Purpose: The lack of relationship between lactate threshold (LT) and running performance in older runners, and the increase in LT with age, has not been previously studied in a longitudinal design. We evaluated the cross-sectional and longitudinal changes in LT with age and compared the changes in LT with changes in performance variables. Methods: Fifty-one male and 23 female runners (39-77 yr) performed two graded treadmill exercise tests with minute-by-minute venous blood lactate analysis, separated by 5.8 ± 1.6 yr (mean ± SD). Body composition was determined by hydrodensitometry and training history by questionnaire. Results: There was no change in LBM over time, but significant decreases in V'O2max and training volume irrespective of age and gender (P < 0.05). LT as a percent of V'O2max increased with age (P < 0.05), demonstrated poor stability over time (r = 0.29, P = 0.01) compared with other parameters measured, and changes in LT were not related to changes in fitness or performance. Conclusion: Based upon these findings, we conclude that the LT may be less precise than V'O2max or performance in the prescription of exercise intensities or as an evaluation tool in older individuals. The concept of lactate threshold (LT), a nonlinear increase in serum lactate during increasing exercise intensity, was first described in 1959 (10). Since its inception, LT, usually expressed as a percentage of maximal aerobic capacity, has been utilized to predict running performance as well as prescribe exercise training intensity. Furthermore, the running velocity at the lactate threshold significantly predicts maximum running performance in young individuals (7,9,13). In recent cross-sectional investigations of the characteristics of competitive active master athletes of various ages, we observed a wide range (25-97% of V'O2max) of values for the LT (23,24). Our observations showed that the %V'O2max at LT (64-77%) significantly increased with age in 40- and 50-to 70 yr-old men and women, and that the LT was a poor predictor of maximum performance in the runners (24). These results led us to question the validity of using the LT to predict performance or prescribe an intensity of exercise for active older adults. Why LT predicts performance less precisely in old adults than in young, however, remains unknown. Possible explanations include age-associated changes in physiologic function and/or uncertainty of established laboratory protocols to accurately assess LT in older adults. However, cross-sectional differences in people of various ages may represent cohort variability among age groups studied, rather than true age-related longitudinal trends. These issues of LT and their relationships with V'O2max and performance have not been previously studied in a longitudinal design in older persons. The purpose of this study was therefore to evaluate the cross-sectional and longitudinal changes in LT with age, and compare the changes in this parameter to changes in performance variables. As well, we wanted to determine whether the rate of change in LT over time changed with advancing age. We hypothesized that changes in LT would not accurately reflect changes in aerobic fitness (V'O2max), training volume (miles run per week), or running performance (10-km run time) in active older men and women.
|Number of pages||8|
|Journal||Medicine and Science in Sports and Exercise|
|Publication status||Published - 2003|