Kinematic and Kinetic Analysis of the Squat With and Without Knee Wraps

Presentation given at the National Strength and Conditioning Association National Conference and Exhibition

Intrasession Reliability and the Relationship Between the Explosive Bench Press and Medicine Ball Chest Pass Assessments of Upper Extremity Power

The bench press throw and explosive bench press (EBP) test have recently received increased attention; however, both of these tests require specialized apparatus and instrumentation which limits their utilization in many settings. Medicine ball chest pass (MBCP) distance is a field test that also attempts to measure upper extremity power, however the optimal load has not been established. PURPOSE: To determine the relationship between EBP peak power and MBCP test distance using 2kg, 3kg and 4kg loads and to determine the intrasession reliability of both tests. METHODS: Twenty-seven healthy collegiate-level baseball players (20.5±1.5yrs; 1.82±.06m; 84.7±8.7kg) performed three MBCP trials using 2kg, 3kg, and 4kg MB loads. Instructions were given to hold medicine ball at shoulder level with feet shoulder width apart and knees straight, and to press the MB for maximal distance without countermovement. Initial impact sites of each trial determined distance. For the EBP trials, a standard 16kg barbell was loaded with and additional 14kg. Each subject was allowed a warm-up of 8 repetitions. Subjects then performed three maximum velocity bench press trials. An electromagnetic sensor (Motion Monitor, IST, Inc) offset from the bar with PVC pipe determined bar displacement. Displacement was then used to determine velocity, when coupled with the bar mass, provided power across each repetition. Both peak power and MBCP distance were averaged across three trials. RESULTS: Strong intrasession reliability was revealed for the bench press and MBCP tests (ICC range=.933 to .977) Although correlational coefficients for 3kg (r=.647, 95% CI=.355 to .824) and 4kg (r=.612, 95% CI=.303 to .804) loads were slightly higher than 2kg (r=.482, 95% CI=.135 to .728) there was no significant difference between the three coefficients (P\u3e.05). CONCLUSIONS: Both the EBP and MBCP tests had strong intrasession reliability. If the EBP test is not feasible, then the slightly stronger relationships support using the 3kg or 4kg loads for the MBCP test as an alternative method of assessing upper extremity power. It should be recognized that although statistically significant, the relationships revealed were only moderate strength, suggesting that the tests may be measuring different aspects of upper extremity power

Medial And Lateral Gastrocnemius Activation Differences During Heel Raise Exercise With Three Different Foot Positions

Instructional guidelines from some national exercise certification organizations recommend performing heel raise exercise with varying initial foot positions to alter the involvement of the gastrocnemius\u27 medial (MG) or lateral (LG) head. PURPOSE: To compare MG and LG activation during the concentric (CP) and eccentric (EP) phases of heel raise exercise using neutral (N), internally-rotated (IR) and externally-rotated (ER) foot positions. The term foot position was maintained for consistency with instructional texts, though the initial foot position reflects hip rotation. METHODS: Twelve healthy subjects (9 male, 3 female; 24.0 ± 3.8yrs) with resistance training experience performed free-weight (bar loaded to 30% body mass) heel raise exercise on a 3.8 cm block. Surface electromyographic (EMG) activity was recorded during five repetitions under each of the N, IR and ER foot positions, divided into CP and EP phases, and ensemble averaged within phase. Mean EMG amplitude, normalized to maximum voluntary contraction, was calculated. Separate two-factor (position by head) repeated measures analysis of variance were used for each phase. Simple main effects post hoc analyses of the significant (P \u3c.05) interactions were conducted. RESULTS: During EP, significantly greater MG activity compared to LG activity was revealed for both N and ER. During CP, significantly greater LG activity compared to the MG occurred for IR. Further, post hoc analyses on the EP revealed that MG activity using ER was significantly greater than MG activity using IR or N. Likewise, analysis of CP revealed that LG activity using IR was significantly greater than LG activity using ER or N. CONCLUSION: Altering foot positions during the heel raise exercise does alter relative muscle activation as measured by surface EMG. The MG is activated to a significantly greater extent than the LG during EP using N and ER, while the LG displays significantly greater muscle activity than the MG during CP using IR. Further research is recommended to elucidate the role of the contraction phases in these differences

Medial and Lateral Gastrocnemius Activation Differences During Heel-Raise Exercise with Three Different Foot Positions

