For muscle growth (hypertrophy), you must allow sufficient rest (sleep cycles) between workouts. I'm talking about working to overload, not just an aerobic workout. Typically, you hear a range of 2 to 5 days rest time between working out the same muscle group. Generally, you need less time if you're younger (<40) or taking steroids/growth hormones. You need more time if you're older (>40) and only taking OTC supplements commonly found in health food stores. I'm on a 4-day schedule, as I fall into the latter group indicated above. How about you?
As a 57 y/o man, I can tell you that this particular closely verifies what I have found out about myself. I have worked out (strength and aerobics) for the better part of 40 years. I still work out 4 days a week with weight training, but admit I am lacking in the aerobics department. My weights have decreased but reps have increased. Since day 1, I have given the muscle group I work on at least 48 hours to recover. I see my protein needs increasing just to maintain my muscle mass as well. I have never used any supplements and rely solely on a diet that is balanced by food made from home. That chart is very close to my personal experience.
I think you have to factor in the nature of the workout, as all workouts are not created equal. The 3 variables, as I understand them, are volume, frequency and intensity, with intensity being the least forgiving. The higher the level of intensity (of effort), the lower your volume and frequency can be, all else being equal. Your chart has the idea right, but I think it visually overstates the apparent speed at which decompensation begins to take place. I don't think you begin to lose your gains quite as quickly in relation to recovery as your chart suggests. But that's just my opinion. Here is a brief video by the author of Body By Science, Doug McGuff. He addresses the three variables and their relationship with one another. Some people will find some of his views a bit extreme (on the low side of volume and frequency), but the general interrelationship of the variables should resonate regardless.
Only 48 hours, or two sleep cycles, isn't much time. You and I are in the same age group and I wait 4 days, figuring 2 days for recovery, another day for growth, and one more because I'm in the older age group and want to give enough time for everything to settle down, including my CNS and joints. I used to space my workouts 48 hours when I was in my 20's and 30's. Are you just maintaining your current muscle mass, or are you actually growing?
Just maintenance at this point...Don't want to be one of those immobile arthritic invalids in my 60's.
I agree that gains aren't lost as fast as that chart suggests. The point of the chart is that you need to allow enough rest time to realize the benefits you're seeking. My understanding of the recovery and growth process is that most of it happens while you are sleeping, when natural growth hormones are produced and muscle protein synthesis occurs.
I read a really interesting book called Squat Everyday by Matt Perryman which basically questions all the conventional wisdom about training and recovery protocols. The author studies neuroscience, psychology, physiology, methodologies from strength athletes of the past and Olympic weightlifting teams and puts together a pretty interesting argument about what the body / mind is actually capable of. I highly recommend this read if you are a fitness nerd.
I'll be candid. The book title is a major turn-off. Kindly share a few of the highlights and possibly a link or two to the research supporting it. Thanks.
The book is like a phd/ philosophical dissertation. If you are brainy and enjoy fitness its worth a read. Look at Amazon reviews.