Clin Physiol Funct Imaging (2014)

doi: 10.1111/cpf.12151

Heterogeneity of rectus femoris muscle architectural adaptations after two different 14-week resistance training programmes Thiago T. Matta1,2, Francisco X. M. B. Nascimento2, Igor A. Fernandes3 and Liliam F. Oliveira1,2 1

Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, 2School of Physical Education and Sports, Laboratory of Biomechanics, Federal University of Rio de Janeiro, and 3Laboratory Crossbridges, Postgraduate Program in Sport and Exercise Science, Gama Filho University, Rio de Janeiro, Brazil

Summary Correspondence Thiago Torres da Matta, Laboratory of Biomechanics, Escola de Educacß~ao Fısica e Desportos, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 540. Ilha do Fund~ao. Rio de Janeiro. 21941-590, Brazil E-mail: [email protected]

Accepted for publication Received 4 December 2013; accepted 20 March 2014

Key words cross-sectional area; fascicle angle; hypertrophy; muscle thickness; resistance exercise; ultrasonography

Purpose This study aimed to determine the architectural changes of rectus femoris muscle at distinctive sites of the thigh length after two different 14-week resistance training programmes. Methods Thirty-five untrained men were randomly allocated into three different groups: conventional resistance training (n = 12), isokinetic training (n = 12) and control (n = 11). Rectus femoris cross-sectional area, thickness and fascicle angle at two specific thigh sites (30% and 50% of the length) were assessed before and after 14 weeks of unilateral knee extension exercise or control. The isometric peak torque of the knee extensors was estimated as a muscle strength index. Results Conventional (30% = 474% versus 50% = 144%) and isokinetic (30% = 318% versus 50% = 114%) training induced significant increases on thickness at both rectus femoris sites. While conventional training resulted in substantial increments on cross-sectional area (30% = 621%, 50% = 195%), isokinetic training provoked a significant increase only at the distal site (50% = 647%). The isometric peak torque increased (224 and 296%, for conventional and isokinetic groups, respectively) after training independently of the training mode, although no significant changes were observed for any dependent variable in the control group. Conclusions In general, the training modes resulted in similar changes on rectus femoris architecture, whereas their magnitude depended on the thigh site.

Introduction Muscle architectural adaptations to resistance exercise depend on several factors such as training status, intensity–volume relationship and muscle activation (Folland & Williams, 2007). These resistance-training-induced muscle architectural changes have been commonly quantified through the application of imaging techniques (Kawakami et al., 1995; Kanehisa et al., 2002; Blazevich et al., 2006). In this scenario, ultrasonography constitutes a safe, relatively low-cost and reliable technique (Lima et al., 2012), which has been validated through comparisons to ‘gold standard’ methods such as magnetic resonance imaging (MRI) and computerized axial tomography (Bemben, 2002; Noorkoiv et al., 2010). While these resistances-training-induced adaptations have been generally measured at a single anatomical site (Hakkinen et al., 2001; Alegre et al., 2006), there has been evidence of a

great variability of architecture parameters along the entire muscle extension (Starkey et al., 1996; O’Brien et al., 2010). For example, the rectus femoris (RF) thickness varies approximately 62% between proximal to distal sites (Starkey et al., 1996), while fascicle angle (FA) presents a great range among muscle sites (O’Brien, et al. 2010). In a review, Folland and Williams (Folland & Williams, 2007) indicated that the morphological adaptations induced by resistance training are related to the muscle length and anatomical predictors. This hypothesis could be attributed by higher RF activation on distal site on maximum knee extension (Miyamoto et al., 2012; Watanabe et al., 2012). Muscle hypertrophy results from repetitive mechanical stimuli (Blazevich, 2006). Conventional machines use a system of asymmetric pulleys that vary the load imposed throughout the range of the motion (Wernbom et al., 2007). Differently, through an electromagnetic system, isokinetic dynamometers

© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd


2 Chronic effects on rectus femoris muscle architecture, T. T. Matta et al.

vary the resistance load to keep a constant velocity and maximum muscle tension throughout the movement. Information on hypertrophy in different muscles architectural organization is still controversial. Studies have evidenced homogeneous hypertrophy among different sites in quadriceps (Blazevich et al., 2007b; Seynnes et al., 2007) and arm muscles (Farthing & Chilibeck, 2003; Matta et al., 2011). On the other hand, non-homogeneous muscle hypertrophy has also been reported (Kawakami et al.,1995; Matta et al., 2011). Therefore, the aim of the present study was to investigate the effects of two different 14-week dynamic leg extension resistance training programmes on RF muscle cross-sectional area, thickness and fascicle angle measured at two different anatomical sites (30 and 50% of the thigh length) through the analysis of ultrasound image. Our hypothesis is that different resistance training protocols would induce heterogenic architectural adaptations on RF muscle and their magnitude would be site dependent based on architecture complexity along this muscle.

