In the quest to build firm, defined abs, many people focus on mat work – crunches, sit-ups, leg raises, bicycles etc., doing a high volume of repetitions. Another approach that fewer people do is add resistance to ab work exercises and reduce the total volume – fewer reps but higher intensity ones. Which is a better approach?
The best method for training a muscle group depends on your goal – are you trying to hypertrophy your ab muscles and get definition? It also depends on the predominant type of muscle fibers in that muscle group.
Muscle Fiber Types
As you know, there are two types of muscle fibers – fast-twitch and slow-twitch. Fast-twitch muscle fibers are large fibers capable of generating large amounts of force for short periods of time. However, fast-twitch muscle fibers are short on endurance and can’t sustain the force they generate, so they peter out quickly.
In contrast, slow-twitch muscle fibers are built for endurance. They aren’t able to generate as much force and power, but they have lots of energy-producing mitochondria to help sustain activity for long periods of time without “pooping out.” They’re great if you’re a distance runner or cycler.
Slow-twitch muscle fibers respond well to high volume, lower resistance exercise since that’s what they’re built for while fast-twitch muscle fibers grow best when you keep the resistance high and the volume lower.
Fiber Type Distribution
Most of us have a roughly equal quantity of fast-twitch versus slow-twitch fibers. Some athletes have a disproportionate number of one or the other. A naturally strong and muscular bodybuilder might have a higher ratio of fast-twitch to slow-twitch fibers while a long-distance runner would likely have a higher proportion of slow-twitch to fast-twitch fibers. This gives them an edge when it comes to running distances. Age is a factor too. As we get older, we tend to lose fast-twitch fibers at a faster rate than slow-twitch, although working those fast-twitch fibers with heavy resistance slows the loss.
Some muscle groups have a higher proportion of one fiber type over another. The abdominal muscles help maintain posture, therefore they have to have endurance since you’re using them all the time, even when you’re sitting and standing. As such, abdominal muscles have a relatively high ratio of slow-twitch to fast-twitch fibers. This doesn’t mean abs don’t have fast-twitch, “power” fibers – they do, but they’re built mainly for endurance.
What does this mean in terms of doing your ab work? You would expect high volume, endurance ab training, what most people do, to be effective since your abs are made up of a relatively high ratio of slow-twitch fibers. Indeed, this seems to be the case. A study using EMG analysis showed crunches and reverse crunches challenge all three abdominal structures – the rectus abdominus muscles, transverse abdominus, and obliques.
Optimizing Ab Work Training
No doubt, especially when you begin ab work training, high-repetition crunches and other mat exercises are a sufficient challenge to your abdominal muscles. The problem is your body adapts to high-volume training when you don’t add resistance. Over time, your abs need more stimulation than they get from doing hundreds of crunches. Don’t forget your abs also have fast-twitch muscle fibers that respond best to high resistance, low-rep training.
To maximize your training, add some resistance to your ab work exercises like weighted crunches. You can do this in a number of ways – by holding a weight plate across your chest when you crunch, a dumbbell or an exercise ball. You can also extend your arms behind your head to create a longer lever to increase the challenge.
If your goal is to build substantial ab definition, progressive overload is what causes the muscles to hypertrophy, not endless crunches with no resistance. You don’t have to add resistance to every set you do, but doing so for some sets will wake up your abs and give them the stimulus they need to grow.
Ab Exercises Alone Won’t Get You There
Don’t depend on abdominal exercises alone, even weighted ones, to get you defined, rock-hard abs. To see ab definition, your body fat percentage has to be below a certain level, under 20%. To optimize that part of the equation, focus on compound weight lifting using moderate to heavy resistance and high-intensity interval training.
Wait! There are still a few more things to consider in your quest to get firm, defined abs. Make sure your diet is in order – you’re consuming enough protein and aren’t eating processed foods and refined carbs. You’ve probably heard that diet accounts for 90% of the results you get. That’s right on target! You can’t build abs with a sloppy diet.
Finally, make sure the stress hormone cortisol isn’t working against you by getting at least 7 hours of sleep a night and finding better ways to deal with stress. Cortisol is an appetite activator and a muscle destroyer – not what you need when you want more ab definition.
The Bottom Line
Give your abs the challenge they need by working them against resistance during some of your workouts, but do this only after you’ve mastered your form without weights. Don’t get stuck in a rut where all you do is unweighted crunches. Throw in some planks too to work your entire core.
Don’t skip the bicycles either. A study carried out by the American Council on Exercise, showed the bicycle crunch is the best exercise for activating the abs, based on EMG measurements. Another exercise that ranked high in this study was ab crunches on an exercise ball. Add some variety! Working your abs in a variety of different ways keeps your muscles from adapting.
You won’t get the abs you’re looking for overnight, but you may not get them at all unless you continue to challenge your abs. Be patient, be consistent with your workouts without becoming “too” consistent, and keep your diet and sleep patterns in order. Doing these things will help you get there quicker.
References:
T-Nation. “Abs on Trial”
American Council on Exercise. “New Study Puts the Crunch on Ineffective Ab Exercises”
Super Abs Resource Manual. Len Kravitz, PhD.
Related Articles By Cathe:
Why You Can Benefit from High-Rep Resistance Training
Muscle Fiber Composition & How It Changes with Age
Can You Change the Ratio of Muscle Fibers You Have Through Training?
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