Taylor J. Marcell

A longitudinal assessment of change in VO2max and maximal heart rate in master athletes.

PURPOSE The purpose of this study was to determine the longitudinal change in VO2max and HRmax in male and female master endurance runners and to compare these changes based upon gender, age, and change in training volume. METHODS Eighty-six male (53.9 +/- 1.1 yr) and 49 female (49.1 +/- 1.2 yr) master endurance runners were tested an average of 8.5 yr apart. Subjects were grouped by age at first visit, change in VO2max, and change in training volume. Measurements included body composition by hydrostatic weighing, maximal exercise testing on a treadmill, and training history by questionnaire. Data were analyzed by ANOVA and multiple regression. RESULTS VO2max and HRmax declined significantly regardless of gender or age group (P < 0.05). The rate of change in VO2max by age group ranged from -1% to -4.6% per year for men and -0.5% to 2.4% per year for women. Men with the greatest loss in VO2max had the greatest loss in LBM (-2.8 +/- 0.7 kg), whereas women with the greatest loss in VO2max demonstrated the greatest change in training volume (-24.1 +/- 3.0 km.wk-1). Additionally, women with the greatest loss in VO2max (-9.6 +/- 2.6 mL.kg-1.min-1) did not replace estrogen after menopause independent of age. HRmax change did not differ by VO2max change or training volume change in either gender. CONCLUSIONS In conclusion, these data suggest that VO2max declines in male and female master athletes at a rate similar to or greater than that expected in sedentary older adults. Additionally, these data suggest that maintenance of LBM and VO2max were associated in men, whereas in women, estrogen replacement and maintenance of training volume were associated with maintained VO2max.

Eccentric muscle action increases site-specific osteogenic response.

PURPOSE Strain magnitude is known to be a primary determinant of the osteogenic response to loading. However, whether bone adaptation to muscle loading is determined primarily by load magnitude is unclear. The purpose of this study was to determine the contribution of load magnitude from muscle action on the site-specific osteogenic response. METHODS Twenty young women (12 exercise, 8 control) served as subjects. Bone mineral density (BMD) of the whole body and mid-femur segment and body composition were determined by dual-energy x-ray absorptiometry. Knee extension and flexion strengths were determined on a KinCom dynamometer, with surface electromyography of the vastus lateralis muscle. Exercise subjects trained three times weekly for 18 wk on a KinCom. One leg trained using eccentric knee extension and flexion, and the opposite leg trained using concentric knee extension and flexion. RESULTS Eccentric exercise demonstrated greater force production with lower integrated electromyographic signal (IEMG) compared with concentric exercise. Significant increases in muscle strength occurred in both exercised legs (P < 0.05), which were of similar relative change. However, only the eccentric trained leg significantly increased mid-femur segment BMD (+3.9%, P < 0.05) and mid-thigh segment lean mass (+5.2%, P < 0.05). CONCLUSIONS These results suggest that eccentric muscle training is more osteogenic than concentric muscle training and that eccentric training is more efficient by attaining higher force production with lower IEMG.

Influence of weight training exercise and modification of hormonal response on skeletal muscle growth

To investigate the influence of carbohydrate (CHO) consumption on the acute hormonal response, and chronic adaptation to weight lifting exercise, two studies were conducted. Following a four-hour fast, seven young men (21.3 +/- 3.5 y) performed (on two occasions) a nine-station weight lifting protocol, completing 3 sets of 10 repetitions at 75% of 1RM (series 1). Randomly assigned, one session included the ingestion of a non-caloric placebo, and the other, a 6% CHO solution. For series 2, two groups of young men (21.3 +/- 1.5 y) participated in 12 weeks of progressive resistance weight training. Training for one group included the ingestion of a non-caloric placebo, and the other, a 6% CHO solution. In series 1, weight lifting exercise with CHO ingestion significantly (p < 0.05) elevated blood glucose and plasma insulin levels above baseline, as well as that occurring with the placebo. This resulted in a significant blunting of the cortisol response (7% with CHO compared to 99% with placebo). These findings indicate that CHO consumption during weight lifting exercise can modify the acute hormonal response to exercise. With series 2, CHO consumption continued to blunt the cortisol response to exercise during the twelve weeks of training. This is in contrast to significantly elevated cortisol levels observed for the placebo control group. Corresponding with the modified response patterns were differences in muscle growth. Weight training exercise with CHO ingestion resulted in significantly greater gains in both type I (19.1%) and type II (22.5%) muscle fibre area than weight training exercise alone. The difference in the cortisol response accounted for 74% of the variance (r = 0.8579, p = 0.006) of change in type I muscle fibre area, and 52.3% of the variance (r = 0.7231, p = 0.043) of change in type II muscle fibre area. These findings suggest that the modification of the cortisol response associated with CHO ingestion can positively impact the skeletal muscle hypertrophic adaptation to weigh training.

