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November 2011

When Pigs Crunch: A Commonsense Approach to Abdominal Training



From sit-ups and crunches, to planks and other “core” exercises, to a wide range of bizarre equipment that promise big results, the past several decades have seen a frantic, non-stop stream of opinions and approaches on how “best” train the abs. In recent years, the pendulum has swung widely from training the abs by doing high-rep crunches to the opposite extreme of eschewing direct abdominal exercises altogether. And just about everyone from the novice exerciser to the experienced fitness professional is confused about what to do.

Recently, numerous researchers, popular books and magazines have recommended avoiding crunches due to the potential for injury to the back. In this article, we’ll briefly examine the conclusions drawn from the research and, in the process, deliver practical, commonsense abdominal-training recommendations that you can utilize with both clients and in your own training.

The Problem With Crunches
Recent studies have concluded that repeated spinal flexion movements appear to increase the likelihood of disc herniation and prolapse. This has led to the proliferation of a vehement “anti-crunch” movement marked by a slew of abdominal training books and articles that are notable for their lack of abdominal exercises. However, once a few people started mentioning these studies and the “no crunches” fad caught on, many people neglected to examine what the studies actually said.

In short, most of these studies demonstrated that when you take the spines of dead pigs and put them through thousands (and in some cases tens of thousands) of spinal flexion cycles, there is a big increase in damage to the spinal structures.

The Problems With the Problem
You’re not a dead pig. You’re a live human—an obvious, but nevertheless extremely important distinction to make when drawing sweeping conclusions from this research. In a recent paper in the Strength and Conditioning Journal, Contreras and Schoenfeld (2011) highlighted three problems with concluding that crunches are unwise based on this research:
1. Living tissues remodel when stressed
2. Fluid flow is non-existent in dead tissue
3. Real-world exercises are not performed for thousands of reps at a time

Biology is driven by one simple rule: stimulus and response. When you stress different structures in your body through exercise, those structures repair and remodel themselves accordingly so they are equipped to handle the stress more effectively the next time it appears. Your spine and supporting structures and musculature are no exception. But the same structures in dead pigs don’t remodel simply because they are no longer alive.

Dead tissue exhibits outflow of fluid when stressed, but no inflow of new fluid occurs. When you flex your living spine, the discs experience outflow of spinal fluid when loaded. Conversely, when you extend and unload the spine, new spinal fluid comes back in. It’s like squeezing out a sponge and them dropping it back in water. When you release the pressure in a fluid-filled environment, the sponge immediately absorbs more fluid. In your discs, this means that when you unload, disc height is restored and normal disc biomechanics resume. When you squeeze the fluid out of dead tissue, it stays squished.

Most exercise programs feature a limited number of repetitions followed by a period of recovery and repair. For example, if you perform three sets of 15 repetitions of a crunch exercise, your training volume on the crunch is 45 total repetitions. This number, of course, cannot possibly be equated to thousands of continuous repetitions on dead tissue that cannot remodel from the imposed stress. This is worse than comparing apples to oranges. It’s like comparing fresh apples to rotten oranges.

Additionally, there are two other factors that raise questions about the validity of using the dead pig spine studies to draw conclusions about living human exercise. First, despite the commonly held belief that spinal degeneration is caused by wear and tear, this process actually plays a minor role in comparison to one’s genetics. Second, it is commonly noted that abdominal exercises increase compressive forces in the spine, with the implication being that this is undesirable. But is it? Contraction of the abdominal muscles also induces an increase in intra-abdominal pressure, which reduces compressive forces and facilitates fluid absorption in the discs. Significantly, none of the dead pig studies incorporated the effects of intra-abdominal pressure.

Potential Positives of Spinal Flexion
We know that spinal motion facilitates nutrient delivery to the discs. This is why the old recommendation to immobilize minor back injuries for several days has fallen out of favor. Interestingly, spinal flexion is superior to neutral and extended positions in promoting fluid exchange in the discs. A crunch-type exercise causes the posterior portion of discs to extend, and this tensile stress has been shown to reduce catabolic inflammatory responses in the discs.

When to Avoid Flexion
1. Immediately upon waking and for approximately one hour afterward. Discs are full of fluid and are at their peak height due to increased fluid retention during sleep. As a result, disc pressure is higher and they are less tolerant of bending stresses. About one hour after waking, discs have lost 90 percent of their height. This is why even people with healthy spines feel stiffer when bending down to grab the newspaper from the driveway in the morning.

2. After prolonged sitting. After a prolonged period of sitting, get up and walk around for five or more minutes before engaging in spinal flexion exercises. As they do during sleep, discs gain height after sitting, so getting up and moving around is recommended for the same reasons identified above.

