The Effect of Different Weight Plate Widths (Bumper vs. Standard) on the Biomechanics of the Bench Press.

ABSTRACT: Fiedler, MJ, Triplett, NT, Hamilton, KC, Needle, AR, and van Werkhoven, H. The effect of different weight plate widths (bumper vs. standard) on the biomechanics of the bench press. J Strength Cond Res 38(4): e143-e149, 2024-Anecdotal evidence suggests that bumper plates impact lifts in powerlifting and weightlifting differently than standard cast iron plates, but whether biomechanical differences exist between lifts using bumper versus standard plates has not been investigated. Eleven resistance-trained subjects performed the bench press at 70, 80, and 90% of their 1 repetition maximum (1RM) while being blinded to whether they were lifting with bumper or standard plates. Motion data were captured by an 8-camera motion capture system, and electromyography (EMG) data were recorded for the anterior deltoid, pectoralis major, and triceps brachii. Repeated-measures analysis of variances showed a significant main weight effect for time under tension (p < 0.001), total work (p < 0.001), and muscle activity through EMG (across all muscles; p < 0.001) and a significant weight × joint interaction effect for average joint moment (p < 0.001) and peak joint moment (p < 0.001). However, there were no significant differences observed between the different weight plates for any of the measures. The main finding of the study suggests that there are no biomechanical differences between using bumper plates compared with standard plates during the bench press lift.

Central arterial stiffness, wave reflection, and heart rate variability following 4-week high-intensity resistance training intervention in young active women.

PURPOSE: Arterial stiffness, expedited wave reflection, and autonomic dysfunction are risk factors for cardiovascular disease, which is the leading cause of death in women in the United States. Evaluation of the effects of resistance training on these factors has been inconclusive, and even less is known about the effects of high-intensity resistance training (HIRT). This study evaluated the effects of a 4-week HIRT intervention on central arterial stiffness, wave reflection, and heart rate variability in young healthy and active women. METHODS: 9 women were recruited and underwent a 4-week control period followed by the intervention. Measurements were recorded pre-control, post-control/pre-intervention, and post-intervention. RESULTS: There were no significant changes to central arterial stiffness, wave reflection, or heart rate variability. There was a significant increase in resting heart rate (bpm: 62 ± 7, 66 ± 10; p = 0.003) and a significant decrease in baroreceptor sensitivity (30 ± 7, 21 ± 7; p = 0.018) pre- to post-intervention. There was a significant decrease in total peripheral resistance pre- to post-intervention (1.076 ± 0.281, 0.916 ± 0.250; p = 0.002). Squat, bench press, and deadlift increased pre- to post-intervention (kg: 62 ± 11, 71 ± 9, p = 0.000; 37 ± 7, 40 ± 7, p = 0.002; 76 ± 19, 84 ± 19, p = 0.000). CONCLUSION: 4 weeks of HIRT can supplement a healthy lifestyle in women by increasing strength while decreasing peripheral resistance and preserving arterial pressures. Further evaluation is necessary to investigate the observed increase in resting heart rate and decrease in baroreceptor sensitivity and to determine long-term effects of this training.

Velocity Change Estimation by Subjective Measures Over a Wide-Load Spectrum in Squat and Bench Press.

ABSTRACT: Chapman, M, Larumbe-Zabala, E, Triplett, NT, and Naclerio, F. Velocity change estimation by subjective measures over a wide-load spectrum in squat and bench press. J Strength Cond Res 35(2S): S51-S56, 2021-This study compared whether the perception of effort measured on a repetition-by-repetition basis during continuous sets to failure is different between squat (SQ) and bench press (BP). After determining the one repetition maximum (1RM) value in both SQ and BP, 18 subjects (28.2 ± 5 years, 50% women) performed 7 sets to failure per exercise, separated by 24-48 hours, alternating SQ and BP, using the following relative load ranges: 30 < 40%, 40 < 50%, 50 < 60%, 60% < 70%, 70 < 80%, 80 < 90%, and >90%. The mean accelerative velocity (MAV) and rating of perceived exertion (RPE) using the OMNI-RES (0-10) scale were measured for every repetition of each set. The ability of the OMNI-RES (0-10) scale to identify velocity changes during continuous sets to volitional failure and to distinguish loading zones divided into 10% slots, from 30 to 100% of 1RM was confirmed for both SQ and BP. The RPE values measured at (a) the first repetition; (b) the repetition where MAV peaks; (c) the repetition where MAV drops by ≤10% compared the maximum and (d) the last repetition, showed no differences (p > 0.05, d < 0.2) between exercises. In conclusion, the same RPE scores can be applied to both exercises, for either estimating the relative load or monitoring changes in MAV during continuous sets to failure.

