Introduction
Humans were built to move. Unfortunately, movement often causes injury and injury often leads to a decreased functional capacity due partly to the lack of ability to be active. The value of an exercise program as a method of rehabilitation from injury has been well documented (Guidelines for Exercise Testing and Prescription, 4th Edition). However, the nature of an injury may prevent individuals from participating in traditional exercise programs that include walking and/or running as the principle mode of exercise.
Fitness is improved by designing an exercise program that will overload the system by manipulating frequency, intensity and duration of exercise (Guidelines for Exercise Testing and Prescription, 4th Edition). According to the principle of specificity of training, performance is improved by incorporating the specific activity in an exercise program. That is, if an individual wants to be a good swimmer, the person should swim. Likewise, if the practitioner wants to improve the land based functional capabilities of a patient, it would seem that the primary exercise should be land based exercise. However, certain individuals may not be able to tolerate land based exercise, in particular running. The same individuals may, however, be able to benefit by participating in a running program.
Deep water running (DWR) has become a popular mode of exercise utilized by athletes (both injured and healthy) as well as many special populations (e.g., pregnant women, individuals with lower back 6pain and cardiac patients) as an alternative to land based running. During DWR, an individual is positioned vertically in neck level water, unable to touch the bottom of the pool. Typically, a flotation device (e.g. Aqua Jogger) is worn to assist the individual in maintaining a vertical position.
One reason DWR has increased in popularity over the years is the concept that the running action during DWR is similar to TMR while eliminating the repetitive high impact forces. With each foot strike during running, ground reaction force impact peaks of 1.5 to 3 times body weights have been recorded (James, Bates, & Osternig, 1972). The magnitude of forces during running can result in overuse injuries (James, Bates, & Osternig, 1972).
Background ReviewInvestigations of DWR have focused primarily on physiological variables such as heart rate (HR) and oxygen consumption (VO2). The purpose of this project was to determine whether or not the running strategy observed during DWR is similar mechanically to the running strategy utilized during treadmill running (TMR).
HR and VO2 responses during DWR compared to TMRIt is well documented that peak HR and VO2 are lower during DWR compared to treadmill running (TMR) at peak exercise (Butts, Tucker, & Greening, 1991; Butts, Tucker, & Smith, 1991; Glass, Wilson, Blessing, & Miller, 1995; Frangolias, Rhodes, & Tauton, 1996; Mercer & Jensen, 1997; Michaud, Rodriguez-Zayes, Anres, Flynn, & Lambert, 1995; Svedenhag & Seger, 1992; Town & Bradley, 1991). The causes for the physiological changes during peak exercise are not known. An explanation is that the amount of active muscle mass is lower during DWR than TMR due to the lack of need to counteract gravity. This hypothesis has not been tested, further research is needed to determine if muscle activity levels explain the different peak physiological responses during DWR and TMR.
It is clear that during peak exercise, VO2 and HR will be lower during DWR than TMR. In contrast, for a given submaximal workload, HR has been reported to be no different during DWR and TMR (Mercer & Jensen, 1997; Michaud, et al. 1995). Interestingly, it has also been reported that both HR and VO2 are lower during DWR than TMR when comparing a given percent of peak responses (Mercer & Jensen, 1996; Michaud, et al. 1995). Figure 1 illustrates HR for a given workload during DWR and TMR for men and women. The figure illustrates two points. First, peak responses are lower during DWR than TMR regardless of gender. Second, the HR - VO2 relationship is similar during submaximal exercise during DWR and TMR. Clearly if a percentage of peak responses are compared, the responses during DWR will be lower than TMR because the peak responses during DWR are lower than TMR. The similarity between the HR-VO2 relationship during DWR and TMR may be evidence that the running styles are similar.
Based on these published data, it would seem that prescription of exercise intensity during DWR could simply be adjusted by some factor from land based levels of exercise intensity (e.g. TMR). Herein lies the problem with prescribing exercise intensity during DWR. Because submaximal HR and VO2 responses are similar between modes of exercise, should the practitioner prescribe exercise intensity based on land based measures of performance? Or, because peak HR and VO2 are lower during DWR than TMR, should the exercise intensity be based on DWR performance? There have been training studies which have documented either no change or slight improvement in land based measures of fitness following 4-8 weeks of a DWR exercise program (Eyestone, Fellingham, George, & Fisher, 1993; Michaud, Brennan, Wilder, & Sherman, 1995; Morrow, Jensen, & Peace, 1996; Quinn, Sedory, & Fisher, 1994; Wilbur, Moffatt, Schott, Lee, & Cucuzzo, 1996). These results appear to suggest that the running styles are similar during DWR and TMR due to the principal of specificity of training.
Mechanics of DWRThere is a need for a better understanding of the mechanics of DWR. Griffin (unpublished thesis, 1993) investigated the changes in kinematics during DWR and TMR. Her analysis focused mainly on maximum and minimum angle excursions of the ankle, knee and hip of 5 subjects during DWR and TMR. The conclusion was that the change in running mechanics between modes of exercise was highly variable between subjects indicating that there was no one consistent shift in running style between subjects. The variability may have been magnified due to the ankle flotation device utilized in the study. It would be expected that high variability of the running style would be exhibited by placing a flotation device on the distal segments due to the difficulty of controlling the flotation device. Therefore, during this study, a flotation device was worn around the waist.
Moening, Scheidt, Shepardson, and Davies have also reported that the joint range of motion of the ankle, knee and hip during DWR and TMR was different between media (1994). However, the authors tested only one subject, whose experience in DWR was not reported. Frangolias, Rhodes, and Taunton (1996) reported that experience is a factor which needs to be controlled when comparing physiological variables during DWR and TMR. Therefore, DWR experience as well as TMR experience should be controlled when examining the mechanics during the two modes of exercise.
The information gained through an analysis of maximum and minimum angle excursions during a running action is limited. During both DWR and TMR, the minimum knee angle will occur during the swing phase of gait. During TMR, the maximum knee angle will occur at toe off or just before heel contact. Similarly, maximum knee extension will occur about mid stance during DWR. If variability is similar across all joints, then identification of the maximum and minimum angle excursions does not allow for a comprehensive comparison between media.
During DWR, stride rate has been reported to correlate positively with HR (Wilder, Brennan, & Schotte, 1993). During a DWR graded exercise test, the authors reported that stride rates ranged from a low of about 60 strides per minute (st/min) during the low intensity levels, to just over 100 st/min at peak effort. It has also been reported that for a given submaximal work load, HR was not different between DWR and TMR (Mercer & Jensen, 1997). The difficulty with comparing the mechanics of DWR and TMR is that the hydrostatic forces of water prevent individuals from moving the lower extremity at fast rates. During TMR, there is no limitation to movement other than gravity. Although there is no published data comparing the HR at different stride rates during DWR and TMR, it is hypothesized that HR will be greater for a given stride rate during DWR than TMR. Part of this project was to test this hypothesis.
Proceed to Next Section- Purpose
Back to Deep Water Running