Maddigan et al have a really interesting study in the current issue of the Journal of Strength and Conditioning Research that compares the weighted sled push to the back squat in terms of muscle recruitment (measured by EMG) and joint angles. This is an interesting study because I’m not aware of too many studies that look at the weighted sled push in terms of muscle activation patterns and this is becoming an increasingly popular exercise in athletic and general fitness settings.
The authors had their subjects determine their ten repetition maximum on the back squat exercise. Their subjects also determined their twenty step maximum (i.e. ten steps with each foot) on the sled push. Once those values were determined, the subjects came back a few days later and performed their 10-RM squat and 20-step maximum on the sled push. As the subjects performed those tests, EMG and joint angle information was recorded.
The results are interesting:
- First, comparing the squat to the sled. Both exercise recruited the rectus femoris and biceps femoris similarly. However, the sled push resulted in more than 60% more gastrocnemius EMG activity than the back squat. In addition, the back squat resulted in almost 34% more erector spinae EMG activity.
- Second, the authors also looked at EMG activity over the time of the exercises (first two reps, middle six reps, last two reps). The rectus femoris, biceps femoris, and gastrocnemius all increased their EMG activity as the number of steps and number of reps increased from one to ten. This increase ranged from almost 23% for the rectus femoris, to almost 13% for the biceps femoris, to almost 11% for the gastrocnemius (the percentage represents the increase from the first two reps to the last two reps). This did not happen with the erector spinae.
- Third, the back squat had greater knee range of motion than the sled push. However, the sled push had a greater knee angular velocity than the back squat.
- Finally, the sled push involved much greater loads than the back squat (approximately 285% of bodyweight on the sled versus 127% on the back squat).
Why is this information important? It’s important because the squat is a stationary exercise. It’s important because the squat trains the athlete to sit down and stand up against resistance. While this is important, many sports involve a horizontal component. The athlete is trying to run somewhere, or jump somewhere, or throw something somewhere, etc. The squat lays a great strength foundation for this, but it does not do a good job training the horizontal application of force. The sled on the other hand, involves pushing a heavy object somewhere – i.e. applying force horizontally. The loads involved in the sled will teach the athlete to apply their strength in a horizontal direction!
Maddigan, M.E., Button, D.C., and Behm, D.G. (2014). Lower-limb and trunk muscle activation with back squats and weighted sled apparatus. Journal of Strength and Conditioning Research, 28(12), 3346-3353.
