From Ergo Log
Most fitness trainers are not keen on crunch machines. All too often they’ve seen clients suffer nasty injuries on them. For those trainers the study that Danish sports scientist Emil Sundstrup published in the International Journal of Sports Physical Therapy contains good news.
Sundstrup discovered that crunches done on a Swiss ball are not only safer than crunches done on a machine, they’re more effective too.
Nearly all exercises for the muscles in the middle section of your body – in fitness jargon, the core – are more effective if you perform them on a Swiss ball rather than doing them on the floor. A Swiss ball is unstable, and maintaining your balance while doing an exercise requires your muscles to work harder.
Sundstrup wanted to find out which of these demand more of your core muscles: crunches done on a machine, or crunches on a Swiss ball. He attached electrodes to the subjects’ muscles and got them to perform both forms of the exercises. He made the Swiss ball exercises heavier by adding an elastic band.
The Swiss ball exercise activated the rectus abdominis – the washboard muscles – significantly more than the machine exercise did, Sundstrup discovered. At the same time, the Swiss ball exercise activated the thigh muscle rectus femoris by a significantly less amount.
“Both crunches performed on a Swiss ball and on an isotonic training machine caused high activation of the abdominal muscles”, the researchers summarise. “Specifically, crunches on a Swiss ball with added elastic resistance induces high abdominal activity accompanied by low hip flexor activity, which could be beneficial for individuals with low back pain.”
“Conversely, the lower levels of abdominal activity and higher levels of rectus femoris activity observed in the isotonic machine exercise warrant caution for individuals with lumbar pain.”
Int J Sports Phys Ther. 2012 Aug;7(4):372-80.