Muscle glycogen accumulation was determined in six trained cyclists (Trn) and six untrained subjects (UT) at 6 and either 48 or 72 h after 2 h of cycling exercise at approximately 75% peak O2 uptake (VO2 peak), which terminated with five 1-min sprints. Subjects ate 10 g carbohydrate . kg-1 . day-1 for 48-72 h postexercise. Muscle glycogen accumulation averaged 71 +/- 9 (SE) mmol/kg (Trn) and 31 +/- 9 mmol/kg (UT) during the first 6 h postexercise (P < 0.01) and 79 +/- 22 mmol/kg (Trn) and 60 +/- 9 mmol/kg (UT) between 6 and 48 or 72 h postexercise (not significant). Muscle glycogen concentration was 164 +/- 21 mmol/kg (Trn) and 99 +/- 16 mmol/kg (UT) 48-72 h postexercise (P < 0.05). Muscle GLUT-4 content immediately postexercise was threefold higher in Trn than in UT (P < 0.05) and correlated with glycogen accumulation rates (r = 0.66, P < 0.05). Glycogen synthase in the active I form was 2.5 +/- 0.5, 3.3 +/- 0.5, and 1.0 +/- 0.3 micromol . g-1 . min-1 in Trn at 0, 6, and 48 or 72 h postexercise, respectively; corresponding values were 1.2 +/- 0.3, 2.7 +/- 0.5, and 1.6 +/- 0.3 micromol . g-1 . min-1 in UT (P < 0.05 at 0 h). Plasma insulin and plasma C-peptide area under the curve were lower in Trn than in UT over the first 6 h postexercise (P < 0.05). Plasma creatine kinase concentrations were 125 +/- 25 IU/l (Trn) and 91 +/- 9 IU/l (UT) preexercise and 112 +/- 14 IU/l (Trn) and 144 +/- 22 IU/l (UT; P < 0.05 vs. preexercise) at 48-72 h postexercise (normal: 30-200 IU/l). We conclude that endurance exercise training results in an increased ability to accumulate muscle glycogen after exercise.

The Gerkin treadmill protocol overpredicts VO(2max) in healthy men and women and, therefore, should not be used for predicting VO(2max) in individual firefighters, particularly if VO(2max) is a criterion for inclusion or exclusion from duty. At this time, a valid treadmill running test is needed for predicting the VO(2max) value of individual firefighters.

The purpose of this study was to determine the effects of 6 weeks of stretching and moderate-intensity resistance training on older adults’ functional fitness. Twenty-two older adults (69 ± 1 year) participated in a resistance-training program, and 15 (70 ± 4 years) participated in a control group. Training involved 3 sessions per week, each consisting of 1 set of 12–15 repetitions of lower and upper body exercises on resistance machines. Before sessions, participants performed 20 min of stretching exercises. A recently developed test battery (Rikli & Jones, 1999) to assess the physical parameters associated with independent functioning in older adults was performed before and after training. The combined stretching and resistance exercise resulted in significant (p≤ .008) improvements on all the functional tests except the 6-min walk. The results indicate that moderate-intensity resistance training in conjunction with stretching can improve functional fitness in older adults, enabling them to more easily perform activities of daily living.

This study determined whether the effects of acute plasma volume expansion (PVX) or 10 days of training on stroke volume during submaximal cycling and on treadmill maximal oxygen uptake (VO2max) were similar between men and women. Subjects performed a submaximal cycle test and a treadmill test to exhaustion under three conditions: control, PVX, and after training. Cycle peak VO2 (VO2peak) and blood volume were measured before and after training. Training consisted of daily 1-h bouts [30 min at 80% peak heart rate (HRpeak) and ten 2-min intervals at 95% HRpeak alternating with 1-min low-intensity pedaling] on a cycle ergometer for 10 consecutive days. Training increased cycle VO2peak in men [P < 0.05; 3.14 +/- 0.13 vs. 3.42 +/- 0.13 (SE) l/min] and women (2.11 +/- 0.10 vs. 2.37 +/- 0.12 l/min) and increased blood volume in men (67.6 +/- 3.0 vs. 72.3 +/- 3.1 ml/kg) and women (62.7 +/- 2.2 vs. 65.6 +/- 2.4 ml/kg). As a result of the greater blood volume with PVX and with training, stroke volume (ml) during submaximal cycling increased in men (control 110 +/- 4; PVX 123 +/- 4; trained 121 +/- 4) and women (control 87 +/- 5; PVX 95 +/- 6, trained 96 +/- 7). Treadmill VO2max (ml.kg-1.min-1) did not change with PVX despite a 6-7% reduction in hemoglobin concentration, whereas training resulted in an increase in VO2max in men (control 47.9 +/- 2.8; PVX 46.7 +/- 2.8; trained 49.9 +/- 2.6) and women (control 38.0 +/- 1.2; PVX 36.9 +/- 1.2; trained 39.2 +/- 1.2). The effects of PVX or training on stroke volume or VO2max did not differ between men and women. An additional finding was an increase in diastolic and mean blood pressures at 65% of cycle VO2peak with PVX and with training in women. Thus men and women hold similar cardiac reserve capacities for increasing stroke volume and, as a result, VO2max is maintained despite a reduction in hemoglobin concentration. However, gender differences in blood pressure regulation with increased blood volume might exist.

We hypothesized that 10 days of training would enhance cardiac output (CO) and stroke volume (SV) during peak exercise and increase the inotropic response to beta-adrenergic stimulation. Ten subjects [age 26 +/- 2 (SE) yr] trained on a cycle ergometer for 10 days. At peak exercise, training increased O2 uptake, CO, and SV (P< 0.001). Left ventricular (LV) size and function at rest were assessed with two-dimensional echocardiography before (baseline) and after atropine injection (1.0 mg) and during four graded doses of dobutamine. LV end-diastolic diameter increased with training (P < 0.02), whereas LV wall thickness was unchanged. LV contractile performance was assessed by relating fractional shortening (FS) to the estimated end-systolic wall stress (sigmaES). Training increased the slope of the FS-sigmaES relationship (P < 0.05), indicating enhanced systolic function. The increase in slope correlated with increases in CO (r = -0.71, P < 0.05) and SV (r = -0.70, P < 0.05). The increase in blood volume also correlated with increases in CO (r = 0.80, P < 0.01) and SV (r = 0.85, P < 0.004). These data show that 10 days of training enhance the inotropic response to beta-adrenergic stimulation, associated with increases in CO and SV during peak exercise.