You may hear the terms “Unilateral”, “Bilateral” or even “Contralateral” and “Ipsilateral” thrown about in the gym or clinic. You may hear about the perceived benefits of incorporating these into your training, but have you ever wondered why this is so? The following article will provide you with insight into when, how and why to include these variations into your training or rehab programs.
So, what do these terms mean?
Bilateral: “Having or relating to two sides” i.e.: performing a squat with both legs, or a row variation with both arms at the same time.
Unilateral: “Relating to or affecting only one side of the body” i.e.: Performing a single leg squat, a lunge or single arm dumbbell press.
Contralateral: “relating to or denoting the side of the body opposite to that on which a particular structure or condition occurs”. A term typically used in a rehab or allied health facility.
Ipsilateral: “belonging to or occurring on the same side of the body”. A term also commonly used in a rehab or allied health facility.
The benefits of unilateral training:
1. The crossover effect.
An adaptation suggested to have first been discovered in 1984, the crossover effect refers to strength increases elicited in one limb, whilst only training the other. Early research was based on someone who tested the grip strength of their left hand and proceeded to train only grip strength in the right for a two-week period. Follow-up testing results showed an increase in left hand grip strength by 43%, despite only having trained the right. These findings have been supported by a meta-analysis performed in 2017 which found that to optimise contralateral strength improvements, training should include fast eccentric sets with moderate volume and rest.
2. Identify and reduce muscular imbalances.
Most people will have some degree of muscular imbalance, which can lead to poor performance and an increased risk of injury. Imbalances can be due to training history, sports and hobbies, previous injury and a number of other factors. Unilateral training assists to identify and address deficits in strength, mobility and motor control. When training to address imbalances, you should start on the side with the deficit and only match it with contralateral side. Whilst this means the contralateral side will be working at a submaximal rate, remember that improvements will continue to occur due to the above noted crossover effect. In the case of significant deficit, it may be beneficial to complete an extra set on the side experiencing deficit in order to further target the deficit.
3. Improved motor control, core stability and sport-specific movement patterns.
Unilateral movements in general will cause an increased demand of the core and pelvic stabiliser muscles due to the offset nature of each movement. The ability to hold your shape throughout a functional unilateral movement will increase the demands on your core in the frontal, sagittal and transverse planes (all three planes of motion). The added control requirements also force an improved stability through movement and hence improved motor control.
When to train bilateral?
Typically, the everyday person with no injury or significant imbalances should include both bilateral and unilateral movements in their training. Typically, bilateral movements should be used as your main strength lifts with unilateral movements added into your accessory movements or used as a main lift on alternate days. When your aim is to move as much weight as possible for maximal strength or power, opt for a bilateral compound movement such as the squat or deadlift (or variations thereof). The benefits of bilateral training include learning movement patterns and motor control in a more stable environment, a more stable position in which to perform the movement (less trunk stabilisation required) and the ability to tolerate greater loads (Think about the physiological and loading response to carrying 100kg in a barbell back squat vs 60kg in a split squat).
And no, you should not squat on a BOSU ball. Ever. (See unilateral training point 3 re. stability).
Some of our go-to unilateral movements for maximising the above noted benefits include:
- Barbell Split Squat. Replace the barbell with an offset kettlebell in the front rack for an added stability challenge.
- Staggered stance RDL. Use dumbbells or kettlebells and hold in the contralateral arm for an added anti-rotation challenge.
- ½ kneeling Single arm dumbbell overhead press.
- Alternating bent over kettlebell row.
Sam Rooney, Accredited Exercise Physiologist