Background: Controversial findings exist in the literature with respect to the efficacy of visually guided weight-shifting (WS) training as a means of improving balance in healthy older adults. Objective: The purpose of this study was to investigate the impact of two direction-specific, visually guided WS training protocols on standing balance of healthy elderly women. Methods: Forty-eight community-dwelling elderly women, all free of any neurological or musculoskeletal impairment, were randomly assigned into: a group that practiced WS in the anterior/posterior direction (A/P group, n = 19), a group that practiced WS in the medio/lateral direction (M/L group, n = 15) and a control group (n = 14). Participants performed 12 training sessions of visually guided WS (3 sessions a week for 25 minutes per session). Static balance was measured before and after training in normal (bipedal) quiet stance (NQS) and sharpened-Romberg stance (SRS) by recording center of pressure (CoP) variations and angular segment kinematics. Results: In NQS, neither of the two training protocols had a significant impact on postural sway measures, although a significant decrease in interlimb asymmetry of CoP displacement was noted for the A/P group. In SRS, A/P training induced a significant reduction of CoP displacement, lower limb pitch and upper trunk roll rotation. Conclusion: The results of the study stress the importance of using direction-specific WS tasks in balance training, particularly in the A/P direction, in order to improve control of static balance in elderly women.

The purpose of this study was to investigate the effects of a vibration training protocol and a conventional strength training program consisting of similar exercises on knee extensors and flexors strength and postural sway in middle-aged women. 38 women were randomly assigned into a Vibration Group (n=12, static and dynamic exercises on a vibration plate, frequency: 15-25 Hz, amplitude: 2-12.8 cm), a Strength Group (n=16, same exercises without vibration) and a Control Group (n=10). Both experimental groups trained for 12 weeks (3 sessions/w). Static balance was assessed in 3 tasks of increasing difficulty: Normal Quiet Stance, Sharpened Tandem, and One-Legged Stance. Postural sway was evaluated using the Centre of Pressure variations in the Anterior/Posterior and Medio/Lateral direction. Eccentric and concentric strength of knee extensors and flexors was recorded using a Cybex dynamometer. After vibration training, postural sway significantly decreased in both directions for the vibration group in all tasks (p<0.05), whereas no significant differences were observed for the other groups. Isokinetic strength significantly (p<0.05) increased for both experimental groups at selected angular velocities. It was concluded that side-alternating vibration could have beneficial effects on static balance control for middle-aged women. Gains in isokinetic strength were quite similar for both experimental groups.

To establish the effect of tendon vibration (TV) on steady submaximal strength and static balance control, 29 women performed isometric plantarflexions at 10, 20, 30 and 50% of MVC and postural tasks of increasing difficulty (Normal Quiet Stance, NQS, Sharpened Tandem Stance and One Leg Stance) with vibrators (80 Hz) applied to the Achilles tendon. Both tasks were performed under four conditions (10 s each): eyes open, eyes closed, eyes closed with TV, eyes open with TV. During the isometric tasks, the application of TV increased the plantarflexion torque at 20 and 30% of MVC, accompanied by a greater (p < 0.001) activation of agonists (Medial Gastrocnemius, MGAS and Soleus, SOL), as well as a greater (p < 0.05) coactivation of the antagonist (tibialis anterior, TA). Non-significant differences were observed at 10 and 50% of MVC. During posture, TV resulted in a backward displacement of the Centre of Pressure only for NQS and an increase (p < 0.01) in EMG activity of the ankle muscles in all balance tasks. The MGAS contraction during TV application was confirmed (by ultrasonography) at ten participants by an increase of the pennation angle and decrease of its fascicle length (p < 0.05). The vibration-induced muscle excitation and accompanying increase in motor output, probably due to excitatory Ia afferent input, was confirmed during strength and postural tasks. However, motor output attenuates when the magnitude of central drive to the ankle muscles increases.

Context: Side-alternating vibration (SAV) may help reduce the risk of falling by improving body balance control. Such training has been promoted as a strength-training intervention because it can increase muscle activation through an augmented excitatory input from the muscle spindles.Objective: To determine the effect of SAV training on static balance during 3 postural tasks of increasing difficulty and lower limb strength.Design: Randomized controlled clinical trial. Setting: Laboratory. Patients or Other Participants: A total of 21 healthy women were divided into training (n ¼ 11; age ¼ 43.35 6 4.12 years, height ¼ 169 6 6.60 cm, mass ¼ 68.33 6 11.90 kg) and control (n ¼ 10; age ¼ 42.31 6 3.73 years, height ¼ 167 6 4.32 cm, mass ¼ 66.29 6 10.74 kg) groups.Intervention(s): The training group completed a 9-week program during which participants performed 3 sessions per week of ten 15-second isometric contractions with a 30-second active rest of 3 exercises (half-squat, wide-stance squat, 1-legged half-squat) on an SAV plate (acceleration ¼ 0.91-16.3g). The control group did not participate in any form of exercise over the 9-week period.Main Outcome Measure(s): We evaluated isokinetic and isometric strength of the knee extensors and flexors and ankle plantar flexors, dorsiflexors, and evertors. Static balance was assessed using 3 tasks of increasing difficulty (quiet bipedal stance, tandem stance, 1-legged stance). The electromyographic activity of the vastus lateralis, semitendinosus, medial gastrocnemius, tibialis anterior, and peroneus longus was recorded during postural task performance, baseline and pretraining, immediately posttraining, and 15 days posttraining.Results: After training in the training group, ankle muscle strength improved (P ¼ .03), whereas knee muscle strength remained unaltered (P ¼ .13). Improved ankle-evertor strength was observed at all angular velocities (P ¼ .001). Postural sway decreased in both directions but was greater in the mediolateral (P , .001) than anteroposterior (P ¼ .02) direction. The electromyographic activity of the peroneus longus increased during the sharpened tandem (P ¼ .001) and 1-legged tasks (P ¼ .007). No changes were seen in the control group for any measures.Conclusions: The SAV training could enhance ankle muscle strength and reduce postural sway during static balance performance. The reduction in mediolateral sway could be associated with the greater use of ankle evertors due to their strength improvement.Key Words: whole-body vibration, posture, peroneus longus, ankle evertors Key PointsA 9-week, side-alternating vibration training program improved static balance control and postural stability, especially in the mediolateral direction. Side-alternating vibration improved ankle strength but not knee strength.