Jill A. Bush

Creatine Supplementation Enhances Muscular Performance During High-Intensity Resistance Exercise

OBJECTIVE This study was undertaken to investigate the influence of oral supplementation with creatine monohydrate on muscular performance during repeated sets of high-intensity resistance exercise. SUBJECTS/DESIGN Fourteen active men were randomly assigned in a double-blind fashion to either a creatine group (n = 7) or a placebo group (n = 7). Both groups performed a bench press exercise protocol (5 sets to failure using each subjects predetermined 10-repetition maximum) and a jump squat exercise protocol (5 sets of 10 repetitions using 30% of each subjects 1-repetition maximum squat) on three different occasions (T1, T2, and T3) separated by 6 days. INTERVENTION Before T1, both groups received no supplementation. From T1 to T2, both groups ingested placebo capsules. From T2 to T3, the creatine group ingested 25 g creatine monohydrate per day, and the placebo group ingested an equivalent amount of placebo. MAIN OUTCOME MEASURES Total repetitions for each set of bench presses and peak power output for each set of jump squats were determined. Other measures included assessment of diet, body mass, skinfold thickness, and preexercise and 5-minute postexercise lactate concentrations. RESULTS Lifting performance was not altered for either exercise protocol after ingestion of the placebos. Creatine supplementation resulted in a significant improvement in peak power output during all 5 sets of jump squats and a significant improvement in repetitions during all 5 sets of bench presses. After creatine supplementation, postexercise lactate concentrations were significantly higher after the bench press but not the jump squat. A significant increase in body mass of 1.4 kg (range = 0.0 to 2.7 kg) was observed after creatine ingestion. CONCLUSION One week of creatine supplementation (25 g/day) enhances muscular performance during repeated sets of bench press and jump squat exercise.

Low-volume circuit versus high-volume periodized resistance training in women.

PURPOSE The purpose of this investigation was to determine the long-term training adaptations associated with low-volume circuit-type versus periodized high-volume resistance training programs in women. METHODS 34 healthy, untrained women were randomly placed into one of the following groups: low-volume, single-set circuit (SSC; N = 12); periodized high-volume multiple-set (MS; N = 12); or nonexercising control (CON) group (N = 10). The SSC group performed one set of 8-12 repetitions to muscular failure 3 d x wk(-1). The MS group performed two to four sets of 3-15 repetitions with periodized volume and intensity 4 d x wk(-1). Muscular strength, power, speed, endurance, anthropometry, and resting hormonal concentrations were determined pretraining (T1), after 12 wk (T2), and after 24 wk of training (T3). RESULTS 1-RM bench press and leg press, and upper and lower body local muscular endurance increased significantly (P < or = 0.05) at T2 for both groups, but only MS showed a significant increase at T3. Muscular power and speed increased significantly at T2 and T3 only for MS. Increases in testosterone were observed for both groups at T2 but only MS showed a significant increase at T3. Cortisol decreased from T1 to T2 and from T2 to T3 in MS. Insulin-like growth factor-1 increased significantly at T3 for SSC and at T2 and T3 for MS. No changes were observed for growth hormone in any of the training groups. CONCLUSION Significant improvements in muscular performance may be attained with either a low-volume single-set program or a high-volume, periodized multiple-set program during the first 12 wk of training in untrained women. However, dramatically different training adaptations are associated with specific domains of training program design which contrast in speed of movement, exercise choices and use of variation (periodization) in the intensity and volume of exercise.

Influence of exercise training on physiological and performance changes with weight loss in men.