Using Perceptual and Neuromuscular Responses to Estimate Mechanical Changes During Continuous Sets in the Bench Press.

Chapman, M, Larumbe-Zabala, E, Gosss-Sampson, M, Triplett, NT, and Naclerio, F. Using perceptual and neuromuscular responses to estimate mechanical changes during continuous sets in the bench press. J Strength Cond Res 33(10): 2722-2732, 2019-This study analyzed the effectiveness of the OMNI-RES (0-10) and the electromyographic signal for monitoring changes in the movement velocity during a set to muscular failure performed with different relative loads in the bench press (BP) exercise. Ten males (30.8 ± 5.7 years) were evaluated on 8 separate days with 48 hours of rest between sessions. After determining the 1 repetition maximum value, participants performed 7 sets to failure with the following relative loads ranges: 30 < 40%, 40 < 50%, 50 < 60%, 60 < 70%, 70 < 80%, 80 < 90%, and >90%. The mean accelerative velocity (MAV), the rating of perceived exertion (RPE), and the normalized root-mean-square (N-RMS) signal from the anterior deltoids were measured for every repetition of each set. The RPE expressed after the first repetition and when the maximum value of MAV was achieved over the sets was lower (p < 0.001, d > 0.80) than the RPE associated with a 10% drop in MAV and at failure. Furthermore, the initial RPE was useful to distinguish different loading zones between the light relative loads (30 < 40% vs. 40 < 50% vs. 50 < 60%) and from these 3 zones to the higher relative load ranges (60 to >90%). Similar, but less clear, differences were observed for the N-RMS. In conclusion, apart from differentiating between relative loads, the RPE and in some cases N-RMS can both reflect changes associated with the initial, maximal, 10% drop in movement velocity, and muscular failure during a continuous set in the BP.

Perceptual, Mechanical, and Electromyographic Responses to Different Relative Loads in the Parallel Squat.

Chapman, M, Larumbe-Zabala, E, Gosss-Sampson, M, Colpus, M, Triplett, NT, and Naclerio, F. Perceptual, mechanical, and electromyographic responses to different relative loads in the parallel squat. J Strength Cond Res 33(1): 8-16, 2019-The effectiveness of the OMNI-RES (0-10) Scale and the electromyographic signal for monitoring changes in the movement velocity were examined during a set to muscular failure using different percentages of 1 repetition maximum (1RM) in the parallel squat exercise (PSQ). Twelve men (26.3 ± 5.8 years) were evaluated on 8 separate days with 48 hours of rest between sessions. After determining the 1RM value, participants underwent 7 tests until achieving muscular failure with the following percentage ranges: 30 to <40%, 40 to <50%, 50 to <60%, 60 to <70%, 70 to <80%, 80 to <90%, and >90%. An optical rotary encoder measured mean accelerative velocity (MAV), and the OMNI-RES (0-10) Scale was used to express the rating of perceived exertion (RPE) after every repetition of each set. In addition, the normalized root mean square signal of the surface electromyography (N-EMG) was calculated for the vastus medialis muscle. The RPE expressed after the first repetition and when the maximum value of MAV was achieved along the sets was lower (p < 0.001, d > 0.8) than the RPE that corresponded to a 10% drop in MAV and at failure. In addition, the initial RPE was useful to distinguish different loading zones by anchoring the OMNI-RES value to the magnitude of the relative load (<60%, 60 to <70% or ≤70% 1RM). Similar patterns were observed using the N-EMG. In conclusion, apart from differentiating between relative loads during a set to failure in the PSQ, the RPE and the N-EMG can both reflect changes associated with the initial, maximal, 10% drop in movement velocity and the muscular failure.

