Stephen F. Crouse

The acute versus the chronic response to exercise

PURPOSE There is strong and consistent evidence that a single exercise session can acutely reduce triglycerides and increase high-density lipoprotein (HDL) cholesterol (HDL-C), reduce blood pressure, and improve insulin sensitivity and glucose homeostasis. Such observations suggest that at least some of the effects on atherosclerotic cardiovascular disease (ASCVD) risk factors attributed to exercise training may be the result of recent exercise. RESULTS These acute and chronic exercise effects cannot be considered in isolation. Exercise training increases the capacity for exercise, thereby permitting more vigorous and/or more prolonged individual exercise sessions and a more significant acute effect. The intensity, duration, and energy expenditure required to produce these acute exercise effects are not clearly defined. The acute effect of exercise on triglycerides and HDL-C appears to increase with overall energy expenditure possibly because the effect maybe mediated by reductions in intramuscular triglycerides. Prolonged exercise appears necessary for an acute effect of exercise on low-density lipoprotein (LDL) cholesterol (LDL-C) levels. The acute effect of exercise on blood pressure is a low threshold phenomenon and has been observed after energy expenditures requiring only 40% maximal capacity. The acute effect of exercise on glucose metabolism appears to require exercise near 70% maximal, but this issue has not been carefully examined. CONCLUSIONS Exercise has definite acute effects on blood lipids, blood pressure, and glucose homeostasis. Exercise also has acute effects on other factors related to atherosclerosis such as immunological function, vascular reactivity, and hemostasis. Considerable additional research is required to define the threshold of exercise required to produce these putatively beneficial effects.

Effects of Resistance, Endurance, and Concurrent Exercise on Training Outcomes in Men

UNLABELLED The specificity of training principle predicts that combining resistance and endurance training (concurrent training) could interfere with the maximum development of strength and endurance capacity that results from either type of training alone. PURPOSE To determine whether endurance and resistance training performed concurrently produces different performance and physiologic responses compared with each type of training alone. METHODS Untrained male volunteers were randomly assigned to one of three groups: endurance training (ET, N = 12); resistance training (RT, N = 13); and concurrent training (CT, N = 16). The following measurements were made on all subjects before and after 12 wk of training: weight, percent body fat, peak oxygen consumption (VO(2peak)), isokinetic peak torque and average power produced during single-leg flexion and extension at 60 and 180 degrees.s, one-repetition maximum (1RM) leg press, 1RM bench press, vertical jump height, and calculated jump power. RESULTS Weight and lean body mass (LBM) increased significantly in the RT and CT groups (P < 0.05). Percent body fat was significantly decreased in the ET and CT groups. VO(2peak) was significantly improved only in the ET group. Peak torque during flexion and extension at 180 degrees.s(-1) increased in the RT group. Improvements in 1RM leg press and bench press were significant in all groups, but were significantly greater in the RT and CT compared to the ET group. Jump power improved significantly only in the RT group, and no group showed a significant change in vertical jump height. CONCLUSIONS Concurrent training performed by young, healthy men does not interfere with strength development, but may hinder development of maximal aerobic capacity.

The effects of endurance training on functional capacity in the elderly : a meta-analysis

In this investigation, meta-analysis was used to delineate exercise induced changes in the VO2max of older individuals and test a null hypothesis of no significant training effects. Parameters included in the analysis were age of the subjects, length of the training regimen, frequency and duration of exercise bouts, pretraining VO2max, posttraining VO2max, and the difference between pretraining and posttraining VO2max (delta VO2max). Effect size for training-induced improvements in VO2max was calculated, corrected for bias, weighted, and analyzed according to contemporary meta-analysis procedures. The mean effect size was found to be 0.65 standard deviation units, representing an improvement in oxygen consumption of 22.8%. The mean effect size was also significantly different from 0 (P < 0.0001), and the null hypothesis was rejected. Stepwise regression analysis indicated that length of training, pretraining VO2max, and duration of training bouts accounted for 59% of the total variation in delta VO2max. In addition, age was found to be inversely correlated with pretraining VO2max (r = -0.56, P = 0.002), and delta VO2max (r = -0.56, P = 0.003). It was concluded that endurance training significantly increases functional capacity in the elderly, and that the increase is related to subject age, duration of exercise bouts, length of the training regimen, and pretraining VO2max.

