Effect of exercise intensity on exercise-induced lymphocyte apoptosis.

Because lymphocyte apoptosis is significantly elevated immediately following high-intensity exercise in humans, it seems intuitive that the cell death process must be initiated at some point during the task. This study was designed to determine whether exercise-induced lymphocyte apoptosis occurs at a threshold level of intensity, or exists only following maximal or near-maximal exercise intensities. Fourteen untrained subjects completed a discontinuous, incremental treadmill test to exhaustion (.VO(2max)). Blood for films was sampled before the test, immediately after each work stage, and for 1-h postexercise. Blood smears were stained with May-Grünwald Giemsa and lymphocytes were evaluated for characteristic features of apoptosis. The apoptotic index (AI) during exercise at 38 % .VO(2max) was similar to pre-exercise but significantly elevated at an intensity approximating 61 % .VO(2max) (p < 0.0001). Significant increases in apoptosis were noted with additional elevations in exercise intensity (i.e., 76 %, 89 %, and 100 %, p < 0.0001). Following 20 min of recovery, AI was significantly lower than values obtained immediately postexercise (p < 0.0001). Forty minutes of recovery resulted in a further significant decrease (p < 0.0001), and by 1-h postexercise, AI was similar to pre-exercise values. Results indicate that the exercise intensity threshold for inducing an increase in lymphocyte apoptosis occurs between 40 and 60 % .VO(2max). In addition, since values return to baseline within 1 h following exhaustive exercise, it is unlikely that factors responsible for the apoptotic response in lymphocytes maintain a prolonged presence once exercise has been terminated.

Kyphosis in active and sedentary postmenopausal women.

UNLABELLED: EAGAN, M. S., and D. A. SEDLOCK. Kyphosis in active and sedentary postmenopausal women. Med. Sci. Sports Exerc., Vol. 33, No. 5, 2001, pp. 688-695. PURPOSE: This study examined kyphosis in relation to self-reported activity level (sedentary, active) and activity type (weight-bearing land, nonweight-bearing water) in 61 postmenopausal women aged 60-78 yr. METHODS: Specifically, we measured kyphosis, muscle strength (defined as back extensor (BES) and grip (GS) strength), total calcium intake, body fat, height lost since age 30 (HtLost), current activity level for household, leisure and sport activities and their total, as well as occupational and physical activity history and their total. RESULTS: No significant differences (P > 0.05) were found for any variables when subjects were divided into sedentary (N = 18), land (N = 29), and water (N = 14) groups; exercisers (N = 43) and nonexercisers (N = 18); or between the top and bottom tertiles of lifetime active (N = 20) and inactive (N = 20) women. Stepwise multiple regression yielded body fat as the single best predictor of kyphosis accounting for 6.9% of the total variance (P < 0.04) with the resulting equation: kyphosis (degrees) = 22.919 + 0.627*body fat (%) + 0.852*HtLost (cm) + 2.881E-0.03*total calcium intake (mg) (r2 = 0.22, SEE = 7.7). Significant relationships (P < 0.05) included kyphosis with body fat (r = 0.26) and HtLost with age (r = 0.50). Relationships (P < 0.05) regarding muscle strength included: GS and BES with age (r = -0.38, -0.30), HtLost (r = -0.39, -0.36), and occupational activity history (r = 0.28, 0.35), as well as BES with household activity and total activity history (r = 0.28, 0.30). Physical activity history was related (P < 0.05) to current sport, leisure, and total activity history (r = 0.37, 0.42, 0.93, respectively). CONCLUSION: Women who are active when younger seem to be active and stronger as older adults. However, this does not seem to impact kyphosis. The measured variables accounted for a small proportion of kyphosis variance, suggesting that more potent causative factors of this spinal malformation exist.

VO2peak and the gas-exchange anaerobic threshold during incremental arm cranking in able-bodied and paraplegic men.

