Aquatic exercises are widely used for rehabilitation or preventive therapies
in order to enable mobilization and muscle strengthening while minimizing
joint loading of the lower limb. The load reducing effect of water due to
buoyancy is a main advantage compared to exercises on land. However, also drag
forces have to be considered that act opposite to the relative motion of the
body segments and require higher muscle activity. Due to these opposing
effects on joint loading, the load-reducing effect during aquatic exercises
remains unknown. The aim of this study was to quantify the joint loads during
various aquatic exercises and to determine the load reducing effect of water.
Instrumented knee and hip implants with telemetric data transfer were used to
measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x
knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing
activities were performed by the subjects on land and in chest-high water.
Non-weight-bearing hip and knee flexion/extension was performed at different
velocities and with additional Aquafins. Joint forces during aquatic exercises
ranged between 32 and 396% body weight (BW). Highest forces occurred during
dynamic activities, followed by weight-bearing and slow non-weight-bearing
activities. Compared to the same activities on land, joint forces were reduced
by 36–55% in water with absolute reductions being greater than 100%BW during
weight-bearing and dynamic activities. During non-weight-bearing activities,
high movement velocities and additional Aquafins increased the joint forces by
up to 59% and resulted in joint forces of up to 301%BW. This study confirms
the load reducing effect of water during weight-bearing and dynamic exercises.
Nevertheless, high drag forces result in increased joint contact forces and
indicate greater muscle activity. By the choice of activity, movement velocity
and additional resistive devices joint forces can be modulated individually in
the course of rehabilitation or preventive therapies
