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Defining the Line Between Training Hard and Overtraining

Posted Feb 05 2013 6:00am

over-training syndrome runningOvertraining can be a real season-killer. When you push too hard in training and don’t recover enough, your workouts will begin to feel lackluster and you’ll be sapped of energy, even in your daily life.

This week we’ll be looking at the causes and effects of over-training syndrome in runners from a scientific perspective.

There’s no magic cure for it, but understanding some of the problem’s biological roots will help us understand how to prevent it or mitigate its effects.

The research on overtraining syndrome

First, we’ll look at a pair of papers that present the research on induced overtraining syndrome in endurance athletes.

The first, conducted by Laurent Bosquet and co-workers at the University of Montreal, subjected 10 athletes to a 100 percent increase in training (e.g. doubling their normal volume) over a period of four weeks. The researchers physiologically tested them before the month-long block of sharply increased training, immediately after, and again following a two-week recovery period. Seven of the ten athletes developed what the authors deemed “over-training syndrome”— a cluster of illness, injuries, decreased performance, and a feeling of general fatigue both in training and in daily life. While the other three displayed fewer symptoms , they too failed to improve their fitness.

Lab tests showed a significant drop in the athletes’ abilities to produce lactate — a good measure of their anaerobic fitness. More troubling was the failed lactate production increase after the two-week recovery period, which demonstrates that the effects of overtraining can be long-lasting.

The second study involved a group of eight experienced runners who, like the Bosquet, et al. study, undertook a massive increase in training. Over a few weeks, they augmented their training volume by about 50 miles to more than 100 miles in only six days of running, with one off day.

Much like the first study, six of the eight subjects developed overtraining, while the fitness of the other two stagnated. Both qualitative measurements like fatigue and muscle soreness, and quantitative measurements like maximum heart rate and lactate production, decreased significantly during the study. Perhaps most importantly, the ability of the over-trained subjects to sustain a fast pace deteriorated.

The biological genesis

The biological roots of overtraining symptoms are well-summarized in a review article by Laurel Mackinnon at the University of Queensland in Australia.

She catalogues the symptoms of overtraining, which include fatigue, poor sleep quality, a lower maximum heart rate during exercise, muscular soreness, a lack of motivation or “energy” and irritability. The root cause seems to be linked to the body’s response to a massive increase in training volume; one theory is that damage to the musculoskeletal system from the physical and chemical strains of high volume, high intensity training release a cascade of inflammatory and damaging proteins into the body which provokes a system-wide response, explaining the wide range of effects of overtraining syndrome.

This, however, is unproven as of yet, and as Mackinnon points out, it’s unlikely that something as varied and individual as over-training is caused by a sole biochemical process.

Contributing factors to over-training identified in the scientific literature include:

  • Sudden increases in training volume or intensity (no surprise given the results of the first two studies we looked at)
  • Repeating the same training day in and day out
  • Self-reported high stress levels (related to training or not)

Life factors

This last factor should be a reminder that training is heavily influenced by the rest of your life: While a college athlete with no morning classes might be able to handle 80 or 100 miles a week, that schedule could be far too grueling for someone who works in a physically intensive field, like construction.

An inadequate dietary intake also reportedly intensifies its effects, presumably because if the body does not have the raw materials it needs to repair itself.

Whatever the reason, to prevent developing an advanced case of over-training syndrome, Laurel Mackinnon recommends identifying it early while symptoms are still mild (or even while it is the syndrome’s precursor, “over-reaching”) and reducing its causes.

In summary

Avoiding large increases in training volume or vigor is something of a no-brainer for most runners, so the key to preventing over-training syndrome probably lies in managing what you’re doing the other 22 – 23 hours of the day.

Your recovery plays a big role in how much training you are able to handle, and if you are not getting enough sleep or if you are dealing with a lot of life stress, you’ll likely be more susceptible to over-training.

The easy solution is sleeping more and de-stressing, but sometimes that’s just not realistic. The harder thing to do is to recognize that if you do start to feel the effects of over-training, you will need to back off significantly and divert the attention to the recovery.

While the scientific literature details no specific over-training recovery approaches, Bosquet, et al. showed us that it can take at least a few weeks, so be patient and remember to support your body while it rehabilitates.


>1. Bosquet, L.; Léger, L.; Legros, P., Blood lactate response to overtraining in male endurance athletes. European Journal of Applied Physiology 2001, 84 (1-2), 107-114.
2. Lehmann, M.; Dickhuth, H.-H.; Gendrisch, G.; Lazar, W.; Thum, M.; Kaminski, R.; Aramendi, J.; Peterke, E.; Wieland, W.; Keul, J., Training-overtraining. A prospective, experimental study with experienced middle- and long-distance runners. . International Journal of Sports Medicine 1991, 12 (5), 444-452.
3. Mackinnon, L. T., Overtraining effects on immunity and performance in athletes. Immunology and Cell Biology 2000, 78, 502-509.
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