I have been coaching for 19 years and have never seen anyone lose muscle mass from bike riding. I did gymnastics from 1997 to 2001 and put on 10kg of upper body muscle and 9 years later on a diet of aerobic exercise it hasn't shifted. Sure some people diet and lose mass but very rare it would be from the exercise alone. I have seen some cyclists gain mass on riding alone.
Andy Coggan contributed some of his wisdom on wattage group about muscle mass increasing metabolic rate. Turns out that muscle is not very metabolically active by comparison to the more vital organs.
Another chestnut is doing weights to correct muscle imbalances. A quick perusal of the non traumatic injuries from cycling show that the main causes of injury are poor bike fit, too low or too high a cadence and too rapid an increase in training progression (freq, time or intensity). Muscle imbalances don't even make most lists.
Andy Coggan contributed some of his wisdom on wattage group about muscle mass increasing metabolic rate. Turns out that muscle is not very metabolically active by comparison to the more vital organs.
Another chestnut is doing weights to correct muscle imbalances. A quick perusal of the non traumatic injuries from cycling show that the main causes of injury are poor bike fit, too low or too high a cadence and too rapid an increase in training progression (freq, time or intensity). Muscle imbalances don't even make most lists.