Healthy Untrained Men Research Articles

Change in post-exercise vagal reactivation with exercise training and detraining in young men.

We studied the effects of aerobic exercise training and detraining in humans on post-exercise vagal reactivation. Ten healthy untrained men trained for 8 weeks using a cycle ergometer [70% of initial maximal oxygen uptake (VO2max) for 1 h, 3-4 days.week-1] and then did not exercise for the next 4 weeks. Post-exercise vagal reactivation was evaluated as the time constant of the beat-by-beat decrease in heart rate during the 30 s (t30) immediately following 4 min exercise at 80% of ventilatory threshold (VT). The VO2max and the oxygen uptake at VT had significantly increased after the 8 weeks training programme (P < 0.0001, P < 0.001, respectively). The t30 had shortened after training, and values after 4 weeks and 8 weeks of training were significantly shorter than the initial t30 (P < 0.05, P < 0.01, respectively). The change in the t30 after 8 weeks of training closely and inversely correlated with the initial t30 (r = -0.965, P < 0.0001). The reduced t30 was prolonged significantly after 2 weeks of detraining, and had returned almost to the baseline level after a further 2 weeks of detraining. These results suggest that aerobic exercise training of moderate intensity accelerates post-exercise vagal reactivation, but that the accelerated function regresses within a few weeks of detraining.

Comparative Effects of Deep Versus Shallow Squat and Leg-Press Training on Vertical Jumping Ability and Related Factors

Young, previously untrained healthy men (n = 10) and women (n = 8) completed 9 weeks of periodized, machine-based squat training to determine if manipulating range of motion would have a differential effect on vertical jumping ability and related measures. Subjects were pretested and then randomly assigned to 1 of 3 groups: (a) deep squats (n = 6), (b) shallow squats (n = 6), and (c) controls (n = 6). Training took place 3 days per week. Pre-and posttesting included standing (RVJ) and depth (DVJ) vertical jumps for distance; machine deep and shallow squats for 1RM (1 repetition maximum) relative strength; and velocity-controlled squats at 0.51 m·s−1 for relative peak force and at 1.43 m·s−1 for relative peak power. Based on ANCOVA posttest results, the training protocols were ineffective in eliciting improved performance (p > 0.05) in VJ, slow-velocity squatting force, and moderately fast squatting power when performance was compared with the performance of control subjects. Conversely, the group training with deep squats was the only group to perform significantly (p <0.05) better than controls for 1RM shallow squats and significantly (p <0.05) better than both shallow-squat and control groups for 1RM deep squats. Furthermore, the coefficient of transfer for deep squats to both RVJ (2.32) and DVJ (1.68) was substantially greater than for shallow squats (0.31 and 0.11, respectively). It was concluded that deep-squat training appears to elicit the best improvement for both shallow-and deep-squatting performance. However, 9 weeks of machine-based, periodized squat training, regardless of depth, does not appear to appreciably enhance slow-velocity squatting force, moderately fast squatting power, or vertical jumping distance in previously untrained men and women.

Cardiorespiratory responses to fatiguing dynamic and isometric hand-grip exercise.

In occupational work, continuous repetitive and isometric actions performed with the upper extremity primarily cause local muscle strain and musculoskeletal disorders. They may also have some adverse effects on the cardiorespiratory system, particularly, through the elevation of blood pressure. The aim of the present study was to compare peak cardiorespiratory responses to fatiguing dynamic and isometric hand-grip exercise. The subjects were 21 untrained healthy men aged 24-45 years. The dynamic hand-grip exercise (DHGE) was performed using the left hand-grip muscles at the 57 (SD 4)% level of each individual's maximal voluntary contraction (MVC) with a frequency of 51 (SD 4) grips x min(-1). The isometric hand-grip exercise (IHGE) was done using the right hand at 46 (SD 3)% of the MVC. The endurance time, ventilatory gas exchange, heart rate (HR) and blood pressure were measured during both kinds of exercise. The mean endurance times for DHGE and IHGE were different, 170 (SD 62) and 99 (SD 27) s, respectively (P < 0.001). During DHGE the mean peak values of the breathing frequency [20 (SD 6) breaths x min(-1)] and tidal volume [0.89 (SD 0.34) l] differed significantly (P < 0.01) from peak values obtained during IHGE [15 (SD 5) breaths x min(-1) and 1.14 (SD 0.32) l, respectively]. The corresponding peak oxygen consumptions, pulmonary ventilations, HR and systolic blood pressures did not differ, and were 0.51 (SD 0.06) and 0.46 (SD 0.11) l x min(-1), 17.1 (SD 3.0) and 16.7 (SD 4.7) l x min(-1), 103 (SD 18) and 102 (SD 17) beats x min(-1), and 156 (SD 17) and 161 (SD 17) mmHg, respectively. The endurance times of both DHGE and IHGE were short (< 240 s). The results indicate that the peak responses for the ventilatory gas exchange, HR and blood pressure were similar during fatiguing DHGE and IHGE, whereas the breathing patterns differed significantly between the two types of exercise. The present findings emphasize the importance of following ergonomic design principles in occupational settings which aim to reduce the output of force, particularly in tasks requiring isometric and/or one-sided repetitive muscle actions.

