Article

Lower extremity muscle functions during full squats.

School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada.
Journal of applied biomechanics (Impact Factor: 0.9). 12/2008; 24(4):333-9.
Source: PubMed

ABSTRACT The purpose of this research was to determine the functions of the gluteus maximus, biceps femoris, semitendinosus, rectus femoris, vastus lateralis, soleus, gastrocnemius, and tibialis anterior muscles about their associated joints during full (deep-knee) squats. Muscle function was determined from joint kinematics, inverse dynamics, electromyography, and muscle length changes. The subjects were six experienced, male weight lifters. Analyses revealed that the prime movers during ascent were the monoarticular gluteus maximus and vasti muscles (as exemplified by vastus lateralis) and to a lesser extent the soleus muscles. The biarticular muscles functioned mainly as stabilizers of the ankle, knee, and hip joints by working eccentrically to control descent or transferring energy among the segments during scent. During the ascent phase, the hip extensor moments of force produced the largest powers followed by the ankle plantar flexors and then the knee extensors. The hip and knee extensors provided the initial bursts of power during ascent with the ankle extensors and especially a second burst from the hip extensors adding power during the latter half of the ascent.

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Article: Lower extremity muscle functions during full squats.

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    • "Taken out of context of the fossil record, our data would suggest that the enlarged GMAX was evolved for sprinting, climbing, and running. Other research has demonstrated that the GMAX is important for throwing, squatting, uphill walking, and lunges (Marzke et al., 1988; Isear et al., 1997; Ekstrom et al., 2007; Lay et al., 2007; Robertson et al., 2008; Oliver and Keeley, 2010). Identifying only one of these locomotion actions as providing the pressure for the derived GMAX would ignore its importance in numerous other locomotor tasks. "
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    ABSTRACT: It has been suggested that the uniquely large gluteus maximus (GMAX) muscles were an important adaptation during hominin evolution based on numerous anatomical differences between humans and extant apes. GMAX electromyographic (EMG) signals have been quantified for numerous individual movements, but not across the range of locomotor gaits and speeds for the same subjects. Thus, comparing relative EMG amplitudes between these activities has not been possible. We assessed the EMG activity of the gluteal muscles during walking, running, sprinting, and climbing. To gain further insight into the function of the gluteal muscles during locomotion, we measured muscle activity during walking and running with external devices that increased or decreased the need to control either forward or backward trunk pitch. We hypothesized that 1) GMAX EMG activity would be greatest during sprinting and climbing and 2) GMAX EMG activity would be modulated in response to altered forward trunk pitch demands during running. We found that GMAX activity in running was greater than walking and similar to climbing. However, the activity during sprinting was much greater than during running. Further, only the inferior portion of the GMAX had a significant change with altered trunk pitch demands, suggesting that the hip extensors have a limited contribution to the control of trunk pitch movements during running. Overall, our data suggest that the large size of the GMAX reflects its multifaceted role during rapid and powerful movements rather than as a specific adaptation for a single submaximal task such as endurance running. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 01/2014; 153(1). DOI:10.1002/ajpa.22419 · 2.51 Impact Factor
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    • "Taken out of context of the fossil record, our data would suggest that the enlarged GMAX was evolved for sprinting, climbing, and running. Other research has demonstrated that the GMAX is important for throwing, squatting, uphill walking, and lunges (Marzke et al., 1988; Isear et al., 1997; Ekstrom et al., 2007; Lay et al., 2007; Robertson et al., 2008; Oliver and Keeley, 2010). Identifying only one of these locomotion actions as providing the pressure for the derived GMAX would ignore its importance in numerous other locomotor tasks. "
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    • "The TBS used an Olympic weight bar (201.6 N) while the SMS bar weighted (89.6 N). To reduce any variations in technique and to normalize the load, the subject's lifted only 50% of their body weight and were instructed on how to perform the squats according to guidelines of the National Strength and Conditioning Association (NCSA) (Robertson, Wilson et al., 2008). Each subject warmed up 10 min prior to exercise and performed three repetitions of each exercise. "
    Proceedings of the XXVII International Symposium on Biomechanics in Sports; 01/2009
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