Effects of Short-Term Free-Weight and Semiblock Periodization Resistance Training on Metabolic Syndrome.

South, MA, Layne, AS, Stuart, CA, Triplett, NT, Ramsey, MW, Howell, ME, Sands, WA, Mizuguchi, S, Hornsby, WG, Kavanaugh, AA, and Stone, MH. Effects of short-term free-weight and semiblock periodization resistance training on metabolic syndrome. J Strength Cond Res 30(10): 2682-2696, 2016-The effects of short-term resistance training on performance and health variables associated with prolonged sedentary lifestyle and metabolic syndrome (MS) were investigated. Resistance training may alter a number of health-related, physiological, and performance variables. As a result, resistance training can be used as a valuable tool in ameliorating the effects of a sedentary lifestyle including those associated with MS. Nineteen previously sedentary subjects (10 with MS and 9 with nonmetabolic syndrome [NMS]) underwent 8 weeks of supervised resistance training. Maximum strength was measured using an isometric midthigh pull and resulting force-time curve. Vertical jump height (JH) and power were measured using a force plate. The muscle cross-sectional area (CSA) and type were examined using muscle biopsy and standard analysis techniques. Aerobic power was measured on a cycle ergometer using a ParvoMedics 2400 Metabolic system. Endurance was measured as time to exhaustion on a cycle ergometer. After training, maximum isometric strength, JH, jump power, and V[Combining Dot Above]O2peak increased by approximately 10% (or more) in both the metabolic and NMS groups (both male and female subjects). Over 8 weeks of training, body mass did not change statistically, but percent body fat decreased in subjects with the MS and in women, and lean body mass increased in all groups (p ≤ 0.05). Few alterations were noted in the fiber type. Men had larger CSAs compared those of with women, and there was a fiber-specific trend toward hypertrophy over time. In summary, 8 weeks of semiblock free-weight resistance training improved several performance variables and some cardiovascular factors associated with MS.

Short-term Resistance and Plyometric Training Improves Eccentric Phase Kinetics in Jumping.

The purpose of this investigation was to examine the effect of an abbreviated resistance and plyometric training program on force- and power-time curve variables during jumping. Nineteen male subjects were assigned to either a training (n = 9) or control group (n = 10). Training consisted of performing 3 sets of 3 repetition squats (90% of 1 repetition maximum [RM]) and 5 sets of 6 repetition drop jumps from 40 cm twice per week for 4 weeks. A 1RM in the squat and countermovement (CMJ) and static jump (SJ) performance was assessed before and after training. Several variables were analyzed for individual subject force- and power-time curves for the jumps. Average force- and power-time curves for all subjects combined were also analyzed. Absolute and relative squat strength significantly increased in training group (p ≤ 0.05). Calculation of variables from individual subject force-time curves during the CMJ indicated a significant decrease in eccentric time, minimum force, and eccentric impulse and significant increase in eccentric rate of force development in training group. Analysis of individual power-time curves in the CMJ also revealed a significant decrease in minimum power and eccentric work and a significant increase in eccentric rate of power development. No significant changes occurred in the variables measured for the SJ. The results of this study indicate that short-term strength and plyometric training may preferentially influence eccentric performance variables during jumping in comparison with longer term training enhancements to the concentric phase performance.

Muscle activation during push-ups performed under stable and unstable conditions.

