The influence of direct supervision of resistance training on strength performance

PURPOSE: The purpose of this study was to compare changes in maximal strength, power, and muscular endurance after 12 wk of periodized heavy-resistance training directly supervised by a personal trainer (SUP) versus unsupervised training (UNSUP). METHODS: Twenty moderately trained men aged 24.6 +/- 1.0 yr (mean +/- SE) were randomly assigned to either the SUP group (N = 10) or the UNSUP group (N = 8). Both groups performed identical linear periodized resistance training programs consisting of preparatory (10-12 repetitions maximum (RM)), hypertrophy (8 to 10-RM), strength (5 to 8-RM), and peaking phases (3 to 6-RM) using free-weight and variable-resistance machine exercises. Subjects were tested for maximal squat and bench press strength (1-RM), squat jump power output, bench press muscular endurance, and body composition at week 0 and after 12 wk of training. RESULTS: Mean training loads (kg per set) per week were significantly (P < 0.05) greater in the SUP group than the UNSUP group at weeks 7 through 11 for the squat, and weeks 3 and 7 through 12 for the bench press exercises. The rates of increase (slope) of squat and bench press kg per set were significantly greater in the SUP group. Maximal squat and bench press strength were significantly greater at week 12 in the SUP group. Squat and bench press 1-RM, and mean and peak power output increased significantly after training in both groups. Relative local muscular endurance (80% of 1-RM) was not compromised in either group despite significantly greater loads utilized in bench press muscular endurance testing after training. Body mass, fat mass, and fat-free mass increased significantly after training in the SUP group. CONCLUSION: Directly supervised, heavy-resistance training in moderately trained men resulted in a greater rate of training load increase and magnitude which resulted in greater maximal strength gains compared with unsupervised training.     

Effects of high-intensity strength training on cardiovascular function

Thirteen healthy, untrained males (age 44 +/- 1 yr, range 40-55 yr) were studied to determine the effects of 16 wk of high-intensity, variable-resistance, Nautilus strength training on cardiovascular function. A control group consisting of 10 untrained males (age 52 +/- 2 yr, range 40-64 yr) underwent the same evaluation procedures as the training group. Maximal oxygen uptake (VO2max), cardiac output during submaximal exercise, and body composition were determined before and after training. In addition, the physiological responses to an acute training session were evaluated. Muscular strength increased markedly, as evidenced by a 44% average increase in the "one-repetition maximum" in the various exercises. Body weight and percent body fat did not change with training, though fat-free weight did increase (66.9 +/- 2.6 vs 68.8 +/- 2.7 kg, P less than 0.05) significantly. Maximal oxygen uptake did not change significantly in either the training or the control group, and there were no changes in the hemodynamic responses to submaximal exercise after training. These findings indicate, therefore, that high-intensity, variable-resistance strength training produces no adaptative improvement in cardiovascular function. The physiological responses measured during a training session provide evidence that this lack of cardiovascular adaptation may be due to the low percentage of VO2max elicited by this form of exercise.     

Thermoregulatory responses to weight training

Thermoregulatory responses of eight healthy males (age 25.5 +/- 4.5 yrs) were studied during weight training comprising 3 sets of 15 repetitions of 9 exercises performed at a work cadence of 15 repetitions.min-1 with 1-min recovery intervals. The load for each exercise was increased from 50% of the 15-repetition maximum for the first set to 75% and 100% for the second and third sets, respectively. The thermoregulatory response was characterized by only moderate sweat rates (0.69 +/- 0.18 l.h-1) and rectal temperature rises (1.3 degree +/- 0.4 degree C, P less than 0.001), suggesting that dehydration and hyperthermia are unlikely to complicate weight training of the format used in this study. Despite a considerable lactic acidosis, small elevations in serum levels of aspartate aminotransferase and lactate dehydrogenase occurred, the core temperature rise being inadequate for significant cellular damage to ensue. Serum electrolyte levels measured immediately and 24 h post-exercise indicated that electrolyte supplementation is unlikely to be of benefit. Weight training induced a marked reduction of plasma volume (11.8% +/- 3.7%, P less than 0.001) in the presence of a minor water deficit (0.8% +/- 0.23%) and an O2 consumption of 32% +/- 8% of the predetermined treadmill exercise maximal O2 consumption. This finding suggests that exercise intensity as assessed by percentage maximal voluntary contraction rather than percentage maximal O2 consumption might determine the degree of hemoconcentration encountered during exercise.     

