Leg Curl Research Articles

EFFECTS OF A PROGRESSIVE RESISTANCE-TRAINING PROGRAM ON FUNCTIONAL ABILITIES IN OLDER MEN AND WOMEN

The purpose of this study was to investigate the effects of 6 weeks of resistance training on functional activities among elderly men and women between the age of 60 and 79 years (6 ± 1). Twenty-two older adults (8 men and 14 women) participated in the program. A battery of tests designed to assess the physiologic components associated with independent functioning in elderly individuals were performed. These tests included 30-s chair stand (reps), arm curl (reps in 30 sec), back scratch (in, + or -), chair sit-and-reach (in, + or -), 8-fit up-and-go (sec), and 6-min-walk (yd) (Rikli and Jones, 1999). Training involved 3 weekly training sessions consisting of one set of 12–15 reps (until volitional fatigue) for lower and upper body machine exercises (leg press, leg extension, leg curl, arm curl, shoulder press, chest press, seated row, crunches, arm extension). Upon completion of 15 reps, resistance was increased approximately 10 percent during the next session. Prior to each session, subjects performed 20 min of stretching exercises. Training resulted in significant (p <0.05) improvements for all functional tests in both men and women. There were no gender effects with training. The results indicate that a resistance-training program can effectively improve overall fitness in older men and women, thus enabling them to perform functional or daily basic activities with less effort.Table

THE EFFECT OF RESISTANCE TRAINING INTENSITY ON STRENGTH GAIN RESPONSE IN THE OLDER ADULT

The purpose of this study was to examine how resistance training intensity effects strength change responses in the older adult over an 18 week training period. Subjects were divided into the following four groups, each of different training intensity but similar training volumes; Group A (n = 19, age 71.4 ± 4.6) performed 2 sets of 15 repetitions maximum (RM), Group B (n = 13, age 71.5 ± 5.2) performed 3 sets of 9 RM, Group C (n = 17, age 69.4 ± 4.4) performed 4 sets of 6 RM, Group D (n = 14, age 72.3 ± 5.9) served as Controls. No differences existed between groups relative to age or strength level at baseline (p < .05). Training groups exercised two times per week on eight exercises (Leg Press, Lat Pull, Tricep Extension, Bicep Curl, Leg Curl, Shoulder Press, Bench Press, Leg Extension). One repetition maximum (1RM) scores for each exercise were totaled providing an aggregate strength score (TOT). TOT scores were obtained every 6 weeks and the difference in TOT scores between baseline and each 6-week measurement period (Delta TOT) were entered as the dependent variable in statistical analyses. Repeated measures ANOVA and Scheffe post-hoc analyses revealed that at 6 weeks only Groups B and C were Significantly stronger than Group D (p < .01). By 12 and 18 weeks, all training groups were significantly stronger than controls (p < .01). This suggests that with similar training volumes, the level of strength gain in the older adult over 18 weeks of training is independent of training intensities ranging from 15 repetitions maximum to 6 repetitions maximum. However, no difference existed between Groups A, B, and C at any time period. This suggests that with similar training volumes, the level of strength gain in the older adult over 18 weeks of training is independent of training intensities ranging from 15 repetitions maximum to 6 repetitions maximum.

Early-Phase Adaptations of Traditional-Speed vs. Superslow Resistance Training on Strength and Aerobic Capacity in Sedentary Individuals