PURPOSE The purpose of this study was to examine the physiological effects of a weight-loss dietary regimen with or without exercise. METHODS Thirty-five overweight men were matched and randomly placed into either a control group (C; N = 6) or one of three dietary groups; a diet-only group (D; N = 8), a diet group that performed aerobic exercise three times per week (DE; N = 11); and a diet group that performed both aerobic and strength training three times per week (DES; N = 10). RESULTS After 12 wk, D, DE, and DES demonstrated a similar and significant (P < or = 0.05) reduction in body mass (-9.64, -8.99, and -9.90 kg, respectively) with fat mass comprising 69, 78, and 97% of the total loss in body mass, respectively. The diet-only group also demonstrated a significant reduction in fat-free mass. Maximum strength, as determined by 1-RM testing in the bench press and squat exercise was significantly increased for DES in both the bench press (+19.6%) and squat exercise (+32.6%). Absolute peak O2 consumption was significantly elevated in DE (+24.8%) and DES (+15.4%). There were no differences in performance during a 30-s Wingate test for the DE and DES, whereas D demonstrated a significant decline in peak and mean power output. Resting metabolic rate (RMR) (kcal x d(-1)) was not significantly different for any of the groups except for the DE group. There were no significant changes in basal concentrations of serum glucose, BUN, cortisol, testosterone, and high density lipoprotein (HDL) cholesterol for any of the groups. Serum total cholesterol and low density lipoprotein (LDL) cholesterol were significantly decreased for all dietary groups. Serum triglycerides were significantly reduced for D and DES at week 6 and remained lower at week 12 for D, while triglycerides returned to baseline values for DES. CONCLUSIONS These data indicate that a weight-loss dietary regimen in conjunction with aerobic and resistance exercise prevents the normal decline in fat-free mass and muscular power and augments body composition, maximal strength, and maximum oxygen consumption compared with weight-loss induced by diet alone.

Effect of resistance training on women's strength/power and occupational performances.

PURPOSE The effects of resistance training programs on strength, power, and military occupational task performances in women were examined. METHODS Untrained women aged (mean +/- SD) 23 +/- 4 yr were matched and randomly placed in total- (TP, N = 17 and TH, N = 18) or upper-body resistance training (UP, N = 18 and UH, N = 15), field (FLD, N = 14), or aerobic training groups (AER, N = 11). Two periodized resistance training programs (with supplemental aerobic training) emphasized explosive exercise movements using 3- to 8-RM training loads (TP, UP), whereas the other two emphasized slower exercise movements using 8- to 12-RM loads (TH, UH). The FLD group performed plyometric and partner exercises. Subjects were tested for body composition, strength, power, endurance, maximal and repetitive box lift, 2-mile loaded run, and U.S. Army Physical Fitness Tests before (T0) and after 3 (T3) and 6 months of training (T6). For comparison, untrained men (N = 100) (MEN) were tested once. RESULTS Specific training programs resulted in significant increases in body mass (TP), 1-RM squat (TP, TH, FLD), bench press (all except AER), high pull (TP), squat jump (TP, TH, FLD), bench throw (all except AER), squat endurance (all except AER), 1-RM box lift (all except aerobic), repetitive box lift (all), push-ups (all except AER), sit-ups (all except AER), and 2-mile run (all). CONCLUSIONS Strength training improved physical performances of women over 6 months and adaptations in strength, power, and endurance were specific to the subtle differences (e.g., exercise choice and speeds of exercise movement) in the resistance training programs (strength/power vs strength/hypertrophy). Upper- and total-body resistance training resulted in similar improvements in occupational task performances, especially in tasks that involved upper-body musculature. Finally, gender differences in physical performance measures were reduced after resistance training in women, which underscores the importance of such training for physically demanding occupations.

Influence of a compression garment on repetitive power output production before and after different types of muscle fatigue

Compression shorts have become a very popular item of sports apparel. Few data exist about whether they influence athletic performance. The purpose of this study was to determine whether compression shorts affected vertical jump performance after different fatigue tasks (i.e., endurance, strength, and power). In addition, experiments on the influence of a compression garment on joint position sense at the hip and muscle movement velocity upon landing impact was also studied. Healthy college age men and women participated in the various studies. Subjects were thoroughly familiarized with the jump tests and all other experimental techniques. Jumps were performed on an AMTI force plate which was interfaced to a computer with customized software used to determine jump power. Ten consecutive maximal counter movement jumps with arms held at waist level were performed. The compressive garment had no effect on the maximal power of the highest jump in either men or women. The compressive garment significantly enha...

Biorhythmic influences on functional capacity of human muscle and physiological responses.