The role of maximal strength and load on initial power production

PURPOSE: The influence of maximal strength, as measured by the maximal load lifted for one repetition (1RM), on power production in the initial 200 ms of the concentric phase for both rebound and nonrebound movements was investigated. We also investigated the effect of external load upon this relationship. METHODS: Twenty-seven male subjects (21.9 +/- 3.1 yr, 89.0 +/- 12.5 kg) were separated by previously determined bench press IRM into high (100.88 +/- 7.24 kg) and low (72 +/- 6.61 kg) RM groups. Concentric only bench presses and rebound bench presses were compared between and within groups to note the effect of RM across external loads of 40%, 60%, and 80% 1RM, on instantaneous, mean, and peak power output. RESULTS: The results of this study clearly indicated the enhancement of concentric motion by prior eccentric muscle action (336-1332% enhancement in the first 20 ms). Possessing a high RM augmented power production in the initial 200 ms of stretch-shorten cycle activity, across all the external resistances tested (P < 0.05). The temporal characteristics of this enhancement, however, differed across loads. That is, 80% IRM loading showed a later time to peak enhancement (80 ms vs 20 ms). Interestingly, the influence of RM on concentric only motion in the initial 200 ms across the external resistances tested was found to be nonsignificant. CONCLUSIONS: The results suggest that the role of maximal strength during initial power production between concentric and stretch-shorten cycle activity differs, which has important implications for the training of athletes.     

Effects of hydraulic circuit training on cardiovascular function

The effect of hydraulic circuit training (HCT) on cardiovascular (CV) function was assessed in 32 healthy middle-aged males (X age = 42.2 +/- 2.1 yr). Maximal aerobic power (VO2max), with simultaneous measurement of stroke volume (SV) and cardiac output (CO), by impedance cardiography, was assessed pre- and post-training. Subjects were randomly assigned to a nonexercising control group, a cycle training group (cycle), or one of the two HCT groups. Training groups participated in a 9 wk program, 3 d.wk-1. Subjects assigned to HCT exercised on a 9 station circuit, completing 3 circuits.d-1. Each circuit consisted of three 20 s work intervals at each station with a 1:1 work:rest ratio. One HCT group (HCTmax) completed the maximal repetitions possible (RM) during each work interval. The other HCT group (HCTsub) exercised at 70-85% of RM. Following training VO2max (ml.kg-1 min-1) was significantly increased in all training groups (18.0, 12.5, and 11.3% for cycle, HCTsub, and HCTmax groups, respectively; P less than 0.05). The increase in VO2max observed in the cycle group was significantly greater than that recorded by the two HCT groups (P less than 0.05). For all three training groups, the increase in VO2max was associated with increases in SVmax and COmax (P less than 0.05 for both). These findings suggest that both maximal and submaximal HCT programs can elicit improvements in cardiovascular fitness.     

The role of resting duration in the kinematic pattern of two consecutive bench press sets to failure in elite sprint kayakers

This study aimed to investigate the role of rest period duration (RP) on the time course of the acceleration portion (AP) and mean velocity of the concentric phase across two bench press sets to failure with a submaximal load (60 % of the 1RM) using different RP. Ten elite junior kayakers performed, on four different days, two consecutive bench press sets to failure, allowing randomly 1-, 2-, 3- and 4-min RP between sets. AP reached a maximal value of 66 % of the concentric movement time. This maximal AP was observed in repetition number 2 or 3, and then AP declined during the set, with a significant decrease when the number of repetitions was over 80 % of the total number of repetitions performed. AP and lifting velocity patterns of the concentric phase were not altered during a second set to failure, regardless of RP. However, when velocity was expressed in absolute terms, 1-min RP was insufficient to maintain the average lifting velocity during the second set, compared to the first one. These results may be of use in selecting number of repetitions and resting duration in order to ensure optimal maintenance of the accelerative portion of concentric movement time with different resting-period durations.     