We performed a randomized exercise training study to assess the effects of traditional Nautilus-style (TR) or superslow (SS) strength training on muscular strength, body composition, aerobic capacity, and cardiovascular endurance. Subjects were 14 healthy, sedentary women, 19-45 years of age (mean +/- SD age, 32.7 +/- 8.9 years), randomized to either the SS or TR training protocols and trained 3 times per week for 10 weeks. Measurements were taken both before and after training, which included a maximal incremental exercise test on a cycle ergometer, body composition, and 1 repetition maximum (1RM) tests on 8 Nautilus machines. Both groups increased their strength significantly on all 8 exercises, whereas the TR group increased significantly more than the SS group on bench press (34% vs. 11%), torso arm (anterior lateral pull-down) (27% vs. 12%), leg press (33% vs. 7%), leg extension (56% vs. 24%), and leg curl (40% vs. 15%). Thus, the TR group's improvement in total exercise weight lifted was significantly greater than that of the SS group after testing (39% vs. 15%). Exercise duration on the cycle ergometer and work rate significantly improved for both groups, but there was no group-by-training interaction. No significant differences were found for body composition or additional aerobic variables measured. Both strength training protocols produced a significant improvement in strength during a 10-week training period, but the TR protocol produced better gains in the absence of changes in percentage of body fat, body mass index, lean body mass, and body weight. In addition, strength training alone did not improve Vo2max, yet short-term endurance increased.

Single- vs. Multiple-Set Strength Training in Women

The aim of this study was to compare the effects of single-set and multiple-set strength training in women. Twenty-seven women (aged 20-40 years) with basic experience in strength training were randomly allocated to either a single-set group (n = 9), a 3-set group (n = 9), or a nontraining control group (n = 9). Both training groups underwent a whole-body strengthening program, exercising 2 days a week for 6 weeks. Exercises included bilateral leg extension, bilateral leg curl, abdominal crunch, seated hip adduction/abduction, seated bench press, and lateral pull-down. The single-set group's program consisted of only 1 set of 6-9 repetitions until failure, whereas the multiple-set group trained with 3 sets of 6-9 repetitions until failure (rest interval between sets, 2 minutes). Two times before and 3 days after termination of the training program, subjects were tested for their 1 repetition maximum strength on the bilateral leg extension and the seated bench press machine. Data were analyzed using a repeated-measures analysis of variance, Scheffé tests, t-tests, and calculation of effect sizes. Both training groups made significant strength improvements in leg extension (multiple-set group, 15%; single-set group, 6%; p 0.05). However, in the seated bench press only the 3-set group showed a significant increase in maximal strength (10%). Calculation of effect sizes and percentage gains revealed higher strength gains in the multiple-set group. No significant differences were found in the control group. These findings suggest superior strength gains occurred following 3-set strength training compared with single-set strength training in women with basic experience in resistance training.

Effects of Cardiovascular Fitness and Muscle Strength on Hearing Sensitivity

Persons with healthy cardiovascular (CV) fitness have more acute hearing than persons with below-average CV fitness. Possible mechanisms include enhanced circulation, healthier blood lipid profiles, and different sympathetic activity. Muscle strength (MS) and conditioning programs may influence hearing acuity via similar proposed mechanisms. But studies have only examined the relationship of cardiovascular fitness and hearing. This study compared pure tone hearing levels and otoacoustic emissions for 4 groups categorized as high CV-high MS (n = 11), high CV-low MS (n = 10), low CV-high MS (n = 7), and low CV-low MS (n = 15). Twenty-four women and 19 men, mean (±SD) age = 21 ± 4 years underwent hearing tests at 3 frequencies: 2, 3, and 4 kHz. Each group's Vo2max; strength by leg curl, leg extension, bench press, and hand grip; blood lipid profile; body composition; and diet recall were assessed. Pure tone hearing results showed that at 2 kHz, the high CV-high MS group had better hearing than the low CV-high MS group (F = 4.31, p = .04). Otoacoustic emission results demonstrated similar patterns. The fitness-hearing relationship appears to be specifically related to cardiovascular fitness. High MS has an additive effect with CV on hearing.

Cytokines and cell adhesion molecules associated with high-intensity eccentric exercise.

