Cross training vs complete rest

First, however, we ought to consider the alternative to “cross training” during time off due to injury—complete rest. Dr. Jack Daniels, one of the pioneers of the use of threshold training, quantified the drop in fitness that occurs due to time away from running in his best-selling book, Daniels’ Running Formula. Daniels’ work exposes a few important points: first, there is virtually no drop in fitness as a result of missing up to five days of running. After that, your conditioning drops more sharply, then “bottoms off” after about ten weeks (representing your “baseline” fitness as a sedentary individual). After about a week or two away from running, the differences between those who cross-train (by any means) and those who take complete rest begin to emerge. Though the gap is only about two percent after fourteen days, this increases to ten percent (80% of initial fitness vs. 90% of initial fitness) after ten weeks or more. This means that a 4:30 miler who takes 10 weeks completely off will (in theory) regress to 5:32 without cross-training, but only 4:57 with it. So, having realized the benefits of staying fit, we can move on to how to go about doing so.

Studies on the effectiveness of aqua jogging

Aqua jogging has become popular because, unlike cycling or using an elliptical machine, it is quite similar to overground running, at least in terms of the muscles used and your range of motion. A good deal of physiology research was done on aqua jogging in the early and mid-90s, as its popularity was rising.

Aqua jogging and heart rate

One of the earlier and more influential studies was done in 1991 by Nancy Butts, Mary Tucker, and Christine Greening at the University of Wisconsin at LaCrosse.1 Their work compared oxygen consumption and heart rate during a graded exercise test done while aqua jogging and while treadmill running. Although the runners were not able to achieve the same heart rates and oxygen consumption levels in the pool as they did on the treadmill, the researchers noted that the disparity was similar to that between running and cycling, which also elicits lower oxygen consumption and heart rates (when done by runners, at least). This paved the way for aqua jogging to be viewed as “on par” or even superior to other forms of cross training. In an early review of some of the literature on aqua jogging, Reilly, Dowzer and Cable in the UK found that, at low to moderate intensities (comparable to an easy run or marathon pace), deep-water running is actually more demanding on the cardiovascular system, probably due to the increased demands on the upper body, which is poorly trained in runners compared to the legs.2 It’s only when the intensity approaches what you’d encounter in a 5k or 3k race (or shorter) that aqua jogging reaches its limits. Perhaps because of the hydrostatic pressure from being submerged in water, or simply because of unfamiliarity with the exercise, runners aren’t able to push their bodies as hard in the water versus on land. This indicates that aqua jogging is probably better suited for maintaining aerobic fitness versus race-specific anaerobic fitness.

How to make the most of aqua jogging workouts

Building off Reilly et al.’s work, Garry Killgore at Linfield College authored an extensive review of the literature on aqua jogging in February of this year.3 In it, he highlighted the strengths of aqua jogging (namely, how closely it simulates actual running) and made some recommendations on how to take advantage of these.

• First, runners should use a flotation beltwhile aqua jogging if they wish to preserve “normal” biomechanics. While aqua jogging without a belt is certainly possible, you have to adopt a “high knee” gait with a rapid stride turnover to stay afloat. This high-knee style of aqua jogging demands more energy, and therefore might be a better workout, but comes at the cost of running specificity. Killgore recommends a “cross country” style gait, where the leg sweeps back at a larger angle and the foot “pushes” down at the bottom of the stride, much like in real running. Your stride frequency with this cross country gait in the pool will be much lower than if you were running on land. He also cautions against adopting too much of a forward lean, which is the most common form error in novice aqua joggers.

• Second, Killgore found that later studies confirmed that aqua jogging is relatively close to real running in terms of cardiovascular demand at easy to moderate intensities, but falters when it comes to high intensity work. A few tricks, like keeping your head dry, running in a warmer pool, or wearing a tight-fitting synthetic shirt (like an UnderArmour vest), may boost the intensity of your workout somewhat, since one of the inhibitors of aqua jogging intensity is heat loss to the water.

In general, though, Killgore’s review stresses that aqua jogging is more suited towards maintaining fitness, not building it. Though a few studies have found fitness gains in subjects who undergo an aqua jogging regimen, these tend to use sedentary people instead of athletes. On the bright side, however, runners can expect to maintain their fitness for at least six weeks by using an aqua jogging routine when injured. (Click to Tweet) The only caveat is that the aqua jogging should be done at the same intensity, duration, and frequency as your normal training. So, if your training schedule called for a 90-minute long run, it can be a dull hour and a half in the pool! Finally, he notes that your perceived effort while aqua jogging (how “hard” a particular effort feels relative to its actual physiological demands) is slightly increased in the pool. So, to get the same training effect, you’ll have to bump up the intensity a notch over what you’d use when running on land.

Recommendations for better aqua jogging results

While there’s little news that can cheer up a runner who’s been sentenced to four or six weeks off, the research we’ve reviewed in this article shows that not all is lost.

• Aqua jogging is an excellent way to maintain the fitness you had before you were injured, provided you stick to it with the same intensity you usually train with.

• To keep it as close to real running as possible, mechanically speaking, wear aflotation belt and make sure your stride in the pool is as close to your “normal” running stride as you can get it. If you want a harder workout, you can ditch the belt, but understand that the intensity is coming at a cost of what coaches call “specificity”—though it is a hard effort, it is less like running.

• If you’re in need of some aqua jogging workouts to spice things up, check out our extensive Cross Training Guide for Runners. It’s our free guide that provides a mix of easy, medium, and super hard workouts (using a bungee cord tied to one end of the pool, which is guaranteed to get your HR skyrocketing) to add variety to your aqua jogging routine. Did we mention aqua jogging can be painfully boring?

• Finally, keep in mind the particulars of your injury situation when pondering a cross-training regimen. There are some injuries, like a hip flexor strain or various hip and knee ailments that do not handle aquajogging well. If aqua jogging hurts, you shouldn’t be doing it! Work with your doctor or physical therapist to find another way to stay fit while you get healthy.

References   1. Butts, N.; Tucker, M.; Greening, C., Physiologic responses to maximal treadmill and deep water running in men and women. American Journal of Sports Medicine 1991, (19), 612-614. 2. Reilly, T.; Dowzer, C. N.; Cable, N., The physiology of deep-water running. Journal of Sports Sciences 2003, 21 (12), 959-972. 3. Killgore, G. L., Deep-Water Running: A practical review of the literature with an emphasis on biomechanics. Physician and Sportsmedicine 2012, 40 (1).