Which builds more strength and muscle mass: single- or multi-joint exercises?

In strength training, «single-joint exercises» are exercises involving only one joint. «Multi-joint exercises», on the other hand, work several joints at once. One example of a multi-joint exercise is squats, which primarily train the front thigh muscles and buttocks. Leg extensions also work the thigh muscles. However, since they only involve the knee joint rotating at a lever, the manoeuvre is referred to as a single-joint exercise. Both single-joint and multi-joint exercises increase strength and muscle mass. But which is more effective?

The latest study

Conducted in Brazil, the most recent study on this examined the influence of single- and multi-joint training on the biceps (m. brachialis, m. biceps brachii and m. brachioradialis) [1]. In order to reduce the impact of age and gender on adaptation, the researchers recruited 10 non-athletic men (age: 29.2 ±3.9 years) and had them train their biceps for eight weeks. Twice a week, the men carried out a multi-joint bicep exercise with one arm and a single-joint exercise with the other arm. The multi-joint exercise consisted of supinated dumbbell rows (surface of the hand visible, thumbs pointing outwards), while bicep curls were chosen as the single-joint exercise.

Choosing a study design like this rules out the influence of possible high- or non-responders within groups when they’re compared with each other, as each participant serves as their own control. The arms were selected at random. Participants trained their muscles over a period of eight weeks, carrying out four sets of 8– 12 reps in weeks 1– 4. In weeks 5– 8, the number of sets was ramped up to six. Exercises continued to the point of muscle failure. At the same time, the study particpants were asked to follow a diet high in protein and calories. The researchers also gave each person a nutritional supplement consisting of 132 g of carbohydrates, 17 g of whey protein and 1 g of fat before working out.

Bicep muscle thickness was measured via ultrasound at three different points (25%, 50% and 75% of the length proximal to distal), with the thickness representing the perpendicular distance between the muscle and the humerus.

Results and discussion

Eight weeks of resistance training led to an increase in strength in both arms. However, this was specific to the exercise tested. In other words, researchers assessed how much stronger the participants had become by testing the «single-joint» arm with both the single-joint and the multi-joint exercise. The increase in strength was significantly greater (P < 0.001) when the arm designated the single-joint exercise (bicep curl) was tested with the single-joint exercise compared to the multi-joint exercise (dumbbell row). This was also true when the reverse occurred.

One beneficial aspect of this study is that it measured muscle thickness at several points, whereas a comparable study [2] only took one measurement at one point on the arm. This is worth mentioning because the growth of the bicep muscle isn’t homogeneous. Consequently, strength training doesn’t induce uniform growth over the full length of the muscle [3], so it makes sense to measure muscle thickness at several points. The gold standard here would be to measure muscle volume using an MRI, but that’d be far more expensive than doing an ultrasound.

In a review by Gentil et al. [4], the authors concluded that studies examining strength and muscle size in the upper body for single-joint and multi-joint exercises didn’t observe any significant difference between types of exercise. This statement, however, should be taken with a pinch of salt. A systematic review and meta-analysis published recently attests that single-joint exercises have a slight advantage in terms of muscle growth compared to multi-joint exercises [5], just like in the study described above.

Since the study was conducted on non-athletic men, we shouldn’t simply assume the same results apply to athletic men, women, older people or clinical populations. Although researchers made a point of selecting exercises that were similar to each other, their biomechanics and strength demands on the biceps vary. What’s more, the only muscles examined were the biceps, so the study can’t draw conclusions about any other muscle groups.

So, which is more effective – single-joint or multi-joint exercises? To find out, we need more research and, more importantly, mechanistic findings. Personally, I prefer exercises that allow me to train specific muscle groups in isolation i.e. single-joint exercises, in order to exhaust them completely. Another plus point of single-joint exercises is that they’re less demanding in terms of coordination.

References

1. Mannarino P, Matta T, Lima J, Simão R, Freitas De Salles B. Single-Joint Exercise Results in Higher Hypertrophy of Elbow Flexors Than Multijoint Exercise. J Strength Cond Res. 2021;35: 2677–2681. doi:10.1519/JSC.0000000000003234
2. Gentil P, Soares S, Bottaro M. Single vs. Multi-Joint Resistance Exercises: Effects on Muscle Strength and Hypertrophy. Asian J Sports Med. Brieflands; 2015;6: 1–5. doi:10.5812/ASJSM.24057
3. Matta T, Simão R, De Salles BF, Spineti J, Oliveira LF. Strength training’s chronic effects on muscle architecture parameters of different arm sites. J Strength Cond Res. 2011;35: 2677–2681. doi:10.1519/JSC.0B013E3181DBA162
4. Gentil P, Fisher J, Steele J. A Review of the Acute Effects and Long-Term Adaptations of Single- and Multi-Joint Exercises during Resistance Training. Sport Med. Springer International Publishing; 2017;47: 843-855. doi:10.1007/S40279-016-0627-5/TABLES/3
5. Rosa A, Vazquez G, Grgic J, Balachandran AT, Orazem J, Schoenfeld BJ. Hypertrophic Effects of Single- Versus Multi-Joint Exercise of the Limb Muscles: A Systematic Review and Meta-analysis. Strength Cond J. 2023;45: 49–57. doi:10.1519/SSC.0000000000000720