Consumption of High-Oleic Acid Ground Beef Increases HDL-Cholesterol Concentration but Both High- and Low-Oleic Acid Ground Beef Decrease HDL Particle Diameter in Normocholesterolemic Men

On the basis of previous results from this laboratory, this study tested the hypothesis that ground beef high in MUFA and low in SFA would increase the HDL-cholesterol (HDL-C) concentration and LDL particle diameter. In a crossover dietary intervention, 27 free-living normocholesterolemic men completed treatments in which five 114-g ground beef patties/wk were consumed for 5 wk with an intervening 4-wk washout period. Patties contained 24% total fat with a MUFA:SFA ratio of either 0.71 (low MUFA, from pasture-fed cattle) or 1.10 (high MUFA, from grain-fed cattle). High-MUFA ground beef provided 3.21 g more 18:1(n-9), 1.26 g less 18:0, 0.89 g less 16:0, and 0.36 g less 18:1(trans) fatty acids per patty than did the low-MUFA ground beef. Both ground beef interventions decreased plasma insulin and HDL(2) and HDL(3) particle diameters and increased plasma 18:0 and 20:4(n-6) (all P ≤ 0.05) relative to baseline values. Only the high-MUFA ground beef intervention increased the HDL-C concentration from baseline (P = 0.02). The plasma TG concentration was positively correlated with the plasma insulin concentration (r = 0.40; P < 0.001) and negatively correlated with HDL-C (r = -0.47; P < 0.001) and plasma 18:0 (r = -0.24; P < 0.01). Plasma insulin and HDL diameters were not correlated (r = 0.01; P > 0.50), indicating that reductions in these measures were not coordinately regulated. The data indicate that dietary beef interventions have effects on risk factors for cardiovascular disease that are independent (insulin, HDL diameters) and dependent (HDL-C) on beef fatty acid composition.

Physiologic and metabolic response of exercising horses to added dietary fat

Summary Six mature Quarter Horse-type geldings were used in a replicated 3 × 3 Latin square experiment to determine the effects of adding 5 or 10% feed-grade rendered animal fat to the concentrate diet fed to performance horses. The experiment was conducted over a 14-day pre-trial period to acquaint horses to the experimental apparatus, a 28-day conditioning period and 3 diet treatment periods of 21 days, each conducted in a Latin square arrangement. The horses were exercised on a dirt track and diet effects were evaluated during and following a submaximal exercise test (SET) on an equine treadmill. Physiological responses to the SET were determined following each experimental period. Relative to the control, the horses required 21% and 25% less of the concentrate feed (P

Electrocardiograms of collegiate football athletes.

The prevalence of electrocardiogram (ECG) abnormalities in American collegiate football athletes is virtually unknown.

The effects of menopausal status and exercise training on serum lipids and the activities of intravascular enzymes related to lipid transport

The study purpose was to compare the effect of exercise training on serum lipid and apolipoprotein concentrations and the activities of intravascular enzymes related to lipid transport in previously untrained eumenorrheic, premenopausal (PRM) women (n = 21; mean age, 36 +/- 3 years) and estrogen-free postmenopausal (POM) women (n = 16; mean age, 68 +/- 8 years). Subjects trained at a progressive intensity and duration (50% to 75% maximal O2 consumption [VO2max], 200 to 300 kcal/session) 4 d/wk for 12 weeks. Before and after training, VO2max, body weight, relative body fat, and fasting blood samples were obtained following 2 weeks on a standardized diet designed to maintain body weight and during the early follicular stage for the PRM group. Blood samples were analyzed for serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), the cholesterol content of the HDL3 subfraction, apolipoprotein (apo)A-I and apoB, lipoprotein(a), and the activity of lecithin:cholesterol acyltransferase (LCAT). Total and hepatic triglyceride lipase activity (HTGLA) were determined from plasma samples obtained after heparin administration. The cholesterol content of the low-density lipoprotein (LDL) and HDL2 subfractions and endothelial-bound lipoprotein lipase activity (LPLA) were calculated. A two (group) x two (time) multivariate ANOVA (MANOVA), with repeated measures for time indicated that the exercise-induced changes in physiological measurements, serum lipid or apolipoprotein concentrations, or enzyme activities did not differ between groups. Serum concentrations of TC, LDL-C, and HDL3 cholesterol, TG, and apo A-I and apoB were higher in POM women compared with the PRM group (P < .05 for all). For the combined groups, body weight and relative body fat did not change with training, but VO2max increased an average of 18.5% (P < .05). LPLA, HTGLA, and LCAT activity were unaltered with exercise training. Except for a small but significant decrease in HDL-C (-5.5%) and an elevation in apoB (4.3%; P < .05 for both), the concentrations of serum lipids and apolipoproteins did not change over the training period. We conclude that in previously untrained women, menopausal status does not influence the exercise training response of serum lipids or apolipoproteins or activities of intravascular enzymes related to lipid transport.

Comparative efficacy of water and land treadmill training for overweight or obese adults.

