Getting More Acceleration in Your Force – Pneumatics Unpacked

Pneumatics? Air resistance? Does it have any advantages over traditional resistance training? As with the treatise of ballistics, this article is a coming together of concepts around force, velocity, power and explosive power with a pneumatic spin.

Force = Mass x Acceleration

Continuing the theme of developing force capability (F = m x a), let’s see what pneumatics has to offer as a training tool. First, let’s unpack pneumatics a little. Pneumatics relates to air, and so therefore the mass of interest this training device provides, comes in the form of air pressure, which has different inertial properties to free weight or traditional resistance training. More specifically, free weight load has more inertia (resistance to change in motion) and is harder to get moving than the equivalent pneumatics load. Furthermore, once you get free weight moving it has greater momentum (harder to decelerate) than the equivalent pneumatic mass. In sum, pneumatic resistance has less inertia and momentum than free weight resistance, which in turn will affect the force/acceleration, velocity and power profiles when training athletes. If you want to understand pneumatics, to a deeper level I refer you to this article by Frost et al (1).

Force-Velocity Curves

Have a close look at the free weight (FW), ballistic (Ball) and pneumatic velocity curves of a concentric bench press across loads of 15 to 60% 1RM shown in Figure 1. Don’t worry too much about the statistical significance just concentrate on the trends you are seeing. A couple of observations would be: 1) that Ball loading results in greater velocity in the later stages of the movement, the effects of which reduce with increasing load, this confirming what I discussed previously in the "Getting More Acceleration in Your Force - Ballistics Unpacked" article; and, 2) pneumatic velocity appears greater from onset to termination of the movement across loads of 15 to 60%1RM compared to free weight velocity. In terms of the force signals, pneumatic type loading results in greater force outputs than free weights from 70 to 100% of displacement, due to less momentum to decelerate. If you are interested in seeing all these signals in detail refer to Frost et al (2).

Figure 1:  Free weight (FW), ballistic (Ball) and pneumatic (P) velocity curves of a concentric bench press across loads of 15 to 60% 1RM (from the thesis of David Frost)

Pneumatics and Power Development

So does pneumatic loading/training result in better power output compared to free weights? Looking at the velocity curves you would say that it's a no brainer. Frost et al (2) showed that pneumatic mean power was significantly greater (25-36%) across loads of 15-75% 1RM, than the same free weight loading. In terms of peak power Ball and P contractions were ~23% higher than free weight peak power. Interestingly the velocity/force contribution to peak power was ~67/33% for P and 45/55 for Ball. Pneumatic training allows a greater velocity contribution to power output, which may appeal if you are interested in creating a higher velocity athlete.

Figure 2: Stylised power-time curve

Pneumatics and Explosive Power Development

Finally, is pneumatic training good for explosive power development? To reiterate from previous articles, explosive power was related to early power development e.g. the rate of power in 100 ms as shown in Figure 2. Have a look at the velocity graphs again. What do you think or hypothesise? Because of the reduced inertia at the onset of the pneumatic contractions, you can see that early velocity is far higher than the other two contraction types, therefore you might hypothesis that there is increased potential for explosive power adaptation with pneumatic type training. Frost et al (3) compared the effects of 8 weeks of free weight and pneumatic training on a number of variables including power, across a spectrum of loads. It can be observed in Figure 3 that the pre-post changes in power for a 45% 1RM load, were greater in the pneumatic trained group and there was greater power output from 10-90% of displacement. The free weight trained group only improved power output towards the end of the movement. Though not power-time graphs, there may be some evidence for early explosive power adaptation using pneumatic loading, especially if taken in tandem with the velocity curves. A little speculative though. Some of you might have better data or more recent research. Please let us know if you have.

Figure 3: Pneumatic and Free Weight trained changes in power output at 45% 1RM after 8 weeks of training (adapted from Frost et al 2016)

Take Home Messages

In sum, pneumatics allows you to get more acceleration into your force at lighter loads, in comparison with free weight loading, due to the reduced effects of inertia and momentum. Because of this, pneumatic resistance provides an advantage in improving power at lighter relative loads (15-75% 1RM) and also might have benefits for explosive power training, because of it’s mechanical advantages at the onset of a contraction. Just remember free weight and pneumatics have different inertial properties, and therefore can be used to achieve different responses or adaptations to training.  

References

(1) Frost et al. (2010). A biomechanical evaluation of resistance. Fundamental concepts for training and sports performance. Sports Med. 40(4) 303-326. DOI: 10.2165/11319420-000000000-00000

(2) Frost et al. (2008). A comparison of the kinematics, kinetics and muscle activity between pneumatic and free weight resistance. Eur J Appl Physiol. 104; 937-956. DOI: 10.1007/s00421-008-0821-8

(3) Frost et al. (2016). Changes in maximal strength, velocity, and power after 8 weeks of training with pneumatic or free weight resistance. J Strength Cond Res 30(4): 934–944. DOI: 10.1519/JSC.0000000000001179