Effect of loading on unintentional lifting velocity declines during single sets of repetitions to failure during upper and lower extremity muscle actions

The purpose of this study was to examine the effect of different loads on repetition speed during single sets of repetitions to failure in bench press and parallel squat. Thirty-six physical active men performed 1-repetition maximum in a bench press (1 RM (BP)) and half squat position (1 RM (HS)), and performed maximal power-output continuous repetition sets randomly every 10 days until failure with a submaximal load (60 %, 65 %, 70 %, and 75 % of 1RM, respectively) during bench press and parallel squat. Average velocity of each repetition was recorded by linking a rotary encoder to the end part of the bar. The values of 1 RM (BP) and 1 RM (HS) were 91 +/- 17 and 200 +/- 20 kg, respectively. The number of repetitions performed for a given percentage of 1RM was significantly higher (p < 0.001) in half squat than in bench press performance. Average repetition velocity decreased at a greater rate in bench press than in parallel squat. The significant reductions observed in the average repetition velocity (expressed as a percentage of the average velocity achieved during the initial repetition) were observed at higher percentage of the total number of repetitions performed in parallel squat (48 - 69 %) than in bench press (34 - 40 %) actions. The major finding in this study was that, for a given muscle action (bench press or parallel squat), the pattern of reduction in the relative average velocity achieved during each repetition and the relative number of repetitions performed was the same for all percentages of 1RM tested. However, relative average velocity decreased at a greater rate in bench press than in parallel squat performance. This would indicate that in bench press the significant reductions observed in the average repetition velocity occurred when the number of repetitions was over one third (34 %) of the total number of repetitions performed, whereas in parallel squat it was nearly one half (48 %). Conceptually, this would indicate that for a given exercise (bench press or squat) and percentage of maximal dynamic strength (1RM), the pattern of velocity decrease can be predicted over a set of repetitions, so that a minimum repetition threshold to ensure maximal speed performance is determined.     

The effect of continuous repetition training and intra-set rest training on bench press strength and power

AIM: The purpose of this research was to compare the effects of continuous repetition and intra-set rest training on maximal strength and power output of the upper body. METHODS: The 6 repetition maximum (6RM) and bench press throw power output against masses of 20, 30 and 40 kg of 26 elite junior male basketball and soccer players were tested on 2 separate occasions for reliability purposes. Subjects were then randomly assigned to either a continuous repetition (CR - 4 sets x 6 repetitions) or intra-set rest (ISR - 8 sets x 3 repetitions) training regime over 6-weeks. Volume (sets x repetitions x %6RM) between groups was equated and both groups completed all sets in the same time period (13 minutes and 20 seconds). The total concentric work time was determined to identify differences in training regimes. Independent sample t-tests on preintervention and postintervention percentage change scores were analysed for significant differences (p<0.05). RESULTS: The observed coefficients of variation (1.7% to 4.8%) and intraclass correlation coefficients (r=0.87 to 0.98) indicated stability of these measures across testing occasions. The CR group significantly increased 6RM strength (9.7%) compared with the ISR group (4.9%). The total concentric work time was significantly longer in CR training than ISR (36.03+/- 4.03 s and 31.74+/-4.71 s; p=0.13). Power output increases across the 20, 30 and 40 kg loads ranged from 5.8% to 10.9% for both training groups but the between-group percentage change scores were not significantly different. CONCLUSIONS:Bench press training involving 4 sets of 6 continuous repetitions elicited a greater improvement in bench press strength than 8 sets of 3 repetitions at the same percentage load of their 6RM. Both ISR and CR training were equally effective in increasing power output.     

Responses to kayak ergometer performance after kayak and bicycle ergometer training.

