Hope you've taken some time to rest and recover, and have begun doing some other forms of exercise -- swimming, basketball, med ball throws, jump rope, easy running on grass or turf, tennis, soccer, biking, volleyball, walking, stairs, bodyweight exercises and so on. Core work and flexibility are good areas to target this time of year.
You want to retain the most of the gains you made in the past season for strength, speed, skill and stamina. To retain most of what you have, you only need to train in that area once every week or two. To make gains, you need to train in a particular area more often. The closer you get to the beginning of the next season, the more often you should train.
Here is some background on detraining (deterioration of fitness when you stop training). This is if you are doing nothing.
Days 1–2 after last day of training
Adrenaline and beta-endorphin levels drop. Mood is affected negatively, but body stays intact. Aerobic and power capabilities are the same.
Days 3–5
Muscles become tighter and flexibility decreases. Aerobic capability decreases 5% by fifth day off.
Days 6–9
Sleep is more difficult and attention span shortens. Body’s ability to use oxygen (V02 max) drops by 10%. Less oxygenated blood is pumped with each heartbeat.
Days 10–12
Metabolic rate begins to drop, and you add pounds. Max heart rate and cardiac output decreases. Your ability to perform endurance activities declines by 15%. Muscle tone decreases.
Days 13–16
Energy production in muscle cells decreases. This causes sluggishness. Decreased cellular energy production also causes a continual drop in metabolic rate.
Days 17–19
Body becomes less efficient at sweating and cooling itself off. Body gets tired just trying to stay cool. Muscles are get less oxygen and heart pumps less blood with each heart beat.
Days 20–21
V02 max decline goes to 20%, meaning ability to use oxygen decreased by a fifth, making simple aerobic tasks are harder.
Days 22–25
Aerobic conditioning drops to 25%, and anaerobic capability begins to decline. Weight lifting and sprints become increasingly difficult and painful. Muscle mass has decreased by 15% or more.
Days 26–28
Performing aerobic and anaerobic activities that were a regular part of training now become very difficult or impossible.
Days 29–30
Muscle strength is down 30%. Loss of muscle mass means lower resting metabolism. Lifting max weight done when training no longer is possible.
If you continue to detrain until track starts in November, you lose all VO2 gains that were made during the past season, hurdling/jumping skills deteriorate and muscle strength erosion is 40%.
The exact rate at which you return to a sedentary fitness level is determined by your genetics, the shape you were in when you stopped exercising and how long you had been fit prior to detraining. It may not seem fair, but the fitter you are, the faster you lose the benefits of working out.
The bottom line is not to wait for track to start again before you start training. For now, that's in the form of other sports (do a variety of fun activities) and mix in some sprints and strength work once every week or two.
