The war on isolation exercises
Compound v Isolation
All strength and conditioning coaches have heard it before: “compound is king”- rightly so.
Compound or multi-joint exercises are undoubtedly the most potent for increasing strength and power in athletes. Exercises like the barbell squat incorporate many muscle groups and generate large amounts of muscular and neural fatigue. Highly effective and time efficient, these exercises should form the basis of resistance training programs (1).
Next in line are isolation or single-joint exercises which are approached with more of a “do them if you’re not too tired” mentality. Isolation exercises are typically included as an afterthought and coaches tend to overlook their potential benefits for sport performance.
That said, let’s investigate the power of isolation.
The need for training variation
Along with specificity and total training volume, exercise variation is critical for activating and growing muscle groups. Completing a variety of resistance exercise at different angles will generate more fibre breakdown and muscle growth (2). Once an athlete becomes accustomed to a particular resistance exercise and workload, the coach must then select an appropriate variation to continue producing adaptations at the target muscle (3).
Isolation exercises provide variety within a training program. They allow the athlete to target a specific muscle group and overcome strength plateaus. By extension, isolation work assists compound lift performance and helps to keep training programs new and exciting for the athlete (4).
Just think of the variations of bicep curls that exist: barbell curl, preacher curl, hammer curl, Scott curl, Zottman curl, drag curl etc. These can be loaded through a multitude of different loading strategies (e.g. barbell, dumbbell, pin-loaded, cable etc.) with various grips, tempos and rep schemes. Utilising these variations breaks up the monotony of training and targets smaller muscles through a full range of motion.
The need for full range of motion
Isolation ensures that under-stimulated muscle groups are adequately developed.
Bicep curl variations produce more development at the target muscle compared to compound exercises. By contrast, multi-joint pulling exercises such as the seated cable row and chin-up limit the functional change in the length of the bicep throughout the range of motion (due to the angle of the shoulder and elbow joint), thereby limiting its force output and development (5).
The same is true for triceps stimulation during pressing exercises (e.g. overhead press). For optimal activation of the long-head of triceps, the shoulder needs to be flexed at 180° and the elbow placed through a full range of motion (6). This only occurs during specific isolation exercises such as the “skull crusher” and French press, where the long-head undergoes a full stretch and contraction during the movement.
A similar example is the difference in hamstring activation during the squat (compound) and leg-curl (isolation). EMG studies have shown that hamstring activation during the squat is only 50% of that achieved during the leg curl and stiff-legged deadlift (7). This has big implications for sport performance as the hamstrings are heavily involved in sprint deceleration and change of direction (8).
Thus, isolation exercises are needed to optimally engage vital muscle groups that are overpowered during multi-joint resistance exercises.
Breaking down sport specific movement
Strength programs should isolate the key muscle groups involved in sport movement. Isolation exercises ensure that the synergists involved in skilled movement are adequately developed (9).
Boxing as an example:
Boxers are often put through rigorous strength routines focusing on full body explosiveness and pressing power.
In order to maximise gains made by compound movements, small muscles that support the shoulder girdle need to be developed so they can both generate and absorbs forces during punching. The stabilising muscles of the shoulder girdle can only develop when fully lengthened and activated during isolation exercises, e.g. dumbbell external/internal rotations, loaded scapula retraction and lower trapezius activation drills (9,10).
Isolating the stabilising structures of major joints reduces the likelihood of injury.
Single-joint exercises place the targeted muscle under a loaded stretch that exceeds resting length and exposes the tissue to eccentric stresses. This leads to increased reactive strength, enhanced joint stability and heightened protection against eccentric forces (a major cause of hamstring tears and rotator cuff injuries) (5).
Isolation exercises are also beneficial for overcoming muscular imbalances caused by multi-joint exercises.
A common example is using the seated calf raise to reduce gastrocnemius involvement (due to the knee bend) and shift the focus on to the soleus muscle. An overpowering gastrocnemius is common in field/court sport athletes, and by effectively developing the soleus muscle athletes can improve sprint and countermovement jump performance (11).
Similarly, muscle imbalances caused by “bilateral deficits” can be resolved using unilateral single-joint exercises (12). For example, a cyclist completing single-leg leg curl to resolve a bi-lateral difference in hamstring power output when peddling.
Increasing force production
Along with muscle hypertrophy, increasing muscle length-tension caused by isolation exercises supports muscle force production. Training at long muscle lengths increases joint-tendon strength and increases maximal muscle contraction force at all joint angles (5,13).
For example, lengthening the hamstrings during a leg-curl increases muscle fibre stretch tolerance and increase the optimal length of force production (13). This adaptation allows field sport athletes to produce force at long muscle lengths when undergoing dynamic movement (e.g. jumping and stretching to catch or throw a ball).