BACKGROUND/OBJECTIVE: The purpose of this study was to analyze muscle activation when performing push-ups under different stability conditions. METHODS: Physically fit young male university students (N = 30) performed five push-ups under stable conditions (on the floor) and using four unstable devices (wobble board, stability disc, fitness dome, and the TRX Suspension Trainer). The push-up speed was controlled using a metronome, and the testing order was randomized. The average amplitudes of the electromyographic (EMG) root mean square of the anterior deltoid (DELT), serratus anterior (SERRA), lumbar multifidus (LUMB), and rectus femoris (FEM) were recorded. The electromyographic signals were normalized to the maximum voluntary isometric contraction (MVIC). RESULTS: No significant differences were found for the DELT [F(4,112) = 1.978; p = 0.130] among the conditions. However, statistically significant differences were found among the different conditions for the SERRA [F(4,60) = 17.649; p < 0.001], LUMB [F(4,76) = 12.334; p < 0.001], and FEM [F(4,104) = 24.676; p < 0.001] muscle activation. The suspended device was the only condition that elicited higher LUMB and FEM activation compared to the other conditions. Push-ups performed on the floor showed lower SERRA activation than those performed with all unstable devices. CONCLUSION: Not all unstable devices enhance muscle activation compared to traditional push-ups.

Construct and concurrent validation of a new resistance intensity scale for exercise with thera-band® elastic bands.

The construct and concurrent validity of the Thera-Band Perceived Exertion Scale for Resistance Exercise with elastic bands (EB) was examined. Twenty subjects performed two separate sets of 15 repetitions of both frontal and lateral raise exercise over two sessions. The criterion variables were myoelectric activity and heart rate. One set was performed with an elastic band grip width that permitted 15 maximum repetitions in the selected exercise, and another set was performed with a grip width 50% more than the 15RM grip. Following the final repetition of each set, active muscle (AM) and overall body (O) ratings of perceived exertion (RPE) were collected from the Thera-Band® resistance exercise scale and the OMNI-Resistance Exercise Scale of perceived exertion with Thera-Band® resistance bands (OMNI-RES EB). Construct validity was established by correlating the RPE from the OMNI-RES EB with the Thera-Band RPE scale using regression analysis. The results showed significant differences (p ≤ 0.05) in myoelectric activity, heart rate, and RPE scores between the low- and high-intensity sets. The intraclass correlation coefficient for active muscles and overall RPE scale scores was 0.67 and 0.58, respectively. There was a positive linear relationship between the RPE from the OMNI-RES EB and the Thera-Band scale. Validity coefficients for the RPE AM were r(2) = 0.87 and ranged from r(2) = 0.76 to 0.85 for the RPE O. Therefore, the Thera-Band Perceived Exertion Scale for Resistance Exercise can be used for monitoring elastic band exercise intensity. This would allow the training dosage to be better controlled within and between sessions. Moreover, the construct and concurrent validity indicates that the OMNI-RES EB measures similar properties of exertion as the Thera-Band RPE scale during elastic resistance exercise. Key pointsThis new resistance intensity scale is an appropriate and valid tool for assessing perceived exertion during strength training with elastic bands.This scale can be used without reducing the accuracy of the dosage prescribed during training/rehabilitation sessions and while carrying out medium and/or long-term periodization programs or therapeutic interventions.Populations with specific physical or physiological needs could have access to an easy-to-use resource that allows them to carry out their training/rehabilitation programs with greater efficacy and without any risk to health.

Relative strength explains the differences in multi-joint rapid force production between sexes.

The primary aim of this study was to determine whether relative strength explains the differences in the rapid force production (force developed during first 150-, 200-, and 250 ms) of females and males, and to evaluate the relationships between peak force and rapid force production. Sixty-three team sport athletes (females: n = 25, age = 21.5 ± 1.3 years, stature = 166 ± 5 cm, body mass = 60.65 ± 10.04 kg; males: n = 38, age = 21.9 ± 1.1 years, stature = 178 ± 7 cm, body mass = 76.55 ± 12.88 kg) performed a series of isometric mid-thigh pull (IMTP) trials, with all participants' data used for correlational analysis. After testing, females and males were divided into 20 strength-matched pairs, based on their relative peak force (peak force ∙ body mass). There were no meaningful differences between sexes for relative force at 150 ms (g = 0.007 [95% CI -0.627, 0.648]), 200 ms (g = -0.059 [95% CI -0.695, 0.588]) and 250 ms (g = -0.156 [95% CI -0.778, 0.473]). Similarly, when expressed as a percentage of peak force there were no meaningful differences in force at 150 ms (g = -0.015 [95.0%CI -0.650, 0.680]), 200 ms (g = -0.099 [95.0%CI -0.714, 0.559]) or 250 ms (g = -0.272 [95.0%CI -0.856, 0.328]) between strength-matched females and males. Based on the correlations, there were very large to nearly perfect relationships (r = 0.77-0.94, p <0.001) between peak force and rapid force production, with peak force explaining 59%, 77% and 89% of the variance in force at 150-, 200- and 250 ms, respectively. When comparing females and males, relative strength (based on body weight or a percentage of peak force) should be considered, and practitioners should be aware of the role of peak force in rapid force production.

