Do quarter squats transfer best to sprinting?

Strength gains are joint-angle specific.

That means partial squat training makes you stronger at partial squats, but does not transfer to full squats. On the other hand, full squat training makes you stronger at full squats, and while it also tends make you stronger at partial squats, it usually does not work quite as well as partial squats.

This probably happens for two reasons.

Firstly, training at longer muscle lengths (like in full squats) involves regional hypertrophy that builds muscle size where it is best-placed for improving force production at long muscle lengths. Secondly, training at short muscle lengths (like in partial squats) produces greater gains in joint-angle specific neural drive (read more here).

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What about transfer to vertical jumping?

The joint-angle specific nature of strength explains the transfer between full and partial range of motion exercises. But how do full and partial range of motion exercises transfer to vertical jumping?

Many coaches have noted that the joint angles in partial squats are similar to the joint angles at the point of take-off during jumping (or in the stance phase of sprinting gait). Because of this similarity between joint angles, they have suggested that partial squats should transfer better to athletic performance measures like vertical jumping (and sprinting) compared to full squats, as they should produce the greatest gains in strength exactly where we need them.

And this makes a lot of sense.

On the other hand, most research performed to date shows that full squats are not only superior compared to partial squats for improving full squat performance, but also seem to have the edge in terms of improving vertical jump height (Weiss et al. 2000; Hartmann et al. 2012; Bloomquist et al. 2013).

So what is going on?

Recently, to explain this, I suggested that we tend to see a better transfer of full range of motion exercises to vertical jumping because at faster speeds the angle of peak torque moves to a joint angle that corresponds to shorter muscle-tendon lengths. This means that the angle of peak torque during a heavy full squat could actually correspond to an angle of peak torque during a vertical jump starting a partial range of motion.

What about transfer to sprinting?

Until recently, no researchers had assessed the effects of squat training with either a full or a partial range of motion on sprinting performance.

Several studies had been carried out in relation to vertical jumping, but obviously, given that strength is also force-vector specific, sprint running may not follow exactly the same trend as vertical jumping.

It is therefore fascinating that a new study has just been published, in which the researchers reported on the effects of partial and full range of motion squat training on both vertical jumping and on sprinting performances, in a group of collegiate athletes.

Here is what they found.

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The study: Joint-Angle Specific Strength Adaptations Influence Improvements in Power in Highly Trained Athletes, by Rhea, Kenn, Peterson, Massey, Simão, Marin & Krein, in Human Movement (2016).

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What did the researchers do?

The purpose

The study compared the effects of training with either a full squat, a half squat, or a quarter squat exercise on several measures of athletic performance (including vertical jumping and sprinting), in male athletes.

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The measurements

Before and after the training intervention performed in the study, the researchers took measurements as follows:

• Full squat strength – measured by 1RM squat to >110 degrees knee flexion

• Half squat strength – measured by 1RM squat to 85 – 95 degrees knee flexion

• Quarter squat strength – measured by 1RM squat to 55 – 65 degrees knee flexion

• Vertical jump height – measured by vertical jump height using a Vertec

• Sprint running performance – measured over 40 yards, using an electronic wireless timing system

• Transfer – the transfer effect coefficient (TEC) between the squat variations and the athletic performance measures was calculated as the change (effect size) in the non-trained exercise / change (effect size) in the trained exercise

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The subjects

The subjects comprised 28 healthy, male college athletes of all sports at various schools, who had >2 years of consistent year-round training, a parallel squat 1RM of at >1.5 times bodyweight.

Most of the subjects (24) were football players, and the remainder included track (1), basketball (2), and wrestling (1) athletes. The subjects were allocated into three groups: full squats (FULL), half squat group (HALF), and quarter squats (QUARTER).

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The intervention

All subjects performed 4 workouts per week for 16 weeks, using a daily undulating periodization routine, with the load increasing from 8RM, 6RM, 4RM, to 2RM over 4 workouts. Each week involved 2 lower body workouts and 2 upper body workouts. The lower body workouts comprised squats, power cleans, lunges, leg curls, and step ups.

The squat part of the workout involved 4–8 sets of squats (linear increase in volume over the 16-week period). Each group performed the squats at the prescribed depth for their group, followed by the other exercises.

FULL performed squats to a knee angle of >110 degrees of flexion. HALF performed squats where the top of the thigh reached parallel to the floor or to a knee angle of 85 – 95 degrees of flexion. QUARTER performed squats to a knee angle of 55 – 65 degrees of flexion.

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What happened?

Squat strength

As expected, there was joint-angle specificity of strength gains in each of the squat groups. QUARTER improved quarter squat 1RM by the most; HALF improved half squat 1RM by the most; and FULL improved full squat 1RM by the most.

The results are shown in the chart below.

Joint-angle specificity of strength gains!

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Vertical jump and sprint performances

Unexpectedly, QUARTER produced superior gains in both vertical jump height and 40-yard sprint running times, compared with both HALF and FULL.

