Force Application Time: The Principle of Specificity

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Specificity of training is a core principle that dictates training should enhance a specific aspect of athletic performance or a specific physiological / biomechanical outcome.

The term “sport-specific training” gets thrown around frequently, but there is not a clear definition of what “sport-specific” means.

I operate from the definition that sport-specific training is training that enhances a specific aspect of sports performance, like maximum sprint velocity, time to first base, vertical jump height (if jumping is an important KPI for that sport), peak power of a sport-specific movement (like a baseball swing), throwing distance for a young quarterback, ball speed for a pitcher, etc.

Thus, sports performance training should seek to improve specific qualities of sports performance and not blindly aim to improve physical characteristics like mile time, max back squat strength, etc.

Let me be clear: I am not suggesting that aerobic capacity and max strength are not correlated with sport performance…I’m pointing the exact opposite: they are CORRELATED with sport performance. Training should not aim to improve sport performance correlates, it should aim to improve sport performance itself.

To do that, we have to break down what affects sports performance.

One of the most critical—and overlooked—aspects of sports performance is timing. Every movement in athletic performance happens within a specific time frame.

In American football, for instance, the average time between the snap of the ball and the time to collision between offensive and defensive lineman is 0.45s.

During sprinting, ground contact time at max velocity is 0.06 – 0.1s.

Thus, we must consider how training impacts performance within sport-specific time frames.

Hamstring strengthening, for instance, is commonly prescribed as a preventive measure for ACL tears. However, maximum strength takes a minimum of 0.3s to achieve, while ACL tears happen in about 0.06s.

You can improve max hammy force production all day long, but if it doesn’t affect force production over the first 0.06s of initiation, it likely isn’t having any protective effect at all.

The same goes for sprint performance. If you add 50 pounds to your back squat, is that guaranteed to make you sprint faster?

Optimizing force production within the sport-specific timeframe is where athletes will see the most transference to sport performance. Thus, if sport-specific training seeks to enhance specific sport qualities, training should seek to improve force production within the same timeframe that these sport qualities occur over.

If you think I’m against max strength training…not at all. But I recognize that max strength in and of itself is not the goal of training. I love max strength training because it DOES tend to increase the rate of force development which is why improving max strength DOES tend to improve sport performance.

But if max strength ceases to affect force production in the timeframe necessary, or the effect decreases, then it’s time to think about other training variables that influence performance.

The gold standard for assessing force over a specific timeframe (or time of force application) is force plates or isokinetic dynamometry, but not everybody is as lucky as I am to have access to such equipment.

A more practical way to test this is to use exercises that have the same time frame built into them as a conduit.

For a football lineman, for instance, who has 0.45s to generate force before collision, a drop jump with 0.45s ground contact time is a good assessment of the force production capabilities within that timeframe.

Assuming similar body mass and ground contact times (i.e., no technique change), improved drop jump performance indicates improved force production within this very sport-specific timeframe of 0.45s.

In plain English: the higher this lineman jumps, the harder he hits the opposing lineman when the ball snaps.

Thus, in this example, if hitting the opponent harder is the #1 goal of the training program, then the training should be centered around improving drop jump performance.

With nothing more than iPhone and some elbow grease you can film and roughly determine force application time for exercises like jumps, cleans, and other power / velocity based movements. You can’t determine braking time (as in jumps with a countermovement and drop jumps) with film, as you can’t see when muscles fire to begin decelerating the center of mass, but at least you’ll be able to assess acceleration time, which will give you a rough estimate of force application time.

Blindly chasing strength is optimistic. Luckily, strength IS a great thing and it DOES tend to improve sports performance, especially in youth and high school athletes. But the underlying reasons why often has more to do with rate of force development than anything else.

To best improve sport performance, and to best monitor your training programs, you have to consider timing and the sport-specific force application time.

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