Effect of cluster set configurations on power clean technique.

The purpose of this investigation was to examine the effects of cluster set configurations on power clean technique. Ten male, recreational weightlifters performed three sets of six repetitions at 80% of one repetition max with 0 (P0), 20 (P20) or 40 seconds (P40) inter-repetition rest. During the first and second set of P0, the catch and first pull were in a more forward position during repetition 6 as compared to repetition 1, respectively. During the second set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the second pull and the loop. During the third set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the first pull, transition, and beginning of the second pull. No differences in horizontal displacement were found between repetitions 1 and 6 during P20. During each set of P0, vertical displacement decreased between repetitions 1 and 6 (1.02 ± 0.07 m vs. 0.94 ± 0.06 m; Mean ± s). Cluster set configurations led to the maintenance of vertical displacement throughout all sets. The results demonstrate cluster set configurations with greater than 20 seconds inter-repetition rest maintain weightlifting technique to a greater extent than a traditional set configuration.

Relationship between jumping ability and running performance in events of varying distance.

Running performance consists of a combination of aerobic and anaerobic capabilities, varying based on the distance of the event. It may be also dependent on factors relating to lower body power. Lower body power is commonly assessed by various modes of jumping tests. The purpose of this investigation was to determine if jumping performance would have some relationship to running performance in different distance events. This study involved 33 competitive track and field runners who participated in events ranging from 60 to 5,000 m (10 sprinters: height = 1.72 ± 10.26 m, mass = 67.80 ± 10.83 kg; 11 middle-distance runners: height = 1.77 ± 0.08 m, mass = 64.40 ± 8.02 kg; 12 long-distance runners: height = 1.73 ± 0.11 m, mass = 60.42 ± 10.36 kg). All subjects were competitive NCAA Division I athletes. Subjects were tested on a single occasion in a 3-jump test (TSJP), which was the distance covered during 3 two-leg standing long jumps performed in immediate succession. Time in the 60, 100, 200, 800, 3,000, and 5,000 m was obtained from recent race performances. The mean TSJP for sprinters, middle-distance runners, and long-distance runners were 8.24 ± 1.32, 6.59 ± 1.23, and 5.61 ± 0.88 m, respectively. The mean 60, 100, 200, 800, 3,000, and 5,000 m performances were 7.28 ± 0.78, 11.25 ± 0.87, 23.47 ± 2.25, 127.17 ± 15.13, 562.09 ± 60.54, and 987.65 ± 117.19 seconds, respectively. Significant correlations (p ≤ 0.05) were observed between TSJP and running performance for all distances (60 m: 0.97 seconds, 100 m: 1.00 seconds, 200 m: 0.97 seconds, 800 m: 0.83 seconds, 3,000 m: 0.72 seconds, and 5,000 m: 0.71 seconds). The strength of the correlations, in general, was strongest to weakest based on event distance from the shortest distance (60 m) to the longest distance (5,000 m). Thus, the contribution of muscle power, as possibly determined by TSJP, maybe most important in shorter distance races (60, 100, and 200 m). However, because of the significant correlations between TSJP and middle- and long-distance running performance as well, the contribution of muscle power to these events (800, 3,000, and 5,000 m) should be considered as a component for training for both sprinters and middle- and long-distance runners.

Effect of leucine supplementation on indices of muscle damage following drop jumps and resistance exercise.

