Run performance of middle-aged and young adult runners in the heat.

The aging process may impair exercise tolerance in the heat. It is not clear whether this impairment is partly due to a reduction in aerobic capacity. To compare the exercise performance and thermoregulatory responses of middle-aged and young adults with similar aerobic capacities and training statuses, 7 middle-aged (54±2 years; 58±4 ml·kg - 1·min - 1) and 7 young (28±1 years; 61±5 ml·kg - 1·min - 1) male competitive endurance runners underwent 2 10-km self-paced and 2 fixed-workload (90% of race speed) runs until fatigue on a treadmill in hot (40°C) and moderate (20°C) environments on separate days. The runners' total time, average speed, rectal temperature, heat storage rate, physiological strain index, sweat rate, sweat sensitivity, number of heat-activated sweat glands and sweat rate per sweat gland were measured or calculated. Body fat, body surface area, body surface area per body mass, training volume and VO2max were similar between the 2 groups. No differences were observed in total time (59±3; 49±3; 27±2; 54±5 min in the middle-aged and 60±2; 49±3; 27±2; 51±4 min in the young group), average speed, rectal temperature, heat storage rate, physiological strain index, sweat rate (17±7; 15±3; 23±7; 13±2 g.m - 2.min - 1 in the middle-aged and 20±5; 14±4; 22±5; 15±4 g.m - 2.min - 1 in the young group) or sweat sensitivity between age groups (p>0.05) in any trial. The number of heat-activated sweat glands (88±14; 80±18; 90±16; 66±14 cm - 2 in the middle-aged and 43±10; 32±10; 37±11; 31±11 cm - 2 in the young group) was higher, and the sweat rate per sweat gland was smaller, in the middle-aged than the young group (p<0.05) in all of the trials. We conclude that running performance and body thermoregulation are similar between young and middle-aged runners with similar aerobic capacities and training statuses under hot and moderate conditions in self-paced and fixed-intensity runs. The decrease observed in the sweat rate per sweat gland in middle-aged men was compensated for by a higher number of heat-activated sweat glands.

Head hair reduces sweat rate during exercise under the sun.

The purpose of this study was to evaluate the effects of human head hair on thermoregulation during exercise carried out under solar radiation. 10 healthy male subjects (mean±SD: 25.1±2.5 yr; height: 176.2±4.0 cm; weight: 73.7±6.7 kg; VO(2max) 56.2±5.3 mLO(2)·kg (-1)·min (-1)) took part in 2 1 h-long trials of continuous exercise on a treadmill at 50% VO2(max) under solar radiation that were separated by at least 2 days. Whereas for the first trial they retained their natural head hair (HAIR), in the second trial their hair was totally shaved (NOHAIR). Several properties were measured, including environmental heat stress (Wet Bulb Globe Temperature index - WBGT, °C), heart rate, rectal temperature, skin temperature, head temperature, and global sweat rate. The main findings were that whereas there was a lower sweat rate in the HAIR condition (HAIR: 7.08±0.79 vs. NOHAIR: 7.67±0.79 g·m (-2)·min (-1); p=0.03), there were no significant differences in any of the other variables between the HAIR and NOHAIR trials. In conclusion, the presence of head hair resulted in a lower sweat rate.

Muscular force is reduced in neurofibromatosis type 1.

OBJECTIVES: To measure muscular force in neurofibromatosis type 1 (NF1) patients. METHODS: The maximal voluntary muscular force (F(max)) was measured in the first 21 volunteer patients without acute health problems at the routine annual examination in the Neurofibromatosis Outpatient Reference Center during October-November (2007). The NF1 individuals were 9 males and 12 females, aged from 7 to 60 years and physically sedentary. The healthy control group was 21 healthy subjects matched to NF1 group by age, sex and physical activity. A handgrip test instrument was used to measure maximal force. To allow comparisons between physically different patients, forearm circumference (cm) was measured with a tape and forearm cross sectional area was derived to express the force per unit of forearm area. Data were compared using a t Student test (P<0.05). RESULTS: The mean F(max) of NF1 male (260-/+136 N) and NF1 female (217-/+76 N) were lower than expected for their sex and age. Healthy men showed greater F(area) (9.8-/+3.2 N x cm(-2)) than NF1 men (5.7-/+2.6 N x cm(-2)) and healthy women (6.7-/+1.6 N x cm(-2)) showed greater F(area) than NF1 females (5.7-/+1.9 N x cm(-2)). CONCLUSION: Maximal voluntary muscle force was reduced in NF1 patients.