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Tag Archives: squats

De Villarreal et al have a really interesting study in the December issue of the Journal of Strength and Conditioning Research looking at the impact of different exercise protocols on the vertical jump. The authors studied college physical education students using one of five protocols: heavy full-squats, power half squats (i.e. to parallel), weighted counter-movement jumps (CMJ), plyometrics, and a combination of all. Subjects were tested on their vertical jump height and their performance on CMJs with 17kg, 27kg, and 37kg of added resistance.

All training took place 3 times per week for seven weeks:
• Heavy squat group: Gradually increased the resistance over seven weeks while decreasing the volume.
• Power half squat group: Gradually increased the resistance over seven weeks while decreasing the volume. The initial resistance was selected as the resistance that maximized power output, after the first week the resistance was increased each week and leveled out at weeks six and seven.
• Weighted CMJ group: Resistance was selected based upon what maximized power output. Initially the group exercised with 30% less than the amount that maximizes power output, over seven weeks this was increased.
• Plyometric group: sets of five rebound jumps.
• Combined group: Basically combined all the above workouts.

In terms of results:
• All groups increased the heights of their vertical jumps, the heights of their loaded CMJ height at each resistance, and the rate of force development during the loaded CMJs. There were no statistically significant differences between any of the groups.
• There were statistically significant increases in power output during loaded CMJs for the combined group and the weighted CMJ group only. However, all groups increased their power outputs by 3-13% at each resistance after seven weeks of training. So while this may not be statistically significant, it is an increase.

The results are interesting because essentially all the training programs worked. To me the most interesting result in the vertical jump height, the weighted CMJ testing condition isn’t really something that’s going to be duplicated on the field. The authors don’t give us the vertical jump values, only a graph so it is difficult to tease out the improvements in vertical jump. This suggests that heavy squats, squats done explosively, weighted vertical jumps, and plyos all improve vertical jump. The results are also interesting because the group with the greatest volume (the combined group) made the same gains as the other groups.

Now, there are some limitations. First, the subjects were college students. It’s very possible that strength trained athletes would have had different results. Second, the study may not have been long enough to tease out differences between the training programs. Third, all the squats and weighted CMJs are being done in a Smith machine which may impact both adaptations and transferability of the results. Finally, by using weights greater than that which maximized power output (the power squat group) or by using weights less than that which maximized power output (weighted CMJ group) both of these groups may not have made the gains that they could have as a result of the training.

De Villarreal, E.S.S., Izquierdo, M., and Gonzalez-Badillo, J.J. (2011). Enhancing jump performance after combined vs. maximal power, heavy-resistance, and plyometric training alone. Journal of Strength and Conditioning Research, 25(12), 3274-3281.

Brad Schoenfeld had a great review article in the December issue of the Journal of Strength and Conditioning Research on the back squat. A lot of this is information that I’ve seen before from the standpoint of what’s going on at the knee joint, what the various muscles during the squat, and how different techniques (high bar, low bar, feet wide, feet narrow, etc) influence everything.

Having said that, he had an interesting take on the role of the ankle joint during the squat, the gluteus maximus and the squat, and the role of the hamstrings during the exercise.

With regards to the ankle:
• The gastrocnemius is highly active during the squat. It has two functions during this exercise. First, it assists with knee flexion (i.e. the descent). Second, it keeps the tibia from moving relative to the femur. Now, why don’t I get a “pump” in my calves while squatting? According to Schoenfeld, this is because the gastrocnemius (which is bi-articular) functions isometrically during the squat.
• Weak ankle muscles (gastrocnemius, tibialis anterior/posterior) may contribute to greater valgus movement at the knees (i.e. the knees move in towards each other), which puts you at greater risk of ACL issues.
• Poor range-of-motion at the ankle also contributes to greater valgus movement at the knees and leads to the heels lifting off the ground during the descent, which increases ACL forces.

The gluteus maximus is an important muscle during the execution of the squat, functioning as a hip extensor. Its activation is greatest during the full squat. This suggests that if an individual wants to develop this muscle, deep squats are going to be the way to go.

The hamstrings have an interesting role during the squat. They flex the knee, but they also extend the hip. In theory this means that they are active throughout the entire range-of-motion of the exercise. Schoenfeld points this out well when he notes that, as a result, their length is going to remain fairly constant during the exercise (i.e. they will function isometrically). This constant activation is important because it takes the stress off the ACL during the squat. This also reinforces why the hamstrings don’t get much of a “pump” from performing squats.

Schoenfeld, B.J. (2010). “Squatting kinematics and kinetics and their application to exercise performance.” Journal of Strength and Conditioning Performance, 24(12), 3497-3506.