PURPOSE No known previous research has been published to explore the efficacy of underwater treadmill (UTM) exercise training for the obese. Thus, the purpose of this study was to compare changes in physical fitness, body weight, and body composition in physically inactive, overweight, and obese adults after 12 wks of land treadmill (LTM) or UTM training. METHODS Fifty-seven physically inactive, overweight, and obese men (n = 25) and women (n = 32) participated in this investigation. The mean +/- SEM age, weight, body mass index (BMI), and V O2max upon entry were 44 +/- 2 yr, 90.5 +/- 2.4 kg, 30.5 +/- 0.7 kg.m, and 27.1 +/- 0.7 mL O2.kg.min, respectively. Subjects were randomly assigned to exercise three times per week for 12 wk on either LTM (n = 29) or UTM (n = 28) matched for intensity and volume. Session volume was progressively increased from 250 to 500 kcal per session by week 6 and remained at 500 kcal through week 12. Before and after training, V O2max was assessed by the Bruce treadmill protocol with open-circuit calorimetry, and body composition was assessed by dual-energy ray absorptiometry. Data were analyzed by a 2 (training) x 2 (exercise mode) x 2 (gender) ANOVA repeated across training (alpha = 0.05). RESULTS Training responses were not different between genders. After either UTM or LTM training, V O2max was significantly increased (+3.6 +/- 0.4 mL O2.kg.min), whereas body weight (-1.2 +/- 0.3 kg), BMI (-0.56 +/- 0.11 kg.m), body fat percentage (-1.3% +/- 1.3%), and fat mass (-1.1 +/- 0.3 kg) were significantly reduced (pooled means for UTM and LTM). Regional leg lean body mass (LBM) was significantly increased with both CTM and UTM (0.4 +/- 0.3 and 0.8 +/- 0.2 kg, respectively). An increase in total LBM approached significance with UTM training only (+0.6 +/- 0.3 kg, P = 0.0599). CONCLUSIONS UTM and LTM training are equally capable of improving aerobic fitness and body composition in physically inactive overweight individuals, but UTM training may induce increases in LBM.

Maximal Exercise and Acute Mood Response in Women

The present study was designed to characterize and assess the reliability of acute mood responses to maximal exercise in women. All subjects (N = 22; age = 45 +/- 2.5 yr; BMI = 24.3 +/- 0.9 kg/m2) participated in two maximal walking tests spaced approximately one month apart. The abbreviated Profile of Mood States (POMS) questionnaire was administered immediately prior to and within 5 min following maximal exercise at both occasions. Maximal heart rate, rating of perceived exertion, and functional aerobic capacity responses indicated compliance to maximal exertion at both tests. Using repeated measures ANOVA, no significant (p < .05) differences were noted between the two tests for any of the POMS subscales. Significant pre to postexercise increases were noted for fatigue and self-esteem subscales while the tension and vigor affects significantly decreased. Because no interactions were found, these effects are concluded to be independent of the order in which the tests were performed. Additionally, intraclass correlations computed for each respective POMS subscale, ranged between 0.69 and 0.81 for fatigue, tension, vigor, self-esteem, confusion, and total mood disturbance. The anger and depression subscales were noted to have intraclass correlations of 0.29 and 0.43, respectively, and may have been influenced by a floor effect in this study population. It is concluded that the abbreviated POMS questionnaire may be reliably used to assess acute mood responses to maximal exercise in women and that even maximal exertion has the potential to acutely benefit mood by decreasing tension and increasing self-esteem.

Acute Exercise and Training Alter Blood Lipid and Lipoprotein Profiles Differently in Overweight and Obese Men and Women

Our purpose was to elucidate effects of acute exercise and training on blood lipids‐lipoproteins, and high‐sensitivity C‐reactive protein (hsCRP) in overweight/obese men (n = 10) and women (n = 8); age, BMI, body fat percentage, and VO2max were (mean ± SEM): 45 ± 2.5 years, 31.9 ± 1.4 kg·m−2, 41.1 ± 1.5%, and 25.2 ± 1.3 mlO2·kg−1·min−1. Before exercise training subjects performed an acute exercise session on a treadmill (70% VO2max, 400 kcal energy expenditure), followed by 12 weeks of endurance exercise training (land‐based or aquatic‐based treadmill): 3 sessions·week−1, progressing to 500 kcal·session−1 during which subjects maintained accustomed dietary habits. After training, the acute exercise session was repeated. Blood samples, obtained immediately before and 24 h after acute exercise sessions, were analyzed for serum lipids, lipoproteins, and hsCRP adjusted for plasma volume shifts. Exercise training increased VO2max (+3.67 mlO2·kg−1·min−1, P < 0.001) and reduced body weight (−2.7 kg, P < 0.01). Training increased high‐density lipoprotein (HDL) and HDL2b‐cholesterol (HDL‐C) concentrations (+3.7 and +2.4 mg·dl−1, P < 0.05) and particle numbers (+588 and +206 nmol·l−1, P < 0.05) in men. In women despite no change in total HDL‐C, subfractions shifted from HDL3‐C (−3.2, P < 0.01) to HDL2b‐C (+3.5, P < 0.05) and HDL2a‐C (+2.2 mg·dl−1, P < 0.05), with increased HDL2b particle number (+313 nmol·l−1, P < 0.05). Training reduced LDL3 concentration and particle number in women (−1.6 mg·dl−1 and −16 nmol·l−1, P < 0.05). Acute exercise reduced the total cholesterol (TC): HDL‐C ratio in men (−0.16, P < 0.01) and increased hsCRP in all subjects (+0.05 mg·dl−1, P < 0.05), regardless of training. Training did not affect acute exercise responses. Our data support the efficacy of endurance training, without dietary intervention, to elicit beneficial changes in blood lipids‐lipoproteins in obese men and women.