Unaccustomed, eccentrically biased exercise induces trauma to muscle and/or connective tissue. Tissue damage activates an acute inflammatory response. Inflammation requires the effective interaction of different physiological and biological systems. Much of this is coordinated by the de novo synthesis of families of protein molecules, cytokines. The purpose of the present paper was to determine changes in blood levels of various cytokines in response to exercise-induced muscle damage that was effected using high-intensity eccentric exercise. Six healthy, untrained, college-age male subjects were required to perform the eccentric phase of a bench press and a leg curl (4 sets, 12 repetitions/set) at an intensity equivalent to 100% of their previously determined one-repetition maximum. Samples of blood were drawn at the following times: before exercise and 1.5, 6, 12, 24, 48, 72, 96, 120, and 144 h after exercise. These samples were analyzed for interleukins (IL): IL-1beta, IL-6, and IL-10; tumor necrosis factor-alpha; colony stimulating factors (CSF): granulocyte-CSF, macrophage-CSF, and GM-CSF; for cell adhesion molecules (CAM): P- and E-selectin, and intercellular cell adhesion molecule (ICAM-1), and vascular cell adhesion molecule (VCAM-1). Results were analyzed using a repeated-measures analysis of variance (P = 0.05). Compared to baseline values, IL-1beta was reduced (P = 0.03) at 6, 24, and 96-144 h after exercise; IL-6 was elevated (P = 0.01) at 12, 24, and 72 h after exercise; IL-10 was elevated (P = 0.009) between 72 and 144 h after exercise; M-CSF was elevated (P = 0.005) at 12 and 48-144 h after exercise; and P-selectin was reduced (P = 0.01) between 24 and 144 h after exercise. It is concluded that when high-intensity eccentric exercise is compared to strenuous endurance exercise, post-exercise changes in cytokines do occur, but they are generally of a smaller magnitude, and occur at a later time period after the termination of exercise.

Single versus multiple sets in long-term recreational weightlifters.

The purpose of this study was to determine the effects of increasing training volume from one set to three sets on muscular strength, muscular endurance, and body composition in adult recreational weight lifters. Forty-two adults (age 39.7 +/- 6.2 yr; 6.2 +/- 4.6 yr weight training experience) who had been performing one set using a nine-exercise resistance training circuit (RTC) for a minimum of 1 yr participated in this study. Subjects continued to perform one set (EX-1; N = 21) or performed three sets (EX-3; N = 21) of 8-12 repetitions to muscular failure 3 d x wk(-1) for 13 wk using RTC. One repetition maximums (1-RM) were measured for leg extension (LE), leg curl (LC), chest press (CP), overhead press (OP), and biceps curl (BC). Muscular endurance was evaluated for the CP and LE as the number of repetitions to failure using 75% of pretraining 1-RM. Body composition was estimated using the sum of seven skinfold measures. Both groups significantly improved muscular endurance and 1 RM strength (EX-1 by: 13.6% LE; 9.2% LC; 11.9% CP; 8.7% OP; 8.3% BC; and EX-3 by: 12.8% LE; 12.0% LC; 13.5% CP; 12.4% OP; 10.3% BC) (P < 0.05). Both groups significantly improved lean body mass (P < 0.05). No significant differences between groups were found for any of the test variables (P > 0.05). Both groups significantly improved muscular fitness and body composition as a result of the 13 wk of training. The results show that one-set programs are still effective even after a year of training and that increasing training volume over 13 wk does not lead to significantly greater improvements in fitness for adult recreational weight lifters.

Electromyographic Activity of the Hamstrings During Performance of the Leg Curl, Stiff-Leg Deadlift, and Back Squat Movements

To compare the effectiveness of 3 weight-training movements for the hamstrings, 11 weight-trained men performed 3 repetitions at 75% of 1 repetition maximum of the leg curl (LC), stiff-leg deadlift (SLDL), and back squat. Integrated electromyography (EMG) and peak EMG were analyzed in the biceps femoris and semitendinosus independantly during the concentric (CON) and eccentric (ECC) phase of each exercise. Results were as follows: CON-LC and CON-SLDL elicited the greatest integrated EMG activity, with no significant difference between exercises. The CON-squat showed approximately half as much integrated EMG activity as CON-LC and CON-SLDL. Highest peak EMG was found in the CON-LC and CON-SLDL, with no significant difference in these exercises. The CON-squat produced a peak EMG that was approximately 70% of LC and SLDL. We conclude that LC and SLDL involve the hamstrings to a similar degree; however, the back squat involves only about half as much hamstring integrated EMG activity as LC and SLDL.

