The determination of power using isokinetic testing has been shown to be highly reliable. However, isotonic and isokinetic testing involve specific mechanical constraints that likely necessitate different neuromuscular strategies. Therefore, the purpose here was to establish test-retest intrarater reliability (separated by 7 days) of loaded maximal shortening velocity and velocity-dependent pow...

The systolic time intervals have been measured in 76 normal children, aged 1 month to 15 years, from simultaneous recordings of the electrocardiogram, phonocardiogram and carotid arterial pulse or apexcardiogram (left or right). Four different statistical methods were applied to study the separate influence of heart rate (HR) and age on these intervals. Left ventricular ejection time (LVET) had...

Electromyographic (EMG) amplitude and mechanical tension are directly related during isometric contraction. Maximal voluntary isometric contractions are typically elicited through two different procedures; resisting a load, which is eccentric in nature, and contracting against an immovable object, which is concentric in nature. A wealth of literature exists indicating that EMG amplitude during ...

This paper describes a revision of the Hill-type muscle model so that it will describe the chemo-mechanical energy conversion process (energetic) and the internal-element stiffness variation (viscoelastic) during a skeletal muscle isometric force twitch contraction. The derivation of this energetic-viscoelastic model is described by a first-order linear ordinary differential equation with const...

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 diffe...

Background: The purpose of this study was to determine the effects of an acute dose of 5 mg/kg of caffeine on perceived pain of the quadriceps during a sustained submaximal isometric contraction. Methods: A total of 15 low caffeine consuming college aged women (20.5 ± 1.4 y, 66.0 ± 9.0 kg; mean ± SD) participated in this study. 2–7 d after a familiarization trial subjects ingested, in a double ...

Perceived time undergoes distortions when we prepare and perform movements, showing compression and/or expansion for visual, tactile and auditory stimuli. However, the actual motor system contribution to these time distortions is far from clear. In this study we investigated visual time perception during preparation of isometric contractions and real movements of the hand in two different direc...

Cortico-muscular coherence was compared during ramp-and-hold isometric and quasi-isotonic contraction of the ankle joint in human subjects. EEG was recorded from the leg area of the motor cortex. EMG was recorded from the tibialis anterior (TA) muscle. The subjects were requested to maintain a steady low level of dorsiflexion and at intervals of 10 s to increase the contraction level within 1 s...