J Strength Cond Res. 2012 Jul 12. [Epub ahead of print]
Effect of Squat Depth and Barbell Load on Relative Muscular Effort in Squatting.
Bryanton MA, Kennedy MD, Carey JP, Chiu LZ.
ABSTRACT: Resistance training is used to develop muscular strength and hypertrophy. Large muscle forces, in relation to the muscle’s maximum force generating ability, are required to elicit these adaptations. Previous biomechanical analyses of multi-joint resistance exercises provide estimates of muscle force but not relative muscular effort (RME). The purpose of this investigation was to determine the relative muscular effort (RME) during squat exercise. Specifically the effects of barbell load and squat depth on hip extensor, knee extensor and ankle plantar-flexor RME were examined. Ten strength-trained women performed squats (50-90% 1 RM) in a motion analysis laboratory to determine hip extensor, knee extensor and ankle plantar-flexor net joint moment (NJM). Maximum isometric strength in relation to joint angle for these muscle groups was also determined. RME was determined as the ratio of NJM to maximum voluntary torque matched for joint angle. Barbell load and squat depth had significant interaction effects on hip extensor, knee extensor and ankle plantar-flexor RME (p<0.05). Knee extensor RME increased with greater squat depth but not barbell load, whereas the opposite was found for the ankle plantar-flexors. Both greater squat depth and barbell load increased hip extensor RME. These data suggest training for the knee extensors can be performed with low relative intensities but require a deep squat depth. Heavier barbell loads are required to train the hip extensors and ankle plantar-flexors. In designing resistance training programs with multi-joint exercises, how external factors influence RME of different muscle groups should be considered to meet training objectives.
J Strength Cond Res. 2012 Mar;26(3):772-6.
Are changes in maximal squat strength during preseason training reflected in changes in sprint performance in rugby league players?
Comfort P, Haigh A, Matthews MJ.
Because previous research has shown a relationship between maximal squat strength and sprint performance, this study aimed to determine if changes in maximal squat strength were reflected in sprint performance. Nineteen professional rugby league players (height = 1.84 ± 0.06 m, body mass [BM] = 96.2 ± 11.11 kg, 1 repetition maximum [1RM] = 170.6 ± 21.4 kg, 1RM/BM = 1.78 ± 0.27) conducted 1RM squat and sprint tests (5, 10, and 20 m) before and immediately after 8 weeks of preseason strength (4-week Mesocycle) and power (4-week Mesocycle) training. Both absolute and relative squat strength values showed significant increases after the training period (pre: 170.6 ± 21.4 kg, post: 200.8 ± 19.0 kg, p < 0.001; 1RM/BM pre: 1.78 ± 0.27 kg·kg(-1), post: 2.05 ± 0.21 kg·kg(-1), p < 0.001; respectively), which was reflected in the significantly faster sprint performances over 5 m (pre: 1.05 ± 0.06 seconds, post: 0.97 ± 0.05 seconds, p < 0.001), 10 m (pre: 1.78 ± 0.07 seconds, post: 1.65 ± 0.08 seconds, p < 0.001), and 20 m (pre: 3.03 ± 0.09 seconds, post: 2.85 ± 0.11 seconds, p < 0.001) posttraining. Whether the improvements in sprint performance came as a direct consequence of increased strength or whether both are a function of the strength and power mesocycles incorporated into the players’ preseason training is unclear. It is likely that the increased force production, noted via the increased squat performance, contributed to the improved sprint performances. To increase short sprint performance, athletes should, therefore, consider increasing maximal strength via the back squat.
J Strength Cond Res. 2012 Feb 15. [Epub ahead of print]
Influence of squatting depth on jumping performance.
Hartmann H, Wirth K, Klusemann M, Dalic J, Matuschek C, Schmidtbleicher D.
It is unclear if increases in one repetition maximum (1-RM) in quarter squats result in higher gains compared to full depth squats in isometric force production and vertical jump performance. The aim of the research projects was to compare the effects of different squat variants on the development of 1-RM and their transfer effects to Countermovement (CMJ) and Squat Jump (SJ) height, maximal voluntary contraction (MVC) and maximal rate of force development (MRFD). Twenty-three women and 36 men (mean age: 24.11±2.88) were parallelized into three groups based on their CMJ height: deep front squats (FSQ, n=20), deep back squats (BSQ, n=20) and quarter back squats (BSQ¼, n=19). In addition a control group (C, n=16) existed (mean age: 24.38±0.50). Experimental groups trained 2 d·wk for 10 weeks following a strength-power periodization, which produced significant (p≤0.05) gains of the specific squat 1-RM. FSQ and BSQ attained significant (p≤0.05) elevations in SJ and CMJ without any interaction effects between both groups (p≥0.05). BSQ¼ and C did not reveal any significant changes of SJ and CMJ. FSQ and BSQ had significantly higher SJ scores over C (p≤0.05). BSQ did not feature any significant group difference to BSQ¼ (p=0.116) in SJ, whereas FSQ showed a trend towards higher SJ heights over BSQ¼ (p=0.052). FSQ and BSQ presented significantly (p≤0.05) higher CMJ heights over BSQ¼ and C. Post-test in MVC and MRFD demonstrated no significant changes for BSQ. Significant declines in MRFD for FSQ in the right leg (p≤0.05) without any interaction effects for MVC and MRFD between both FSQ and BSQ were found. Training of BSQ¼ resulted in significantly (p≤0.05) lower RFD and MVC values in contrast to FSQ and BSQ. Quarter squat training elicited significant (p≤0.05) transfer losses into the isometric maximal and explosive strength behavior. Our findings therefore contest the concept of superior angle specific transfer effects. Deep front and back squats guarantee performance-enhancing transfer effects of dynamic maximal strength to dynamic speed-strength capacity of hip and knee extensors compared to quarter squats.
A Comparison Of Muscular Activation During The Back Squat And Deadlift to the Countermovement Jump” (2011). Theses and Dissertations. Paper 1.
Robbins, David CSCS, NASM-CPT
The purpose of this study was to determine whether the back squat (BS) or deadlift (DL) is most similar to the countermovement jump (CMJ) in terms of peak muscular activation. The muscles assessed in this study were the erector spinae (ES), gluteus maximus (GM), biceps femoris (BF), vastus medialis (VM), and gastrocnemius (GN). These five muscles were chosen do to their involvement in all of these exercises. Ten college-aged males (24±1.18yrs) with a minimum of 1 year strength training experience volunteered for this study. Participants must have been strength trained and could BS and DL 1.5 x bodyweight. Results showed that only the peak muscular activation of the GN was significantly different (p<0.05) among all muscles between the BS (3.97mV) and CMJ (8.36mV). There were no significant differences between the DL (6.20mV) and CMJ in muscular activation. However when a Pearson Product Correlation was performed, the CMJ and DL showed a weak correlation among all muscles (ES=0.27, GM=0.42, BF=0.46, VM=0.45, GN=0.24). The CMJ and BS only showed a weak correlation among the ES, BF and GN (0.44, 0.22, and 0.32 respectively) and strong correlation for the GM and VM (r = 0.73, 0.77, respectively). This study suggests that in terms of peak muscular activation, the DL is more similar to the CMJ than the BS since no significant differences were found in muscular activation. However, muscle activation of the VM and GM during the BS was strongly correlated to the CMJ.
