DIFFERENCES IN SEMG BETWEEN NORMAL SQUATS AND ACCENTUATED ECCENTRIC LOADED SQUATS IN COMPETITIVE COLLEGIATE WEIGHTLIFTERS

The purpose of the present work was to compare the effect of accentuated eccentric loaded (AEL) squats to normally loaded (NOR) squats on surface measured muscle activation (sEMG) in competitive weightlifters. Eight experienced, competitive weightlifters (six males, two females) completed both an AEL and NOR squat session (seven days apart), comprised of nine sets of squats, and was identical to their normal scheduled training. sEMG data from the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) was collected (at 1000Hz) during the entirety of the concentric (CON) phases of the AEL and NOR sessions. RMANOVAs (set x session-type) were calculated and no statistical differences were found (p > 0.05) while promising statistical effect sizes (?2 partial 0.073 to 0.273) were observed

Differences in sEMG Between Normal Squats and Accentuated Eccentric Loaded Squats in Competitive Collegiate Weightlifters

The purpose of the present work was to compare the effect of accentuated eccentric loaded (AEL) squats to normally loaded (NOR) squats on surface measured muscle activation (sEMG) in competitive weightlifters. Eight experienced, competitive weightlifters (six males, two females) completed both an AEL and NOR squat session (seven days apart), comprised of nine sets of squats, and was identical to their normal scheduled training. sEMG data from the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) was collected (at 1000Hz) during the entirety of the concentric (CON) phases of the AEL and NOR sessions. RMANOVAs (set x session-type) were calculated and no statistical differences were found (p \u3e 0.05) while promising statistical effect sizes (?2 partial 0.073 to 0.273) were observed

Gaining more from doing less? The effects of a one-week deload period during supervised resistance training on muscular adaptations.

Based on emerging evidence that brief periods of cessation from resistance training (RT) may re-sensitize muscle to anabolic stimuli, we aimed to investigate how a 1-week deload interval at the midpoint of a 9-week RT program affected muscular adaptations in resistance-trained individuals. Thirty-nine young men (n=29) and women (n=10) were randomly assigned to one of two experimental, parallel groups: An experimental group that abstained from RT for 1 week at the midpoint of a 9-week, high-volume RT program (DELOAD) or a traditional training group that performed the same RT program continuously over the study period (TRAD). The lower body routines were directly supervised by the research staff while upper body training was carried out in an unsupervised fashion. Muscle growth outcomes included assessments of muscle thickness along proximal, mid and distal regions of the middle and lateral quadriceps femoris as well as the mid-region of the triceps surae. Adaptations in lower body isometric and dynamic strength, local muscular endurance of the quadriceps, and lower body muscle power were also assessed. Results indicated no appreciable differences in increases of lower body muscle size, local endurance, and power between groups. Alternatively, TRAD showed greater improvements in both isometric and dynamic lower body strength compared to DELOAD. Additionally, TRAD showed some slight psychological benefits as assessed by the readiness to train questionnaire over DELOAD. In conclusion, our findings suggest that a 1-week deload period at the midpoint of a 9-week RT program appears to negatively influence measures of lower body muscle strength but has no effect on lower body hypertrophy, power or local muscular endurance

Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up

Studies examining acute, high-speed movement performance enhancement following intense muscular contractions (frequently called "post-activation potentiation"; PAP) often impose a limited warm-up, compromizing external validity. In the present study, the effects on countermovement vertical jump (CMJ) performance of back squat exercises performed with or without elastic bands during warm-up were compared. After familiarization, fifteen active men visited the laboratory on two occasions under randomized, counterbalanced experimental squat warm-up conditions: (a) free-weight resistance (FWR) and (b) variable resistance (VR). After completing a comprehensive task-specific warm-up, three maximal CMJs were performed followed by three back squat repetitions completed at 85% of 1-RM using either FWR or VR Three CMJs were then performed 30 seconds, 4 minutes, 8 minutes, and 12 minutes later. During CMJ trials, hip, knee, and ankle joint kinematics, ground reaction force data and vastus medialis, vastus lateralis, and gluteus maximus electromyograms (EMG) were recorded simultaneously using 3D motion analysis, force platform, and EMG techniques, respectively. No change in any variable occurred after FWR (P > 0.05). Significant increases (P < 0.05) were detected at all time points following VR in CMJ height (5.3%-6.5%), peak power (4.4%-5.9%), rate of force development (12.9%-19.1%), peak concentric knee angular velocity (3.1%-4.1%), and mean concentric vastus lateralis EMG activity (27.5%-33.4%). The lack of effect of the free-weight conditioning contractions suggests that the comprehensive task-specific warm-up routine mitigated any further performance augmentation. However, the improved CMJ performance following the use of elastic bands is indicative that specific alterations in force-time properties of warm-up exercises may further improve performance