The purpose of this study was to determine the effect of leucine supplementation on indices of muscle damage following eccentric-based resistance exercise. In vitro, the amino acid leucine has been shown to reduce proteolysis and stimulate protein synthesis. Twenty-seven untrained males (height 178.6±5.5 cm; body mass 77.7±13.5 kg; age 21.3±1.6 years) were randomly divided into three groups; leucine (L) (n=10), placebo (P) (n=9) and control (C) (n=8). The two experimental groups (L and P) performed 100 depth jumps from 60 cm and six sets of ten repetitions of eccentric-only leg presses. Either leucine (250 mg/kg bm) or placebo was ingested 30 min before, during and immediately post-exercise and the morning of each recovery day following exercise. Muscle function was determined by peak force during an isometric squat and by jump height during a static jump at pre-exercise (PRE) and 24, 48, 72, and 96 h post-exercise (24, 48, 72, 96 h). Additionally, at these time points each group's serum levels of creatine kinase (CK) and myoglobin (Mb) along with perceived feelings of muscle soreness were determined. None of the C group dependent variables was altered by the recurring testing procedures. Peak force was significantly decreased across all time points for both experimental groups. The L group experienced an attenuated drop in mean peak force across all post-exercise time points compared to the P group. Jump height significantly decreased from PRE for both the L and P group at 24 h and 48 h. CK and Mb was significantly elevated from PRE for both experimental groups at 24 h. Muscle soreness increased across all time points for the both the L and P group, and the L group experienced a significantly higher increase in mean muscle soreness post-exercise. Following exercise-induced muscle damage, high-dose leucine supplementation may help maintain force output during isometric contractions, however, not force output required for complex physical tasks thereby possibly limiting its ergogenic effectiveness.

Effect of inter-repetition rest on ratings of perceived exertion during multiple sets of the power clean.

The purpose of this study was to examine the effects of inter-repetition rest (IRR) on ratings of perceived exertion (RPE) in the power clean exercise in a multiple set protocol using peak power as an indication of fatigue. Ten resistance-trained males participated in four testing sessions which consisted of determination of a one repetition maximum (1RM) in the power clean exercise (session 1) and performance of three sets of six repetitions at 80% of 1RM with 0 (P0), 20 (P20), or 40 s (P40) IRR (sessions 2-4). Fatigue during all three conditions was indicated by a significant decrease in power of 9.0% (P0), 3.0% (P20) and 2.1% (P40), respectively. Significant difference in the rate of power decrease in P40 indicates less fatigue in comparison to P0 and P20. P40 resulted in a significantly lower RPE compared to P0 and P20 (7.43 ± 0.34, 6.46 ± 0.47, and 5.30 ± 0.55, respectively). RPE increased significantly (p ≤ 0.01) within each set (5.26 ± 0.37, 6.46 ± 0.44, and 7.46 ± 0.53; sets 1, 2, and 3, respectively). Significant difference in average RPE between the conditions indicates that RPE is not a determinant of intensity (% of 1RM) but the rate of fatigue (decreases in peak power). In addition, the fact that RPE increased between sets 1, 2 and 3 during all conditions support the same conclusion. The results demonstrate that increasing IRR in power clean training decreases the perception of effort and is inversely related to the rate of fatigue.

Effect of interrepetition rest on power output in the power clean.

