Without going into a large amount of detail regarding the ANS, suffice to say that we generally want our ANS to be balanced or slightly parasympathetic (unless we are getting ready for training or a competition). This is better for overall recovery. Overtraining often results in the ANS being shifted to the sympathetic side. If this is the case we want to choose passive recovery methods that promote the parasympathetic side. This helps bring our ANS back into balance and results in a faster recovery rate.
Some methods that can shift you back toward Parasympathetic are hot bathing / hot whirlpool for 15-20 minutes, relaxation massage, stretching, and even meditation. Although some of these methods are foreign to some, they do work.
A stipulation on that is that sometimes overtraining can push the ANS the opposite way and leave you parasympathetic dominant. In this case, you still show impaired recovery. The above methods won’t help, either. This time you’ll need to employ methods intended to strengthen the sympathetic side of the ANS. Some examples of these methods are contrast showers, hot-cold therapy, vigorous massage, and so on.
In general the first set of methods tends to be more relaxing while the second set of methods tends to be more invigorating. The key to knowing which set to use is knowing the state of your ANS. For some additional information on this, please refer to the above section on “Monitor your status”.