The Interrelationships of Fitness Characteristics in Division 1 Athletes

The purpose of this dissertation was to explore the interrelationships of several important fitness characteristics in Division 1 athletes. Sport performance magnitude is the summation of an individual athlete’s technical, psychological, and fitness characteristics. Athletes who excel in any or all characteristics perform better in their chosen sports. General fitness characteristics that are important to almost all sports include strength, power, vertical jump height, shortdistance sprinting ability, muscularity, and body fat percentage. These variables have been shown in previous research to independently affect athletic performance outcomes, but their relationships to one another are less clear. Eighty Division I athletes from 4 sports were examined in a variety of fitness characteristics as part of a continuous athlete monitoring program. Data on strength, power, vertical jump height, short-distance sprinting speed, muscularity, and body fat percentage were collected and analyzed. Analysis revealed several important relationships. Firstly, strength is highly related to muscularity, with lean body mass as one of the most important determinants of strength. Secondly, athletes who can produce high relative (scaled per body mass) forces and powers tend to be considerably higher jumpers and much faster sprinters. Lastly, leaner athletes out-perform less lean athletes in almost every metric, especially relative strength and power, vertical jumping ability, and sprinting ability

CHARACTERISTICS OF DIVISION 1 ATHLETES RELATING TO BODY COMPOSITION

Michael A. Israetel1,Chris MacDonald2, Hugh S. Lamont3, Michael Ramsey4, Satoshi Mizuguchi4 &Michael H. Stone4; 1University of Central Missouri, Warrensburg, MO; 2Coastal Carolina University, Conway, South Carolina; 3California Lutheran University, Thousand Oaks, California; 4East Tennessee State University, Johnson City, TN. Athletes tend differ physically from both non-athletes and each other. In particular, differences between athletes of differing rank and athletic performance ability have been documented in a variety of sports. One of these differences is in body composition. While there is a rich literature on the subject, the relationship between measures of body composition and various performance measures has not been well studied in Division 1 Athletes. PURPOSE: The purpose of this study was to investigate the relationship between muscularity (as measured via lean body mass), fat stores (as measured by percent body fat) and several other sport-related fitness characteristics, including strength, power, and vertical jump height. METHODS: Eighty Division I collegiate athletes were assessed over the course of two days in various strength, power, speed, and body composition tests. Data from these tests was assessed via correlation to establish basic relationships. Additionally, athletes were separated into the “highest” and “lowest” groups (according to their lean body mass to percent fat ratio), and several statistical tests were applied to the groups in order to attempt to ascertain the magnitude of the relationships between body composition and other fitness characteristics measured. RESULTS: Results indicated that athletes with more lean body mass and less body fat tend to be relatively stronger (force scaled to body mass of 54.2N∙kg-1 vs. 49.4 N∙kg-1, p\u3c0.05), more powerful (CMJ peak power per body mass 68.3W∙kg-1 vs. 58.0 W∙kg-1, p\u3c0.05) and jump higher than their counterparts (CMJ height 35.1cm vs. 29.7cm, p\u3c0.05). CONCLUSION: These findings reinforce the importance of body composition in athletic performance. From a practical standpoint, the results of this study suggest that body composition advantages (more muscle, less fat) may be associated with higher relative strength, power, and vertical jumping abilities. Strength and conditioning programs at the Division 1 level may benefit from monitoring and attempting to improve the body composition of their athletes

Acute Postactivation Potentiation Using Isometric and Dynamic Mid-Thigh Clean Pulls in Trained Weightlifters, Powerlifters, and Sprint Cyclist