The effect of interrepetition rest (IRR) periods on power output during performance of multiple sets of power cleans is unknown. It is possible that IRR periods may attenuate the decrease in power output commonly observed within multiple sets. This may be of benefit for maximizing improvements in power with training. This investigation involved 10 college-aged men with proficiency in weightlifting. The subjects performed 3 sets of 6 repetitions of power cleans at 80% of their 1 repetition maximum with 0 (P0), 20 (P20), or 40 seconds (P40) of IRR. Each protocol (P0, P20, P40) was performed in a randomized order on different days each separated by at least 72 hours. The subjects performed the power cleans while standing on a force plate with 2 linear position transducers attached to the bar. Peak power, force, and velocity were obtained for each repetition and set. Peak power significantly decreased by 15.7% during P0 in comparison with a decrease of 5.5% (R1: 4,303 ± 567 W, R6: 4,055 ± 582 W) during P20 and a decrease of 3.3% (R1: 4,549 ± 659 W, R6: 4,363 ± 476 W) during P40. Peak force significantly decreased by 7.3% (R1: 2,861 ± 247 N, R6: 2,657 ± 225 N) during P0 in comparison with a decrease of 2.7% (R1: 2,811 ± 327 N, R6: 2,730 ± 285 N) during P20 and an increase of 0.4% (R1: 2,861 ± 323 N, R6: 2,862 ± 280 N) during P40. Peak velocity significantly decreased by 10.2% (R1: 1.97 ± 0.15 m·s(-1), R6: 1.79 ± 0.11 m·s(-1)) during P0 in comparison with a decrease of 3.8% (R1: 1.89 ± 0.13 m·s(-1), R6: 1.82 ± 0.12 m·s(-1)) during P20 and a decrease of 1.7% (R1: 1.93 ± 0.17 m·s(-1), R6: 1.89 ± 0.14 m·s(-1)) during P40. The results demonstrate that IRR periods allow for the maintenance of power in the power clean during a multiple set exercise protocol and that this may have implications for improved training adaptations.

A comparison of men's and women's strength to body mass ratio and varus/valgus knee angle during jump landings.

The purpose of this investigation was to compare valgus/varus knee angles during various jumps and lower body strength between males and females relative to body mass. Seventeen recreationally active females (age: 21.94 ± 2.59 years; height: 1.67 ± 0.05 m; mass: 64.42 ± 8.39 kg; percent body fat: 26.89 ± 6.26%; squat one-repetition maximum: 66.18 ± 19.47 kg; squat to body mass ratio: 1.03 ± 0.28) and 13 recreationally active males (age: 21.69 ± 1.65 years; height: 1.77 ± 0.07 m; mass: 72.39 ± 9.23 kg; percent body fat: 13.15 ± 5.18%; squat one-repetition maximum: 115.77 ± 30.40 kg; squat to body mass ratio: 1.59 ± 0.31) performed a one-repetition maximum in the squat and three of each of the following jumps: countermovement jump, 30 cm drop jump, 45 cm drop jump, and 60 cm drop jump. Knee angles were analysed using videography and body composition was analysed by dual-energy X-ray absorptiometry to allow for squat to body mass ratio and squat to fat free mass ratio to be calculated. Significant differences (P ≤ 0.05) were found between male and female one-repetition maximum, male and female squat to body mass ratio, and male and female squat to fat free mass ratio. Significant differences were found between male and female varus/valgus knee positions during maximum flexion of the right and left leg in the countermovement jump, drop jump from 30 cm, drop jump from 45 cm, and drop jump from 60 cm. Correlations between varus/valgus knee angles and squat to body mass ratio for all jumps displayed moderate, non-significant relationships (countermovement jump: r = 0.445; drop jump from 30 cm: r = 0.448; drop jump from 45 cm: r = 0.449; drop jump from 60 cm: r = 0.439). In conclusion, males and females have significantly different lower body strength and varus/valgus knee position when landing from jumps.

Muscle-fiber type and blood oxidative stress after eccentric exercise.

Acute strength exercise elicits a transient oxidative stress, but the factors underlying the magnitude of this response remain unknown. The purpose of this investigation was to determine whether muscle-fiber type relates to the magnitude of blood oxidative stress after eccentric muscle activity. Eleven college-age men performed 3 sets of 50 eccentric knee-extensions. Blood samples taken pre-, post-, and 24, 48, 72, and 96 hr postexercise were assayed for comparison of muscle damage and oxidative-stress biomarkers including protein carbonyls (PCs). Vastus lateralis muscle biopsies were assayed for relative percentage of slow- and fast-twitch muscle fibers. There was a mixed fiber composition (Type I = 39.6% ± 4.5%, Type IIa = 35.7% ± 3.5%, Type IIx = 24.8% ± 3.8%; p = .366). PCs were elevated 24, 48, and 72 hr (p = .032) postexercise, with a peak response of 126% (p = .012) above baseline, whereas other oxidative-stress biomarkers were unchanged. There are correlations between Type II muscle-fiber type and postexercise PC. Further study is needed to understand the mechanisms responsible for the observed fast-twitch muscle-fiber oxidative-stress relationship.