Comparative Effects of Deep Versus Shallow Squat and Leg-Press Training on Vertical Jumping Ability and Related Factors

Young, previously untrained healthy men (n = 10) and women (n = 8) completed 9 weeks of periodized, machine-based squat training to determine if manipulating range of motion would have a differential effect on vertical jumping ability and related measures. Subjects were pretested and then randomly assigned to 1 of 3 groups: (a) deep squats (n = 6), (b) shallow squats (n = 6), and (c) controls (n = 6). Training took place 3 days per week. Pre-and posttesting included standing (RVJ) and depth (DVJ) vertical jumps for distance; machine deep and shallow squats for 1RM (1 repetition maximum) relative strength; and velocity-controlled squats at 0.51 m·s−1 for relative peak force and at 1.43 m·s−1 for relative peak power. Based on ANCOVA posttest results, the training protocols were ineffective in eliciting improved performance (p > 0.05) in VJ, slow-velocity squatting force, and moderately fast squatting power when performance was compared with the performance of control subjects. Conversely, the group training with deep squats was the only group to perform significantly (p <0.05) better than controls for 1RM shallow squats and significantly (p <0.05) better than both shallow-squat and control groups for 1RM deep squats. Furthermore, the coefficient of transfer for deep squats to both RVJ (2.32) and DVJ (1.68) was substantially greater than for shallow squats (0.31 and 0.11, respectively). It was concluded that deep-squat training appears to elicit the best improvement for both shallow-and deep-squatting performance. However, 9 weeks of machine-based, periodized squat training, regardless of depth, does not appear to appreciably enhance slow-velocity squatting force, moderately fast squatting power, or vertical jumping distance in previously untrained men and women.

Endurance exercise training does not alter lipolytic or adipose tissue blood flow sensitivity to epinephrine.

We evaluated the relationship between lipolysis and adipose tissue blood flow (ATBF) in response to epinephrine and the effect of endurance exercise training on these responses. Five healthy untrained men underwent a four-stage incremental epinephrine infusion (0.00125, 0.005, 0.0125, and 0.025 microgram. kg fat free mass(-1). min(-1)) plus hormonal clamp before and after 16 wk of cycle ergometry exercise training. Whole body glycerol and free fatty acid (FFA) rates of appearance (R(a)) in plasma were determined by stable isotope methodology, and ATBF was assessed by (133)Xe clearance. After each training session, subjects were fed the approximate number of calories expended during exercise to prevent changes in body weight. Glycerol R(a), FFA R(a), and ATBF increased when plasma epinephrine concentration reached 0.8 nM, but at plasma epinephrine concentrations >1.6 nM ATBF plateaued, whereas lipolysis continued to increase. Exercise training increased peak oxygen uptake by 24 +/- 7% (2.9 +/- 0.2 vs. 3.6 +/- 0.1 l/min; P < 0. 05) but did not alter body weight [70.5 +/- 3.8 vs. 72.0 +/- 3.8 kg; P = nonsignificant (NS)] or percent body fat (18.4 +/- 1.6 vs. 17.8 +/- 1.9%; P = NS). Lipolytic and ATBF responses to epinephrine were also the same before and after training. We conclude that the lipolytic and ATBF responses to epinephrine are coordinated when plasma epinephrine concentration is </=1.6 nM, but that at higher epinephrine concentrations, lipolysis continues to increase while ATBF remains constant. Endurance exercise training does not change lipolytic or ATBF sensitivity to epinephrine infusion in vivo during resting conditions.

