PAULO HENRIQUE MARCHETTI
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- MUSCLE ACTIVATION DIFFERS BETWEEN PARTIAL AND FULL BACK SQUAT EXERCISE WITH EXTERNAL LOAD EQUATED(2017) SILVA, Josinaldo J. da; SCHOENFELD, Brad J.; MARCHETTI, Priscyla N.; PECORARO, Silvio L.; GREVE, Julia M. D.; MARCHETTI, Paulo H.Changes in range of motion affect the magnitude of the load during the squat exercise and, consequently, may influence muscle activation. The purpose of this study was to evaluate muscle activation between the partial and full back squat exercise with external load equated on a relative basis between conditions. Fifteen young, healthy, resistance-trained men (age: 26 +/- 5 years, height: 173 +/- 6 cm) performed a back squat at their 10 repetition maximum (10RM) using 2 different ranges of motion (partial and full) in a randomized, counterbalanced fashion. Surface electromyography was used to measure muscle activation of the vastus lateralis, vastus medialis, rectus femoris, biceps femoris (BF), semitendinosus, erector spinae, soleus (SL), and gluteus maximus (GM). In general, muscle activity was highest during the partial back squat for GM (p = 0.004), BF (p = 0.009), and SL (p = 0.031) when compared with full-back squat. There was no significant difference for rating of perceived exertion between partial and full back squat exercise at 10RM (8 +/- 1 and 9 +/- 1, respectively). In conclusion, the range of motion in the back squat alters muscle activation of the prime mover (GM) and stabilizers (SL and BF) when performed with the load equated on a relative basis. Thus, the partial back squat maximizes the level of muscle activation of the GM and associated stabilizer muscles.
- Acute bouts of upper and lower body static and dynamic stretching increase non-local joint range of motion(2016) BEHM, David George; CAVANAUGH, Tyler; QUIGLEY, Patrick; REID, Jonathan Christopher; NARDI, Priscyla Silva Monteiro; MARCHETTI, Paulo HenriqueThere are conflicts in the literature concerning the crossover or non-local effects of stretching. The objective of this study was to evaluate whether static (SS) and dynamic (DS) stretching of the shoulders would affect hip flexor range of motion (ROM) and performance and reciprocally whether SS and DS of the lower body would affect shoulder extension ROM and performance. A randomized crossover study design examined the acute effects of upper and lower body SS and DS on lower and upper body performance measures, respectively. Experimental sessions included upper and lower body control tests, upper body (shoulder horizontal abduction) SS and lower body (hip abduction) SS, upper body (shoulder horizontal abduction and adduction) DS and lower body DS (hip abduction and adduction). Passive static and dynamic ROM (hip flexion, shoulder extension), leg flexor and elbow flexor maximal voluntary contraction isometric force, fatigue endurance and electromyography were measured. There were significant shoulder ROM increases following lower body SS (P < 0.010, a dagger % = 8.2 %) and DS (P < 0.019, a dagger % = 9 %). There was a significant hip flexor ROM (P < 0.016, a dagger % = 5.2 %) increase following upper body SS. There were no significant main effects or interactions for dynamic ROM or muscle force and activation variables. The lack of stretch-induced force and fatigue changes suggests that rather than a mechanical or neural drive mechanism, an enhanced stretch tolerance was likely the significant factor in the improved ROM.