Rest is a well-known way to build strength and avoid overtraining syndrome. One of the real issues with people who come late to cycling is that they believe they can ride all the time with no ill effect. Not so.

When exercising beyond warm-up, the muscles fibres are damaged. The increase in strength comes when those muscle fibres repair and that generally happens when you are sleeping or resting.

Overtraining syndrome is identified by a heightened heart rate when waking in the morning, and failure to get it above normal levels for a given zone of exercise. It's quite possible for a HR in a zone to be 30bpm below what it should be, and it won't go any higher.

Rest is severely underestimated in any sort of physical activity. And a person engaging in a training program should ensure that there are adequate rest days, especially after strenuous workouts, whether with intervals, hillclimbing or weights.

Personally, I love rest...