Recent events have delayed the follow up to the first post on microcycle structure here, but we're back on track. If you stayed awake through the first post, you'll remember the study of the race horses who trained 272 days straight, alternating one hard day, one easy day. For 260 days, the training load of the hard days was increased, while the easy days remained the same. Noting the absence of any signs of 'overtraining', the researchers changed tactics and instead elevated the training load of the easy days via increased intensity. The experiment was halted 12 days later when the horses proved incapable of handling the training load.
Soon after this study, Foster et al. (1996) published a paper examining the relationship between training load and athletic performance. They measured training load by having the athletes provide a rating of perceived exertion (RPE; on a scale of 1-10) for the training session, and multiplying RPE by the duration of the session (in minutes). The subjects were simply asked "on a scale of 1-10, how was your workout?" This "global RPE" was a subjective measure of the stress of the entire workout, from warm-up to cool-down, including rest periods. The training load, measured as RPE x Minutes, was termed "Session RPE".
A follow-up study by Foster (1998) used Session RPE to monitor the training load of 25 athletes (primarily speed skaters) for a period of 6 months to 3 years. The athletes ranged from 'low level' to National and Olympic team members, but all subjects were in structured training programs with regular competition schedules. The training load of all workouts in a week were summed to arrive at a weekly training load (LOAD) for each athlete. In addition, the daily mean training load and the standard deviation of the weekly training load were also calculated. Using this data, Foster developed two other measures of training stress:
MONTONY: daily mean divided by standard deviation
STRAIN: the product of MONTONY and the WEEKLY TRAINING LOAD
So Foster had three tools with which to consider the training stress applied to the athletes: LOAD, MONOTONY and STRAIN.
Over the course of the study, Session RPE and the incidence of illness were tracked for each athlete, working from the premise that chronic and/or acute heavy training loads were associated with immunosuppression and increased risk of illness. Illnesses were considered to be the result of an increase in LOAD, MONOTONY and/or STRAIN if they occurred within 10 days of a spike in one or more of these measures. Using this data, Foster established individual thresholds for LOAD, MONOTONY and STRAIN above which illness was more likely to occur. When the incidence of illnesses was correlated with indicies of training, the following results were obtained:
84% of illnesses were associated with a preceding spike in TRAINING LOAD above individual threshold.
77% of illnesses were associated with a preceding spike in MONTONY above individual threshold.
89% of illnesses were associated with a preceding spike in STRAIN above individual threshold.
The charts below show the weekly LOAD, MONOTONY and STRAIN scores over the course of 91 days (13 weeks) of training for an individual athlete. The black blocks across the top indicate periods of illness.
You've probably noticed that not every spike above threshold resulted in illness, and not every illness was preceded by a spike in all indices. In fact, 55% of the spikes in LOAD which exceed threshold did not result in illness; 52% of the spikes above the MONOTONY threshold did not result in illness; and 59% of the spikes in STRAIN above threshold did not result in illness. These findings shouldn't be surprising to coaches. On one hand, we know that athletes sometimes get sick during periods of low training stress, simply due to exposure to viruses and other bugs. Conversely, we also know that athletes can withstand heavier training cycles without getting sick - in fact the whole point of training is to introduce progressively greater training stresses in order to induce adaptations.
Nonetheless, Foster's findings indicate a strong trend between the incidence of illness and LOAD, MONTONY and STRAIN in endurance athletes. Taken together, we can use the info from Foster's speedskaters and Bruin's horses to give us some direction in structuring weekly training cycles in the next post.
Foster, C., Daines, E., Hector, L., Snyder, A.C., and Welsh, R. Athletic performance in relation to training load. Wisconsin Medical Journal, 95(6): 370-374, 1996. Abstract.
Foster, C. Monitoring training in athletes with reference to overtraining syndrome. Medicine and Science in Sports & Exercise, 30(7): 1164-1168, 1998. Abstract.