Overview of Non-Swimming Aquatic Research Richard G. Ruoti, PhD, PT Bux-Mont Physical Therapy, Warminster, PA Research from 1967 through 1994 on non-swimming aquatic exercise has been reviRwed to determine the physiologic parameters involved. The literature is replete with studies that deal with swimming but few have demonstrated the efficacy of non-swimming activity in an aquatic environment. The results of the reviRw indicate that aquatic exercise performed in warm water-given the proper parameters of warm-up, intensity, duration, frequency, mode of training, and cool down-can influence maximal oxygen consumption, heart rate at rest and during exercise, upper body strength, and muscular endurance. It has also been noted that there is a paucity of clinical studies; therefore the need for application of this physiologic data appears paramount. As more clinical studies are performed, physicians can feel confident in referring their patients to aquatic physical therapists and other licensed professionals. Keywords: Aquatic research; aquatic physiology; physical therapy; aquatic exercise
With the ever-increasing interest in aquatic exercise and rehabilitation, the need to justify treatment increases concomitantly. Many studies have been done on swimming and the physiological response to swimming. Less well documented, however, is the effect of non-swimming aquatic exercise, such as water calisthenics and water running, usually performed in a vertical position. Objective, well-controlled experimental research on therapeutic techniques is grossly inadequate. The purpose of this article is to present an overview of the research on the physiological parameters of non-swimming exercise.
TEMPERATURE A few studies have investigated temperature as a variable in aquatic exercise. Costill et al. i ,2 performed two in 1967, in which the effect of water temperature on submaximal exercise and aerobic work capacity was examined. Six water temperatures were used, ranging from 17.2°C through 32.78°C. A small group of subjects used an underwater ergometer for various tests. Despite the
huge temperature variation, no significant alteration of aerobic capacity was observed in the different water temperatures. Almost a decade later McArdle et al. 3,4 examined the effect of temperatures at 18°C, 25°C, and 33°C. Six male subjects participated in the study, and measurements of oxygen consumption (V02), cardiac output (Q), stroke volume (SV), and heart rate (HR) were observed. The study found no significant difference between V02 in air and in the 33°C water temperature. However, significantly higher V02 values were recorded during submaximal work in 18°C and 25°C water. McArdle and his colleagues concluded that the high oxygen cost in colder water was primarily "due to energy expended by shivering as an attempt to maintain core temperature." He further concluded that working in warmer water demonstrated responses similar to those of subjects working on land. Although these early studies were not training studies, they do suggest that metabolic responses can be elicited in water. McArdle's study reported increased responses at higher temperatures. Many others have based their studies on water temperature on the physical constraints of the experimental pool or on anecdotal information. ] Back Musculoskel Rehabill994; 4(4):315-318 Copyright © 1994 Butterworth-Heinemann
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In addition, various studies have held temperature constant for their specific research while manipulating other variables, such as (1) strengthening effects, (2) V02 and (3) HR.
STRENGTH Increases in strength are not usually expected in aerobic exercise. It is sometimes reported, however, that water calisthenics will increase strength. The literature is sparse in this area and limited to specific populations. Gehlsen et al. 5 measured muscular strength and endurance of patients with multiple sclerosis after they had completed an aquatic fitness program. The training involved some swimming strokes, but also contained water calisthenics. Posttesting revealed upper extremity strength improvements, but lower extremity strength improvements were limited to knee extensors. Likewise, McGettigan and Ruoti studied the effects of a water exercise program on an elderly population. Strength testing of the lower extremities indicated results similar to Gehlsen's. Subjects demonstrated a significant increase in knee extensor strength but no difference was found for knee flexors (McGettigan and Ruoti, unpublished observation). * Although Henker et al. 6 demonstrated that water running is effective in maintaining leg strength in runners, Hamer and Morton 7 found no significant change on scores obtained for a 2-minute fatigue test after an 8-week study involving running in one-meter-deep water.
OXYGEN CONSUMPTION Probably one of the most extensively researched variables in aquatic exercise deals with submaximal and maximal V02. Most physiologists consider V02max to be one of the best overall measurements of physical fitness. Numerous studies l - 3 ,5-I5 have examined the effect of aquatic McGettigan j, Ruoti RG. Biokinetics Research Laboratory, Temple University, Philadelphia, 1990.
