The Strength Curve, Power, and CrossFit

When you're performing an exercise for the first time, you're not likely to test your limit. 

If you did, you'd find that you can move a weight that feels heavy many times. Beginners, characteristically, have a shallow strength curve: they can pick up 100lbs ten times, but can't lift up 125lbs once. 

STRENGTH CURVE BEGINNER

As training continues, and strength increases, they'll discover that their strength curve begins to increase its angle: they can no longer lift their one-rep max limit weight ten times in a row.

STRENGTH CURVE ADVANCED
Let's consider the poles of the strength training spectrum: a high-rep circuitfox, and a powerlifter.

CircuitFox ™:  30lbs feels challenging on the "leg machines," but she can do it fifty times before the chime sounds. She can't do 40lbs at all.

Old-fat-jiggling-machine1
Powerlifter: can squat 900lbs once, but can't do 875lbs for a double.

Sumo
Strength doesn't follow a linear curve. You can't project your best lift from a series of lesser lifts.

1rm bench calculator

At our Pump N Run, I hit a bodyweight bench press for 20 reps. Even as a competitive powerlifter, I never came within 70lbs of my projected 1-rep max according to this 'calculator.'

Besides the early-exposure motor learning that accompanies these lifts, the predominant limitation is the Central Nervous System. The CNS controls which fibres fire; how quickly they ramp up, from lower-twitch to high-twitch; and how hard they'll contract. Together, these three make up an important part of training called Rate of Force Development.

Improving any of the three (recruitment, efficiency, or maximum) will improve Rate of Force Development. However, in training to improve RFD at the expense of everything else, we sacrifice the ability to perform near-max lifts for high repetitions. This is especially true of the Olympic lifts, which rely on peak coordination between all THREE elements of RFD. As your 1-rep max increases, the percentage of 1RM you can do for 5 reps decreases. A powerlifter or long-jumper wouldn't care; they're after the one-and-done, all-or-nothing attempt. 

CrossFitters, though, are after high volumes AND large loads. How do we improve both our max lifts AND our ability to lift near-max weights? By shifting our priorities back and forth.

Consider 'Grace.' A novice CrossFitter may struggle to lift 135lbs overhead…period. Is the novice better served to practice doing 30 reps of ground-to-overhead with 95lbs, or to try to build his max clean and jerk to 150lbs? The answer is yes. To both. But the max comes first. The curve must be pulled up from the top, not pushed up from the bottom.

STRENGTH CURVE CROSSFITTER
Generating more power in one movement is a two-part process, involving both RFD improvement AND reduction of inhibitors. Your body has automatic "emergency brakes" – part of the Golgi Tendon feedback loop – that tell your CNS to slow down or risk injury. Unfortunately, this inhibatory response is set at very low levels, and the more sedentary you are, the worse your inhibition levels. As inhibition is reduced, though, recruitment speed improves, and the weight goes up. Inhibition is reduced through the use of maximum speed OR maximum load. This is where plyometrics fit into power development, by the way. 

When bar speed, jump height, or foot turnover begins to slow, you're no longer improving RFD. When you're doing high-rep box jumps, you're not improving power (though you ARE improving capacity at the lower weight.) 

Want to get Grace as Rx: 135lbs for 30 reps, ground to overhead? Build up your max. Improve your ability to generate power. Lesser weights – even your old maxes – will feel easier without the pressure of the emergency brake. 

Low weights are great for improving efficiency of movement. To really improve your body's ability to generate power, though, you must lift heavy and fast.

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