LIPOLYTIC AND ADIPOSE TISSUE BLOOD FLOW SENSITIVITY TO EPINEPHRINE BEFORE AND AFTER ENDURANCE TRAINING

1723 We evaluated the relationship between lipolysis and adipose tissue blood flow (ATBF) in response to epinephrine and the effect of endurance exercise training on these responses. Five healthy untrained men (26±3 yr) underwent a four-stage incremental epinephrine infusion (0.00125, 0.005, 0.0125, and 0.025 μg·kg fat free mass−1·min−1) plus hormonal clamp before and after 16 weeks of cycle ergometry exercise training. Whole-body glycerol and free fatty acid (FFA) rates of appearance (Ra) in plasma were determined by stable isotope methodology and ATBF was assessed by 133Xe clearance. After each training session, subjects were fed the approximate number of calories expended during exercise to prevent changes in body weight. Glycerol Ra, FFA Ra, and ATBF increased above basal values (P<0.05) when plasma epinephrine concentration reached 0.8 nM (58±16%, 62±15%, 235±44%, respectively) and increased progressively as plasma epinephrine concentration increased to 1.6 nM. However, at plasma epinephrine concentrations >1.6 nM, ATBF plateaued while lipolysis continued to increase. Exercise training increased peak oxygen uptake by 24±7% (P<0.05) but did not alter body weight (70.5±3.8 vs. 72.0±3.8 kg; P=NS), or %body fat (18.4±1.6 vs. 17.8±1.9%; P=NS). Lipolytic and ATBF responses to epinephrine were also the same before and after training. We conclude that the lipolytic and ATBF responses to epinephrine are coordinated when plasma epinephrine concentration is ≤ 1.6 nM, but at higher epinephrine concentrations lipolysis continues to increases while ATBF remains constant. Endurance exercise training does not change lipolytic or ATBF sensitivity to epinephrine in vivo.

Exercise-Induced Silent Myocardial Ischemia in Master Athletes

High-physical activity levels are associated with reduced risk of symptomatic coronary artery disease (CAD). However, there are a number of reports of exercise-related sudden death and myocardial infarction in aerobically trained athletes. This study compared the prevalence of exercise-induced silent myocardial ischemia on maximum graded exercise tests with tomographic thallium scintigraphy in 70 master male athletes (63 ± 6 years, mean ± SD) (maximum aerobic capacity, V̇O 2max >40 ml/kg/min) and in 85 healthy untrained men (61 ± 7 years) with no history of CAD. The prevalence of silent ischemia (exercise-induced ST-segment depression on electrocardiogram and perfusion abnormalities on thallium scintigraphy) was similar in athletes and untrained men; 16% of the athletes (11 of 70) had silent ischemia compared with 21% of the untrained men (chi-square = 0.81, p = 0.36). No athletes had hyperlipidemia, systemic hypertension, or diabetes mellitus. However, the apolipoprotein E4 allele was present in 9 of the 11 athletes with silent ischemia compared with 2 of 32 athletes with normal exercise tests (chi-square = 24, p = 0.0001). These results suggest that older male athletes with the apolipoprotein E4 allele are at increased risk for the development of exercise-induced silent ischemia.

