Leroy L. Long III and Manoj Srinivasan wrote a paper entitled Walking, running, and resting under time, distance, and average speed constraints: optimality of walk–run–rest mixtures.
We smiled when we read their study that stated, “…we study human choice between walking and running in a more ecological (non-treadmill) setting. We asked subjects to travel a given distance overground in a given allowed time duration.
During this task, the subjects carried, and could look at, a stopwatch that counted down to zero. As expected, if the total time available were large, humans walk the whole distance. If the time available were small, humans mostly run. For an intermediate total time, humans often use a mixture of walking at a slow speed and running at a higher speed…”
This conclusion reminds us of the difference between doing a short set and a long set, either in the pool or in the open water.
If we set off on a set of 5 x 100 in the pool or a 1-mile swim in the ocean, we automatically set off at a certain pace. In contrast, if the set is 5 x 800 in a pool or a 6-mile swim in the ocean, we automatically swim at a slower pace calculating all the time a natural balance between swimming fast and feeling comfortable enough to enjoy the workout.
But the researchers describe their conclusions with characteristic eloquence. “…With analytical and computational optimization, we show that using a walk–run mixture at intermediate speeds and a walk–rest mixture at the lowest average speeds is predicted by metabolic energy minimization, even with costs for transients—a consequence of non-convex energy curves. Thus, sometimes, steady locomotion may not be energy optimal, and not preferred, even in the absence of fatigue…”
In our own case, we find our workouts are a mix of various speeds. Sometimes, we speed up if we feel good. Sometimes, we slow down and we occasionally stop. This is especially true when we swim with people of various abilities. But it seems that this variable mixture of efforts and speed is a good thing according to the researchers.
“…we conjecture that similar walk–run mixtures may be energetically beneficial to children following a parent and animals on long leashes. Humans and other animals might also benefit energetically from alternating between moving forward and standing still on a slow and sufficiently long treadmill.”
Experienced coaches have always given swimmers a mix of goals within each workout. We remember back in the 1970′s when English Channel record holder Penny Dean would give an ocean workout in Southern California where we had to alternate speeds (i.e., medium, fast, all-out) between lifeguard towers, jetties and piers. Other coaches from Gerry Rodrigues and Bruckner Chase to Shelley Taylor-Smith and Siga Rose also combine a mix of fast sets in the ocean, including doing ins-and-outs, during their open water training sessions.
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