Monday, 18 August 2014

The "Overshoot Phenomenon" (Part 2)

Carrying on from the previous post, both Andersen et al. (2000 & 2005) showed decreases in Type IIX and increases in Type IIA muscle fibres post training compared to baseline. Once these measures were taken, a 3 month detraining period was implemented. Detraining meaning no resistance training was performed and the subjects returned to their normal daily lives (subjects in both studies were sedentary, no previous regular resistance training and no regular exercise within the last year).

So what happens after a detraining period?

The proportion of Type IIX muscle fibres increased past baseline PRE training values while the proportion of Type IIA muscle fibres significantly decreased below PRE training values.  This is known as the “overshoot.” (Type IIX surpassing pre training values).

What about performance post detraining period?

Andersen et al. (2005) used isokinetic, maximal unloaded knee extension and evoked muscle twitch to measure performance.

Isokinetic testing if anyone didn't know what this machine was

Isokinetic muscle strength and power at 30˚ and 240˚ decreased back to pre training levels. However, angular velocity, angular acceleration, total moment of force, and power during the maximal unloaded knee extension all significantly increased past PRE and POST training values. Furthermore, peak twitch rate of force development (RFD) significantly increased post detraining compared to pre and post training.

An interesting point to note is that the subjects produced greater force post detraining at greater velocities compared to both pre and post training. Also, subjects produced more power compared to pre and post training at greater angular velocities. From these data, we could speculate that the overshoot may only relate to high velocity unloaded movements (E.g. punching, sprint cycling). However, I have also heard this method being used in bobsled with the starting push with great success so even some loaded velocity movements may benefit.

Part 3 will add a study looking at the overshoot with more of a performance based view in professional athletes to see whether or not this phenomenon can be seen in a sporting context. 

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