We saw in chapter 2 that the core stability muscles (transversus and internal oblique especially) tighten and pull the abdominal wall flat, while the external oblique and rectus muscles actually move the trunk against resistance. But, if we practise core stability and perfect the abdominal hollowing technique (exercises 14-18, pages 91-5) how will this change the way we perform normal abdominal exercises in the gym such as sit-up, crunches, and leg raises? Part of the answer to this question was discussed in chapter 6 when we saw that abdominal doming is caused by performing an abdominal exercise without firstly hollowing the abdominal wall by working the core stabilisers. Researchers at James Cook University in Australia¹ used EMG recording of the abdominal muscles to determine the difference between performing a standard abdominal exercise, and of performing the same exercise but using abdominal hollowing first. They found that by initiating the exercise with hollowing, subjects did indeed activate their transversus and internal obliques muscles before their rectus. This process is called selective recruitment and is an important method of dictating the order in which a group of muscles contracts. It confirms the importance of hollowing to ‘set’ the stability of the trunk before performing any sit-up type exercise.

Exercises such as sit-ups and leg raises have been used since Victorian times, and crunches and trunk curls became fashionable in the late 1960s and early 1970s. The 1980s saw research into spinal stabilisation and the gradual adoption
of these exercises into the fitness world under the general term ‘core exercise’. Instructors and manufacturers are continually inventing new exercises and training devices in the search for better movements, but are these exercises really better, or just more of the same? This was the subject of research from California State University in Sacramento².

These researchers looked at three exercises: an abdominal frame (exercise 47, page 128); hanging knee raise (exercise 73, page 158) using straps; and a ‘powerwheel’ which is a commercial exercise similar to exercise 56, page 138. They found that the powerwheel gave the most intense muscle contraction and used the spinal muscles and latissimus dorsi as well, indicating its use as an overall stabilising movement. The powerwheel also activated the hip muscles due to the leg motion involved. These new exercises are effective for general stabilising movements, but not for muscle isolation actions.

Many physiotherapists and personal trainers stress the importance of correctly performed abdominal exercises, and in chapter 7 we saw some of the potential dangers of poor exercise technique. But does research support this approach?

One of the most important teaching points of sit-up type exercises is to warn users not to link their hands behind their neck and pull the head forwards (cervical flexion). Neurosurgeons in Denton, USA³ described the tragic case of a 14-year-old boy who was a competitive wrestler. This subject performed sit-ups with his hands behind his head as part of a daily fitness routine. After one such workout he suddenly experienced total loss of movement (paresis) of his arms and weakness of his legs. He was rushed to hospital and underwent an MRI scan. One of the ligaments (ligamentum flavum) in his neck had been stretched so forcefully that it compressed his spinal cord, effectively cutting off its blood supply. This type of injury is normally only ever seen in older people who have severe degeneration of the bones in their neck. Thankfully the teenager recovered, but this case should sound a warning bell in every gym. Had this boy pulled a little bit harder or exercised slightly longer in this workout he may have been permanently paralysed.

Doctors from the department of neurology at Penn State College of Medicine in America⁴ again looked at sit-up exercises, but this time at the tragic effects of holding the breath (valsalva maneuver) while straining to perform the exercise. An important teaching point with resistance exercise is to keep breathing – ‘breathe out on effort’ is an old adage still familiar to most gym users. These two reports showed what happened when exercisers did not adhere to this practice.

The first report was of a 37-year-old male who had been using rapid sit-ups without breathing correctly. He suddenly developed right-sided weakness and loss of sensation and was rushed to hospital. When there, it was noticed that his facial muscles on the right side had dropped and his strength reduced. In short, he had suffered a stroke! Over the next few days he developed a severe headache and a scan revealed that one of the most important blood vessels going to his brain (posterior cerebral artery) had been blocked. After five days he began to improve, but required intensive neurological physiotherapy to recover.