Isolation exercises may also involve utilising open kinetic chain-exercises (where the lower portion of the limb is mobile) to support sporting movements. By activating key muscle groups during single-joint exercises, the athlete can gain better intermuscular coordination and neural recruitment of the target muscle group (14).
An example might be a footballer using the leg extension machine to promote the development of his/her quadriceps. By augmenting the optimal length of the muscle and gaining neural control of the knee extensors, the athlete will experience increased kicking power and knee stability during dynamic movement.
A valuable warm-up tool
Activating muscle groups using single-joint exercises before a resistance training session can increase force production during multi-joint exercises (14). For example, using banded hip abduction drills before squatting to increase femoral external rotator activation and improve squat technique.
Low-load isolation exercises are also useful as a warmup tool for targeting weak or underactive muscles and promoting neural activation of those fibres. In turn, this prevents the onset of technique breakdown and reduces perceived difficulty during multi-joint movements (5).
To sum up
Compound exercises are king.
However, isolation exercises can increase the effectiveness of a strength and conditioning program through the following mechanisms:
- Providing variation and increasing athlete interest
- Increase sport specific force production
- Targeting muscles through a full range of motion
- Exposing muscles to eccentric stressors and reducing imbalances
- Increasing length-tension relationships
- Activating muscles pre-session
- de França, H., Branco, P., Guedes Junior, D., Gentil, P., Steele, J. and Teixeira, C. (2015). The effects of adding single-joint exercises to a multi-joint exercise resistance training program on upper body muscle strength and size in trained men. Applied Physiology, Nutrition, and Metabolism, 40(8), pp.822-826.
- Trebs AA, Brandenburg JP, Pitney WA. Pitney. (2010). An electromyography analysis of 3 muscles surrounding the shoulder joint during the performance of a chest press exercise at several angles. J Strength Condit Res; 24(7): 1925-1930
- Fonseca, R., Roschel, H., Tricoli, V., de Souza, E., Wilson, J., Laurentino, G., Aihara, A., de Souza Leão, A. and Ugrinowitsch, C. (2014). Changes in Exercises Are More Effective Than in Loading Schemes to Improve Muscle Strength. Journal of Strength and Conditioning Research, 28(11), pp.3085-3092.
- Gilson, T., “Cisco Reyes, G. and Curnock, L. (2012). An Examination of Athletesʼ Self-Efficacy and Strength Training Effort During an Entire Off-Season. Journal of Strength and Conditioning Research, 26(2), pp.443-451.
- Schoenfeld, B. and Contreras, B. (2012). Do Single-Joint Exercises Enhance Functional Fitness? Strength and Conditioning Journal, 34(1), pp.63-65.
- Le Bozec S, Maton B, and Cnockaert JC. (1980). The synergy of elbow extensor muscles during dynamic work in man. I. Elbow extension. Eur J Appl Physiol 44: 255–269.
- Wright GA, DeLong TH, and Gehlsen G. (1999). Electromyographic activity of the hamstrings during performance of the leg curl, stiff-leg deadlift and back squat movements. J Strength Cond Res 13: 168–174.
- Timmins, R., Opar, D., Williams, M., Schache, A., Dear, N. and Shield, A. (2014). Reduced biceps femoris myoelectrical activity influences eccentric knee flexor weakness after repeat sprint running. Scandinavian Journal of Medicine & Science in Sports, 24(4), pp.e299-e305.
- Szymanski, D. (2013). Preseason Training for Youth Baseball Players. Strength and Conditioning Journal, 35(3), pp.63-76.
- Loturco, I., Artioli, G., Kobal, R., Gil, S. and Franchini, E. (2014). Predicting Punching Acceleration From Selected Strength and Power Variables in Elite Karate Athletes. Journal of Strength and Conditioning Research, 28(7), pp.1826-1832.
- Nagano A, Komura T, Fukashiro S, and Himeno R. (2010). Force, work and power output of lower limb muscles during human maximal-effort countermovement jumping. J Electromyogr Kinesiol 15: 367–376.
- Newton, R. and Kraemer, W. (1994). Developing Explosive Muscular Power: Implications for a Mixed Methods Training Strategy. STRENGTH AND CONDITIONING JOURNAL, 16(5), p.20.
- Aquino CF, Fonseca ST, Goncalves GGP, Silva PLP, Ocarino JM, and Mancini MC. (2010). Stretching versus strength training in lengthened position in subjects with tight hamstring muscles: A randomized controlled trial. Man Ther 15: 26–31.
- Mastalerz, A. (2009). Efficiency of single and multiple-joint exercises in high intensity training. Gait & Posture, 30, pp.S148-S149.