When it comes to strength and fitness, more training doesn’t always mean better results. This is because your fitness increases not during your actual training but in the time afterwards. The training itself fatigues your body and triggers physiological processes that, given enough time to play themselves out, result in your body adapting to the training and supercompensating (coming back even stronger/fitter than it was before you trained). But the key is allowing enough time for this to happen.
If you have a challenging training session then train again before your body has had a chance to recover properly, you will be training in a fatigued state, and your performance will actually decrease over time, as well as make you more susceptible to injuries.
On the other hand, if you allow your body enough time to recover, but then wait too long until your next session, the principle of reversibility (“use it or lose it”) comes into play and de-training will occur – your fitness will plateau or be reduced. This isn’t the end of the world though – you can always just pick up where you left off.
An optimum training program allows your body (and mind!) just the right amount of time to recover between training sessions to allow for improvement.
How much recovery time is needed is different for everyone, and depends on a number of factors unique to each person (your unique body, health status, age, fitness, strength), your nutritional intake as well as the intensity of the session. Keep in mind that rest doesn’t need to be staying totally inactive – active recovery activities like gentle swimming, jogging, stretching or walking (at a much lower intensity than you would normally participate) are almost always useful.
It’s important to listen to your body – regularly check your resting heart rate (this should decrease as you get fitter), energy levels, mood, increases or decreases to your strength and fitness and how your sessions are feeling physically and mentally and let this guide you as to whether you need to increase or decrease your number of training days.