ACCURACY OF SEVEN EQUATIONS FOR PREDICTING 1-RM PERFORMANCE OF OLDER ADULTS

1958 While numerous 1-RM prediction equations have been tested in younger active populations, their accuracy is unknown among older sedentary adults. This study compared seven prediction equations (Brzycki, Epley, Lander, Lombardi, Mayhew et al., O'Conner et al., and Wathan) for estimating 1-RM performance of older sedentary adults using Hammer Strength Iso-Lateral resistance exercise machines. Data were collected from 49 healthy volunteers (26 males, 23 females) aged 53.55±3.34 (mean±SD) years. 1-RM was obtained for chest press (CP), high lat pull (HL), leg curl (LC), leg press (LP), shoulder press (SP), low lat pull (LL), incline chest press (IC), leg extension (LE), biceps curl (BC) and triceps extension (TE). Repetitions to failure (RTF) for each exercise were determined while counterbalancing the design for order. Each subject was randomly assigned a percentage of their 1-RM ranging from 50-90% for each exercise. Subjects performed as many repetitions as possible with the predetermined resistance. Accuracy of predicted 1-RM (1-RMP) was evaluated by relative accuracy (correlation between 1-RM and 1-RMP), similarity (paired t-test between 1-RM and 1-RMP), and average error (sqrt[Σ(1RMP-1RM)2/n]). Correlations ranged from .41 (r2=.17) to .98 (r2=.96) (p<.005). However, with the exception of the Brzycki and Lander predictions for LP and TE, the lowest correlation was .81 (r2=.67) indicating that rank ordering of subjects by 1-RMP and 1-RM was similar. Similarity statistics revealed that the Brzycki and Lander equations showed no statistically significant mean differences (p>.05) in 1-RM for BC, LL, LE, LC, and TE, while the Epley and Wathan equations performed well for HL, LP and TE. When RTF ≤10 the average error expressed as a percent of mean 1-RM ranged from 7-20% over all formulas and exercises. The error increased to a range of 12-150% over the full range of RTF (1-40). The Brzycki and Lander's predictions produced unacceptable error (>75%) for LP and TE when RTF >30. Overall, the Epley and Wathan formulas produced the least error (13-22%) over the full range of RTF. In conclusion, all formulas rank ordered subjects similarly to 1-RM and produced similar average error when RTF ≤10. The Epley and Wathan formulas provided the best overall performance over all exercises and the full range of RTF.

TESTOSTERONE REPLACEMENT AND RESISTANCE EXERCISE TRAINING IN HIV-INFECTED MEN: EFFECTS ON BODY COMPOSITION AND STRENGTH

1308 Low levels of serum testosterone (T) are common during the course of HIV infection, potentially contributing to depletion of lean tissue and muscle dysfunction. Muscle wasting is associated with poor disease outcome, debility, and poor quality of life in HIV-infected men. Testosterone and resistance exercise training (RET) improve lean body mass and strength in other sarcopenic states. We therefore examined the efficacy of these anabolic interventions on body composition and strength in 49 HIV-infected mean with >5% weight loss and serum T <350 ng/dL in a randomized, double-blind, placebo controlled trial. Subjects were randomly assigned to one of four groups: I, placebo, no exercise (n=12); II, T, no exercise (n=15); III, placebo plus RET (n=11); IV, T plus RET (n=11). Testosterone enanthate, 100 mg, was given IM weekly for 16 weeks. The men in the RET groups underwent 16 weeks of a progressive, standardized program of strength training 3 d/wk utilizing the leg press, leg curl, chest press, lat pull, and seated press exercises. Fat-free mass by DEXA increased significantly from baseline in the two T groups and the exercise alone group (mean increase was 2.3, 2.4, and 2.6 kg for groups II, III, and IV, respectively, p <0.005), but not in the placebo no exercise group. Muscle strength increased significantly for each of the five exercises in all but group I (mean overall gain in strength was 0, 14, 28, and 25% in groups I-IV, respectively, p <0.005). We conclude that physiologic T replacement and RET augment fat-free mass and strength in HIV-infected men with low T levels and weight loss. Resistance exercise training alone appears to provide the same improvements as T alone or in combination with RET in this population. Further studies are needed to assess the effects of T and RET in HIV disease outcomes.

