Most people train one day on one day off and id say the earliest symptoms of over training would be lack of improvement over a extended time and or deterioration of improvement. As far as Im concerned the tables should only form part of your training regime and not be the sole method of increasing times. Id say add apnea walks and supervised dynamics to your training and also include wet statics to your dry times. This teaches your body to react in a similar fashion in most circumstances and also teaches you what you can expect from your body. Remember also to add some cardio workout to you training programe as you need to have at least some level of constant fitness to be at peak performance, but you probably know that allready. Aproach dive training as you would any other sport and there would not be any reason for not improving

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Dive safe and shoot straight
- Hénré -
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"Thinking is the hardest work there is, which is probably why so few engage in it"
- Henry Ford -