Ten moderately active male volunteers, age 19-30 years, completed one month of training on either a kayak or a bicycle ergometer (five men in each group). The men completed sixteen 30 minute sessions of continuous work at an intensity which maintained their HR within 85-90% of its maximum, as previously determined on the kayak ergometer. After this training period the kayak group demonstrated significant decreases in VO2, VE, HR and blood lactate in submaximal kayak ergometer work and a significant increase in VO2 during maximal kayak ergometer work. These changes contributed to a significantly higher maximal kayaking work output. The bicycle-trained group did not make any of these improvements on the kayak ergometer. However in their last training session on the bicycle ergometer they were able to work at a higher submaximal load while maintaining the same heart rate as in the first training session. It was concluded that the circulatory and metabolic adjustments to kayak work are greater with kayak training than with bicycle training.     

Effect of reduced training on muscular strength and endurance in competitive swimmers

Following 5 months of competitive training (approximately 9,000 yards.d-1, 6 d.wk-1), three groups of eight male swimmers performed 4 wk of either reduced training (3,000 yard.session-1) or inactivity. Two groups reduced their training to either 3 sessions.wk-1 (RT3) or 1 session.wk-1 (RT1), whereas the third group (IA) did no training. Measurement of muscular strength (biokinetic swim bench) showed no decrement in any group over the 4 wk. In contrast, swim power (tethered swim) was significantly decreased (P less than 0.05) in all groups, reaching a mean change of -13.6% by week 4. Blood lactate measured after a standard 200-yard (183 m) front crawl swim increased by 1.8, 3.5, and 5.5 mM over the 4 wk in groups RT3, RT1 and IA, respectively. In group RT1, stroke rate measured during the 200-yard swim significantly increased (P less than 0.05) from 0.54 +/- 0.03 to 0.59 +/- 0.03 strokes.-1 while stroke distance significantly decreased (P less than 0.05) from 2.50 +/- 0.08 to 2.29 +/- 0.13 m.stroke-1 during the 4-wk period. Both stroke rate and stroke distance were maintained in group RT3 over the 4 wk of reduced training. Group IA was not tested for stroke mechanics. Whereas maximal oxygen uptake decreases significantly (P less than 0.05) over the 4 wk in group RT1 (4.75 to 4.62 l.min-1), no change in maximal oxygen uptake was observed in group RT3. These results suggest that aerobic capacity is maintained over 4 wk of moderately reduced training (3 sessions.wk-1) in well-trained swimmers. Muscular strength was not diminished over 4 wk of reduced training or inactivity, but the ability to generate power during swimming was significantly reduced in all groups.     

Physiological consequences of U.S. Army Ranger training

PURPOSE: Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones. METHODS: In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal.d, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 +/- 4.4 y; 176.1 +/- 7.8 cm; 78.4 +/- 8.7 kg; 14.7 +/- 4.2% body fat) before and after the course. RESULTS: Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass. CONCLUSION: Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (>or=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.     

Weight lifting training and left ventricular function in adolescent subjects

AIM: Training during adolescence may influence the myocardium's adaptation. Effects of exercise training on left ventricular function differ depending whether they result from pressure or volume overload. Accordingly, the present study was designed to examine, by echocardiography studies, the effects of endurance versus weight lifting training modes on left ventricular contractility in healthy adolescent boys. METHODS: Sixty healthy adolescent boys were randomly and evenly divided into 3 groups: weightlifting training, run-training, and control. Exercising groups underwent 28-week training programs, 3-4 times a week, 35 min each session. The weight lifting program for consisted of training on 6 dynamic resistive machines at resistance corresponding to 6-repetition maximum. The running program was composed of aerobic exercise training at 65% of their VO(2max). RESULTS: At rest, only in the runners end diastolic volume and end systolic pressure-volume ratio differed significantly (P<0.05) from pre- to post-testing. During post-testing session at peak exercise, runners compared to weightlifters demonstrated improvement respectively in: wall stress (245+/-42 and 290+/-35 103 dyn.cm(2)), end systolic pressure-volume ratio (7.2+/-.7 and 6.4+/-.5 ratio) and ejection fraction (82+/-5% and 76+/-5%). Maximal oxygen uptake (48.2+/-3.2 and 43.8+/-3.5 mL.kg(-1).min(-1)), also improved significantly (P<0.05). Maximal load was significantly (P<0.05) higher in the runners and weight lifters than in the control group with significantly (P<0.05) higher values for the weight lifters than runners. CONCLUSION: This study has showed that in adolescent boys the mode of exercise training leads to significant differences in left ventricular function and contractility, related to differences in volume-after-load relationship and not to fundamental differences in the properties of the myocardium.     