HEARING ACUITY IS RELATED TO CARDIOVASCULAR NOT MUSCULAR FITNESS

1197 Research reports on the relation between physical fitness and hearing acuity have indicated that persons with healthier cardiovascular (CV) fitness have more acute hearing than persons with low CV fitness. Possible mechanisms include enhanced circulation, healthier blood lipid profile, or greater sympathetic activity. Muscle strength (S) and conditioning programs may influence hearing acuity via similar proposed mechanisms. But only CV fitness relative to hearing has been studied. This study compared pure tone hearing (in a quiet setting) and hearing after noise exposure (TTS), among four groups categorized as high CV fit, high S (n-11), high CV, low S (n=11), low CV, high S (n=6), and low CV, low S (n=14). 23 females and 19 males, mean age 21+/− 4 years underwent different types of hearing tests at three frequencies: 2,3,and 4 kHz. VO2 max, strength by leg curl, leg extension, bench press, and hand grip, blood lipid profile, body composition, and diet recall were assessed. Subject selection into categories for high and low CV and S were determined according to published standards. Puretone hearing results showed that at 2 kHz, the high CV, low S group had better hearing than low CV, high S, F=4.76, p=.03 and high CV, high S had better hearing than low CV, high S, F=3.86, p=.05; at 3 kHz, high CV, low S had better hearing than low CV, high S, F=4.82, p=.03; at 4 kHz, high CV, low S had better hearing than low CV, high S, F=3.12, p=.08. TTS was better in the high CV, low S group compared to high S, low CV but only at 2 kHz, F=3.90, p=.05. No relations between body composition, blood lipid proflie, diet recall, and hearing were found. In conclusion, the fitness-hearing relation appears to be specifically related to cardiovascular fitness, not muscle strength and endurance.

Electromyographic Activity of the Hamstrings During Performance of the Leg Curl, Stiff-Leg Deadlift, and Back Squat Movements

ABSTRACTTo compare the effectiveness of 3 weight-training movements for the hamstrings, 11 weight-trained men performed 3 repetitions at 75% of 1 repetition maximum of the leg curl (LC), stiff-leg deadlift (SLDL), and back squat. Integrated electromyography (EMG) and peak EMG were analyzed in the bi

RESISTANCE TRAINING AND ACTIVITIES OF DAILY LIVING IN OLDER ADULTS 606

We examined the effects of a 16-week resistance training (RT) program on muscular strength (MS) and activities of daily living (ADL) in 18 female and 4 male subjects (56-90 yrs; 71±8.5). A one repetition maximum (1RM) lift was used to evaluate upper and lower body MS in dominant (D) and non-dominant(ND) limbs. ADL were evaluated using the Chair-to-Counter test, a component of the Amundsen test battery. Subjects trained 3x/wk, 1 hr, 3 sets-6 reps at 70% of 1RM. Statistical analysis (ANOVA) revealed significant strength gains (p<0.05) in upper body MS for the: biceps curl(BC)-ND; triceps extension (TE)-D; lateral arm raise (LR)-D, ND; arm flexion(AF)-D, ND, as well as lower body MS for knee extension (KE)-D, ND; leg curl(LC)-D, ND and hip flexion (HF)-D, ND. Performance in theChair-to-Counter test improved by 16.1% (p<0.05) after training. A Pearson Product Moment Correlation (r) was applied to tests of MS and ADL prior to (T1) and after RT (T2). Table These findings suggest MS and ADL were significantly enhanced in older adults following 16 weeks of RT. Furthermore, the changes in correlations from T1 to T2 suggest the improvements in the ability to perform ADL were related to increases in MS.