Methods Thirty-five healthy young men without previous experience with resistance training were randomly assigned into one of the three different groups: (i) conventional (n = 12, age 193  09 years, height 175  007 m and body mass 718  102 kg), (ii) isokinetic (n = 12, age 191  03 years, height 176  007 m and body mass 724  113 kg) and (iii) control (n = 11, age 195  13 years, height 170  007 m and body mass 699  86 kg). Exclusion criteria included any history or symptoms of either neuromuscular or cardiovascular disorders, reporting of previous lower extremity injuries or surgery and the use of ergogenic substances. Participants signed an informed written consent to the experimental setup approved by the Ethical Review Board of the Clementino Fraga Filho University Hospital (number 020/11- FR 409254). Participants included into both conventional and isokinetic groups were submitted to a 14-week non-periodized resistance training programme based on the American College of Sports Medicine recommendations for muscle hypertrophy (Garber et al., 2011). Participants trained twice a week. These sessions were separated from at least 48 to a maximum of 72 h apart. Training programmes consisted of three sets of a unilateral (right lower limb) concentric-eccentric knee extension exercise. Sets were separated by a 1-min rest interval. Training sessions were initiated with a specific warm-up that consisted of 10 submaximal repetitions with 50% of the training load. The conventional training group performed 9–11 maximum repetitions on a variable resistance knee extension machine (Technogym; Biomedical Line, Gambettola, Italy). The conventional-trainingrelated load was determined at the beginning (48 h before the first session) of the programme and then increased by about 5% if the participant was able to perform more than 11 repetitions in the remaining sessions. The isokinetic group performed three sets of 10 repetitions at an angular velocity of 60o s 1 on

a dynamometer (Cybexâ Humac2009â/NormTM; Henley Health, USA). Total time of contraction was equalized between training groups through the control of the velocity of both conventional concentric and eccentric phase (via a metronome, approximately 1 s for contraction phase). Training volume equalization was partially conducted via the control of the number of sets and repetitions. Training load was not included in the volume control due to the inherent overload characteristics of both resistance training modes. Knee extension isometric peak torque and RF muscle architecture variables were assessed before and after the 14-week follow-up period. These measurements were separated from the first and last training session by an interval of at least 48 to a maximum of 72 h. For the maximum isometric voluntary contraction (MIVC), participants were kept in a sitting position (hip flexion of 85° and knee flexion of 70° (0° full knee extension) on isokinetic dynamometer (Blazevich et al., 2009). Participants then performed two consecutive five-second MVICs with 1-min rest interval between trials. The highest peak torque between the two tests was considered for analysis. The RF muscle architecture was assessed by B-mode ultrasound with a linear array probe (80 cm, and 75 MHz EUB-405; Hitachi, Japan). The participants lay supine with both hip and knee fully extended and relaxed. To acquire muscle thickness (MT) and cross-sectional area (CSA), the ultrasound probe was centred with respect to each location on the transverse plane of the segment at 50% and 30% (proximal and distal, respectively) of the entire right thigh length – distance from the superior border of the patella and great trochanter (Blazevich et al., 2009). CSA was obtained through the mark of internal edges of the RF muscle fascia (Fig. 1a) (Bemben, 2002). MT was determined as the distance between the deeper and upper RF muscle aponeurosis (Miyatani et al., 2002). Measured with the probe oriented longitudinally towards the centre of the patella at the same sites, the fascicle angle (FA) was defined as the angle between the echoes of the deep RF aponeurosis and those from interspaces among fascicle (Blazevich et al., 2007a,b) (Fig. 1b). The images preand post-training were acquired using the same protocol using the baseline anatomical measures as reference. The images were analysed with public-domain software (Image J, v.1.42; National Institutes of Health, USA). These imaging analysis presented high levels of intraclass correlation for all dependent variables (CSA50%, ICC = 0970, CV = 3%; CSA30%, ICC = 0965, CV = 72%; MT50%, ICC = 0953, CV = 23%; MT30%, ICC = 0961, CV = 42; FA50%, ICC = 0780, CV = 6%; FA30%, ICC = 0852, CV = 48%). Statistical analysis Mean and standard deviation (mean  SD) were calculated to describe both central tendency and variability, respectively. The Shapiro–Wilk test confirmed that muscle architecture and knee extensor peak torque data were normally distributed. For the experimental hypothesis, significant interactions were

© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd

Chronic effects on rectus femoris muscle architecture, T. T. Matta et al. 3



Figure 1 Rectus femoris muscle cross-sectional area (CSA) and thickness (MT) (a) at 50% of thigh length, and fascicle angle (FA) (b).

examined through the application of a three-way [time (before vs after 14 weeks), group (convencional versus isokinetic versus control) and site (50 versus 30%)] ANOVA with repeated measures on factors time and site. Training-induced changes on isometric peak torque and the relative changes on muscle architecture variables were examined through the application of a two-way ANOVA with repeated measures on the factors ‘group’ and ‘site’, respectively. When a significant main effect or interaction was detected, the least significant difference Fisher post hoc test was used to identify substantial differences. The significance level was set at a ≤ 005. Statistical analyses were carried out with the commercial statistical software (Statistica 70, Statsoft, Inc., Tulsa, OK, USA).


Figure 2 Relative changes of cross-sectional area after 14 weeks. *P

Heterogeneity of rectus femoris muscle architectural adaptations after two different 14-week resistance training programmes.

This study aimed to determine the architectural changes of rectus femoris muscle at distinctive sites of the thigh length after two different 14-week ...
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