Oxygen uptake and plasma catecholamines during submaximal and maximal exercise after long-term beta-receptor blockade

Beta-receptor antagonists lower exercise heart rate and cardiac output, and can thus be expected to interfere with oxygen transport, and hence physical performance, particularly at higher levels of activity. Therefore, the effects of a 4-week and 15-month treatment period with the beta 1-selective receptor blocker acebutolol (500 mg daily) on oxygen uptake and plasma catecholamines during submaximal steady-state and maximal exercise and on maximal work load were studied in eight WHO stage 1 hypertensive men (mean age 36.4 years). Oxygen uptake, ventilation, and plasma noradrenaline, adrenaline, and dopamine concentrations during steady-state exercise were not significantly different from control conditions either after 4 weeks or after 15 months of receptor blockade, although heart rates were significantly (27% and 25%, respectively; P less than 0.01) reduced. After the 4-week treatment period, maximal oxygen uptake (3.9% reduction, NS) and maximal work load (2.4% reduction, NS) tended to be slightly lower after acebutolol compared with control values; maximal oxygen pulse was significantly (P less than 0.05) increased. However, after long-term treatment of 15 months, maximal oxygen uptake was virtually identical compared with pretreatment values, and maximal work load tended to be higher (5.2%, NS); plasma noradrenaline and adrenaline concentrations were significantly (P less than 0.05) enhanced. Since beta 1-selective receptor blockers do not affect maximal oxygen uptake and maximal work capacity after long-term treatment, they appear preferable for patients taking part in preventive and rehabilitative training programs.     

Effects of low- and high-repetition resistive training on lipoprotein-lipid profiles

Thirty-seven healthy untrained males (age = 21 +/- 1 yr; range = 19 to 35 yr) were studied to determine the effects of 10 wk of low- and high-repetition resistive training on lipoprotein-lipid profiles. Subjects were assigned to 1 of 3 groups: a low-repetition group (N = 15) that trained using 4 to 6 repetitions maximum or a high-repetition group (N = 14) that used 14 to 16 repetitions maximum in their training or to an inactive control group (N = 8). The number of sets was adjusted to equalize workloads. Muscular strength increased significantly in both training groups as indicated by the increase in the one-repetition maximum test (P less than 0.05). VO2max, body weight, and percent body fat did not change in either of these groups. However, fat-free weight increased significantly in both training groups (both P less than 0.05). The low-repetition training program resulted in no significant changes in the plasma concentrations of triglycerides (104 +/- 15 vs 89 +/- 8), total cholesterol (150 +/- 7 vs 141 +/- 6), high-density lipoprotein (HDL)-cholesterol (40 +/- 1 vs 41 +/- 2), and HDL2-cholesterol (7 +/- 1 vs 7 +/- 1). A similar pattern was observed for the high-repetition group ([i.e., no significant changes in the concentrations of triglycerides (87 +/- 10 vs 89 +/- 8), total cholesterol (148 +/- 6 vs 162 +/- 6), HDL-cholesterol (40 +/-2 vs 40 +/- 2), and HDL2-cholesterol (6 +/- vs 1 vs 7 +/- 2)]. All lipid values were expressed in milligrams per deciliter (mean +/- SE).(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuromuscular responses in male and female athletes to two successive strength training sessions in one day.