Resting energy expenditure, peak oxygen uptake (VO2peak) and the gas-exchange anaerobic threshold (Than) were measured during incremental arm cranking (15 W x min(-1)) in six able-bodied (AB) and six paraplegic (P) subjects. Only male subjects with traumatic spinal cord injuries in the area of the 10-12th thoracic segment were included in the P group. All AB and P subjects were physically active. Mean (SE) values for age and body mass were 28 (2) years and 78.9 (3.9) kg for the AB group and 32 (4) years and 70.8 (7.9) kg for the P group (P>0.05). Resting energy expenditure values were not found to be significantly different between AB [5.8 (0.2) kJ x min(-1)] and P [5.1 (0.3) kJ min(-1)] subjects. Mean VO2peak values were 29.3 (2.4) ml x kg(-1) min(-1) and 29.6 (2.2) ml x kg(-1) x min(-1) for the AB and P groups, respectively (P>0.05). Absolute oxygen uptake values measured at two gas-exchange anaerobic threshold (Than) were not significantly different between the two groups. However, the Than occurred at a significantly higher percentage of VO2peak in the P [58.9 (1.7)%] group than in the AB [50.0 (2.8)%] group (P<0.05). Moreover, respiratory exchange ratio (R) values obtained at the Than and at 15, 45, 60, 75 and 90 W of incremental exercise were significantly lower in the P group than in the AB group. Heart rates were significantly elevated at every submaximal work stage (15-120 W) in the P group compared to the AB group (P<0.05). These findings suggest that chronic daily wheelchair activity produces local adaptations in the functional upper-body musculature, which reduce glycogenolysis and increase the rate of lipid utilization (lower R) during arm exercise. These local adaptations may be in part responsible for the significantly higher Than observed for arm exercise in P subjects, even though VO2peak values were essentially the same for both groups.

Excess postexercise oxygen consumption and recovery rate in trained and untrained subjects.

The purpose of this study was to determine whether aerobic fitness level would influence measurements of excess postexercise oxygen consumption (EPOC) and initial rate of recovery. Twelve trained [Tr; peak oxygen consumption (VO2 peak) = 53.3 +/- 6.4 ml . kg-1 . min-1] and ten untrained (UT; VO2 peak = 37.4 +/- 3.2 ml . kg-1 . min-1) subjects completed two 30-min cycle ergometer tests on separate days in the morning, after a 12-h fast and an abstinence from vigorous activity of 24 h. Baseline metabolic rate was established during the last 10 min of a 30-min seated preexercise rest period. Exercise workloads were manipulated so that they elicited the same relative, 70% VO2 peak (W70%), or the same absolute, 1.5 l/min oxygen uptake (VO2) (W1.5), intensity for all subjects, respectively. Recovery VO2, heart rate (HR), and respiratory exchange ratio (RER) were monitored in a seated position until baseline VO2 was reestablished. Under both exercise conditions, Tr had shorter EPOC duration (W70% = 40 +/- 15 min, W1.5 = 21 +/- 9 min) than UT (W70% = 50 +/- 14 min; W1.5 = 39 +/- 14 min), but EPOC magnitude (Tr: W70% = 3.2 +/- 1.0 liters O2, W1.5 = 1.5 +/- 0.6 liters O2; UT: W70% = 3.5 +/- 0.9 liters O2, W1.5 = 2.4 +/- 0.6 liters O2) was not different between groups. The similarity of Tr and UT EPOC accumulation in the W70% trial is attributed to the parallel decline in absolute VO2 during most of the initial recovery period. Tr subjects had faster relative decline during the fast-recovery phase, however, when a correction for their higher exercise VO2 was taken. Postexercise VO2 was lower for Tr group for nearly all of the W1.5 trial and particularly during the fast phase. Recovery HR kinetics were remarkably similar for both groups in W70%, but recovery was faster for Tr during W1.5. RER values were at or below baseline throughout much of the recovery period in both groups, with UT experiencing larger changes than Tr in both trials. These findings indicate that Tr individuals have faster regulation of postexercise metabolism when exercising at either the same relative or same absolute work rate.

The effect of upper body exercise intensity and duration on post-exercise oxygen consumption.

