Haynes, A., et al. 2020. Land-walking vs. water-walking interventions in older adults: Effects on aerobic fitness. Journal of Sport and Health Science, doi.org/10.1016/j.jshs.2019.11.005.
Naylor, L.H., et al. 2020. Land- versus water-walking interventions in older adults: Effects on body composition. Journal of Science and Medicine in Sport, 23, 164–70.
Why Water Workouts?
It’s well established that low cardiorespiratory fitness is an independent predictor for cardiovascular disease and all causes of mortality (Haynes et al. 2020). Haynes and colleagues cite research indicating that a 1 MET improvement in aerobic capacity has been shown to result in a 15% decrease in mortality from cardiovascular disease (1 MET = 3.5 milliliters of oxygen consumed per kilogram of body weight per minute). For certain populations, such as older adults, however, land exercises that improve aerobic capacity may need to be adjusted to avoid musculoskeletal injury. Haynes et al. propose that, to be optimal for older adults, exercise recommendations must focus on maximizing benefits while minimizing risks.
Enter water-based workouts. Water-based exercise programs have often been employed with older populations and those with elevated injury risk because of the lower gravitational forces and reduced impact on the skeletal system. Nonetheless, there’s very little long-term data on how cardiorespiratory fitness and body composition are affected by water walking versus land walking(at the same relative intensity).
Australian research teams Haynes et al. and Naylor et al. investigated this topic in a single study, reporting their findings across two publications.
The researchers recruited 72 older men and women volunteers (average age = 62), assigning them to 6 months of water walking, land walking or no additional activity (the control group). Investigators tested maximal aerobic capacity and body composition change as the main outcome variables at the beginning of the study and after the 24-week intervention. The hypothesis was that water walking and land walking would improve aerobic fitness and body composition similarly and would be more beneficial than no intervention.
In water walking, the lower limbs work against the resistance of water. Importantly, balance and fall prevention are often concerns for exercising men and women as they age. The water environment minimizes the risk of falls and possible joint injury. Therefore, if water walking is as efficacious for health as land walking is, then walking in water is a safe option for many older participants—and those at risk of falls—to consider.
Inclusion criteria for participants were that they were ≥ 50 years old and relatively inactive (< 60 minutes of purposeful physical activity per week); were nonsmokers (for > 12 months prior to the study) and only light drinkers (alcohol intake less than 280 grams per week); and had no injuries, illnesses or diseases (i.e., cardiovascular disease, diabetes, stroke or heart attack) that would forbid study participation. The women in the study were all postmenopausal.
Those meeting these criteria underwent a university physical exam to meet other target criteria, including a body mass index < 40, resting blood pressure of < 160 millimeters of mercury systolic and < 100 mm Hg diastolic, fasting blood cholesterol < 7 millimoles per liter, and urea and creatinine levels that ruled out the presence of abnormal kidney function.
Participants were randomly assigned to a water walking, land walking or inactive control group. There were three supervised exercise sessions per week for the water walking and land walking. The water walking took place in chest-deep (reaching xiphoid process) water at a university pool (20 meters wide x 30 meters long) heated to 28–30 degrees Celsius (82–86 degrees Fahrenheit). The land walking took place on flat, paved ground and grass terrain outdoors, in and around the university grounds.
Exercise intensity, based on the VO2max pre-test, was initially set at 15 minutes at 40%–45% of heart rate reserve (HRR), progressing to 50 minutes at 55%–65% HRR over the course of the study. Session 2 of each week was an interval workout with 1-minute work intervals at that week’s specified intensity alternating with 30 seconds of rest. Over the 24 weeks, the interval workout changed to 2-minute work intervals (at the week’s specified intensity) alternating with 2-minute recovery intervals. Heart rates were monitored continuously and recorded by the trainers every 5 minutes. Walking speed was adjusted to match the intensities of the water walking and land walking. All sessions included a light aerobic, dynamic range-of-motion warmup and concluded with a cooldown. Participants who were randomly assigned to the control group were instructed not to change their pre-study physical activity during the study.
A graded maximal-effort treadmill test, conducted in 3-minute increments, with 12-lead ECG monitoring was used to assess maximal aerobic capacity at the start and after the 24-week intervention. Waist and hip measurements were taken to determine BMI. Dual X-ray absorptiometry (DXA) was used to ascertain body segment and whole-body fat and lean tissue values, as well as android (abdominal) and gynoid (hip) regional fat areas.
Results and Discussion
Of the 72 original participants, one withdrew from the study during the 6-month period; thus, data analysis was conducted on 71 volunteers. One interesting extra measure the researchers took was to collect post-study data on the main variables at 48 weeks. Between week 24 and week 48, participants had no required contact with the researchers. Participants were free to exercise or not exercise, as they chose.
Data for the main outcome variables at pre-test and at 24 and 48 weeks is shown in “Aerobic Performance and Body Composition Results,” below.
The VO2max values significantly increased in the land-walking and water-walking groups as compared to the control group. Maximal aerobic capacity improved equally in both exercise groups. Also, a critical, statistically significant difference in body composition was seen in the percentage of android fat. The two walking groups made a significant (and equal) decrease in android fat as compared to the control group. Android adiposity, also called visceral fat, is characterized by intra-abdominal fat. This fat pattern is associated with increased risk of cardiovascular disease, hyperlipidemia, hypertension, type 2 diabetes and insulin resistance (Okosun, Seale & Lyn 2015). No other differences in body mass, BMI or body fat were observed.
Interestingly, the water-walking group showed a significant improvement in lower-limb lean mass (muscle) as compared with the control group. This was not observed with comparisons of the land-walking group to the control group. Haynes et al. propose that water walking may offer a combination of aerobic and resistance exercise.
This is perhaps the longest, most well-designed training study ever conducted on water walking, and it shows that the cardiorespiratory and body composition benefits of this type of exercise areequal to those of land walking at the same intensity.
Importantly, both walking groups progressed to moderate-intensity steady state and interval-training workouts during the 6-month study. And both walking groups saw a significant (and positive) decrease in visceral fat, the fat pattern associated with major diseases (i.e., cardiovascular disease, hyperlipidemia, hypertension, type 2 diabetes and insulin resistance).
Naylor et al. highlight that aging is associated with a decrease in muscle mass and an increase in fat mass. However, with water walking there was an increase in lower-limb muscle mass and a decrease in abdominal body fat. Using dual-energy X-ray absorptiometry proved most beneficial for determining precisely where body composition changes were taking place. The 48-week data, based on participants self-selecting whether to continue the exercise program on their own after 24 weeks, indicated that compliance may have been dipping.
These findings suggest how important fitness pros can be in motivating older clients to maintain their exercise programs and in providing an effective option that minimizes some of the risks of land-based interventions. The evidence is powerful: Water workouts really do provide an effective “splash.”