Riemann, BL, Limbaugh, GK, Eitner, JD, and LeFavi, RG. Medial and lateral gastrocnemius activation differences during heel-raise exercise with three different foot positions. J Strength Cond Res 25(3): 634-639, 2011-Despite little objective support, heel-raise exercises are commonly performed using varying foot positions in an attempt to alter medial (MG) and lateral (LG) gastrocnemius involvement. This investigation compared MG and LG activation during the concentric phase (CP) and eccentric phase (EP) of the heel-raise exercise using neutral (NE), internally rotated (IR), and externally rotated (ER) foot positions. Twenty healthy subjects (10 men, 10 women; age = 23.7 ± 3.1 years) with resistance training experience performed free-weight (130-135% body mass) heel-raise exercise on a 3.81-cm block. Surface electromyography activity was recorded during 10 repetitions of each foot position. Electromyography activity from 5 successful repetitions was normalized to maximum voluntary isometric contraction, ensemble averaged within phase (CP, EP), and the mean amplitude determined. Significant (p \u3c 0.05) muscle-by-foot position interactions were revealed for both phases. The ER position prompted significantly greater MG activation than LG during both phases, whereas the IR position elicited significantly greater LG activation than MG. These data support the notion that altering foot position during heel-raise exercise will prompt varying degrees of MG and LG activation. Although this study cannot predict whether muscle-activation differences between foot positions will translate into greater training adaptations, it does provide some initial objective evidence upon which practitioners can base the selection of gastrocnemius exercises

Medial and Lateral Gastrocnemius Activation Differences During Heel Raise Exercise With Three Different Foot Positions

Presentation given at the 2009 Annual Meeting of the American College of Sports Medicine

Intrasession Reliability and the Relationship Between the Explosive Bench Press and Medicine Ball Chest Pass Assessments of Upper Extremity Power

Presentation given at the Annual Meeting of the American College of Sports Medicine

Effects of Unweighting on Heart Rate Response and Speed/Incline Adjustments Necessary in Elite Runners

The AlterG Treadmill, which makes use of lower body positive pressure (LBPP), enables runners to train at race-pace speeds yet with variable body weights (BW) and resultant ground reaction forces. The AlterG is marketed as an “unweighting” tool useful during lower body injury. There is lack of research investigating the additional speed and/or incline necessary at lower BW to achieve the equivalent intensity possible at 100% BW. PURPOSE: To quantify AlterG speed and incline adjustments necessary at two levels of unweighting in order to achieve intensities equivalent to those at 100% BW running. METHODS: Following an initial V02max test, seven elite male runners (average age = 30.1 yrs; ht = 177.4 cm; wt = 77.1 kg; V02max = 64.1 ml/kg/min) underwent two unweighted running trials (75% BW and 50% BW). The trials ended when subjects reached their heart rate at 90% V02max. Heart rate, speed, and incline were recorded throughout each trial. RESULTS: When subjects were unweighted to 75% BW and ran at their heart rate equivalent of 70% V02max, they required an average speed increase of 1.7 mph and an average incline increase of 4.3%; at 80% V02max, 2.8 mph and 3.1% incline, respectively; at 90% V02max, 3.4 mph and 2.0% incline, respectively. When subjects were unweighted to 50% BW and ran at their heart rate equivalent of 70% V02max, they required an average speed increase of 2.7 mph and an average incline increase of 5.1%; at 80% V02max, 4.1 mph and 4.7% incline, respectively; at 90% V02max, 3.9 mph and 4.1% incline, respectively. Further, the average speed increase at 75% BW across all target intensities to reach the equivalent heart rate at 100% BW was 3.1 mph, yet there was only a 0.8 mph additional increase necessary when BW dropped from 75% to 50%. Likewise, the average incline increase at 75% BW relative to 100% BW was 3.1%, while the decrease from 75% BW to 50% BW required only an additional 1.9% incline. CONCLUSION: Unweighting due to LBPP requires an increase in running speed and incline in order to maintain training intensity levels in elite male runners. Since the increases in speed and incline necessary to achieve target intensities do not appear to be linearly related to the level of unweighting, further research is necessary to identify the variables at which maximum intensity can be achieved while ground reaction forces are minimal

Effects of Unweighting on Heart Rate Response and Speed/incline Adjustments Necessary in Elite Runners

Presentation given at 2012 Annual Meeting of the American College of Sports Medicine