Human quadriceps cross‐sectional area, torque and neural activation during 6 months strength training

Abstract

Quadriceps muscle and fibre cross-sectional areas (CSA), torque and neural activation were studied in seven healthy males during 6 months of weight training on alternate days with six series of eight unilateral leg extensions at 80% of one repetition maximum. After training, the quadriceps cross-sectional area increased by 18.8 +/- 7.2% (P < 0.001) and 19.3 +/- 6.7% (P < 0.001) in the distal and proximal regions respectively, and by 13.0 +/- 7.2% (P < 0.001) in the central region of the muscle. Hypertrophy was significantly different between and within the four constituents of the quadriceps. Biopsies of the vastus lateralis at mid-thigh did not show any increase in mean fibre cross-sectional area. Maximum isometric voluntary torque increased by 29.6 +/- 7.9%-21.1 +/- 8.6% (P < 0.01-0.05) between 100 degrees and 160 degrees of knee extension, but no change in the optimum angle (110 degrees-120 degrees) for torque generation was found. A 12.0 +/- 10.8% (P < 0.02) increase in torque per unit area together with a right shift in the IEMG-torque relation and no change in maximum IEMG were observed. Time to peak isometric torque decreased by 45.8% (P < 0.03) but no change in time to maximum IEMG was observed. In conclusion, strength training of the quadriceps results in a variable hypertrophy of its components without affecting its angle-torque relation. The increase in torque per unit area, in the absence of changes in IEMG, may indicate changes in muscle architecture. An increase in muscle-tendon stiffness may account for the decrease in time to peak torque.

Skeletal muscle substrate metabolism during exercise: methodological considerations

“…It is true that saphenous blood flow is relatively low, but some blood must be drained from the proximal thigh muscle, which has a slightly higher lactate concentration than blood from the more distal part to compensate for the low lactate level in the saphenous vein. This point of view is in accordance with the explanation given earlier for O 2 saturation, and agrees with the observation that after training the proximal part of the kneeextensor muscle enlarges more than the more distal portions both in young (Narici et al 1989(Narici et al , 1996 and older individuals (Kryger, 1998). Available data on glucose reveal similar concentrations when sampling in the proximal and distal direction of the femoral artery, with a tendency for glucose concentration to be slightly higher in the proximal direction ( Fig.…”

Espessura e qualidade musculares medidas a partir de ultrassonografia: influência de diferentes locais de mensuração. DOI: 10.5007/1980-0037.2011v13n2p87

“…No entanto, como mencionado acima, avaliar a EM, em diferentes pontos, é necessário para uma análise mais detalhada das adaptações morfológicas em resposta ao treinamento 24 . Nesta perspectiva, a utilização de mapas de avaliação, como por exemplo, os propostos por Narici et al 29 , podem ser uma alternativa para o controle dos pontos de avaliação da EM em estudos longitudinais, podendo reduzir os erros na reavaliação dos locais (pontos) de avaliação.…”

Changes in agonist neural drive, hypertrophy and pre-training strength all contribute to the individual strength gains after resistance training

“…Consequently, resistance training (RT) is frequently employed when aiming to: improve athletic performance (Wilson et al 1996;Comfort et al 2012); enhance mobility of middle-aged and older adults (Brochu et al 2002;Brandon et al 2003); reduce injury risk (Brooks et al 2006;Noyes and Barber Westin 2012); prevent or slow the progression of joint degeneration (Zhang and Jordan 2010). On a cohort level, neural (agonist activation, Komi et al 1978;Narici et al 1996;Tillin et al 2011Tillin et al , 2011antagonist co-activation, Carolan and Cafarelli 1992;Häkkinen et al 1998) andmorphological (hypertrophy, O'Hagan et al 1995;Tracy et al 1999;Erskine et al 2010a; muscle architecture, Aagaard et al 2001;Seynnes et al 2006;Blazevich et al 2007) adaptations have been widely documented to occur after RT and are presumed to explain the observed improvements in strength. However, on an individual basis there is great variability in the changes in strength after RT (Folland et al 2000;Hubal et al 2005), and relatively little is known about the contribution of specific physiological mechanisms to these individual changes, including which is the most important adaptation for determining strength gains.…”