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May 12, 2016 7:25:05 AM

Unilateral exercises (UNI - meaning training one limb at a time) are becoming more popular in the world of strength and condition. Bilateral exercises (BLI) have had a strong foot hold in the world of strength training, but do unilateral exercises offer benefits beyond those of their bilateral buddies. Let's find out:



Bilateral Force Deficit (BLFD) Phenomenon:

The bilateral force deficit (BLFD) is a phenomenon in which the force produced per limb, when added together is greater than the total force generated with both limbs work simultaneously (2,3) . An example of this would be an athlete who's able to perform a single leg press with 110 lbs but only able to leg press 200 lbs with two legs. Research has found that the BLFD is greater in untrained athletes than trained athletes. Having said that, significant strength imbalances between limbs can exist even for athletes competing at the collegiate level.


BIL vs. UNI:

BIL and UNI have shown similar improvements in strength and power. Research has shown that BIL and UNI are equally effective at improve lower body strength and 40 meter speed in rugby players (4).  

UNI however, has been shown to be a more effective method of increasing single-leg vertical jumping ability than BIL (5). 


Unilateral Hamstring Training:

The results from the single-leg vertical jump test are fascinating because a large number of athletic movements are unilateral, not bilateral. A good example of this is sprinting. Sprinting speed relies heavily on each legs ability to generate massive amounts of force, very quickly in the horizontal direction. In theory, applying unilateral strength training to the glute ham raise movement, would be critical for improving an athlete's speed. 




Unilateral Strength Imbalances:

If you train regularly or train athletes regularly, you know that athletes can have significant strength imbalances between limbs. Balancing strength between limbs, specifically an athlete's right and left hamstrings is paramount for improving performance and decreasing the risk of injury.


Facilitating Unilateral Hamstring Training:

Until now, there has not been a glute ham machine (GHM) design that allows an athlete to perform a single-leg glute ham raise. The SpeedBot GHM design allows athletes to overcome the extreme torque angle relationship of a natural glute ham raise and maintain balance and control while performing ULI glute ham raise movement. More importantly because of the change in lever dynamics, athletes are able to perform the concentric phase of the single leg glute ham raise. For more on information on the change in dynamics - check out: The Single Best Hamstring Exercise


How To Strengthen Hamstrings With Unilateral Hamstring Training:

So how do we go about strengthening our hamstrings with unilateral training. If your goal is to build speed and power, then we'd recommend focusing on 3-5 sets of 3 reps with as little band resistance as possible. Your goal should be to perform high-quality, explosive reps.


Why 3 Reps?

We've found that athlete's power and velocity tends to taper after 3 reps. Focusing on quality reps per set is key to developing explosive power. If you want to do more than 9 total reps, increase the number of total sets, instead of the number of reps per set.


Training For Endurance:

Depending on where you or your athletes are at in their training macrocycle, it may be beneficial to perform more reps to focus on developing muscle endurance. Reps can certainly be added if the training focus is more geared towards endurance or speed-endurance. For more glute ham raise variations to help improve speed endurance check out: Improving Speed Endurance


Coaching Points:

General Points:

  • Unilateral glute ham raises are not intended for athletes who have just started strength training. Athletes should go through a "foundational" period that includes eccentric, isometric, concentric and loaded movements before including the UNI glute ham raise movement in their programming. 
  • Use a band that provides enough resistance so the athlete is able to perform the movement safely and effectively (i.e. make sure that the athlete doesn't hinge (excessively) at the hips unless the training focus is on performing a modified Razor Curl.) Single leg glute ham raise is an extremely difficult and there's no shame in using a high tension band.

Position and Movement Points:


  • Have the athlete place their opposite foot above the ankle roller with the ball and toe firmly pressed against the foot plate. This will help athlete maintain good positioning throughout the movement.
  • Have the athlete apply pressure with the ball of the foot and toe on the top of the foot plate during the concentric, isometric and eccentric portion of the movement to help maintain a level position throughout the UNI glute ham raise movement.
  • Maintain as much dorisflexion as possible with the foot that is locked into position under the ankle roller. This will ensure a more powerful contraction and will translate more effectively to sprinting.
  • Make sure the athlete's feet remain straight up and down on the foot plate and make sure that the knee doesn't externally rotate during the concentric phase of the glute ham raise movement.


We truly believe that the unilateral glute ham raise should be a staple movement for all strength and conditioning coaches. ULI not only balances strength between the right and left hamstrings, it also offers a higher level of training specificity for movements like sprinting.



If you enjoyed this article, we've got plenty more for you! Please check out our Next Level Hamstring Training eBook. It's probably the best hamstring training eBook ever written!



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1) Mullican, Kurt and Ramsey, Nijem. Are Unilateral Exercises More Effective Than Bilateral Exercises? Strength and Condititioning Journal 38: 68-70. 2016.

2) Bobbert MF, de Graaf WW, Jonk JN, and Casius LJ. Explanation of the bilateral deficit in human vertical squat jumping. J Appl Physil (1985) 100: 493-499, 2006.

3) Kuruganti U and Murphy T. Bilateral deficit expressions and myoelectric signal activity during submaximal and maximal isometric knee extensions in young, athletic males. Eur J Appl Physiol 102: 721-726, 2008.

4) Secher NH,. Isometric rowing strength of experienced and inexperiened oarsmen. Med Sci Sports 7: 280-283, 1975

5) McCurdy KW, Langford GA, Dosher MW, Wiley LP, and Mallard KG. THe effects of short-term unilateral and bilateral lower-body resistance training on measures of strength and power. J Strength Conditioning Research 19: 9-15, 2005.

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