This study assessed excess post-exercise oxygen consumption (EPOC) following upper body exercise (UBE) of different intensity and duration. Ten subjects, 5 male and 5 female (age: 26.7 +/- 4.9 yr; peak UBE oxygen uptake [VO2peak]: 1.78 +/- 0.57 l. min-1, 25.6 +/- 5.8 ml.kg-1. min-1) performed three randomized tests on an arm crank ergometer: 1) low intensity, short duration (LS) = 35% VO2peak for 15 min; 2) low intensity, long duration (LL) = 35% VO2peak for 30 min; 3) high intensity, short duration (HS) = 70% VO2peak for 15 min. Subjects reported for all tests in the morning and in a fasted and rested state. Exercise was preceded by a 30 min seated baseline. Recovery VO2 was continuously monitored until baseline was re-established. EPOC duration (p < 0.01) and magnitude (p < 0.01) were significantly greater following HS, while LL and LS did not differ in response (duration and magnitude: HS = 14.0 +/- 6.5 min, 32.5 +/- 24.6 kJ; LL = 5.5 +/- 4.4 min, 12.3 +/- 8.6 kJ; LS = 5.7 +/- 4.9 min, 10.3 +/- 5.3 kJ). HS also had higher HR (73 +/- 10 b.min-1, p < 0.01) at end-EPOC compared to LL (64 +/- 8 b.min-1) and LS (66 +/- 8 b.min-1), and baseline HS values (63 +/- 8 b. min-1). Results from this study indicate that UBE intensity has a greater effect on EPOC than exercise duration under these conditions. UBE appears to have similar EPOC patterns as lower body exercise.

Effects of long-term moderate exercise on iron status in young women.

The impact of long-term (6-month) moderate exercise on the iron status of previously sedentary women was determined by randomly assigning 62 college-age women into one of the following four groups: 1) 50 mg.d-1 iron supplement, low iron diet (N = 16); 2) Placebo, free choice diet (N = 13); 3) Meat supplement to achieve 15 mg.d-1 iron intake (N = 13); and 4) Control, free choice diet (N = 20). All groups except the Control group exercised 3 d.wk-1 at 60%-75% of their heart rate reserve. VO2max was measured at baseline and week 24. Blood was sampled at baseline and every 4 wk thereafter for 24 wk to measure iron status and to elucidate the causes for alterations in iron status. Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels (< 15 ng.ml-1). Serum iron, total iron binding capacity and transferrin saturation were not compromised with exercise. Mean hemoglobin level in the Placebo/Ex group was significantly (P < 0.05) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24. However, changes in serum albumin, haptoglobin, and erythropoietin data from the study cannot explain these changes.

Fitness level and postexercise energy expenditure.

This study was designed to investigate the effect of fitness level on excess postexercise oxygen consumption (EPOC) in five endurance trained and five sedentary male volunteers. The possible influence of differences in body weight and exercise energy expenditure were controlled by employing a weight-supported (cycle ergometer), 300 kilocalorie exercise. Exercise intensity was equal to 50% of each subject's previously determined peak oxygen uptake (VO2). VO2 was measured for 1 hr prior to exercise to establish the baseline value, and continuously in the postexercise period until the baseline value was achieved. Duration of EPOC was 16.6 +/- 3.1 minutes and 20.4 +/- 7.8 minutes in the fit and unfit groups, respectively (p > 0.05). Magnitude of EPOC, which was not significantly different between the groups, averaged 12.2 +/- 3.1 kcal in the fit and 12.2 +/- 4.3 kcal in the unfit group. The results suggest that EPOC following a weight-supported exercise of an intensity and duration frequently used by individuals who begin an exercise program for weight control is not compromised by differences in body weight or fitness level.

Iron status in exercising women: the effect of oral iron therapy vs increased consumption of muscle foods.

