Pain tolerance, sleep and nonlocal fatigue

This article was originally posted by Ryan at the original Blogs.

I came across some interesting topics in the past week. Here are three of my favorites:

Pain tolerance

I remember for some time hearing about how runners are tough. We can withstand more pain than the average person. The question I always had was whether this was simple correlation or there was some causation involved. Do people who are more tolerant to pain choose running or does running increase our pain tolerance?

Recent research has suggested that running does increase our pain tolerance. Then, the question became through what mechanisms? Does experiencing low levels of discomfort and/or pain in our legs toughen our legs up or does something change in our central nervous systems that allows us to withstand more pain throughout our bodies?

Well, this suggests it’s the latter:

But the volunteers in the exercise group displayed substantially greater ability to withstand pain. Their pain thresholds had not changed; they began to feel pain at the same point they had before. But their tolerance had risen. They continued with the unpleasant gripping activity much longer than before. Those volunteers whose fitness had increased the most also showed the greatest increase in pain tolerance.

Pain thresholds and tolerances were tested using people’s arms, Mr. Jones pointed out, while the exercisers trained primarily their legs. Because the changes in pain response were evident in the exercisers’ upper bodies, the findings intimate that “something occurring in the brain was probably responsible for the change” in pain thresholds, Mr. Jones said.



There has been a lot of talk at various places recently about sleep. Talk of people needing less than they think, getting too much and so on. Personally, I never bought into it. I know that, personally, I don’t function well on less than 8 hours a night and, if I can get 9 or more, I often feel a significant boost the next day.

This article suggests I’m on to something.

After Stanford University basketball players spent five to seven weeks sleeping at least 10 hours a night (when they had been sleeping six to nine hours), their performance shot up like they’d doped. They had faster sprint times and shooting accuracy. They also felt their overall physical and mental well-being improved during games and practice.

So what of all the 7 vs. 8 or more talk? Well, it came from a study that may not have been so well designed:

"It is important to understand that this 7 vs. 8 hours finding was not a carefully controlled study but is an association found retrospectively…this pertains only to longevity," Veasey wrote. It’s entirely possible that illness caused people surveyed to sleep longer, not the other way around.

I mentioned correlation vs. causation in reference to the pain tolerance study. Well, here it is again. The "7 hours is better" line is based on correlation. They didn’t show that 7 hours causes better health or longevity.

Many of us live extremely busy lives. Running is one of many things we need to fit into the day. I’m not going to tell you how much to sleep. However, we put our bodies through a lot. If you have the option to turn in a little earlier or sleep in a little later, take advantage of it.

Remember, sleep is critical to recovery and recovery is a critical part of training. As much as possible, don’t skimp on sleep.

Nonlocal fatigue

Finally, an interesting question to ponder. Does fatigue in our arms affect how our legs can perform? Does fatigue in our legs affect how our arms can perform?

According to this, the answers seem to be yes and no.

Anyway, the basic result was this: Whether you fatigue an arm or a leg, the opposite leg will be tired in a subsequent bout of exercise. Conversely, whether you fatigue an arm or leg, the opposite arm will not be tired in a subsequent bout of exercise. So the arms and legs (or at least the elbow flexors and knee extensors) appear to behave differently with respect to nonlocal fatigue. Why would this be? The short answer is the researchers don’t know.

In short, fatigue in an arm or leg affects the opposite leg. Fatigue in an arm or leg does not affect the opposite arm. Now, there is at least one other study that contradicts the "opposite arm" part of that result so don’t get too excited yet. Also, this finds the result but doesn’t find the reasoning behind the result so we don’t know why our legs fatigue when our arms are exercised.

However, I think this is useful information to be aware of. If nothing else, I think it’s interesting.

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