Center Mass Position in Forefoot Running Prevents Energy Loss

Forefoot running prevents energy loss in many ways. One way is by reducing the horizontal distance between the center mass and initial foot strike position.

In forefoot running, your center mass needs to be near your initial foot strike position. How come? The payoff is less energy expenditure, especially at faster running speeds and I will explain why in a moment. In contrast, a larger horizontal distance between the center mass and initial foot strike position increases braking and is typically associated with heel strike running.

The usual method of biomechanics recommends running upright and to never slouch forward. However, running too upright increases the distance between the center mass and initial foot strike position. Therefore, you are better off to slouch forward, like most Kenyan distance runners.

Keeping the Distance Between Your Trunk and Foot Strike Position Small

There are 4 factors involved in shortening the horizontal distance between your trunk and initial foot strike position during forefoot running:

1. Reduce anterior posterior trunk sway
2. ‘Lock’ center of mass in anterior position
3.  Increase cadence
4. Reduce stride length

Anterior posterior trunk sway affects the horizontal distance between the center mass and initial foot strike position. If the trunk sways back and forth, the horizontal distance between the trunk and initial foot strike position will correspondingly increase and decrease. Runners do best when they have minimal anterior posterior trunk sway and if they manage to keep their center mass more anterior relative to the lower leg (Mero et al., 1992).

Ultimately, stabilizing the trunk allows the horizontal distance between the center mass and initial foot strike position to remain relatively constant. However, the key is to keep this distance as short as possible.

• A runner may have minimal trunk sway, yet exhibit a horizontal distance between the center mass and initial foot strike position that is larger than normal. Again, heel strike runners are a perfect example of this.

• Ideally, you want to maintain an anterior position of the center of mass in forefoot running, meanwhile prevent your trunk from shifting back.

Furthermore, higher cadence reflects a shorter stride length, which keeps the center mass near initial foot strike position during forefoot running.

• In contrast, a longer stride length induces posterior acceleration of the trunk which increases braking and press force of the lower extremity during running.

Another benefit to having a small horizontal distance between center mass and initial foot strike position is that it reduces mechanical work at the knee.  Here’s a video showing how to use your center mass to making running easier on your knee:

The Take Home Message

A large horizontal distance between the center mass and initial foot strike position may account of the far slower turnover rates in a typical heel striker as compared to a forefoot runner.

The first step is to push your center mass forward when forefoot run and avoid reaching out with your swing leg. Nonetheless, a forward center mass position is mostly where your momentum comes from which is why shifting the center of mass back results in braking.

 

More From Run Forefoot:

• Tarahumara Indians: How they Run
• Heel Strike Exacerbates Overpronation
• Barefoot Sandals Prevents Runners Knee
• More Cushioning Does Not Mean Less Impact
• Forefoot Running Shoes

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References:

Lin et al. Impact of center of mass acceleration on the performance of ultramarathon runners. J Human Kinetics, 2014;44, 41-52.

Mero A, Komi PV, Gregor RJ. Biomechanics of sprint running. A review. Sports Med, 1992; 13: 376-392

Mero A, Komi PV, Gregor RJ. Biomechanics of sprint running. A review. Sports Medicine, 1992; 13(6): 376-392