An athlete can be hurt without knowing it, and thus suffer in performance. These are the clues to look out for, and the avoiding action to take.
Sometimes when you are feeling great about your training, you appear to be injury-free, and you are looking forward to achieving new heights in performance, your muscles may actually be in a state of chaos. No hobbling - or even niggling - pain will necessarily reveal this chaotic state, and only a disappointing performance in a key competition will show that something has gone seriously wrong. The poor performance will be an indication that your training has injured your muscles significantly - and yet kept you in the dark about the nature of the problem.
How can athletes be unaware of the damage they are doing to themselves during training? Unfortunately, some muscle problems can exist below an athlete's 'radar screen'; they may significantly interfere with muscle function and yet produce few or no symptoms that something is wrong.
For example, think about what happens to a runner after completing a marathon. A week after the marathon is over, the runner usually feels great, with no pain, stiffness, or swelling to announce that anything is wrong with his/her muscles (unlike the day after the race, when discomfort is often intense). However, if the runner's muscles were biopsied and the cells examined under a high-power microscope, many problems would be apparent. Research carried out by Michael Warhol at Harvard Medical School has revealed that portions of some muscle cells would be missing, other cells would be swollen, muscle membranes would be ruptured, blood vessels could be damaged, glycogen levels would be low, and mitochondria might be degenerating ('Skeletal Muscle Injury and Repair in Marathon Runners after Competition,' American Journal of Pathology, Vol. 118, pp. 331-339, 1985). Despite all this mayhem, the marathoner would report 'feeling fine'.
What the Dutch researchers found
Unfortunately, it doesn't take a marathon to induce such muscle damage. Several years ago, Harm Kuipers and his excellent research team at the University of Limburg in Maastricht in the Netherlands followed a group of athletes over 18 months of training, during which training volume and racing distance progressively increased. Kuipers and crew kept careful track of changes in the muscle cells of the athletes in order to determine how much damage occurred at different training volumes ('Structural and Ultrastructural Changes in Skeletal Muscle Associated with Long-Distance Training and Running,' International Journal of Sports Medicine, Vol. 10, pp. S156-159, 1989).
For the first six months of the study, the athletes trained fairly lightly, averaging only 28 kilometres (17 miles) of running per week and never venturing beyond 12 kilometres (7.4 miles) on any single run. At the end of this six-month period, the athletes completed a 15k road race. Kuipers's careful monitoring revealed that no athletes had muscle problems (torn membranes, leaky cells, mitochondrial break-downs, etc) during the six-month period leading up to the race, and only 14% of the individuals displayed muscle damage after the 15k event.
Over the next five months, the athletes increased their training load, working up to 50 kilometres (31 miles) per week and occasionally completing a 22k (13.6-mile) run. At the end of five months, the athletes competed in a 25k road race. As you might expect, the prevalence of muscle injury increased during this period, with 33% of athletes displaying significant muscle damage just before the competition. Interestingly, the frequency of muscle injury did not increase as a result of the race, indicating that the training itself was the primary source of muscle insult. It is difficult to imagine that the large number of injured athletes (one out of three participants in the study) produced their best-possible performances in the 25k test.
Over half showed significant muscle damage
Finally, the athletes averaged about 77 kilometres (48 miles) per week over the last seven months of the training programme. The longest run within this period was 32 kilometres (20 miles), and the athletes completed a marathon to cap the 18-month training progression. Corresponding with the heavier training load, 57% of the athletes exhibited significant muscle damage just before the marathon, and yet these individuals expected to run their best-possible race. The damage was present even though the athletes had tapered before the marathon, with the taper including a very mild 20-kilometre (12-mile) training week just before the race. The athletes also reported feeling fine, even though their muscles looked like a train wreck.
Such damage is not a trivial thing. For one thing, it is simply impossible for muscles to perform at optimal levels when muscle-glycogen levels are low, energy-producing mitochondria are damaged, and contractile proteins within muscle cells are disrupted. For another, these kinds of problems can not be cleared up overnight. Warhol's research at Harvard University suggests that it may take three months for muscles to be restored after such damage, and complete restoration may occur only if an athlete trains lightly or not at all. Warhol also made a disturbing discovery: individuals who utilise high volumes of training for prolonged periods often have a rich supply of connective tissue between their muscle cells, which Warhol calls a 'fibrotic response to repetitive injury'. Warhol believes that this fibrous, non-muscular tissue might be a replacement for muscle cells destroyed during overly extensive training. Such fibrous tissue, of course, has no capacity to contract and produce propulsive force.
Action to take
As an athlete, what should you do to achieve your greatest-possible improvement in fitness without doing damage to your muscular system?
First, you should make sure that your training programme contains adequate recovery time - at least one day off each week and at least one week of light training for every three weeks of strenuous work. Recovery periods allow your muscles to 'catch up' on key repair processes, which are often retarded by the relentless pace of high-frequency, high-volume training.
Second, you should attempt to emphasise quality over quantity in your training. High training intensity is the most potent producer of fitness, and pathological changes in muscle cells appear to be much more closely related to training volume rather than training speed. For example, when Kuipers and company compared what happened to runners' muscles following a marathon and a 25k race, they found the muscle damage to be much more extensive after the marathon, even though the 25k competition was completed at a much faster pace ('Muscle Damage and Recovery after a Marathon Compared to a 25 Km Race,' Medicine and Science in Sports and Exercise, Vol. 16, p. 200, 1984).
Third, you should engage in functional strength training two to three times a week. Such strength training should revolve around movements which actually mimic the biomechanics of your chosen sporting activity, so that you will be truly stronger as you participate in your sport and your muscles will be less likely to get frayed around the edges as a result of your training and competition (compared with weak muscles, strong muscles are less damaged by the forces created during exertion).
Finally, you should devise a performance test with which you can assess your progress over time. For runners, this might be a six-minute test on the track, for cyclists it could be a 10k 'sprint,' for swimmers it could easily be an 800-metre, all-out effort, and so on. Such tests can be completed every four to six weeks or so during training, and if you are feeling OK but your test results are getting worse rather than better, chances are good that there are muscle problems 'below your radar screen'. The solution is not to work harder and damage your muscles further; the optimal strategy is usually to significantly reduce training volume, maintain fitness with an occasional intense workout, and thus give your muscles a chance to recover from all the abuse you have put them through. For most athletes whose performances have headed south, such periods of lightness will help to wipe away muscular chaos and get performance capacity on an upward slope again.