David Costill (*) has shown that consecutive hard days result in a continuing depletion of muscle glycogen. Although cardiac glycogen is replaced within 1-4 hours of heavy exercise, muscle and liver glycogen take much longer. 50% of runners did not reach pre-training glycogen levels with 55% carbohydrate. Some individuals did not replenish their glycogen levels with 5 days rest and 80% carbohydrate ingestion.
Hard training female athletes are also more susceptible to iron deficiency anaemia, particularly in the 14-18 age band.
It is recommended that the first food taken after heavy exercise is carbohydrate, e.g. pasta, potatoes, bread etc. If insufficient is taken, your recovery will be delayed.
Veterans: Runners of long standing expect to continue the demanding schedules of their youth, but do not realise they need longer to recover.
In the short term recovery days are vital, but also in the macrotime, i.e. easy weeks and once a year an easy month.
1. Weight. Because 3 molecules of water are associated with each molecule of glycogen, glycogen depletion will result in weight loss.
2. Pulse rate. A reduction in haemoglobin concentration in the blood due to reduced red cell volume or increased plasma volume will mean more blood is required to satisfy basal oxygen requirements, and thus heart rate will increase. Check this in the morning on waking.3. How you feel. This may be misleading in the microtime, but if you feel tired for 3 days or more, beware.
(*) Ref. "A Scientific Approach To Distance Running" D Costill