An Analysis of Cardiovascular Response in Water and on Land
Many athletes wonder which method of cardio is most effective. It's a difficult question to answer because some variables aren’t easily quantified in a scientific setting, such as which exercise an athlete enjoys the most. The most enjoyable mode of cardio is the one the athlete will do often enough to get any benefit.
But there are some facets of cardiovascular training that we can measure, like ventilation, oxygen levels in the blood, and heart rate. These topics have been covered quite a bit in the literature for decades, but there are still areas that need further exploration. For example, in a study this month in the Journal of Strength and Conditioning Research, researchers compared aquatic exercises to dry land training to see which one correlated with maximum cardiovascular response.
Previous research has demonstrated surprisingly dramatic differences between various types of cardio training. The differences can be explained by what sort of exercises are chosen, how much musculature is recruited, and how the protocols are carried out. The most commonly compared cardio training modes are the three found in a triathlon: biking, running and swimming. To give you an idea of how these exercises differ, cycling typically recruits fewer total muscles than running. Cycling may also rely more heavily on the quads to engage in the movement. Because of this, many people below an elite level will find that cycling feels harder to maintain at any given heart rate.
In this particular study, the researchers compared aquatic exercises to running on a treadmill. Historically, swimming has been the most difficult mode of cardio to compare to the others. When you are swimming, your body is partially or completely suspended, so the muscles are used in different ways from land-based cardio methods. Because of these significant differences, it can be difficult to draw a fair comparison between swimming and other modes of cardio.
The researchers in the study noted that this comparison has been attempted in previous research, but that the tests may not have been a legitimate comparison. For example, you can compare running on land to running in water, but you need to choose a specific pace to compare to measure the fitness variables. Running at 100 RPM on land is very different from doing the same exact thing in water, so it’s no wonder that variables like VO2 max and heart rate are also different when you compare running and swimming.
To resolve this issue, the researchers used the fitness variables themselves as the points of comparison. In other words, instead of trying to come up with a protocol in the water and one on land that match each other perfectly, they measured ventilation (breathing), something that occurs regardless of the training method you choose. The researchers chose three ventilation levels and measured cardiovascular response at each level. The first level corresponded roughly with the aerobic threshold, and the second corresponded with the anaerobic threshold. The third was a maximum exertion level.
The only two markers that were similar across each exercise method were breathing and oxygen use, and only at the aerobic threshold level. Heart rate, VO2 max, and breathing were all significantly higher when running compared to training in the water at higher intensity.
With these results, we can see that at higher intensity running on dry land seems to yield a greater cardiovascular response. However, for those who participate in aquatic sports, training at a slightly higher heart rate level than you normally would on land should be just as effective for sub-maximal intensities.
1. Cristine L. Alberton, et. al., “Maximal and Ventilatory Thresholds Cardiorespiratory Responses to Three Water Aerobic Exercises Compared to Treadmill on Land,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000304