exercise on V02max, or have used V02 when correlating other variables. Although some studies were single-bout activities, others were training studies ranging in length from 8 to 12 weeks. These studies consistently demonstrated that V02max increased with training, or would increase in a water environment, provided that sufficient intensity, duration, and frequency parameters were met. It was also determined that the V02 and HR increased linearly during submaximal activity, which is consistent with results obtained with exercise on land. These results were achieved after various types of water activity, including calisthenics, walking, running, running while performing an upper body activity, and running with buoyant assistive devices. As noted, many studies were single-bout activities and therefore did not demonstrate a training effect. Training studies did show, however, increases in V02 as high as 16%, again demonstrating values comparable to those obtained with land-based training. 16
HEART RATE HR has been studied or monitored by virtually every physiological aquatic study cited. Some 17 ,18 looked specifically at HR in water versus on land. Because it is difficult to quantify work in two different environments, physiological measurements are used to determine if the work performed is comparable. Studies utilizing single-bout aquatic activities have consistently demonstrated elevated HRs comparable to those achieved with similarly imposed stresses on land. Likewise, training studies have demonstrated significant increases in work with lower sub maximal HRs and lower resting HRs at the conclusion of the training. These data are important because most persons participating in aquatic exercise and rehabilitation programs do not have the luxury of undergoing a monitored stress test. Therefore, HR could be an effective way to prescribe exercise that is both safe and of sufficient intensity to cause a training effect.
Non-Swimming Aquatic Research
The research dealing specifically with temperature and non-swimming activity is limited. Nevertheless, most of the studies 5 ,7,8,1O,12-14,18 that demonstrated positive effects controlled water temperature in t.he range of 26°C-30°C (X = 28.64°C). Therapeutic pools tend to have higher temperatures and may be more effective for rehabilitation application, but there are few temperature-controlled studies dealing with patient populations and therefore conclusions cannot be warranted based on current available data. It does appear, however, that if exercise is performed at a sufficient int.ensity and duration, the effect oftemperature is somewhat forgiving ifin the mid-range described above. Generally, V02max is either increased or maintained with aquatic exercise. Some studies demonstrate gains comparable to those in land-based activity, but others do not. They do, however, still show significant improvement to warrant aquatic activity as a stimulus for V02 improvement. The variety of exercises that promote V02 improvement includes adaptations of familiar land-based calesthenics, aerobic dance movements, water walking, jogging, bobbing, running, and modified swim strokes. The use of HR for exercise prescription for water-based exercise remains controversial. It has been suggested by some authors 4 that a lower age predicted HR be used when prescribing water exercise; other research studies do not support reduction. Perhaps the answer lies in separating horizontal from vertical exercise, as well as depth of water. Swimming involves greater use of the upper extremities while non-swimming exercise includes more lower extremity involvement. Changes in SV may occur with horizontal positioning but hydrostatic forces may also influence SV via centralization of peripheral blood flow and increased left ventricular end-diastolic volume. Likewise, immersion depth appears to be influential in HR depending on whether the heart is submerged or not. Research has shown that cardiovascular adjustments are made in aquatic exercise, but a precise prescription for intensity remains elusive.
A reVIew of the literature allows the following conclusions:
1. Aquatic exercise can be performed in a wide
range of temperatures, but warmer temperatures appear to be more favorable for nonswimming activity. Some studies demonstrated an increase in V02max in water compared to land activities, while others did not. All studies reviewed, however, indicated that significant increases in V02max can occur with exercise in water. After adequate conditioning, resting HR decreases to values comparable to a training bradycardia resulting from terrestrial training. Also, HRs elevate sufficiently to cause cardiovascular conditioning similar to landbased activity. Upper body strength can increase in deconditioned people, but lower extremity strength gains appear to be limited to leg extensors. Given the proper parameters of an exercise prescription of warm-up, intensity, duration, frequency, mode of training, and cool-down, non-swimming water exercise can produce a training effect.
RECOMMENDATIONS This review has been limited to essentially nonpatient populations. Studies have been performed with cardiac patients that have included both swimming and non-swimming aquatic exercise. Current research with patient populations includes studies in orthopedics and pediatrics, but this is not enough. The majority of articles reviewed have dealt with non-swimming aquatic exercise. Swimming, however, often plays a significant role in exercise training. Therefore, the effects of nonswimming aquatic rehabilitation, the effects of swimming-oriented rehabilitation programs, and a combination of both forms of activity need to be elucidated. Considerable research is needed to
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justify treatment not only to patients and insurance carriers, but equally important, to the profession. Specific questions about exercise prescription, HR, and water temperature need to be answered. It is incumbent upon rehabilitation professionals to evaluate and attempt to determine in some way the validity of our efforts with studies involving patients with a variety of diagnoses. Although there are currently few aquatic physical therapy protocols for a given diagnosis, physicians can feel
confident in referring their patients to skilled aquatic physical therapists for rehabilitation. Based on current research, a variety of populations would benefit from the cardiovascular effects and musculoskeletal strengthening and conditioning afforded by aquatic exercise. Cardiac, obstetric, neurologic, orthopedic, spinal cord injured, and pediatric aquatic rehabilitation protocols need to be developed, researched, and quantified.
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