Acute neuromuscular responses to two successive strength training sessions performed in the same day were investigated in nine male (MSA) and ten female (FSA) strength athletes. The loads for the leg extensor muscles varied between 70 and 80% of one repetition maximum (IRM) during the morning session (I) (from 10.00 to 11.00 hours) and between 70 and 100% of IRM during the afternoon session (II) (from 16.00 to 17.00 hours). Significant decreases occurred in maximal isometric strength both in MSA from 3855 +/- 791 to 3744 +/- 882 N (p < 0.05) and in FSA from 2493 +/- 553 to 2371 +/- 523 N (p < 0.05) during session I, while only slight (ns) changes took place in the maximal neural activation (IEMG) of the exercised muscles. During session II a great decrease of 8.5 +/- 6.3% (p < 0.01) took place in maximal strength (from 3911 +/- 786 to 3556 +/- 590 N) accompanied by a shift (worsening) in the average force-time curve in MSA, while only a slight change of 2.7 +/- 6.5% (ns) occurred in maximal strength (from 2462 +/- 529 to 2398 +/- 453 N) in FSA. The individual changes in the maximum averaged IEMG of the exercised muscle during session II were correlated (p < 0.05) to the individual changes in maximal strength. The present results suggest that high but submaximal loading of the neuromuscular system may result in an acute decrease in maximal strength of the exercised muscles taking place rather similarly both in males and females.(ABSTRACT TRUNCATED AT 250 WORDS)     

Specificity of run training on VO2 max and heart rate cganges during running and swimming

To further evaluate the specificity of aerobic training, maximum physiologic measures (VO2, VE, HR, and R) and submaximal exercise heart rate were determined in control (N = 8) and experimental (N = 11) subjects prior to and following 10-week interval run training. Experimental subjects significantly increased (P less than 0.01) treadmill VO2 max by 252 ml O2 or 6.3%. This was siginificantly larger (P less than 0.01) than the 87 ml O2 or 2.6% increase (P less than 0.05) observed during swimming. Max HR decreased significantly in both forms of exercise. In addition, heart rate at two submaximal work levels during running and swimming was significantly lower after training.No changes in metabolic and physiologic measures were demonstrated for the controls after the 10-wk period. These results further support the concept of the specificity of the metabolic adaptation to aerobic training and strongly suggest that local adaptations in skeletal muscle significantly contribute to improvement in VO2 max. However, running may produce a general training adaptation in maximal and submaximal heart rate.     

Effects of 7 successive days of unaccustomed prolonged exercise on aerobic performance and tissue damage in fitness joggers

The effects of 7 successive days of prolonged jogging on aerobic performance and biochemical markers of muscle and red blood cell damage were examined in 10 moderately fit men, ages 27 +/- 2 yr (mean +/- SE). The subjects jogged for 2 h per day at 78 +/- 4% of maximal heart rates and covered a total of 129 +/- 2 km, nearly eight times their regular weekly training distance. At baseline, maximal oxygen uptake (VO2max) during treadmill tests averaged 3.45 +/- 0.24 L/min, or 44.7 +/- 1.4 ml/kg/min. On follow-up tests 2d after the week of increased training, VO2max (3.56 +/- 0.17 L/min) and treadmill performance were not significantly improved. Body weight declined from 79.5 +/- 4.6 kg to 77.8 +/- 4.4 kg (p less than 0.05) because of reduced body fatness (16.8 +/- 2.3% to 13.6 +/- 1.7%, p less than 0.05). Weight-adjusted VO2max increased to 46.4 +/- 2.0 ml/kg/min (p less than 0.05). However, heart rate and systolic blood pressure were not significantly changed at rest, or during submaximal and maximal treadmill exercise. Mean hemoglobin concentration at treadmill testing declined from 14.9 +/- 0.3 g/dl to 13.3 +/- 0.3 g/dl (p less than 0.05). Leg muscle soreness, especially in the thigh region, persisted in all subjects after 3 d. Soreness was accompanied by chronic elevations (p less than 0.05) in serum levels of myoglobin, creatine kinase (CK), lactic dehydrogenase (LD), aminoaspartate, and the isoenzymes CK-MB and LD1,2. Serum haptoglobin levels after jogging fell from 86 +/- 9 mg/dl to 60 +/- 8 mg/dl (p less than 0.05), suggestive of footstrike hemolysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Constant vs variable resistance knee extension training

