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Karin Tammik, Mariann Matlep, Jaan Ereline, Helena Gapeyeva and Mati Pääsuke

Isometric voluntary force production and relaxation capacity of the quadriceps femoris (QF) muscle was compared between 12 children with spastic diplegic cerebral palsy (CP) and healthy controls, age 10–11 years. Children with CP had less (p < .05) maximal voluntary-contraction force, voluntary activation, and rate of force development than controls. Visual reaction to contraction did not differ significantly in measured groups, whereas the reaction time to relaxation and halfrelaxation time were longer (p < .05) in children with CP. The authors concluded that in children with CP, the capacity for rapid voluntary force production and relaxation is reduced to a greater extent than isometric maximal force.

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Wolfgang Seiberl, Daniel Hahn, Florian Kreuzpointner, Ansgar Schwirtz and Uwe Gastmann

The purpose of this study was to investigate if force enhancement (FE) in vivo is influenced by stretch-induced changes of muscle architecture. Therefore, 18 subjects performed maximum voluntary isometric (100° knee flexion angle) and isometric-eccentric-isometric stretch contractions (80°–100° ω = 60°s−1) whereby pennation angle and fascicle length of vastus lateralis was determined using ultrasonography. We found significant (2-way repeated ANOVA; α = 0.05) enhanced torque of 5–10% after stretch as well as significant passive FE but no significant differences in muscle architecture between isometric and stretch contractions at final knee angle. Furthermore, EMG recordings during a follow-up study (n = 10) did not show significant differences in activation and mean frequency of contraction conditions. These results indicate that FE in vivo is not influenced by muscle architectural changes due to stretch.

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Atsuki Fukutani and Toshiyuki Kurihara

Recent studies have reported that resistance training increases the cross-sectional areas (CSAs) of tendons; however, this finding has not been consistently observed across different studies. If tendon CSA increases through resistance training, resistance-trained individuals should have larger tendon CSAs as compared with untrained individuals. Therefore, in the current study, we aimed to investigate whether resistance training increases tendon CSAs by comparing resistance-trained and untrained individuals. Sixteen males, who were either body builders or rugby players, were recruited as the training group, and 11 males, who did not participate in regular resistance training, were recruited into the control group. Tendon CSAs and muscle volumes of the triceps brachii, quadriceps femoris, and triceps surae were calculated from images obtained by using magnetic resonance imaging. The volumes of the 3 muscles were significantly higher in the training group than in the control group (P < .001 for all muscles). However, a significant difference in tendon CSAs was found only for the distal portion of the triceps surae tendon (P = .041). These findings indicate that tendon CSA is not associated with muscle volume, suggesting that resistance training does not increase tendon CSA.

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Norihide Sugisaki, Kai Kobayashi, Hiroyasu Tsuchie and Hiroaki Kanehisa

thickness and 100-m-sprint performance. However, according to the findings of Hoshikawa et al, 2 the quadriceps femoris muscle cross-sectional area (CSA) for junior male sprinters was negatively correlated to 100-m-sprint performance. For the psoas major muscle, Copaver et al 1 observed significant

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Conall F. Murtagh, Christopher Nulty, Jos Vanrenterghem, Andrew O’Boyle, Ryland Morgans, Barry Drust and Robert M. Erskine

maximum muscle power. Indeed, quadriceps femoris M vol has been shown to be strongly related to mean power produced during bilateral vertical CMJs in adults and children ( r 2  = .9) 6 and moderately related in male children alone ( r 2  = .3). 7 Nonetheless, bilateral vertical CMJ performance is not

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Taija Finni and Sulin Cheng

The positions of EMG electrodes over the knee extensor muscles were examined in 19 healthy men using MR images; electrodes were placed according to the SENIAM (surface electromyography for non-invasive assessment of muscles) guidelines. From axial images, the medial and lateral borders of the muscles were identified, and the arc length of the muscle surface was measured. The electrode location was expressed as a percentage value from the muscle’s medial border. EMGs were recorded during isometric maximal contraction, squat jumps, and countermovement jumps and analyzed for cross-correlation. The results showed that variations in lateral positioning were greatest in vastus medialis (47% SD 11) and rectus femoris (68% SD 15). In vastus lateralis, the electrode was usually placed close to the rectus femoris (19% SD 6). The peak cross-correlation coefficient varied between 0.15 and 0.68, but was not associated with electrode location. It is recommended that careful consideration is given to the medial-lateral positioning of the vastus lateralis electrodes especially, so that the electrodes are positioned over the mid-muscle rather than in close proximity to rectus femoris.

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María Hernández, Fabrício Zambom-Ferraresi, Pilar Cebollero, Javier Hueto, José Antonio Cascante and María M. Antón

lower extremities and the functional capacity in this population. We hypothesized that muscle power output of the quadriceps femoris would have stronger association with physical activity and functional capacity than maximum dynamic strength in older men with COPD. Methods Participants An observational

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Nobuaki Tottori, Tadashi Suga, Yuto Miyake, Ryo Tsuchikane, Mitsuo Otsuka, Akinori Nagano, Satoshi Fujita and Tadao Isaka

, previous studies have shown that a larger quadriceps femoris (QF) may be related to higher sprint performance because of a strong correlation between maximal knee extensor torque and sprint performance ( 4 , 10 , 13 , 21 ). Furthermore, Sugisaki et al ( 34 ) reported that a larger CSA of the adductors (ADD

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Kenneth Meijer, Peter Bosch, Maarten F. Bobbert, Arthur J. van Soest and Peter A. Huijing

The influence of parameter values (i.e., fiber optimum lengths and moment arms) and simplification of the geometry of a Hill-type muscle model on the prediction of normalized maximal isometric knee extension moment to knee joint angle relationship was studied. For that purpose, the geometry of m. quadriceps femoris was modeled in considerable detail, and all parameter values were determined on one set of cadaver specimens that had been selected for muscular appearance. The predicted relationship was compared to that measured in human subjects over the full range of physiological knee angles, and a good correspondence was found (r = .96). The good correspondence could be attributed to the substitution of realistic parameter values into the model. Incorporating complex muscle geometry into the model resulted in a small additional improvement of the prediction. It was speculated that the variation in results of cadaver measurements among studies reflects true differences caused by individuals' levels of physical activity in the period preceding death.

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Janne Sallinen, Arto Pakarinen, Mikael Fogelholm, Elina Sillanpää, Markku Alen, Jeff S. Volek, William J. Kraemer and Keijo Häkkinen

This study examined the effects of strength training and diet on serum basal hormone concentrations and muscle mass in aging women. Fifty-one women age 49 to 74 y were divided into two groups: strength training and nutritional counseling (n = 25), and strength training (n = 26). Both groups performed strength training twice a week for 21 wk. Nutritional counseling was given to attain sufficient energy and protein intake and recommended intake of fat and fiber. We found that the cross-sectional area of the quadriceps femoris increased by 9.5 ± 4.1% in the nutritional counseling group versus 6.8 ± 3.5% in the strength training only group after training (P < 0.052). Nutritional counseling evoked dietary changes such as increases in the proportion of energy from protein and the ratio of poly-unsaturated and saturated fatty acids. Strength training increased testosterone and testosterone/sex hormone-binding globulin ratio after the first half of training, but these returned to baseline values at the end of the entire training period. Changes in serum basal hormone concentrations did not differ between the groups. Our results support the conclusion that nutritional counseling can contribute to the increase in the muscle cross-sectional area during prolonged strength training in aging women.