UNLABELLED Previously, this laboratory has demonstrated that exhaustive aerobic exercise performance is not subject to significant chronobiological variation between 0800 and 2000 h, but certain physiological responses to maximal aerobic effort do fluctuate significantly within that time frame. PURPOSE The purpose of the present investigation was to determine whether muscle performance, and selected physiological responses to resistance exercise, was significantly influenced by time of day effects. METHODS Ten healthy, but untrained, men (21.1+/-0.6 yr, mean +/- SE) volunteered to participate in the study. In a balanced and randomized study design, each subject performed resistance exercise protocols on an isokinetic dynamometer with maximal effort at 0800 h, 1200 h, 1600 h, and 2000 h. Selected physiological and hormonal data were recorded before and immediately following the exercise stimulus. RESULTS The data demonstrated significant chronobiological oscillation in peak torque, average power, maximal work in a single repetition, and total work per set. Interestingly, this oscillation was manifested only at the fastest velocities of limb movement utilized. Pre- and postexercise rectal temperature exhibited significant time of day fluctuation, as did postexercise blood pressure. Plasma levels of testosterone and cortisol also displayed significant biorhythmicity under both pre- and postexercise conditions. However, exercise-induced responses (pre- to postexercise differences) of those steroid hormones did not exhibit significant biorythmic variation. Although plasma concentrations of both testosterone and cortisol were highest at 0800 h, testosterone to cortisol ratios were greatest at 2000 h. CONCLUSIONS In summary, these data suggest that maximal muscle performance does vary within the segment of the day when exercise typically occurs (0800-2000 h) but that this variation is specific to speed of movement.

Resistance training combined with bench-step aerobics enhances women's health profile.

PURPOSE The purpose of this study was to investigate the comprehensive physiological alterations that take place during the combination of bench-step aerobics (BSA) and resistance exercise training. METHODS Thirty-five healthy, active women were randomly assigned to one of four groups that either a) performed 25 min of BSA only (SA25); b) performed a combination of 25 min of BSA and a multiple-set upper and lower body resistance exercise program (SAR); c) performed 40 min of BSA only (SA40); or d) served as a control group (C), only performing activities of daily living. Direct assessments for body composition, aerobic fitness, muscular strength, endurance, power, and cross-sectional area were performed 1 wk before and after 12 wk of training. RESULTS All training groups significantly improved peak VO(2) (3.7 to 5.3 mL O(2).kg(-1).min(-1)), with the greatest improvement observed in the SAR group (P = 0.05). Significant reductions in preexercise heart rates (8-9 bpm) and body fat percent (5--6%) were observed in all training groups after training. Significant reductions in resting diastolic blood pressure were observed for the SAR and SA40 groups (6.7 and 5.8 mm Hg, respectively). Muscular strength and endurance only improved significantly in the SAR group (21 and 11% respectively). All groups demonstrated increased lower body power (11--14%), but only the SAR group significantly improved upper body power (32%). Thigh muscle cross-sectional areas measured via magnetic resonance imaging (MRI) increased primarily for the SAR group. CONCLUSION BSA is an exercise modality effective for improving physical fitness and body composition in healthy women. The addition of resistance exercise appears to enhance the total fitness profile by improving muscular performances, muscle morphology, and cardiovascular fitness greater than from performing BSA alone. Therefore, the inclusion of both modalities to an exercise program is most effective for improving total body fitness and a womans health profile.

The effects of plasma cortisol elevation on total and differential leukocyte counts in response to heavy-resistance exercise