Effects of exercise on circulating vascular adhesion molecules in healthy men

Based on previous studies showing an increase in circulating soluble intercellular adhesion molecule-1 (siCAM-1) after exercise, we hypothesized that exercise may also increase serum levels of the vascular cell adhesion molecule-1 (sVCAM-1) and sE-selectin. In a prospective controlled clinical trial, serum levels of sE-selectin, siCAM-1 and sVAM-1 were measured before and after two different exercise protocols in healthy untrained men. Lactate levels increased up to 12.7 mmol/L (95% confidence interval: 10.1–15.9) and 3.6 mmol/L (CI: 2.4–4.7) after ergometry and after an one hour endurance exercise at 60% of the maximal work intensity, respectively (p = 0.028 vs baseline and controls). The maximal increase in lymphocyte counts of 106% (CI: 63–146), which was only of short duration, was higher immediately after ergometry as compared to that observed after endurance exercise (p = 0.028). However, the maximal increase in neutrophil counts of 178% (CI: 120–298) which was seen at 2 hours after endurance exercise was higher than that seen after ergometry (p = 0.028). In contrast, only small changes of circulating adhesion molecules were seen immediately after ergometry: siCAM-1 increased by 11% (CI: 4–25; p = 0.028), and similar tendencies were also observed for sVCAM-1 and sE-selectin. No other consistent and time-dependent changes of circulating adhesion molecules were observed and all differences and changes were ≤11%. In sum our study provides evidence that recreational sporting activities in untrained healthy subjects at normal altitude have little influence on serum levels of the circulating vascular adhesion molecules sE-selectin, sVCAM-1 or siCAM-1.

Muscle enzyme activity in humans: role of substrate availability and training.

To study the effect of nutrient intake (substrate flux) and training on muscle enzyme activities, 36 untrained healthy men adapted for 7 wk to a fat-rich or a carbohydrate-rich diet. Ten of the 18 subjects on each diet completed an endurance training program, and the remaining 8 served as controls. Maximal oxygen uptake was increased (11%) in the trained groups (P < 0.05). Irrespective of training, beta-hydroxyacyl-CoA-dehydrogenase activity in the vastus lateralis muscle was significantly increased by an average of 25% after adaptation to a fat-rich diet and was unchanged after adaptation to a carbohydrate-rich diet. In contrast, irrespective of diet, muscle citrate synthase activity and hexokinase activity were increased (P < 0.05) after adaptation to training by 17 and 18% in the group fed the carbohydrate, rich diet and by 17 and 12% in the group fed the fat-rich diet, respectively, and were unchanged in the two control groups. We suggest that diet can affect muscle enzymatic adaptation, presumably through an effect on the substrate flux.

Effects of exhaustive endurance exercise and its one-week daily repetition on neutrophil count and functional status in untrained men.

Whereas endurance exercise is known to induce marked neutrophilia, it remains to be fully understood as to whether the cell functions are altered as well as whether the adaptability of the responses to training occurs. To address both of these issues, we undertook the present longitudinal investigation in ten healthy untrained men (20-24 years, VO2max 39.1 +/- 4.2 ml/kg/min). The exercise protocol was 7 consecutive sessions of the same workload performed each day for 1.5 h at an intensity of 70% of VO2max. Peripheral blood samples were obtained before, immediately after, and 1 h after exercise on Days 1, 4, and 7, and served for determination of total and differential leukocyte counts, chemotaxis and chemiluminescence of neutrophils. Acute endurance exercise caused marked peripheral neutrophilia with significant increase in both absolute number and relative proportion of band neutrophils (p < 0.01, respectively), indicating partial recruitment of bone marrow neutrophils. While chemotaxis remained unaltered following exercise, reactive oxygen species generation of neutrophils, measured by luminol-dependent chemiluminescence upon stimulation with opsonized zymosan, was not only significantly enhanced following exercise (p < 0.01), but also associated with the proportional increase in band neutrophils (r = 0.727, p < 0.05), suggesting that neutrophils mobilized from the bone marrow following endurance exercise may possess higher responsiveness. On the other hand, the magnitude of the exercise-induced changes was reduced gradually by daily repeated exposure to endurance exercise, but none of the trends were significant except the decline in resting segmented neutrophil counts (p < 0.05) at least during a 1-wk period of repeated exercise sessions.

The effect of N-acetylcysteine on exercise-induced priming of human neutrophils. A chemiluminescence study.

