Aug 18, 2008 – Crunches are great, but there is a way to do them that optimizes back support while stimulating all of the muscles that make up the core belt.
This is what Canadian researchers discovered1 who analyzed the activation of the abdominal muscles according to twelve postures adopted during sit-ups (sit-up, curl-up and crunch). For this study, they used 14 men aged 20 to 31 in good athletic shape.
The researchers were interested in three variables: the distance traveled by the hands on the ground during a straightening, the position of the knees (stretched or bent) and that of the feet (anchored or not).
The ideal position
According to the researchers, optimal activation of the abdominal muscles occurs when the trunk is raised 45 degrees and the hands, sliding along the body, travel a distance of 10 cm on the ground. This is called the half-righting position.
When the tilt of the trunk exceeds 45 degrees (and the hands travel 15 cm), most of the abdominal muscles practically stop working, while the muscles of the hips are unnecessarily strained.
Likewise, it is when the hands move 10 cm on the ground that the greatest activation of the inferior rectus muscle, which is usually difficult to activate, as well as the external oblique muscles is obtained. When the hands slide only 5 cm, the anterior rectus muscle of the thigh is less activated, while at 15 cm, the upper rectus is less strained.
Whether or not one bends the knees does not greatly affect the activation of the muscles, according to the researchers. On the other hand, fixing the feet does not provide any benefit for the abdominal muscles, but more activates the rectus anterior muscle of the thigh.
However, in addition to the half-upright, other positions evaluated help prevent back pain by improving trunk support and spinal stability.
” The crunches (when the hands travel 5 cm) are effective for the upper part of the abs, while cross-crunches (curl-up) work the oblique muscles more, ”concludes David G. Behm of the University of Newfoundland and lead author of the study.
Claudia Morissette – HealthPassport.net
1. Parfrey KC, et al, The effects of different sit- and curl-up positions on activation of abdominal and hip flexor musculation, App. Physio. Nutr. Metab. Flight. 33. 2008. http://rparticle.web-p.cisti.nrc.ca [Consulté le 15 août 2008]