Forty-seven previously sedentary women participating in a 12-wk moderate aerobic-exercise program were randomly assigned to one of four dietary groups: 50-mg/d iron supplement and a low food-iron diet (50 FE + EX), 10-mg/d iron supplement and a low food-iron diet (10 FE + EX), placebo and unrestricted diet (P + EX), and meat supplement and high food-iron diet (M + EX). A sedentary control group (n = 13) received no dietary interventions. Hematocrit, total iron-binding capacity, and hemoglobin, serum iron, serum ferritin, and serum albumin concentrations were measured every 4 wk. Hemoglobin values decreased at the end of 4 wk in all exercising groups compared with the control group. Iron status in the 50 FE + EX and M + EX groups improved after week 4 as indicated by an increase in serum ferritin, serum iron, and hemoglobin concentrations, and a decline in total iron-binding capacity. Thus, short-term, moderate aerobic exercise resulted in compromised iron status that was offset to varying degrees by ingesting iron or meat supplements. However, meat supplements were more effective in protecting hemoglobin and ferritin status than were iron supplements.

Postexercise energy expenditure following upper body exercise.

This study was designed to examine the magnitude and duration of excess postexercise oxygen consumption (EPOC) following upper body exercise, using lower body exercise for comparison. On separate days and in a counterbalanced order, eight subjects (four male and four female) performed a 20-min exercise at 60% of mode-specific peak oxygen uptake (VO2) using an arm crank and cycle ergometer. Prior to each exercise, baseline VO2 and heart rate (HR) were measured during the final 15 min of a 45-min seated rest. VO2 and HR were measured continuously during the postexercise period until baseline VO2 was reestablished. No significant difference between the two experimental conditions was found for magnitude of EPOC (t [7] = 0.69, p greater than .05). Mean (+/- SD) values were 9.2 +/- 3.3 and 10.4 +/- 5.8 kcal for the arm crank and cycle ergometer exercises, respectively. Duration of EPOC was relatively short and not significantly different (t [7] = 0.24, p greater than .05) between the upper body (22.9 +/- 13.7 min) and lower body (24.2 +/- 19.4 min) exercises. Within the framework of the chosen exercise conditions, these results suggest EPOC may be related primarily to the relative metabolic rate of the active musculature, as opposed to the absolute exercise VO2 or quantity of active muscle mass associated with these two types of exercise.

Effect of exercise intensity on postexercise energy expenditure in women.

This study was designed to examine the effect of exercise intensity on the magnitude and duration of excess postexercise oxygen consumption (EPOC) in women. On separate days and in a counterbalanced order, seven moderately active young adult women performed a 850 kJ cycle ergometer exercise at an intensity of 40 or 60% of their previously determined peak oxygen uptake (VO2). Baseline VO2 and heart rate (HR) were recorded during the last 10 min of a 45 min seated rest. VO2 and HR were measured continuously during recovery until VO2 returned to baseline. There was no significant difference noted in the baseline measures between the two exercise programmes. Magnitude of EPOC was comparable (P greater than 0.05) being mean (s.d.) of 30(17) and 36(13) kJ after 40 and 60% exercises respectively. Although the EPOC duration was 53% longer following the 40% exercise than following 60% (27(15) min and 18(8) min, respectively) this difference was not statistically significant. These exercise conditions failed to produce a prolonged EPOC in the women of this study, and values recorded for magnitude of EPOC indicate that it was not significant with regard to the overall energy expenditure of the activity. It was concluded that both magnitude and duration of EPOC seemed to be independent of the chosen exercise intensities used by the women in this study.

Circulatory and thermal adjustments to prolonged exercise in paraplegic women.

The circulatory and thermal responses to 90 min of wheelchair ergometer exercise were examined in five wheelchair dependent (WD) women with low level spinal dysfunction and five able-bodied (AB) women who served as a comparison group. Metabolic rate during exercise was 221 W for WD and 255 W for AB (P greater than 0.05). Oral temperature (Tor), mean skin temperature (Tsk), oxygen uptake (VO2), heart rate (HR), and cardiac output (Qc) were assessed periodically throughout the exercise period. Ambient conditions were 24-25 degrees C and 38-52% relative humidity. A significant group X time interaction was found for Tor (P less than 0.001) and Tsk (P less than 0.001). Tor of the WD group steadily increased during the exercise, whereas the AB group showed a stable Tor. Tsk of WD increased rapidly during the first 5-10 min of exercise and continued to rise at a slower rate throughout the exercise. In contrast, Tsk of AB rose to a peak during the first 10 min and then showed a decreasing trend. VO2 and HR remained stable in both groups throughout the exercise period. Following an initial increase in Qc from minute 10 to minute 20 in both groups, values for WD continually decreased until Qc at 80 min was 14% lower than at 10 min. The findings suggest that the WD women had greater thermoregulatory strain than the AB women as indicated by a higher Tor and Tsk and by an inability to maintain Qc due to paralysis of the lower limbs and perhaps an increase in cutaneous blood volume.