Maximal aerobic power, lactate threshold, and running performance in master athletes.

PURPOSE This study sought to determine how lactate threshold (LT) is related to running performance in older male and female runners, if LT changes significantly with age, and if gender alters the relationship between LT and performance in older runners. METHODS Subjects were 168 master runners (111 men, 57 women) selected from a longitudinal study, who ran at least 10 miles x wk(-1) for 5 yr or more. VO2max was measured on a treadmill and body composition by hydrostatic weighing. Blood samples taken each minute of exercise were analyzed for lactate concentration and LT determined as the breakpoint in lactate accumulation. Performance times and training histories were self-reported by questionnaire. RESULTS Men had significantly greater body mass, fat-free mass (FFM), and VO2max (L x min(-1); mL x kg(-1) x min(-1)) than women. FFM and VO2max (L x min(-1); mL x kg(-1) x min(-1)) declined with age in both men and women. Running performance was significantly different between men and women and declined with age in both. LT (L x min(-1); mL x kg(-1) x min(-1)) was significantly different between men and women, and declined significantly with age in men, whereas LT (%VO2max) did not differ between men and women and increased significantly with age in both. VO2max (mL x kg(-1) x min(-1)) was the most significant predictor of performance in both men and women, whereas LT (L x min(-1)) added to the prediction of 5-km and 10-km performance in women. CONCLUSION The results of this study demonstrate that VO2max (mL x kg(-1) x min(-1)) is a better predictor of performance than LT in older male and female runners. Additionally, LT as a percentage of VO2max increases significantly with age.

Age-related blunting of growth hormone secretion during exercise may not be solely due to increased somatostatin tone

Age-related declines in growth hormone (GH) secretion may result from augmented somatostatin (SRIH) tone and/or diminished GH-releasing hormone (GHRH) secretion. We assessed GH release during exercise without and with pyridostigmine (PYR), which indirectly suppresses SRIH. GH levels were measured throughout exercise and recovery in 12 young men (mean +/- SEM, 20.8 +/- 0.4 years) and seven old men (66.1 +/- 1.9). The area under the GH curve (GH-AUC) was greater in young versus old men during a short-term maximal exercise test (12.9 +/- 2.8 v 1.5 +/- 0.2 ng x min(-1) x mL(-1), P = .002) and a 1-hour 60% maximal (submaximal, 10.0 +/- 1.5 v 3.0 +/- 1.0 ng x min(-1) x mL(-1), P = .001) cycle exercise bout. PYR increased the GH-AUC in young and old men during maximal (20.9 +/- 5.2 v 4.9 +/- 1.8) and submaximal (12.3 +/- 1.6 v 4.7 +/- 1.5) exercise (P < .05). The greater GH response to maximal versus submaximal exercise suggests a role for adrenergic modulation of GHRH during exercise. However, the failure of PYR to restore the responses of the old to those of the young suggests that increased SRIH tone does not completely explain the age difference in GH secretion during exercise.

Longitudinal analysis of lactate threshold in male and female master athletes.

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 [OV0312]O(2max) and training volume irrespective of age and gender (P < 0.05). LT as a percent of [OV0312]O(2max) 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 [OV0312]O(2max) or performance in the prescription of exercise intensities or as an evaluation tool in older individuals.