The effect of strenuous aerobic exercise on the liberation of reactive oxygen species production by human granulocytes was investigated in 9 untrained healthy men. The influence of supplementation with N-acetylcysteine, a pro-glutathione free radical scavenger, on this was also investigated. Subjects performed two identical maximal exercise tests (mean time 14.06 +/- SD 0.84 min) on a bicycle ergometer. Venous blood samples were taken before and after maximal exercise, with and without N-acetylcysteine supplementation (total dose 2400 mg within three days). Isolated granulocytes were stimulated in vitro with phorbol myristate acetate or zymosan particles coated with autologous serum. The production of reactive oxygen species was measured by luminol-enhanced chemiluminescence. An enhancement (priming) by 52% in the production of reactive oxygen species, as measured by the AUC, occurred after exercise when zymosan was used as stimulant. This priming effect was abolished following N-acetylcysteine supplementation. In contrast, phorbol myristate acetate stimulation did not show any influence of exercise in the chemiluminescence reaction without or with N-acetylcysteine supplementation. In conclusion, priming of granulocytes could be induced by a relative short bout of exercise. The priming of granulocytes due to exercise could be measured in this study by zymosan-stimulated luminol-enhanced chemiluminescence.

Training intensities for aerobic exercise determined on untrained healthy men.

The purpose of this study was to determine the aerobic training intensity from the maximal and submaximal running exercise in 21 untrained adult men. To accomplish this, we evaluated the relationship between physiological (oxygen intake and heart rate) and physical parameters (running speed) of training intensity, and determined the training intensity at the submaximal exercise. Oxygen intake and heart rate were measured by a treadmill test. The maximal oxygen intake (VO2 max), and the aerobic threshold (AerT) and anaerobic threshold (AT) were measured to determine respiratory gas exchange. Running capacity was measured by a 12-min running and treadmill test. For the maximal exercise, there was a significant correlation (r = 0.88, P < 0.01) between VO2 max and 12-min running distance (speed). In addition, the oxygen intake and heart rate at AerT and AT in the submaximal exercise were linearly correlated with running speed. Three levels of training intensity at the submaximal exercise were termed: light, moderate, and heavy. Since AerT was the lower limit intensity and AT was the upper limit, we took the middle of their values as the moderate intensity. The end point for the determination of the training intensity at the submaximal exercise was estimated to be 85% VO2 max and 180 beats.min-1.

Cardiac demands of heavy snow shoveling

<h3>Objective.</h3> —To assess the physiologic responses to manual (shoveling) vs automated (electric snow thrower) snow removal in healthy, untrained men. <h3>Design.</h3> —Observational, controlled trial. <h3>Setting.</h3> —A community-based, acute care, teaching-research hospital. <h3>Participants.</h3> —A volunteer sample of 10 apparently healthy untrained men (mean ±SD age = 32.4±2.1 years) met all eligibility criteria and completed the study. <h3>Intervention.</h3> —Each subject cleared two 10±2-cm-high, 15-m-long tracts of heavy, wet snow in the cold (2°C), using self-paced manual and automated methods, in random order, with 10- to 15-minute rest periods between each 10-minute bout of work. <h3>Main Outcome Measures.</h3> —Heart rate, blood pressure, oxygen uptake, and perceived exertion during snow removal were compared with values obtained during maximal arm-ergometer and treadmill tests. <h3>Results.</h3> —Mean heart rate during shoveling was 154 and 173 beats per minute at 2 and 10 minutes, respectively, corresponding to 86% and 97% of maximal heart rate. Relative heart rate (percentage of maximal heart rate) during shoveling was inversely related to aerobic fitness (<i>r</i>= —0.65;<i>P</i>=.05). The highest heart rate and perceived exertion responses during shoveling, arm-ergometer, and treadmill testing were comparable. Systolic blood pressure during snow shoveling (198±17 mm Hg) was significantly greater (<i>P</i>&lt;.003) than during arm ergometry or automated snow removal and slightly greater than during maximal treadmill testing (181 ±25 mm Hg). Oxygen uptake during shoveling was similar to that for arm ergometry (5.7 vs 6.3 metabolic equivalents), but lower than for treadmill testing (9.3 metabolic equivalents). Cardiorespiratory and perceived exertion responses were reduced during automated snow removal. <h3>Conclusion.</h3> —Heavy snow shoveling elicits myocardial and aerobic demands that rival maximal treadmill and arm-ergometer testing in sedentary men. These responses may contribute to cardiovascular events reported after heavy snowfalls. (<i>JAMA</i>. 1995;273:880-882)

Fat metabolism during low-intensity exercise in endurance-trained and untrained men.