Body composition and resting energy expenditure in long term spinal cord injury.

Body composition and resting metabolic rate (RMR) were measured in 4 spinal cord injured (SCI) paraplegic men. The level of lesion ranged from T4 to L1, and the duration of disability averaged 7.4 +/- 3.3 (SEM) years. Hydrodensitometry was used to determine percent body fat, fat mass and lean body mass (LBM). RMR was measured following a 12-hour fast and 24 hours post-exercise using a ventilated hood. RMR was also predicted from LBM values based on the equation of Cunningham (1980). Results of the body composition measurements indicated a greater than average amount of body fat for men of this age group. RMR and LBM were significantly correlated (r = 0.98, p less than 0.02). However, measured RMR values were lower than predicted in 3 of the 4 subjects, especially when LBM was relatively low. Further investigation into the relationship between LBM and RMR in SCI individuals is warranted using a larger sample size and with subjects representing a wide range of lesion level.

Circulatory and metabolic responses of women to arm crank and wheelchair ergometry.

This study compared the circulatory and metabolic responses of arm crank ergometer (ACE) exercise to those of wheelchair ergometer (WCE) exercise during maximal and submaximal intensities. Maximal intensity exercise was defined as the highest power output (PO) achieved on each ergometer. The submaximal responses were compared at an equivalent absolute (PO = 25W) and relative (66% peak oxygen uptake [VO2]) intensity. On separate days and in random sequence, nine untrained able-bodied women performed a discontinuous incremental test for peak VO2 using either ACE or WCE. Each exercise bout was approximately six minutes, interspersed with four-minute rest periods. VO2 and heart rate (HR) were measured during each stage of the test and blood lactate concentrations were measured five minutes postexercise. Peak PO, ventilation (VE), and HR were significantly higher (p less than 0.05) on the ACE, with no significant difference in peak VO2 or postexercise blood lactate concentration. When compared at equivalent submaximal PO levels (25W), VO2, VE, and HR were significantly higher (p less than 0.05) on the WCE than on the ACE. In contrast, ACE exercise elicited a higher PO (p less than 0.05) at an equivalent relative metabolic load (66% peak VO2). These results suggest that in women wheelchair ergometry is less metabolically efficient than arm crank ergometry at submaximal exercise intensities. However, at maximal intensity exercise, ACE exercise imposes greater central circulatory stress. The finding that a higher peak HR was elicited by the ACE than the WCE suggests that exercise testing needs to be ergometer-specific when the results are to be used for exercise prescription.

Effect of exercise intensity and duration on postexercise energy expenditure.

The purpose of this study was to examine 1) the effect of two exercise intensities of equal caloric output on the magnitude (kcal) and duration of excess postexercise oxygen consumption (EPOC) and 2) the effect of exercise of equal intensity but varying duration on EPOC. Ten trained male triathletes performed three cycle ergometer exercises: high intensity-short duration (HS), low intensity-short duration (LS), and low intensity-long duration (LL). Baseline VO2 was measured for 1 h prior to each exercise condition. Postexercise VO2 was measured continuously until baseline VO2 was achieved. The duration of EPOC was similar for HS (33 +/- 10 min) and LL (28 +/- 14 min), and both were significantly longer (P less than 0.05) than the EPOC following LS (20 +/- 5 min). However, total net caloric expenditure was significantly more (P less than 0.05) for HS (29 +/- 8 kcal) than for either LS (14 +/- 6 kcal) or LL (12 +/- 7 kcal). The exercise conditions used in this study did not produce a prolonged EPOC. However, the exercise intensity was shown to affect both the magnitude and duration of EPOC, whereas the exercise duration affected only the duration of EPOC. Moreover, the duration of EPOC and the subsequent caloric expenditure were not necessarily related. Based on the resulting magnitude of the postexercise energy expenditure, it is possible that EPOC may be of some value for weight control over the long term.

