How far can you go with eccentric body exercises?

Question

Oops! This got longer than what I have intended, so please bear with me!

Let me start off by saying that it's the first time I see a website about fitness where I can hope of receiving empirical answers, instead of the usual knuckle-dragging ones!

I'm no stranger to fitness, gyms and bodybuilding (although not as sharp as I would like to be on the biological side of things), and have great experience with all considering that in the last 4 years I've transformed into an excellent, healthy physique. However, it is only recently that I've been trying to pin down the most efficient ways of inducing muscular hypertrophy. The internet mostly brought up anecdotal or commercially-influenced evidence, and most papers I've found have been contradictory to one another.

This led me to turn to auto-experimentation. Each month I would pick a different workout routine and log my results. However, since measuring actual muscle gain is not feasible, the only things I measured were the amounts of soreness I would receive the following day. In other words, my evidence is unreliable.

A few months ago I encountered this paper published by BRAD J. SCHOENFELD, wherein it explains possible variables that affect muscle growth. To summarize, among many factors, the most practical and relevant seem to be:

• Total damage afflicted to the muscle.
• Amount of metabolic stress during workout.
• Duration of mechanical tension in the muscle.

To my understanding, the best way to afflict muscular damage is slow, eccentric movements, therefor allowing assorted fibers to "slip and get torn off" as they extend, as illustrated here:

The best example of doing so is rapidly going UP in a push up, then ever-so-slowly descending down to earth.

All things considered, I composed a routine: a repeating loop of extremely slow descending, fast ascending push ups until relative exhaustion (usually around half a dozen) followed by an extremely slow descending, fast ascending squats. Repeated indefinitely. Note that there is NO time to rest in between, although after trying this I sometimes give myself 30 to 60 seconds if I feel especially exhausted.

After a week of waiting, I began this workout. On the first day, I experienced my muscles shaking towards 30 minutes, which is normal after that time of not working out. After I started to automatically drop in the squat section from my legs feeling like noodles, I called it a day. Total workout of around 40 minutes.

In the next day I felt soreness which you feel after not exercising for a while or for the first time. I skipped this day and the day after it.

4th day, felt no muscle shakes towards the end, and eventually stopped due to limbs feeling like noodles after about an hour. On the next day, I felt soreness, yet very marginal and unlike the one described previously.

I would like people to take shots at disassembling and disproving my understanding and practice, there are a lot of questions, so I guess it would turn into a discussion or a long answer list. I've heard a lot of talk that you cannot gain muscle (or at least not as much) from only bodyweight exercises, and I must disagree, simply because my half year at the gym was as mundane as my years doing bodyweight exercises. Overall, to clarify, I am always making progress, I am simply always looking to make it more efficient.

Questions:

1. Are periods of rest between sores necessary at all? How does working out day after day hamper hypertrophy?
2. Is it advisable to skip the concentric contraction part of the push up/squat routine by using external help, and only relying on eccentric workouts? (slowly descending down, using external help to get up, repeat...)
3. Is my thought model for inducing damage to the muscle optimal?
4. How much of a wild card is the so-called "metabolic stress" from the paper I mentioned? Anyone have any experience or thoughts?
5. My primary work outs include push ups, squats, pull ups and/or chin ups, and lastly, sprinting. I've been doing these for the last year and a half and witnessed a great increase in muscular size. Pretty void, but can anyone suggest anything to improve?

Looking forward for answers! Sorry for the lengthy post and any pretentiousness that might have leaked! It would be wonderful if answers would be constructed biomechanically, rather than hocus pocus mike chang anecdotes.

Answer 1

First of all, I don't think that soreness is measurable nor a tool to estimate your workout efficiency. That being said, yes - your muscles need to recover before you train them again. The resting time recommendation varies, but most trainers recommend 1-2 days of rest after a workout for the particular muscle groups you worked on. Working out the same group of muscle over and over without letting it rest will put you in risk for damaging the muscle themselves, and for damaging tendons/joints due to improper form led by muscular exhaustion.

That means that a full-body workout is generally limited to 3 times a week while training programs where training sessions are split into muscle groups offer up to 6 days of trainings a week. There is a common advice to have a "deload week" once a 6-8 weeks to let your body some more rest, but I didn't see any research about this advice. Lastly (or firstly), most articles start with the disclaimer "Unless you're not a professional athlete...", which refers to people who train more than once a day, but as far as I read you don't belong to this group

Regarding the eccentric-concentric part, there are two main assumptions (source):

1. The eccentric part of the move causes the most damage.
2. In the eccentric part of the move we are "stronger", means we can move the same weight easier than in the concentric part.

Thus, for most of the muscle groups it's pretty hard to get to the eccentric part with a challenging weight without cheating in the concentric part (which is okay sometimes). This is a very important subject in the biceps training, where you'll often hear a recommendation to cheat a bit in the concentric part of the curl (using momentum) in order to perform more slow eccentric repetitions. For delts, i.e., you can perform only the eccentric part of the front raise by doing clean & press first.

When it comes to squats, it indeed causes more damage when performing the eccentric part moderately slow, but:

1. It's a push movement and the help you can get with momentum is limited.
2. It's one of the main compound movements which in a functional movement (something that demonstrates a real life function), and therefore it's recommended to use it to improve your strength and not only for hypertrophy.

About your program, I'd always suggest to stick to some starting program, which can be found easily on the web, in order to get "back to business". After that, as Arnold said, you need to surprise your body. That means that there's no one optimal training plan, but you have to change it over time, again, and again, and again...

EDIT: The following figure may answer your question (dashed is concentric):

Although I don't consider soreness ("tenderness", in the research) as a tool of measurement, this graph states pretty clearly the influence of both movements: eccentric causes more damage, but concentric does damage as well. To sum it up, when speaking about hypertrophy, I'd say that keeping TUT is more important than avoiding/cheating on the concentric part for more eccentric repetitions, and therefore I choose to slightly cheat on the concentric part using momentum when possible (mainly biceps), but not to avoid them and I also do not cheat on functional exercises (squats, bench presses, etc).

The full research can be found here.