Your body can run very well without much or even any carbohydrate but insufficient protein can quickly lead to poor recovery from exercise, stalled progress and even bone and joint problems. (fitnessandpower.com)
High levels of cortisol can also result in poor recovery after intense training. (sixstarpro.com)
Some people with poorer recovery times may benefit the most from two sessions a week. (thehealthyhomeeconomist.com)