"Replace, don't stack, new training modalities onto existing volume When someone who has trained for strength for two to three years wants to build endurance or improve VO2 max, the common mistake is adding cardio and stamina sessions on top of an already full strength schedule rather than substituting some days. The hosts noted that "the mistake that people make is they pile it on top of their strength training," which leads to overtraining and poor results in both areas. The corrective approach is to drop one or two of your current strength days and replace them with endurance work — you will keep most of your muscle, gain cardiovascular fitness surprisingly fast, and can always course-correct within two to three weeks if you do not like the balance. Source: Sal Di Stefano, Adam Schafer, Mind Pump Podcast, Blue Collar Fitness & Scale Weight Pitfalls"