The effects of arm crank training on the physiological responses to submaximal wheelchair ergometry.

The purpose of this investigation was to examine the cardiovascular and metabolic effects of a 5 wk arm crank (AC) training program on submaximal wheelchair (WC) ergometry in able-bodied women. The 6 subjects in the training group (TG) and 4 in the control group (CG) performed a 10 min WC exercise prior to and following the training period at a power output (PO) that elicited 70% of the pre-training peak oxygen uptake (VO2). Steady state VO2, heart rate (HR), cardiac output (Qc) and stroke volume (Vs) were measured. Resting and post-exercise blood lactate concentrations (LA) were measured, the difference was recorded as net LA. The TG exercised on the AC 3 d.wk-1 at a PO that elicited 85% of each subject's recorded peak HR. Each session consisted of four 4 min exercise bouts preceded by a 2 min warm-up and interspersed with 2 min rest periods. After training, the TG had a significantly (p less than 0.05) lower HR, larger Vs and lower LA in response to the WC exercise. Qc and VO2 were not significantly altered. The results demonstrate that the AC exercise program used in this study produced a physiological training effect which was observed during submaximal WC exercise of an intensity frequently encountered during daily WC ambulation. It appears that short-term, moderate intensity AC training offers an adequate stimulus to reduce the stress imposed by wheelchair locomotion.

A longitudinal study of energy expenditure in males during steady-state exercise.

Our purpose was to investigate longitudinal changes in gross energy expenditure (GEE) of 20 middle-aged and older men during submaximal exercise in 1969 and in 1985. GEE (kcal/min) was estimated using the caloric equivalent for each liter of oxygen consumed at the measured respiratory exchange ratio during submaximal exercise. The men performed a 10-min submaximal cycle ergometer exercise test at a power output (PO) of 100 W. Pedalling frequency was 50 rpm. Results showed a significant 5.9% decrease in GEE (p less than .01) from 8.5 +/- 0.8 (M +/- SD) kcal/min in 1969 to 8.0 +/- 0.4 (M +/- SD) Kcal/min in 1985. In addition, the effects of chronological age and leisure time physical activity on GEE were assessed and found to be nonsignificant, although a significant decrease in GEE over time (p less than .02) was observed in both groups. The present results support a decrease in GEE in middle-aged and older men over the 16-year time period. Furthermore, this decrease in GEE persisted regardless of chronological age or leisure time physical activity status.

The mechanical efficiency of wheelchair dependent women during wheelchair ergometry.

Few previous studies have attempted to study the response of disabled women to work in a wheelchair. The purpose of this study was to investigate the mechanical efficiency of wheelchair dependent women (WCD) during progressively loaded wheelchair ergometry. Five WCD subjects with an average confinement of 17.8 years were compared to five able bodied women (AB). Neither maximal oxygen uptake, 1.121 WCD and 1.485 AB (L X min-1) or maximal power outputs, 41.6 WCD and 44.1 AB (watts) were significantly different for the groups. The WCD group, however, demonstrated significantly higher mechanical efficiencies at comparable power outputs, p greater than 0.05. This difference remained when comparisons at about 60, 80, and 90% of VO2 max were made. The average efficiencies over these metabolic levels were 14% WCD and 10.6% AB. Stroke length consistently reduced as power outputs increased with the values lower for the WCD subjects. Average values for the submaximal workloads were 3.17 WCD and 3.76 AB (m x stroke-1) which meant a difference that was 18.6% greater in length for the AB group. The possible influence of this upon the efficiency of wheelchair locomotion was discussed.