Control of resistance training intensity by the OMNI perceived exertion scale.

The purpose of this study was to determine the applicability of the rating of perceived exertion (RPE) scale as a means of controlling resistance training intensity and establishing the relationship between the RPE value, load, and mechanical power (MP) produced during the bench press. Eleven men (22.1 ± 1.0 years) were evaluated on 8 separate days with 48 hours of rest between sessions. After determining the 1 repetition maximum (1RM) value, each subject underwent 7 tests until achieving muscular failure with the following percentage ranges: 30-40, >40-50, >50-60, >60-70, >70-80, >80-90, and >90%. A rotary encoder and the OMNI-RES (0-10) scale were used to estimate the power and to determine the perception of effort (RPE) expressed after each repetition of each set. The RPE produced from the start to the end of each set was related to the percentage of the load and the variability of the MP measured. Additionally, except for the >90% range, significant differences (p < 0.05) between the initial RPE (RPE I) and the average RPE of the first 3 repetitions (RPE 1_3 rep) with respect to the RPE produced with a 10% reduction in MP were identified for all the ranges. These relationships demonstrate the utility of RPE for controlling resistance training intensity.

Myoelectric activation and kinetics of different plyometric push-up exercises.

The kinetic and myoelectric differences between 3 types of plyometric push-ups were investigated. Twenty-seven healthy, physically active men served as subjects and completed both familiarization and testing sessions. During these sessions, subjects performed 2 series of 3 plyometric push-up variations in a counterbalanced order according to the following techniques: Countermovement push-ups (CPUs) were push-ups performed with the maximum speed of movement; jump push-ups (JPUs) were similar to clapping push-ups; and fall push-ups (FPUs) required kneeling subjects to drop and then attempt to return to their initial position. Vertical ground reaction forces were determined by using a force plate. Myoelectric activity was recorded by means of electromyography. Impact force and impact rate of force development were significantly (p < 0.05) higher for FPUs than for JPUs. The maximum rate of force development was higher for CPUs (p < 0.05) than for JPUs, and the maximum force was higher for the CPUs than for the FPUs (p < 0.05). There were differences among exercises for the mean muscle activation of the pectoralis major (PM; p < 0.001), triceps brachii (p < 0.001), external oblique (p < 0.005) and anterior deltoid (p < 0.001), and in the maximum muscle activation of the PM (p < 0.001). Plyometric push-ups with countermovement achieved a higher maximum force and rate of force and did not cause impact forces. Thus, this type of push-up exercise may be regarded as the best for improving explosive force. The FPU exercise achieved higher levels of muscular activation in the agonist and synergist muscle groups, and greater impact forces and impact force development rates.

Power output in the jump squat in adolescent male athletes.

The load that maximizes power output in the jump squat (JS) in college-aged athletic males has been reported to be 0% of 1 repetition maximum [1RM] squat strength) or in other words body mass. No data exist concerning adolescent athletic males. In addition, strength levels have been theorized to possibly affect the load that maximizes power output in the JS. The purpose of this investigation was to identify the load that maximizes power output in the JS in adolescent athletic men, and concurrently describe their strength level and its effect on the load that maximizes power output. Eleven high-school male athletes were tested on 2 occasions, first determining their 1RM in the squat (1RM = 141.14 ± 28.08 kg; squat 1RM-to-body mass ratio = 1.76 ± 0.15) and then performing JS testing at loads equal to 0% (body mass), 20, 40, 60, and 80% of squat 1RM. Peak power (PP), peak force, peak velocity (PV), and peak displacement were measured at each load. Jump squat at the 0% load produced significantly (p ≤ 0.05) higher PP, PV, and peak displacement in comparison with the 40, 60, and 80% loading conditions. It was concluded that the load that maximizes power output in the JS is 0% of 1RM in adolescent athletic men, the same as found in college-aged athletic men. In addition, strength level relative to body mass did not affect the load that maximized power output. Practically, when devising a training program to increase PP, it is important to include JSs at body mass along with traditional strength training at heavier loads to increase power output across the entire loading spectrum.