Deconstructing the power resistance relationship for squats: A joint‐level analysis

Abstract

Generating high leg power outputs is important for executing rapid movements. Squats are commonly used to increase leg strength and power. Therefore, it is useful to understand factors affecting power output in squatting. We aimed to deconstruct the mechanisms behind why power is maximized at certain resistances in squatting. Ten male rowers (age = 20 ± 2.2 years; height = 1.82 ± 0.03 m; mass = 86 ± 11 kg) performed maximal power squats with resistances ranging from body weight to 80% of their one repetition maximum (1RM). Three-dimensional kinematics was combined with ground reaction force (GRF) data in an inverse dynamics analysis to calculate leg joint moments and powers. System center of mass (COM) velocity and power were computed from GRF data. COM power was maximized across a range of resistances from 40% to 60% 1RM. This range was identified because a trade-off in hip and knee joint powers existed across this range, with maximal knee joint power occurring at 40% 1RM and maximal hip joint power at 60% 1RM. A non-linear system force-velocity relationship was observed that dictated large reductions in COM power below 20% 1RM and above 60% 1RM. These reductions were due to constraints on the control of the movement.

Short-term effects of sports taping on navicular height, navicular drop and peak plantar pressure in healthy elite athletes

“…A 19-camera motion capture system (Oqus, Qualisys, Sweden) sampling at 250 Hz was used to record navicular position data of passive reflective markers of each participant. [ 15 ] All cameras were arranged and installed to smoothly measure the position in a 10-m walkway. Before navicular data collection, a global frame was created based on calibration trials via nonlinear transformation for 60 seconds.…”

UltraTrack: Software for semi-automated tracking of muscle fascicles in sequences of B-mode ultrasound images

“…B--mode ultrasound imaging was performed using a 96--256 element linear array ultrasound transducer (LV7.5/60/96Z, Telemed, Lithuania) operating at a central 257 frequency of 6 MHz, a depth of 65 mm and sampling images at 80 frames per second. The participant was a 258 healthy young male athlete and he performed two repetitions of a squatting movement (for details see 259 [8]). The image sequence was recorded using EchoWave II software as a TVD file and converted to MAT file 260 using our custom TVD_2_MAT script described in section 3.1.…”

Information from dynamic length changes improves reliability of static ultrasound fascicle length measurements

“…Objective data of muscle fascicle lengths is therefore needed. As such, an increased interest in identifying muscle fascicle geometry has been emerging, as muscle fascicle length and orientation can provide valuable information about muscle performance (e.g., Abe, Kumagai & Brechue, 2000 ; Blazevich, 2006 ; Farris et al, 2016a ; Farris et al, 2016b ) as well as clinical or training adaptations ( Mohagheghi et al, 2007 ; Blazevich et al, 2014 ; Hoffman et al, 2016 ). B-mode ultrasound imaging is the most commonly used method to determine muscle fascicle geometry, because it is cost- and time-effective and it allows for measurements during dynamic tasks, such as walking ( Fukunaga et al, 2001 ; Ishikawa et al, 2005 ), running ( Lichtwark & Wilson, 2006 ; Ishikawa, Pakaslahti & Komi, 2007 ), and jumping ( Kurokawa, Fukunaga & Fukashiro, 2001 ; Farris et al, 2016a ; Farris et al, 2016b ).…”