To compare the effect of constant resistance (CR) and variable resistance (VR) training on full range-of-motion (ROM) strength development, 22 men and 27 women (age = 26 +/- 5 yr) were randomly assigned to either a CR training group (N = 17), a VR training group (N = 17), or a control group (N = 15) that did not train. The CR and VR groups trained 2 to 3 d.wk-1 for 10 wk. Subjects completed one set of full ROM (120 to 0 degrees of flexion) bilateral knee extensions with an amount of weight that allowed 8 to 12 repetitions during each training session. For the VR group, resistance was varied with a cam supplied by the manufacturer (Nautilus). For the CR group, the cam was removed and replaced with a round sprocket. Prior to and after training, maximal voluntary isometric torque was measured at 9, 20, 35, 50, 65, 80, 95, and 110 degrees of knee flexion. Analysis of covariance indicated that the VR and CR groups gained strength at all angles (P less than or equal to 0.05) when compared to the control. [table: see text] There was no difference (P greater than 0.05) between the CR and VR groups at any angle, and the magnitude of strength gained was similar (P greater than 0.05) among angles for both groups. These data indicate that both CR and VR knee extension training elicit full ROM strength development.     

Resistance training with vascular occlusion: metabolic adaptations in human muscle

Two recent studies have reported increases in strength and whole muscle cross-sectional area after low-intensity resistance training (LIT) with vascular occlusion (OCC) that are greater than LIT alone (e.g., 22, 25). The OCC stress might be expected to induce metabolic alterations that are consistent with compromised oxygen delivery rather than an increase in strength per se, but this has not been studied. PURPOSE: We examined the effect of LIT and LIT+OCC on resting metabolites in m. biceps brachii and elbow flexor strength. METHODS: Eight men (19.5 +/- 0.4 yr) performed 8 wk of LIT at approximately 50% of one-repetition maximum (2 sessions per week; 3-6 sets, 8-10 repetitions, final set to failure); one arm trained with OCC and the other without (CON). :Biopsies obtained before and 72 h after the final training bout revealed that resting [glycogen] was higher (P 相似文献   

Atrioventricular plane displacement in untrained and trained females

PURPOSE: Female athletes often demonstrate changes in cardiac dimensions that are less prominent than in male athletes, and results from longitudinal studies are conflicting. The atrioventricular plane displacement (AVPD) in the heart is used as an index of left ventricular systolic function with the assumption that it is a more sensitive method for measuring myocardial contractility compared with left ventricular ejection fraction. The aim of the present study was to determine the effect of a short period of endurance training on cardiac dimensions in sedentary female subjects and to measure the AVPD at rest and during submaximal workload. METHODS: Twelve sedentary female subjects (21.9 +/- 1.3 yr, 168.8 +/- 3.5 cm, 64.0 +/- 6.6 kg, and 42.6 +/- 2.9 mL x kg(-1) x min(-1) in maximal oxygen uptake) were examined with echocardiography before and after a period of interval training (varying from 2 to 5 min at 90-95% of maximal heart rate, 3 d x wk(-1), 8 wk). RESULTS: Maximal oxygen uptake increased by 18% to 50.4 +/- 3.1 mL x kg(-1) x min(-1) (P < 0.001). Left ventricular mass increased from 123.9 to 139.2 g (P = 0.007). There was a significant increase in posterior wall thickness but no change in cavity size. The AVPD did not change at rest but increased significantly from 15.6 to 17.6 mm (P < 0.001) during exercise at 85-90% of maximal heart rate. CONCLUSION: This study shows that a short period of aerobic endurance training induces changes in the female heart, both in cardiac dimensions at rest and in left ventricular systolic function at submaximal workload. AVPD during submaximal exercise discriminate well between the untrained and trained healthy heart.