Try an arginine supplement

When administered alone, arginine may increase HGH levels. Despite the fact that most people consume amino acids like arginine in conjunction with exercise, numerous studies demonstrate little or no rise in HGH levels. Taking arginine on its own, without exercise, has been shown in tests to greatly raise levels of this hormone.

Other non-exercise research back up the usage of arginine to increase HGH. One research looked at the effects of ingesting 45 or 114 mg of arginine per pound (100 or 250 mg per kg) of body weight, or 6-10 or 15-20 grams per day. The lesser amount had no impact, however, people taking the greater dose had a 60% boost in HGH levels while sleeping.