Bilateral mean onset latencies in ms (95% CI) for the four trunk muscles at the initiation of bilateral shoulder flexion for the three movement amplitudes.

<p>The dashed line indicates the mean onset of left and right deltoid. * Indicates a significant difference within muscles between arm movement amplitudes</p

The relationship between EMG amplitude and angular impulse.

<p>The relationship between the mean EMG amplitude in % of that at maximum voluntary contraction (95% CI) for the four muscles investigated and the mean absolute angular impulse in Nms (95% CI) for each muscle, arm movement amplitude (small, medium and large) and phase (acceleration and deceleration).</p

Recordings from one subject.

<p>Mean angular velocity and acceleration of shoulder flexion, mean reactive torque on the trunk at shoulder height, and mean normalized EMG in % of that at maximum voluntary contraction of the four different trunk muscles for three repetitions of a medium sized arm movement. The dashed line indicates mean onset of deltoid EMG and the shaded areas illustrate the two intervals of EMG amplitude measurements. The solid vertical lines indicate: 1 = start of acceleration of shoulder flexion, 2 = start of deceleration of shoulder flexion and 3 = end of shoulder flexion. Note the two peaks of activation in TrA corresponding to both acceleration and deceleration of the arm movement.</p

The experimental set-up.

<p>In (A) the three different arm movement amplitudes are illustrated with the solid arm showing the start position of all movements and the three dashed arms representing the three different end positions. In (B) and (C), the marker positions used are shown and in (C) also the reactive torque (α) on the trunk around the centre of rotation and the linear forces in the antereo-posterior (F_x) and caudo-cranial (F_z) directions during the deceleration of an arm movement is illustrated.</p

Massage induces an immediate, albeit short-term, reduction in muscle stiffness

Using ultrasound shear wave elastography, the aims of this study were: (a) to evaluate the effect of massage on stiffness of the medial gastrocnemius (MG) muscle and (b) to determine whether this effect (if any) persists over a short period of rest. A 7-min massage protocol was performed unilaterally on MG in 18 healthy volunteers. Measurements of muscle shear elastic modulus (stiffness) were performed bilaterally (control and massaged leg) in a moderately stretched position at three time points: before massage (baseline), directly after massage (follow-up 1), and following 3 min of rest (follow-up 2). Directly after massage, participants rated pain experienced during the massage. MG shear elastic modulus of the massaged leg decreased significantly at follow-up 1 (−5.2 ± 8.8%, P = 0.019, d = −0.66). There was no difference between follow-up 2 and baseline for the massaged leg (P = 0.83) indicating that muscle stiffness returned to baseline values. Shear elastic modulus was not different between time points in the control leg. There was no association between perceived pain during the massage and stiffness reduction (r = 0.035; P = 0.89). This is the first study to provide evidence that massage reduces muscle stiffness. However, this effect is short lived and returns to baseline values quickly after cessation of the massage

Trunk Muscle Activation at the Initiation and Braking of Bilateral Shoulder Flexion Movements of Different Amplitudes.

The aim of this study was to investigate if trunk muscle activation patterns during rapid bilateral shoulder flexions are affected by movement amplitude. Eleven healthy males performed shoulder flexion movements starting from a position with arms along sides (0°) to either 45°, 90° or 180°. EMG was measured bilaterally from transversus abdominis (TrA), obliquus internus (OI) with intra-muscular electrodes, and from rectus abdominis (RA), erector spinae (ES) and deltoideus with surface electrodes. 3D kinematics was recorded and inverse dynamics was used to calculate the reactive linear forces and torque about the shoulders and the linear and angular impulses. The sequencing of trunk muscle onsets at the initiation of arm movements was the same across movement amplitudes with ES as the first muscle activated, followed by TrA, RA and OI. All arm movements induced a flexion angular impulse about the shoulders during acceleration that was reversed during deceleration. Increased movement amplitude led to shortened onset latencies of the abdominal muscles and increased level of activation in TrA and ES. The activation magnitude of TrA was similar in acceleration and deceleration where the other muscles were specific to acceleration or deceleration. The findings show that arm movements need to be standardized when used as a method to evaluate trunk muscle activation patterns and that inclusion of the deceleration of the arms in the analysis allow the study of the relationship between trunk muscle activation and direction of perturbing torque during one and the same arm movement

Massage induces an immediate, albeit short-term, reduction in muscle stiffness

© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.Using ultrasound shear wave elastography, the aims of this study were: (a) to evaluate the effect of massage on stiffness of the medial gastrocnemius (MG) muscle and (b) to determine whether this effect (if any) persists over a short period of rest. A 7-min massage protocol was performed unilaterally on MG in 18 healthy volunteers. Measurements of muscle shear elastic modulus (stiffness) were performed bilaterally (control and massaged leg) in a moderately stretched position at three time points: before massage (baseline), directly after massage (follow-up 1), and following 3min of rest (follow-up 2). Directly after massage, participants rated pain experienced during the massage. MG shear elastic modulus of the massaged leg decreased significantly at follow-up 1 (-5.2±8.8%, P=0.019, d=-0.66). There was no difference between follow-up 2 and baseline for the massaged leg (P=0.83) indicating that muscle stiffness returned to baseline values. Shear elastic modulus was not different between time points in the control leg. There was no association between perceived pain during the massage and stiffness reduction (r=0.035; P=0.89). This is the first study to provide evidence that massage reduces muscle stiffness. However, this effect is short lived and returns to baseline values quickly after cessation of the massage