Continuing my long and storied habit of dropping names on this site, I was chatting up Alwyn Cosgrove yesterday for the purposes of an article I'm writing on tempo training (which I wrote about a few weeks ago).  Tempo training, as I noted, has begun to wane in popularity; you don't see too many books on strength training which put those cumbersome numbers ("322," "211", or even "4020") next to the set and rep notations for most exercises any more.  Following the time-honored trajectory which sees every new training technique hailed out of the gate as the best thing since Man Met Barbell, then rapidly dropped like it stank to high heaven, tempo training was first lauded as The Missing Link to muscle growth and atheticism, then summarily dismissed as clumsy and superfluous. 

(Not that missing link.)

But Alwyn had some interesting things to say.  Among them, that a primary goal of tempo training--lifting weights at set speeds to elicit specific responses from the body--is to inhibit OR facilitate the stretch-shortening response.

What does that mean?  Despite its clumsy name (someday there should be an 'awkward name-off' among physiological concepts; this might make the top ten), the stretch-shortening cycle is a pretty simple concept:  along with your tendons, fascia (the tough membrane surrounding muscle tissue), and other connective tissues, muscles resemble elastics strung between two different points of the body.  The biceps, for instance, originate at the front of the shoulders and insert at the elbows. 

When you stretch these elastic tissues, their tendency is to snap back to their normal length, like thick bungee cords, making movement easier.  In the pushup, for example, it's much easier to dip the body to the floor and return to a straight-armed position immediately, rather than pausing in the "down" position before you push yourself up.  That's largely because the stretched-out tissues of the chest, shoulders, and triceps help you snap yourself back to the "up" position, and your muscles don't have to work as hard.

Pause at the bottom of the movement, though, and much of that elastic energy is gone:  the tendons become more like taut ropes than loaded springs, and thus the muscles have to do more of the work to push the floor away. 

If you control the duration of the eccentric (lowering) portion of each exercise you do, you can control the extent to which the stretch-shortening reflex helps you lift a weight:   lower a weight slowly, pause, and lift, and the effort will be almost all muscular.  Lower a weight under control and lift it immediately without pausing, and the effort will be part muscular and part passive work done by the connective tissues.

Both methods have their place:  slowing down and focusing on muscle alone tends to elicit more of a hypertrophy response; it will also build more absolute--or brute--strength than lifting fast.  Speeding up and deliberately eliciting a stretch-shortening response from the muscles will build explosive force and athleticism. 

Great concepts, and no counting required.