You Cannot Crunch Your Way to Abs: Science Says So

Tom Kelso

Contributor - Strength and Conditioning

St. Louis, Illinois, United States

Strength and Conditioning

When I give my Strength Training 101 presentation to new recruits at the St. Louis Police Academy, one of the questions I hit them with is this:


All other factors being equal, which of these three options would be the most effective in the attempt to reduce abdominal fat?

  1. Abdominal crunches – two sets of 30 repetitions to muscular fatigue
  2. Abdominal crunches – four sets of 30 repetitions to muscular fatigue.
  3. Leg Press – two sets of 20 repetitions to muscular fatigue.



You Cannot Crunch Your Way to Abs: Science Says So - Fitness, fat loss, abdominals, ab exercises, weight management, energy expenditure, calorie burning, ab crunchesInevitably, most choose the second option, a few pick option one, and rarely does anyone opt for the leg press choice. After all, if two sets of an abdominal exercise are effective, then doubling the effort must be better, right? The truth is option three is the correct answer, which completely stuns them.


Hey Mr. Kelso, I can’t recall seeing a late-night infomercial with some dude on a leg press machine trying to shred abdominal fat.


Performing two demanding sets of leg presses utilizes more energy as compared to two or four demanding sets of abdominal exercises. More muscle tissue is involved – thus ultimately more calories are burned – so it is the best option, all other factors being equal. Remember, to lose body fat, a calorie deficit must exist. Additionally, one cannot spot reduce body fat!



Infomercials and ignorance aside, a study was recently conducted at Southern Illinois University Edwardsville to determine the effect of abdominal exercises on abdominal fat. 24 sedentary people (14 men and 10 women) between the ages of 18 and 40 years were randomly assigned to one of the following two groups: control group (CG) or abdominal exercise group (AG). Anthropometrics, body composition, and abdominal muscular endurance were tested before and after training. The AG performed two sets of 10 repetitions on seven abdominal exercises, five days per week for six weeks. The CG received no intervention, and all participants maintained a similar diet throughout the study.


The results of the study showed…hang on now… you are sitting down?…ready?




You Cannot Crunch Your Way to Abs: Science Says So - Fitness, fat loss, abdominals, ab exercises, weight management, energy expenditure, calorie burning, ab crunchesTheir epic conclusion was this: six weeks of abdominal exercise training by itself was not sufficient to reduce abdominal subcutaneous fat and other measures of body composition. However, abdominal exercise training did significantly improved muscular endurance to a greater extent than the CG. On the post-test, the AG performed a significantly greater amount of curl-up repetitions (47 ± 13) compared to the CG (32 ± 9).




Seriously, will we ever arrive at the day when those in the training world completely understand abdominal exercises are a poor choice for fat reduction? Probably not, as long as new abdominal devices and programs keep coming down the infomercial turnpike.


Fat reduction tutorial, time immemorial:

  1. Create a calorie deficit. Eat better foods.
  2. Perform high calorie-demand exercise. Involve the large muscles of the body.
  3. Train your abdominals sensibly, but understand you are working MUSCLE, not fat.
  4. Stay up late at night so you can laugh at the latest abdominal gizmo infomercial.
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