In vivo human gastrocnemius architecture with changing joint angle at rest and during graded isometric contraction.

Abstract

1. Human gastrocnemius medialis architecture was analysed in vivo, by ultrasonography, as a function of joint angle at rest and during voluntary isometric contractions up to the maximum force (MVC). 2. At rest, as ankle joint angle increased from 90 to 150 deg, pennation increased from 15-8 to 27-7 deg, fibre length decreased from 57 0 to 34 0 mm and the physiological cross-sectional area (PCSA) increased from 42-1 to 63-5 cm2. 3. From rest to MVC, at a fixed ankle joint angle of 110 deg, pennation angle increased from 15-5 to 33-6 deg and fibre length decreased from 50-8 to 32'9 mm, with no significant change in the distance between the aponeuroses. As a result of these changes the PCSA increased by 34 8%. 4. Measurements of pennation angle, fibre length and distance between the aponeuroses of the gastrocnemius medialis were also performed by ultrasound on a cadaver leg and found to be in good agreement with direct anatomical measurements. 5. It is concluded that human gastrocnemius medialis architecture is significantly affected both by changes of joint angle at rest and by isometric contraction intensity. The remarkable shortening observed during isometric contraction suggests that, at rest, the gastrocnemius muscle and tendon are considerably slack. The extrapolation of muscle architectural data obtained from cadavers to in vivo conditions should be made only for matching muscle lengths.

Human medial gastrocnemius force–velocity behavior shifts with locomotion speed and gait

“…To combat this possibility, in the present study care was taken to align the ultrasound probe such that fascicles could be visualized from the deep to the superficial aponeurosis. This approach has been shown to be accurate in cadavers (38) and repeatable in vivo (39). The sampling rate of 50 Hz for ultrasound images might be considered low for some of the analyzed speeds.…”

Can pennation angles be predicted from EMGs for the primary ankle plantar and dorsiflexors during isometric contractions?

“…Muscle fiber length and pennation angle changes with muscle contraction intensity (Maganaris et al, 1998;Maganaris, 2003;Narici et al, 1996). Contractile effort is reflected in the magnitude of the electromyogram (Buchanan et al, 2004), and therefore the EMG signal may be a predictor of fiber length and pennation angle change.…”

“…Muscles with large pennation angles such as the soleus allow more fibers to be arranged in parallel within a given cross sectional area, thereby increasing a muscle's force generating potential. Fiber pennation angle varies with muscle contraction intensity and fiber length (Maganaris et al, 1998;Maganaris, 2003;Narici et al, 1996), and thus such changes should be considered when using musculoskeletal models to estimate muscle force.…”

Measurement of ageing effects on muscle tone and mechanical properties of rectus femoris and biceps brachii in healthy males and females using a novel hand-held myometric device

“…Laboratory techniques for assessing tone and mechanical properties objectively, such as ultrasound imaging with dynamometry (Narici et al 1996;Muraoka et al 2005) and magnetic resonance elastography (Dresner et al 2001) are not clinically feasible. There is the need for objective, reliable, valid, robust, easy to use and cost effective ways of assessing skeletal muscle tone and mechanical properties in a clinical setting.…”