THE EFFECTS OF IBUPROFEN ON DELAYED MUSCLE SORENESS AFTER ECCENTRIC EXERCISE840

The purpose of this study was to examine the effects of ibuprofen (an anti-inflammatory drug) on delayed muscle soreness, induced by eccentric exercise. Nineteen subjects age (x±s) 24.6±3.3 yr., height 176.2±11.1 cm. weight 77.3±18.7 kg and body fat 17.2±4.2% performed eccentric leg curl exercise in order to induce muscle pain in the hamstrings. Thereafter 10 subjects randomly received a placebo (double blind) and 9 an ibuprofen pill of 400 mg every 8 hours within a period of 48 hours. Blood samples of 15 ml for the measurement of creatine kinasse (CK) and white blood cells (WBC) were taken after 4-6, 24 and 48 hours of exercise. The maximal strength (1-RM), as well as the power and the range of motion decreased significantly (p<0.05) after 24 hours and after 48 hours of exercise in both the placebo and the ibuprofen group. Perceived pain increased in both groups after 24 and 48 hours (p<0.05), although the ibuprofen group yielded a significantly lower value (p<0.05) after 24 hours. The WBC were significantly increased after 4-6 hours (p<0.05). The CK values of the ibuprofen group were also significantly lower (p<0.05) after 24 and 48 hours revealing a significant interaction with the placebo group. The anti-inflammatory drug used in the present study relieved the pain and facilitated the repair of muscle damage induced by eccentric exercise. These results permit athletes to follow an eccentric exercise program in order to enhance their athletic performance.

EFFECT OF GLYCINE INGESTION AND ACUTE RESISTANCE EXERCISE ON GROWTH HORMONE RELEASE IN MALE WEIGHTLIFTERS 220

Previous research has shown an increase in growth hormone(GH) release following glycine infusion. The purpose of this study was to examine the effect of ingesting 12g of powdered glycine alone, and when combined with acute resistance exercise on GH release. 5 weight trained males (86.4kg,25yrs) participated in 3 randomly presented conditions separated by 5-8 days, with all sessions at the same time of day to minimize diurnal GH variations. Conditions were glycine alone (G), resistance exercise alone(RX), and glycine plus exercise(GRX). Blood from a forearm vein catheter was analyzed for GH(via RIA), hemoglobin, and hematocrit. Exercise consisted of 4 sets of 10 reps for the following exercises: squat, leg press, leg extension, leg curl, calf press, front lat pulldown, pulley rows, and dumbbell rows. Sets were separated by 1 minute rest. Blood was collected 15 minutes post-arrival (base), immediate post-ingestion (0)30,60,90,120 minutes post-ingestion. GH values are shown below (ng/ml). All values were corrected for plasma volume shifts. For RX and GRX conditions, the 30 and 60 samples were collected after the calf press and dumbbell rows, respectively. Table No differences were found between RX and GRX primarily due to a large subject intervariability. Some subjects showed a dramatic GH release with glycine alone and with exercise plus glycine ingestion, suggesting that a percentage of the population may be more sensitive to glycine ingestion.

Effects of low-volume resistive exercise on beta-endorphin and cortisol concentrations.

It has been recently suggested that high and sustained lactate levels may elicit increases in peripheral B-EN concentrations (16). We have observed elevated and sustained lactate concentrations in response to a low-volume resistive exercise protocol (14) that were similar to those from other exercise protocols that produced elevated beta-endorphin (B-EN) concentrations. Thus, the purpose of the study was to determine the effects of a low-volume (21,700 J) resistive exercise repetition maximum (RM) protocol using weight machines on peripheral lactate, B-EN and cortisol concentrations. Subjects completed 3 sets of bench press, lat-pull, leg extension, and leg curl exercise at a 10-RM load. Blood samples were collected and rating of perceived exertion (RPE, 15-point Borg scale) was assessed before exercise (-40 and -10 min), after each exercise, and after the exercise session (+ 35 min); blood samples were collected at 7 additional post-exercise times. RPE increased significantly throughout the exercise. Lactate concentrations rose significantly to peak at 8.54 mM at LE. B-EN and cortisol concentrations (-10) of 4.63 +/- 0.54 pmol.l-1 and 12.09 +/- 1.44 micrograms.dl-1, respectively, were not significantly elevated over time. The data suggest that a low-volume resistive exercise protocol using weight machines elevates lactate concentrations without altering B-EN and cortisol concentrations.

