Adaptations during strength training

Hi,

I have some questions about physiological adaptations to strength training.  (I'm talking about general training for alpine climbing, like upper and lower body strength and core strength, not specific training for rock climbing, like finger strength.)

What I'm curious about are the specific adaptations that occur during the general, max strength, and muscular endurance periods of strength traning (as outlined by Uphill Athlete for example). 

Some specific questions:

• There used to be some debate about whether strength training lead to more muscle cells, larger muscle cells, some combination of the two, or other more subtle changes. What is our corrent understanding?
• During which periods are adaptations mostly neuromuscular (fibers firing together) and during which periods do adaptations of other kinds occur (enzymes and so on).
• Do we have any idea how connective tissue changes, for example, collagen in tendons and ligaments, and so on.

Any input appreciated, from general to deep-in-the-weeds science stuff.

My fairly basic understanding is this.

Both- training can increase the size and number of muscle cells.

You can bias hypertrophy (increase in muscle size) by lifting lighter loads for more reps or neurological gains (muscles fibers firing in unison) by using heavier loads and fewer reps. I’m not actually sure if there are ways to target more muscle fibers or increase in number of cells or if there  is a functional difference/reason to care which is happening.

Endurance has kind of a similar split-you can bias vascularization (which will increase the level of effort you can sustain for long periods) by doing longer duration  submaximal work (an easy benchmark here is that if you can’t easily sustain a conversation you are working too hard) or you can bias mitochondrial  density (which will increase your max output) by performing shorter bouts of more intense work. 

Tendons are interesting. They don’t get a lot of perfusion of blood the tissue like most other parts of your body. They seem to rely on mechanical load to flush and perfuse the tissue (my understanding is the lengthening and contraction of the tissue itself and the tissues surrounding act to pump lymph blood etc into and out of the tissue rather than relying on the pressure provided by the heart. This is why simply resting a tendon/ligament injury even for months often does not heal it), as well as for signaling to repair/strengthen the tissue, and seem to be receptive to that stimulus every six hours. It seems that a tendons strength is a reflection both of the size/thickness of the tendon but also the patterning of how the collagen fibers that comprise it are laid down. In the absence of load the fibers will be laid down in a random every which way manner, but with regular loading they get laid down in an organized manner to better resist those loads. This is another reason why just resting a soft tissue injury is not a great idea-its best to start giving it whatever load it can tolerate pretty quickly, and ramp up the intensity as it can tolerate more. 

Hi Nowhere, 

I know some time has passed, but I want to jump back in and say that, after reading a bunch of papers and doring some research, my impression is that what you wrote above is very knowledgeable and concise summary of some complex changes--thanks so much for that.  

What I can add are that early in a strength training program (or early in the traning life of an athlete) the adaptations seem to be mostly 1) neuromuscular, and 2) involve shifts in muscle fiber type (for example from more "fast twitch" oriented to more "endurance" oriented."  The gains in strength early in training can not be attributed to what little hypertrophy or hyperplasia that have occcured.  

Now THAT is interesting from the perspective of climber.  Unless we are talking about finger strength specifically (and that's not my goal here) the aim is usually to increase strength as much as possible while increasing mass a little as possible--so whatever changes we can promote that do not involve hypertrophy are positive.  As far as I can tell, that mainly involves not lifting to failure--maintaining strict form, no shaking, not complete inability to do one more rep, and so on.  That might prevent te most absolute gains in strength, but it will also limit hypertrophy.  The way forward for climbers?

As to targeting more "endurance" or more "pure strength" by biasing the strength traning protocol one way or the other...I'm just not sure.  

On one hand, it makes sense to tailer a strength program to the specific force, duration, speed, joint angle, requirements of one's sport.

Onn the other hand, I wonder if it's not more effecient to to endurance training (like uphill hiking or running) for endurance, and do stength training (like squats or pulls ups) for strength.  

Not sure.  

Anyway, thanks for chiming in.  Your input was really solid.