Exercises such as calf raises, leg curls and ab crunches are frequently used by personal trainers and strength & conditioning coaches with a background in bodybuilding or physiotherapy. In these exercises, it is attempted to train certain muscles such as the gastrocnemius or the hamstrings in isolation. It is believed that this isolated single-joint training eventually leads to an improved sport performance.
However, muscles such as the gastrocnemius and the hamstrings function in a complex inter-muscular coordination pattern in many sport movements. Specifically, these muscles span two joints (i.e., they are bi-articular) and have a crucial role in energy transportation from one joint to the other joint (4, 5). Single-joint training of these muscles therefore contrasts the functioning of these muscles in many sport movements.
Several sport coaches have long believed that this isolated single-joint training does not contribute to performance. Evidence from computational modelling studies and recent experimental studies among humans suggests that these coaches may have been right. In fact, the evidence suggests that isolated single-joint training may even be detrimental to performance!
“Evidence suggests that single-joint training may be detrimental to performance!”
Single-joint training and performance
In a classic modelling study by Bobbert and Van Soest (1) it was shown that an increase in muscle strength without an improved coordination lead to a decrease in vertical jump performance. Specifically, they increased the strength of the leg extensors by 20%, but they did not adjust the onset of muscle activation and showed that jump performance decreased by almost 10 cm.
Recently, these results have been replicated in human participants. Dalen, Welde, van den Tillaar and Aune (2) divided sport science students in a single-joint and multi-joint group. The single-joint group performed a ballistic squat without plantar flexion and a plantar flexion movement separately, while the multi-joint group performed a ballistic squat in which the plantar flexion movement was incorporated (figure 1).
The idea was that both groups trained the strength of the gastrocnemius, but the energy transporting role of the gastrocnemius (i.e., the coordination) was not trained in the single-joint group, while it was trained in the multi-joint group.
They showed that both groups improved their 1-RM squat, but only the multi-joint group improved the vertical jump performance. Moreover, the single-joint group actually showed a small decrease in jump performance, probably as a result of detrimental changes in the coordination (3).
These findings highlight the importance of coordination as an increase in strength by single-joint training of bi-articular muscles did not contribute to an improved performance and was even detrimental to performance!
Conclusion and practical applications
– Single-joint training of bi-articular muscles contrasts the functioning of these muscles during sports movements and may actually be detrimental to performance;
– Exercises such as hamstrings curls, knee extensions, calf raises, triceps extension, biceps curls and ab crunches probably all isolate the functioning of the bi-articular muscles and may therefore be detrimental to performance;
– Trainers should carefully think about the functioning of muscles during sports and incorporate exercises in which these muscles are trained in appropriate coordination patterns.
1. Bobbert MF and Van Soest AJ. Effects of muscle strengthening on vertical jump height: A simulation study. Med Sci Sports Exerc 26: 1012-1020, 1994.
2. Dalen T, Welde B, van den Tillaar R, and Aune TK. Effect of single vs. multi joint ballistic resistance training upon vertical jump performance. Acta Kinesiologiae Universitatis Tartuensis 19: 86-97, 2013.
3. Leirdal S, Roeleveld K, and Ettema G. Coordination specificity in strength and power training. Int J Sports Med 29: 225-231, 2008.
4. van Ingen Schenau GJ. From rotation to translation: Constraints on multi-joint movements and the unique action of bi-articular muscles. Hum Mov Sci 8: 301-337, 1989.
5. van Ingen Schenau GJ, Pratt CA, and Macpherson JM. Differential use and control of mono-and biarticular muscles. Hum Mov Sci 13: 495-517, 1994.