Whole body lipid kinetics were evaluated during basal resting conditions, 4 h of treadmill exercise eliciting an oxygen uptake of 20 ml.kg-1.min-1, and 1 h of recovery in five untrained and five endurance-trained men. Glycerol and free fatty acid (FFA) rate of appearance (Ra) values in plasma were determined by infusing [2H5]glycerol and [1-13C]palmitate, respectively, and lipid oxidation was determined by indirect calorimetry. The lipolytic response to 4 h of exercise, expressed as the average glycerol and FFA Ra values, was similar in both trained (9.85 +/- 1.02 and 24.64 +/- 3.76 mumol.kg-1.min-1, respectively) and untrained subjects (11.29 +/- 0.99 and 24.13 +/- 0.39 mumol.kg-1.min-1, respectively). However, mean triglyceride oxidation was greater during exercise in the trained than in the untrained group (7.51 +/- 0.26 and 5.67 +/- 0.51 mumol.kg-1.min-1, respectively; P < 0.001). During recovery, glycerol and FFA Ra values decreased more rapidly in trained than in untrained subjects. We conclude that highly trained male endurance runners use more fat as a fuel during low-intensity exercise than do untrained healthy men despite similar rates of lipolysis and FFA uptake from plasma. Therefore, the increase in fat oxidation must be related to an increased percentage of FFA uptake oxidized, a greater contribution from intramuscular triglyceride stores, or both. Additionally, lipid kinetics return to baseline more rapidly in trained than in untrained subjects after completing an exercise bout of the same absolute intensity.

Effects of strength training on total and regional body composition in older men

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical conditioning in elderly people

Maximal isometric force, coordination, balance, reaction time, flexibility, maximal oxygen uptake, blood lipids and oral glucose tolerance were measured in 59 healthy untrained men and women, 60–82 years of age, before and after 5 months of 3 different kind of physical activities: gymnastics, swimming and senior dance. As a control group, 14 untrained men and women, 61–64 years of age, were recruited from a large study in Copenhagen. The results demonstrate significant improvements in neuromuscular function and blood lipids. In contrast, only minor changes were observed in glucose metabolism and maximal oxygen uptake. Five months of training, twice a week, seems therefore sufficient to induce marked changes in the neuromuscular function and blood lipids of elderly people, whereas the lack of significant changes in glucose metabolism and maximal oxygen uptake still need to be explained.

Effects of aerobic and anaerobic training on plasma lipoproteins.

We studied the effects of anaerobic and aerobic training on lipoprotein concentrations in 45 healthy untrained men. Thirty-three subjects exercised four times per week during nine weeks on a bicycle ergometer. Sixteen trained with an intensity above the anaerobic threshold (blood lactate concentration > 4 mmol.l-1) and 17 trained with an intensity below the anaerobic threshold. In addition, twelve subjects served as controls. The calculated caloric expenditure of the two training groups was similar. In all three groups, total cholesterol, total high-density lipoprotein (HDL), HDL subfractions (HDL2, HDL3), and low-density lipoprotein (LDL) were measured. Training had a significant influence on HDL, HDL2, LDL/HDL, HDL2/HDL3, and cholesterol/HDL. With anaerobic training these variables changed in the opposite direction compared with aerobic training which influenced the lipoprotein profile in the desired direction. Cholesterol, HDL3, and LDL did not alter during the nine weeks of training. After nine weeks of training, the higher the blood lactate concentration during exercise (representing training intensity) was, the higher resting LDL/HDL ratio was found. The correlation between these two variables was highly significant. We conclude that training above the anaerobic threshold has no or even negative effects on blood lipoprotein profiles. Therefore, beneficial adaptations in lipoprotein profile must be achieved with moderate training intensities below the anaerobic threshold.

