 m steeplechase runners, body weight alone and body weight and AnT accounted for 94% (p < .01) and 98% (p < .05) of the variance, respectively. The results suggest that, among elite middle-distance runners, these parameters deserve attention as potential predictors of performance.