Individuals who perform land-based training exercises, such as running or jogging, may be required to discontinue that activity if an injury occurs.  One treatment for running – related injuries is to simply decrease or discontinue running for 4-6 weeks.   Runners fear that such a break will lead to a decrease in fitness or an increase in body weight, and few are willing to endure long periods of inactivity.  It is well known that the cessation of activity results in a significant loss of functional capacity. A 4 to 6 week period of inactivity will lead to a 14 to 16% reduction in V0₂.  Thus, we use aquatic –based therapy for “active-rest” from the injury.  The goal is to maintain cardiovascular endurance, mobility strength, and flexibility while “resting” the injury.

Many athletic organizations today, from those in high schools to those representing the professional athletes, are recognizing the benefits of including an aquatic rehabilitation component, when an injury is sustained.  Deep-Water Running (DWR) has become the newest form of aquatic therapy for injured athletes.  It has been accepted as a popular and effective form of cardiovascular conditioning for both rehabilitation and training.  It is becoming popular among runners as a training exercise during periods of injury because there is less musculoskeletal stress than normal running.  Runners are also replacing part of their existing training program with DWR to reduce overuse injuries.  DWR enables the athlete to continue in an activity that is specific to running without incurring the possible harmful effects of weight-bearing work.

DWR consists of simulated running in the deep end of the pool aided by a flotation device (vest or belt) that maintains the head above the water.   The athlete may be held in one location by a tether cord, essentially running in place, or may actually run through the water the length or width of the pool.

·       During DWR, the body is tilted slightly forward approximately 5 degrees past the vertical, with the spine in neutral position.  The bend should occur at the hips, not the waist.

·       The head is held comfortably out of the water, facing forward; avoid neck extension.

·       The arm action is the same as for land running, with the primary movement occurring at the shoulder and with hands relaxed but slightly closed.

·       Ankles should perform both dorsiflexion and plantar flexion

·       Hip flexion should reach about 60-80 degrees.

·       No contact is made with the bottom of the pool, thus eliminating impact.

·       This form of running in the water closely follows the pattern used on land.  However, the center of gravity on land is at the hips. In water, the center of buoyancy is the lungs.  To get use to this change, the athlete must retrain the body to use the abdominal muscles to maintain correct vertical posture.

The athletic community has been attracted to DWR as a way to maintain cardiovascular conditioning while recovering from injury.  The literature has shown that DWR can duplicate the sport-specific of running, and with 4 to 6 weeks of DWR, there is drop in V02 max of 5 to 7%.  DWR allows runners to put in miles without incurring the impact of land-based training.  Also, land-based runners who water-train maximize speed gains—and these gains can transfer to land performance.      

Water’s buoyancy virtually eliminates the effects of gravity, supporting 90% of the body’s weight in deepwater reducing impact and creating greater flexibility.  Water acts as a cushion for the body weight-bearing joints, reducing stress on muscles, tendons, and ligaments.  The depth of the water directly affects the amount of impact transferred through the musculoskeletal system.  Moving deeper in the water decreases the impact for a given exercise.  Moving to the shallower end of the pool increases the load on the body.  Using variable depths is a very useful when recovering from an injury or after a hard training session or to partially unload the body.

Exercise intensity is an important part in any program.  Conventional exercise prescription for DWR has relied on heart rate and perceived exertion.  Three methods are useful for exercise intensity: heart rate, RPE and cadence.  The American College of Sports Medicine: Guidelines for Graded Exercise Testing and Exercise Prescription (1986) suggests that, for a training effect, one should exercise at a level of 55 - 90% maximal heart rate.  This method is most used when one wishes to train at a constant rate, that is, the target heart rate.  It is important for alternative training to be conducted at or close to actual training intensities.   

Heart Rates

Water temperature, compression, reduced gravity, partial pressure and the dive reflex can all affect heart rates when training in the aquatic environment. It is recommended that a 6-second heart rate count be used in the water.  Heart rate levels in the water tend to be lower than those attained on land.  If an aquatic exercise heart rate is to be used to measure intensity, a 13 or 17 bpm should be taken from the minimal and maximal training thresholds.  The physiological changes that occur when an athlete is submerged up to the neck in water will cause the heart rate to be from 10 to 15% lower than for similar effort on land.

Rate of Perceived Exertion

The most common used scale of perceived exertion of the Borg scale, a 15-point scale with verbal descriptions ranging from very, very light to very, very hard.

Borg Scale of Perceived Exertion

In DWR, though, the Brennan scale is a very popular.  It is a 5-point scale designed for DWR, with verbal descriptions ranging from very light to very hard.  The participant subjectively determines intensity level.  The Brennan scale facilitates the incorporation of both speed and distance work into the athlete’s workout.

How Hard Are You Working in the Pool?  

Brennan Rate of Perceived Exertion

Level 1:  (very light):  a light jog or recovery run

Level 2:  (light):  a long steady run

Level 3:  (somewhat hard):  a 5-10K road race pace

Level 4:  (hard):  a 400-800m track speed

Level 5:  (very hard):  sprinting  (a 100-200 m track speed)

*Note:  The cycles/min are approximate numbers for a well-conditioned athlete.  Substitute the cadence numbers that are appropriate for your training level.

Cadence

Another form of monitoring intensity is counting cadence.  Brennan (1997) has an athlete count the number of times the right knee comes forward and up.  That count is taken on the last 30 seconds of each interval.  Doubling the count gives the cycles per minute (cpm).

Wilder and associates (1993b and c) discovered a high correlation between cadence, an environment –specific measure, and heart rate during DWR.  In their study, they found that cadence could be used as a measure for exercise prescription for DWR.

Heart rates are used primarily during long runs, prolonged periods of exercise at a specific rate (target heart rate).  RPE exertion and cadence are most often used for interval sessions.  RPE is most useful in group settings, where cadence is most appropriate for individual sessions.

Deep-water Running Cadence Chart

Workout Options

Athletes with lower extremity injuries start in deepwater.  A 6-week program includes DWR, incorporating all the training methods used in a land-based program.  Long runs, interval training, and strength runs can be incorporated into a training schedule.   Resistive equipment can be introduced about week three.

After 6 weeks, the athlete can be moved from deep water to chest level, which is about 25% loading.  After several weeks, the athlete can be moved to waist level, which is about 50% loading.  The belt is kept on to further reduce the impact.  To begin progressing on land, the belt is removed to increase the loading effect and transfer to land.  Today, an athlete that is injured does not have to sit on the sidelines.  One can begin training in the water almost immediately.