Assessment of post-competition peak blood lactate in male and female master swimmers aged 40-79 years and its relationship with swimming performance.

The main purpose of this study was to measure the post-competition blood lactate concentration ([La](b)) in master swimmers of both sexes aged between 40 and 79 years in order to relate it to age and swimming performance. One hundred and eight swimmers participating in the World Master Championships were assessed for [La](b) and the average rate of lactate accumulation (La'; mmol l(-1) s(-1)) was calculated. In addition, 77 of them were also tested for anthropometric measures. When the subjects were divided into 10-year age groups, males exhibited higher [La](b) than women (factorial ANOVA, P < 0.01) and a steeper decline with ageing than female subjects. Overall, mean values (SD) of [La](b) were 10.8 (2.8), 10.3 (2.0), 10.3 (1.9), 8.9 (3.2) mmol l(-1) in women, and 14.2 (2.5), 12.4 (2.5), 11.0 (1.6), 8.2 (2.0) mmol l(-1) in men for, respectively, 40-49, 50-59, 60-69, 70-79 years' age groups. When, however, [La](b) values were normalised for a "speed index", which takes into account swimming speed as a percentage of world record, these sex-related differences, although still present, were considerably attenuated. Furthermore, the differences in La' between males and females were larger in the 40-49 age group (0.34 vs 0.20 mmol l(-1) s(-1) for 50-m distance) than in the 70-79 age group (0.12 vs 0.14 mmol l(-1) s(-1) for 50-m distance). Different physiological factors, supported by the considered anthropometric measurements, are suggested to explain the results.