Countermovement vertical jump (CMVJ) performance may be acutely facilitated via potentiation (PAP) due to central and peripheral factors. PURPOSE: To investigate the effects of two methods of PAP in trained weightlifters (n=16); group 1: stronger (n=7) and group 2: weaker (n=9) upon unweighted countermovement jumps (CMVJs) over a 15 minute time period. METHODS: A series of maximal unweighted CMVJs were performed prior to, then at, 30, 60, 120, 180, 300, 480, 660, 780, and 900 seconds following two conditions: isometric mid-thigh clean pulls (C1) and dynamic mid-thigh clean pulls (C2). Dependent variables included, jump height (JH, cm), peak power (PP, W), peak velocity (PV, m·s-1), and peak force (PF, N). RESULTS: A series of repeated measures ANOVA: conditions (2); time points (10); groups (2) were performed on JH, PP, PV, and PF (p\u3e.05). Significant main effects for JH existed by condition (C1\u3eC2) (p=.001, ES=.571, 1-β=.979, mean diff=.053cm), group (G1\u3eG2) (p=.018, ES=.339, 1-β=.702, mean diff=.053), and time (60s\u3e900s, 120s\u3e900s, 180s\u3e900s) (p=.014, ES=.148, 1-β=.910).Within subjects main effects for JH were seen for the stronger group for JH by condition (C1\u3eC2) (p=.055, ES=.757, 1-β=.947, mean diff=.053cm), and weaker group by condition (C1\u3eC2) (p=.025, ES=.487, 1-β=.676, mean diff=.054cm). Significant main effects existed for PP by condition (C1\u3eC2) (p=.000, ES=.631, 1-β=.995, mean diff=427.9W), group (G1\u3eG2) (p=.008, ES=.405, 1-β=.819, mean diff=1660.1W), and time (60s\u3e480s, 60s\u3e660s, 60s\u3e780s, 60s\u3e900s\u3e120s\u3e900s, 180s\u3e480s, 180s\u3e660s, 180s\u3e780s) (p=.000, ES=.355, 1-β=1.00, mean diff=240.1W ).Within subjects main effects for PP were seen for the stronger group for condition (C1\u3eC2) (p=.055, ES=.761, 1-β=.951, mean diff=516.8W), and time (120s\u3e900s) (p=.000, ES=.471,1-β=.999, mean diff=319.5W). In the weaker group; significant main effects by condition (C1\u3eC2) (p=.025, ES=.485, 1-β=.672, mean diff=339.1W) and time (120s\u3e900s, 180s\u3e480s, 180s\u3e900s, 300s\u3e900s) (p=.003, ES=.281, 1-β=.963, mean diff=319.5W). Significant main effects were seen for jump PV by condition (C1\u3eC2) (p=.001, ES=.536,1-β=.962, mean diff=.177 m·s-1), group (G1\u3eG2) (p=.022, ES=.320, 1-β=.665, mean diff=.298m/s) and by time (60s\u3e900s, 120s\u3e900s, 180s\u3e900s) (p=.016, ES=.145, 1-β=.904). Within subjects main effects for jump PV in the stronger group by condition (C1\u3eC2) (p=.007, ES=.727, 1-β=.911, mean diff=.165m/s), and time (120s\u3e900s) (p=.036, ES=.269, 1-β=.840, mean diff=.073 m·s-1). In the weaker group there were significant main effects for jump PV by condition (C1\u3eC2) (p=.028, ES=.474, 1-β=.654, mean diff=.188 m·s-1). A significant main effect for jump PF by group (G1\u3eG2) (p=.014, ES=.363, 1-β=.747, mean diff=647.0N) and time (60s\u3ebaseline) (p=.05, ES=.122, 1-β=.824, mean diff=71.0N) was seen. Within subjects, a significant main effect for jump PF in the weaker group by time (60s\u3e780s) (p=.012, ES=.247, 1-β=.919). There were no significant interactions for any of the dependent variables (p \u3e.05). CONCLUSION: Isometric mid-thigh clean pulls appear to have a greater potentiating effect than dynamic mid-thigh pulls on PP and PV during subsequent CMVJ0’s, and stronger weightlifters tend to have a more favorable response to both conditions. PRACTICAL APPLICATION: Whole-body isometric movements may be a more effective at eliciting a potentiation response than dynamic movements in strength and power athletes

Changes in Relationship Between Static Jump Height, Strength Characteristics, and Body Composition With Training

Abstract available in the Medicine & Science in Sports & Exercis

Progressive overload without progressing load? The effects of load or repetition progression on muscular adaptations

Background Progressive overload is a principle of resistance training exercise program design that typically relies on increasing load to increase neuromuscular demand to facilitate further adaptations. However, little attention has been given to another way of increasing demand—increasing the number of repetitions. Objective This study aimed to compare the effects of two resistance training programs: (1) increasing load while keeping repetition range constant vs (2) increasing repetitions while keeping load constant. We aimed to compare the effects of these programs on lower body muscle hypertrophy, muscle strength, and muscle endurance in resistance-trained individuals over an 8-week study period. Methods Forty-three participants with at least 1 year of consistent lower body resistance training experience were randomly assigned to one of two experimental, parallel groups: A group that aimed to increase load while keeping repetitions constant (LOAD: n = 22; 13 men, nine women) or a group that aimed to increase repetitions while keeping load constant (REPS: n = 21; 14 men, seven women). Subjects performed four sets of four lower body exercises (back squat, leg extension, straight-leg calf raise, and seated calf raise) twice per week. We assessed one repetition maximum (1RM) in the Smith machine squat, muscular endurance in the leg extension, countermovement jump height, and muscle thickness along the quadriceps and calf muscles. Between-group effects were estimated using analyses of covariance, adjusted for pre-intervention scores and sex. Results Rectus femoris growth modestly favored REPS (adjusted effect estimate (CI90%), sum of sites: 2.8 mm [−0.5, 5.8]). Alternatively, dynamic strength increases slightly favored LOAD (2.0 kg [−2.4, 7.8]), with differences of questionable practical significance. No other notable between-group differences were found across outcomes (muscle thicknesses, <1 mm; endurance, <1%; countermovement jump, 0.1 cm; body fat, <1%; leg segmental lean mass, 0.1 kg), with narrow CIs for most outcomes. Conclusion Both progressions of repetitions and load appear to be viable strategies for enhancing muscular adaptations over an 8-week training cycle, which provides trainers and trainees with another promising approach to programming resistance training

Changes in Measures of Power in NCAA Division I Female Soccer Athletes Through Competitive Seasons

Abstract available in the Medicine & Science in Sports & Exercis