Eccentric muscle performance of elbow and knee muscle groups in untrained men and women

Maximal voluntary eccentric (ECC) and concentric (CON) capacity of knee and elbow muscle groups was investigated in healthy untrained men (N = 40) and women (N = 50), 21-67 yr of age. Purposes of the study were to describe torque-velocity and ECC-CON relationships, and to compare these relationships among muscle groups and between genders. Average torque was measured at angular velocities of 30 degrees and 120 degrees.s-1 from knee flexor (KF), knee extensor (KE), and elbow flexor (EF) muscle groups unilaterally, using an isokinetic protocol including gravity compensation. Data were analyzed using ANOVA procedures, and a significance level of 0.01 was used for all hypothesis testing. Torque-velocity relationships were similar for each muscle group and gender; i.e., ECC average torque did not change as a function of velocity and CONC torque decreased as angular velocity increased. Women generated greater ECC relative to CONC torque than men in upper and lower extremity muscle groups. Muscle groups differed in ECC relative to CONC capacity in both men and women, with ECC/CONC ratios being greater for KE and EF than KF. In all muscle groups, the magnitude of ECC-CONC differences increased as angular velocity increased. Genders differed in relative strength balance between muscle groups, with men exhibiting greater KF/KE and EF/KF torque ratios than women for both ECC and CONC actions. Results of this study contribute to the body of women.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Aging on Changes in Plasma Potassium During Exercise

Exercising skeletal muscle releases large amounts of potassium into plasma. beta-adrenergic receptors enhance reuptake of potassium into muscle. Since beta-adrenergic responses decline with aging in many tissues, the elderly might be predisposed to hyperkalemia during exercise. Venous plasma potassium (K+) was measured during graded bicycle exercise (30 W initial workload with 3-minute 30 W increments) in 18 healthy young men (24.0 +/- 2.9 yrs; mean +/- SD), 18 healthy untrained elderly men (70.0 +/- 3.6 yrs), and 7 elderly master athletes (70.0 +/- 4.6 yrs). Subjects exercised to exhaustion. Exercise times and maximal oxygen uptake were: young (N = 14; 19.6 +/- 4.4 min, 42.1 +/- 3.8 ml/kg/min), elderly (N = 13; 11.7 +/- 1.9 min, 26.6 +/- 8.0 ml/kg/min), elderly master athletes (N = 6; 16.8 +/- 2.4 min, 40.2 +/- 10.2 ml/kg/min). The rate of increase in K+ was greater in both elderly (89 +/- 59 mumol/l/min) and elderly master athletes (88 +/- 26) compared with healthy young men (60 +/- 30), p < .05. Despite this greater rate of increase, the elderly group did not achieve higher maximal K+ concentrations than the young because of the much shorter duration of exercise in the elderly group. For subjects performing a maximal exercise test, the maximal increase in K+ was similar in the elderly (1.15 +/- 0.91), but significantly greater in elderly master athletes (1.70 +/- 0.31), compared with healthy young men (1.31 +/- 0.45). Changes in K+ during short-lasting exercise are similar in untrained healthy elderly men compared with healthy young men, but elderly master athletes have greater changes in K+ during exercise. The greater rate of increase in potassium in healthy and athletic subjects supports the hypothesis of an age-related impairment of the beta 2-adrenergic process that mediates potassium flux into skeletal muscle.

Voluntary and electromyostimulation forces in trained and untrained men

Electromyostimulation (EMS) evoked responses of lower extremity muscles of sedentary or disabled subjects have been extensively studied to improve muscular strength and delay atrophy. However, it is not apparent whether EMS can serve a similar function in upper extremity muscles and in athletes. We compared the forces of maximal voluntary isometric contraction (MVC), percutaneous EMS-evoked tetanus, and EMS superimposed on MVC of the elbow flexors in six strength-trained and six untrained healthy men. Stimulation consisted of a 2.5-kHz alternating current sine wave modulated at 50 bursts.s-1 with a 50% duty cycle. Reliability of the criterion measures was assessed over 4 d and ranged from R = 0.746 to R = 0.948. Strength-trained men had 29% higher MVC than untrained controls (P less than 0.001). Untrained men tolerated 21.9 mA and trained men 31.3 mA of EMS current (P less than 0.021), yet tetanic forces were similar: 92.5 N vs 96.0 N (P greater than 0.196). These tetanic forces corresponded to 32% (untrained) and 24% (trained) of MVC (P less than 0.047). When EMS was superimposed on MVC, compared with MVC alone, force was significantly (P less than 0.048) lower by 10% (31 N, untrained) and 13% (55 N, trained). These data suggest that, independent of training status, percutaneous EMS reduces maximal voluntary elbow flexion forces and that tetanic forces may not be sufficiently high for purposes of muscular strength development or prevention of atrophy.