We think stacking workouts is extremely healthy. We also think it is very natural. While the rest of the world is resting muscles (legs, back, chest, shoulders, biceps, triceps, abs) for 48 hours after working them, GPPeeps are making astounding gains in health and fitness by stacking one, several, or even several weeks worth of the same types of workouts together. Sometimes back, to back, to back. Why?
It's how we (humans) act in nature.
In the natural world (many of us don't entirely live in it anymore), things happen in seasons. During certain seasons you would be very physical in the SAME ways for days, weeks, or even months at a time. For example, in Utah sometimes we get snow storms for several days at a time. During these snow storms, many of us find ourselves participating in the very rigorous, physical activity of shoveling snow.
Snow shoveling is every bit as physically demanding as ANY workout you'll experience at a gym. Yet we don't really think about resting our bodies after shoveling out from a snow storm for 48 hours as "they" suggest, right? We don't really have that option when another foot of snow is dropped overnight. Where heavy snow happens often, people become very strong and fit from shoveling snow day after day. Your body is genetically programmed to gain health in these same ways - day after day, week after week, month after month. It is a farce to think that you have to rest it as often as the fiterati would have you do.