The Musculoskeletal System
Deep-water immersion positively affects the musculoskeletal system as well, particularly with vasoconstriction. On land, for instance, sympathetic vasoconstriction tightens the vessels of skeletal muscle to resist blood pooling. But in water, immersion pressure removes the biologic need for vasoconstriction, thus increasing blood flow to muscle tissue. In fact, resting muscle blood flow increases by 225 percent during neck immersion.
Aquatic immersion creates many effects upon renal blood flow and the renal regulatory systems. For instance, the flow of blood to the kidneys increases immediately upon immersion, which produces an increase in urine production, as well as sodium and potassium excretion. Sodium excretion also increases as a function of depth due to the shifting of circulating central blood volume.
Deep Water Running
Immersion up to the neck during deep water running is often utilized for its conditioning effect. Although some controversy exists about the optimal training program for athletes who need joint off-loading during a recovery period, it is known that deep-water aquatic exercise can indeed increase conditioning in that population. In fact, water running equals land running in its effect upon the maintenance of VO2 max. when training intensities and frequencies are matched.
Similarly, when maximum gains in VO2 during aquatic exercise are compared with equivalent land-based exercise in unfit individuals, the aquatic exercise achieves equivalent results. And water-based exercise programs may be used to sustain or increase aerobic conditioning in athletes who need joint offloading. Studies have shown excellent crossover benefits.
By understanding the principles and benefits of aquatic physics, coaches, trainers, athletes and rehabilitation clinicians can design aquatic programs that complement and enhance land-based programs so as to provide increased levels of fitness and function.