Follicular and luteal phase hormonal responses to low-volume resistive exercise

The purpose of the study was to 1) determine the effects of a low-volume resistive exercise protocol on serum concentrations of estradiol (E2), progesterone (P4), growth hormone (GH), testosterone (T), and androstenedione (AN) and 2) ascertain whether the endocrine responses are affected by the phase of the menstrual cycle. Eleven untrained, healthy women were assigned to either an early follicular or luteal testing group. The subjects completed three sets of bench press, lat-pull, leg extension, and leg curl exercises at a 10 repetition maximum load on fixed machines with 2-min of rest between sets. Blood samples were collected through an indwelling cannula before, during, and after the exercise. Area-under-the-response-curve (AUC) data demonstrated that E2 concentrations were significantly elevated in both follicular and luteal phases with a greater response in the luteal phase. Moreover, data suggest there is a luteal phase-induced increase in GH and AN in response to the low-volume resistive exercise; however, P4 and T concentrations in untrained women are not increased by low-volume resistive exercise with 2-min rest periods, nor does the altered hormonal milieu produced by the phase of the menstrual cycle affect these hormonal responses.

Growth hormone, IGF-I, and testosterone responses to resistive exercise

It has been suggested that growth hormone (GH), testosterone (T), and insulin-like growth factor I (IGF-I) play large roles in muscle tissue growth; however, in only two investigations IGF-I responses to resistive exercise have been examined. Eight young males who had not weight trained for a minimum of 5 months participated in the study. Three sets of bench press (BP), lat-pull (LP), leg extension (LE), and leg curl (LC) exercises were performed at a 10-RM load for 10 repetitions or until failure. Blood samples were collected from an IV catheter before exercise (-30 min and -10 min), after each individual exercise (BP, LP, LE, LC), and after the exercise session (+5, +15, +25, +35, +95 min; +5:35, +22:30, and +23:30 h). GH, IGF-I, and T determinations were corrected for plasma volume change. GH significantly increased (P < 0.05), but IGF-I did not change. Correction for plasma volume accounted for significant increases in T, but did not account for GH and IGF-I results. These data suggest that moderate resistive exercise may increase GH concentrations, whereas elevated T levels can be accounted for by exercise-induced alteration of plasma volume.

Relationship between Repetitions and Selected percentages of One Repetition Maximum

Ninety-one subjects were tested to determine the number of repetitions they could perform at 40, 60, and 80 percent of one repetition maximum (percent 1 RM) for each of seven specified weight training lifts. Thirty-eight subjects from a previous study (18) were also included in the data analysis. The subjects represented four categories: untrained males (n = 38), untrained females (n = 40), trained males (n = 25) and trained females (n = 26). The results indicated that there was a significant difference (p < 0.05) in the number of repetitions that males and females can perform at the selected percent 1 RM among the seven weight training lifts, as well as in the number of repetitions performed at these percentages across lifts. When comparing untrained and trained males, a significant difference (p < 0.05) was found in the number of repetitions performed at all selected percent 1 RM for the arm curl, knee extension and sit-ups. Significant differences (p < 0.05) were also found at 60 percent 1 RM for the leg curl and at 60 and 80 percent 1 RM for the lateral pulldown. No significant differences (p > 0.05) were found for any percent 1 RM for the bench press and the leg press. When comparing untrained and trained females, a significant difference in performance (p < 0.05) was found among all seven lifts at 40 percent 1 RM. Significant differences (p < 0.05) were found at 60 percent 1 RM for the knee extension, bench press, sit-ups, leg curl and leg press; and at 80 percent 1 RM for the bench press, sit-ups and leg press. The findings of this study indicate that a given percent of 1 RM will not always elicit the same number of repetitions when performing dafferent lifts.

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women

Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.