The purpose of this study was to examine the impact of heavy-resistance exercise-induced elevations of plasma cortisol on circulating leukocyte counts. Nine healthy, recreationally weight-trained men volunteered for this investigation. Two exercise protocols were employed. Protocol 1 (P-1) consisted of eight sets of ten-repetition maximum leg-press exercise with 1-min rest periods between sets. Protocol 2 (P-2) was identical except for 3-min rest periods. A non-exercise protocol was used as a control treatment (C). Venous blood samples, heart rates and ratings of perceived exertion were obtained pre-, mid- and 5 min post-exercise. In order to examine the maximal influence of cortisol on leukocyte counts, we placed the subjects highest magnitude of cortisol change in response to one of the heavy-resistance exercise protocols in what we designated as the response protocol (R) and the other value was placed into what was designated as the non-response protocol (NR) for analysis. Significant increases in cortisol occurred from pre- to post-exercise for P-1 [mean (SD) 241.4 (25.0) to 302.0 (60.0) nmol · 1−1] and in the R conditions pre- to mid- and pre- to post-exercise [218.0(0.0) to 302.4(37.1) to 326.8 (51.9) nmol · 1−1]. No significant changes in cortisol occurred for P-2, NR or the control conditions. Significant increases in total leukocyte counts occurred from pre- to mid- and pre- to post-exercise both for R [5.6 (0.4) to 7.4 (0.3) to 7.3 (0.3) cells · 109 · 1−1] and NR [5.7 (0.3) to 6.9 (0.4) to 7.1 (0.4) cells · 109 · 1−1]. No significant changes in differential leukocyte counts occurred. In addition, no significant correlations between cortisol and total or differential leukocyte counts were observed. These data indicate that acute increases in total leukocytes along with no changes in differential leukocyte counts can occur in response to heavy-resistance exercise that does not significantly elevate plasma cortisol concentrations.

Neuromuscular disturbance outlasts other symptoms of exercise-induced muscle damage

This study examined the biochemical, immunological, functional, and neuromuscular responses associated with exercise-induced muscle damage in the quadriceps of untrained men. Muscle damage and soreness was elicited with maximal concentric/eccentric muscle actions at 0.53 rads s(-1). Significant (P<0.05) soreness was evident 1, 2, and 3 days following muscle insult, while plasma creatine kinase, a marker of muscle damage, was elevated 3 and 5 days post-insult. Plasma interleukin-Ibeta was significantly increased within 5 min, and remained elevated 1, 2, 5, and 7 days post-insult. Maximal isometric quadriceps function was impaired (P<0. 05) for 5 days following muscle challenge. Maximal isokinetic performance at 1.09 rads s(-1) was diminished (P<0.05) for 2 days post-insult; no significant decrements at 3.14 rads s(-1) were noted. Average electrical activation (iEMG) of the quadriceps was unaltered, but iEMG activity of the rectus femoris - where soreness was focused - was significantly increased. Neuromuscular efficiency (torque/iEMG) was compromised throughout the 10-day post-insult period investigated. While other symptoms of exercise-induced muscle damage dissipate within 7 days, neuromuscular perturbation persists for at least 10 days.

Exercise and recovery responses of adrenal medullary neurohormones to heavy resistance exercise.

PURPOSE The purpose of this study was to examine the effect of dynamic resistance exercise on the response patterns of adrenal medullary neurohormones in strength-trained men. METHODS Ten strength-trained men (21.7+/-0.58 yr) gave informed consent and performed two resistance exercise protocols, high force and high power, of equal total work in a randomized order separated by 1 wk. Blood samples were obtained pre-exercise (baseline), 0 (R-0), 15 (R-15), and 240 (R-240) min postexercise and under resting control conditions for each time point. RESULTS There were no significant differences in control concentrations for each time point and no difference in pre-exercise values between the two resistance exercise protocols for plasma lactate, epinephrine, plasma peptide F (P-F), or norepinephrine (NE). Plasma lactate significantly (P< or = 0.05) increased from baseline for both protocols; however, concentrations were higher in response to the high force protocol. Plasma epinephrine was significantly increased from baseline at R-0 and returned to baseline at R-15 for both protocols. In contrast, plasma P-F was significantly decreased at R-0 from baseline; however, at R-240 P-F had significantly increased to >80% baseline for both protocols. CONCLUSIONS These results indicate that the adrenal medulla was activated in response to the acute stress of both types of heavy resistance exercise. Furthermore, during longer recovery periods, the adrenal medulla was also active above baseline conditions as increased concentrations of proenkephalin fragments (i.e., P-F) were detected in the circulation.