The results are shown in the chart below.

Surprising superior effects of quarter squats!

The TEC calculations used to assess transfer produced the same results. QUARTER produced the greatest transfers to both vertical jump height (TEC = 0.53) and 40-yard sprinting time (TEC = -0.41). In contrast, FULL produced the smallest transfers (TEC = 0.06 and -0.09).

Additionally, when assessing the relationships between the squat 1RM variations and the performance measures, there were similar findings.

Quarter squat 1RM was more closely correlated with vertical jump height (r = 0.64) than either half squat 1RM or full squat 1RM (r = 0.31 – 0.43). And quarter squat 1RM was also more closely correlated with 40-yard sprint running time (r = 0.74) than either half squat 1RM or full squat 1RM (r = 0.49 – 0.57).

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What does this mean?

Squat strength

First of all, this study confirms that strength is joint-angle specific. Training with full squats produced the best gains in full squat 1RM; training with partial squats produced the largest gains in partial squat 1RM.

In fact, this study extends these findings even further. It shows that squat strength isextremely joint-angle specific.

Training with full squats produced the largest gains in full squat 1RM; training with half squats produced the largest gains in half squat 1RM; and training with quarter squats produced the largest gains in quarter squat 1RM.

So targeting exactly the right angle is critical when performing squats, if you want to increase squat strength to a specific depth.

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Vertical jump height

This study provides a completely new perspective compared to previous research exploring the effects of squat range of motion during training on gains in vertical jump height.

Based on this study, there may be benefits of training using partial squats for improving vertical jump height in collegiate athletes. In fact, it indicates that quarter squats may even be better than either half squats or full squats.

Even so, since previous studies have always found that full squats are better for vertical jumping than partial squats (Weiss et al. 2000; Hartmann et al. 2012; Bloomquist et al. 2013), the matter is certainly not closed. The jury is now out on whether partial squats are better or worse for that improving vertical jump height. We need more studies to determine the final answer.

Moreover, the population may be critical for determining the right squat depth.

Since full range of motion exercises are superior to partial range of motion exercise in terms of hypertrophy, full squats may be better than partial squats for untrained or intermediate lifters to achieve their full athletic potential quickly. On the other hand, hypertrophy may well be less relevant for advanced athletes with resistance training experience.

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Sprinting

This study indicates that there may be benefits of training using partial squats for improving sprinting. In fact, it indicates that quarter squats may even be better than either half squats or full squats3.

Since no previous study has compared the effects of training with full and partial squats on sprinting ability, some may now argue that quarter squats should be the default squat variation for improving sprinting! And yet, many previous studies have reported improvements in sprint running performance while using full and half squats, without comparing different ranges of motion, so this seems a little premature.

And, just as for vertical jumping, the population may be key for determining the right squat depth. Younger athletes may require full range of motion exercises simply to achieve hypertrophy. On the other hand, increasing muscle mass may not be a key goal for advanced athletes, with longer resistance training experience.

Moreover, if partial squats do improve sprinting performance more than full squats, the reasons why remain unclear.

Sprinting performance is strongly determined by the ability to produce horizontal force, which is driven by muscle forces generated by the hip extensors, most especially the hamstrings (Morin et al. 2015). And yet squats are not particularly useful for training the hamstrings muscles.

So why are partial squats useful at all?

Partial squats could transfer better to sprinting than full squats because they stimulate the hip extensors more than the knee extensors (Bryanton et al. 2012; Gorsuch et al. 2013), although differences in hip and knee extensor activation between partial and full squats are not always observed (Contreras et al. 2016).

This lack of agreement might be because of inter-individual variability in the way that the hip extensors are used. Figuring out the various strategies by which each of the hip extensors (gluteus maximus, hamstrings, and adductor magnus) contribute to hip extension in the squat according to squat depth and between individuals may be key to figuring out this puzzle (Vigotsky & Bryanton, 2016).

Alternatively, as suggested by the authors of this paper (Rhea et al. 2016), partial squats may produce a joint-angle-specific stimulus to certain muscles that better matches the joint angles using during high-speed running. Future research will need to uncover the underlying mechanisms!

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Conclusions

This new study reinforces the principle that strength is joint-angle specific, and indeed shows that squat strength is extremely joint-angle specific, with quarter, half and full squats all displaying specificity of strength gains. It also shatters the current paradigm that full squats are always superior for improving athletic performance (but bear in mind that this study did not measure gains in muscle size).

Only rarely do genuinely remarkable studies emerge in the field of strength and conditioning, that invite coaches to tear up the rulebook. More commonly, they appear in physiology or biomechanics, where research is constantly pushing the boundaries of what we know about how the neuromuscular system works.

We are fortunate to have see two such studies appear in a matter of months (and both in sprinting no less!) as this eye-opening training study follows hot on the heels of the first hip thrust training study, which supported the force-vector theory of training, and established the hip thrust as a key exercise for anyone looking to improve sprinting performance.