Unstable surfaces are commonly used during lower extremity rehabilitation exercises. These unstable surfaces generally increase muscle activation on a subconscious level, thus training the sensorimotor system.

Many types of devices provide unstable surfaces for training, including balance boards, foam Stability Trainer pads, and air-filled Stability Disks and cushions. These devices vary in the interactions between the foot and the floor:


For example, a rigid balance board provides a stable interface between the foot and device, but an unstable interface between the floor and device. An air-filled cushion and foam pad can provide an unstable foot-to-device interface, but a stable device-to-floor interface.

Researchers at Hacettepe University in Ankara, Turkey wanted to quantify and compare the level of ankle muscle activation on 2 types of balance platforms: rigid (TheraBand Wobble Board), and compliant (air-filed BOSU ball). They hypothesized that exercises on the compliant surface would require more ankle activation than exercises performed on the wobble board.

24 healthy, sedentary subjects (12 females and 12 males, average 23 years old) participated in the study. The researchers measured the surface EMG of their fibularis longus (FL), tibialis anterior (TA), and medial gastrocnemius (mGC) while the subjects performed 4 exercises with their dominant leg on each device:

  1. Forward lunge at 60° of knee flexion
  2. Side lunge at 60° of knee flexion
  3. Single leg stance with eyes open
  4. Single leg squat held at 45° of knee flexion

Harupt2013-exercisesThere was no significant difference in EMG activation of the ankle muscle between the wobble board and BOSU ball. Both devices produced the highest levels of EMG activation in each muscle during the single-leg exercises.

The 2 lunge exercises produced much less activation (4 to 25% MVIC) compared to 14-51% during single leg exercises. The FL and mGC were maximally activated (51% and 38%) during the single-leg stance exercise, while the TA was most active during the single-leg squat (28%).

% MVIC: Fibularis Longus Tibialis Anterior Medial Gastroc
Lunge (2 exs) 8-11 % 13-25% 4-6%
Single Leg Stance 47-51% 14-18% 35-38%
Single Leg Squat 30-34% 26-28% 14-17%

The researchers concluded, “the design of the balance platform (rigid versus compliant surface) did not influence the activation level of the muscles.” Furthermore, they suggested that the lunge exercises may be useful during early stages of ankle rehabilitation because of the low levels of muscle activation.  Further research should evaluate the difference in hip muscle activation with these different devices.

In summary, the TheraBand wobble board can provide moderate activation of the ankle muscles during a single-leg stance or single-leg squat exercise, at levels similar to a more expensive BOSU ball.

REFERENCE: Harput G, Soylu AR, Ertan H, Ergun N.Activation of selected ankle muscles during exercises performed on rigid and compliant balance platforms. J Orthop Sports Phys Ther. 2013 Aug;43(8):555-9. doi: 10.2519/jospt.2013.4456. Epub 2013 Jun 11.

Disclosure: Performance Health supported this study with the wobble boards


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