3. If you have confirmed spinal pathology such as disc herniation or flexion intolerance.

Practical Application
Having identified some of the fallacies related to the conclusion that crunches are an unwise exercise choice, the question still remains: What is the best way to train the abdominals?

Total Training Volume and Rest Between Sessions
As the owner of a living spine, you want to allow time for the tissues to remodel after imposing the stress on them. For exercises involving spinal flexion, allow a 48-hour recovery period, which is consistent with the typical guidelines for muscle protein resynthesis in other areas of the body. After all, the abdominals are muscles and, as such, are governed by the same rules as other muscles. The recommendation for total volume of spinal flexion repetitions, regardless of the number of different exercises used in a training session, should be approximately 60 repetitions.

Two Types of Exercises
There are two types of exercises for the abdominals that fitness professionals can focus on: stability and mobility. Exercises characterized primarily by stability involve little spinal motion and, thus, little-to-no change in the length of the abdominal muscles, but may feature significant motion of the extremities while a static spinal posture is maintained. Many static exercises are done with a neutral or slightly flexed spine. By contrast, mobility exercises are characterized by significant motion in the trunk caused by length changes in the abdominal musculature. In essence, mobility exercises feature movement of the trunk, while stability exercises feature little-to-no movement of the trunk (but may exhibit significant mobility in the extremities).

With beginners and intermediate exercisers, the training focus can be shifted by focusing one workout on stability exercises and the next workout on mobility exercises. For more advanced individuals, the stability and mobility movements can be combined in a given training session provided the tissues are allowed adequate time to recover.

Repetitions Per Set

  • For mobility exercises, six to 15 repetitions are recommended given the fact that these exercises are used to increase strength and hypertrophy. Also, be sure to closely adhere to the 60 repetitions of total training volume per session.
  • For “true stability” exercises with little to no movement (e.g., plank), limit the duration of each set to no more than 30 seconds. In fact, multiple repetitions of a shorter duration (three sets of 10 seconds each) would most likely be more beneficial since the value in the exercise is in creating and releasing the plank with control.
  • For other stability exercises where a fixed trunk position is held while the extremities are in motion to create a greater stability challenge, six to 20 repetitions are recommended depending on the nature and difficulty of the movement.

Sample Exercises
A recent study in the Journal of Orthopedic & Sports Physical Therapy compared several abdominal exercises (eight stability ball exercises and two bodyweight exercises) and concluded that the roll-out and the pike were the most effective exercises in activating the upper and lower rectus abdominis and external and internal obliques, while minimizing lumbar paraspinal muscle activity (Escamilla et al., 2011). The first of the two sample exercises shown below is a combination of these two exercises, which greatly stimulate the abdominal muscles while placing less stress on the small spinal muscles. The second sample exercise is a “smarter crunch” variation that provides stimulus to more than just the rectus abdominis by using asymmetrical loads. By working other muscles in addition to the rectus abdominis, you increase the benefits of the crunch while also spreading the load across more muscles, thereby reducing the risk of the load transferring to the deeper spinal structures. Generally speaking, the more muscles that are recruiting during a crunch, the less stress is going to be placed on the bones and joints. 


Layout Pike With Stability Ball
Category: Stability
Reps: 6–10

Position: Begin facedown with your torso on top of the ball. Walk your body forward on your hands and assume a push-up position with your hands on the floor and your shins on top of the ball.
1. Brace your abs, bend from the hips, and drive your hips up toward the ceiling.
2. Your torso will stack over your head and hands while your legs roll up the ball. Your feet will be on the ball at the end of the movement.
3. As you lower your hips to return, drive your body back and down past the starting position so that your chest lowers toward the floor and the ball rolls up the front of your legs. In the final position, your body is fully extended in a straight line from your hands to your feet.
Performance Tips: Although the top pike position looks more dramatic, the bottom position is actually more challenging. This is because the point of contact with the ground—your hands—is far away from your abs. The fact that you are accelerating into the end position from a pike makes stopping at the bottom even harder. It may be helpful to do the first couple of reps a bit more slowly. To increase the challenge, walk your hands farther out. To make it easier, keep them closer to the ball during the set-up for the exercise.


Torso Offset Crunch With Stability Ball
Category: Mobility
Reps: 8–10 to each side

Position: With your body on top of the ball, your torso parallel to the floor, and your knees bent and directly above your feet, place both hands behind your neck with the elbows bent and out to the sides. Take a couple of very small steps to the right so that your torso is positioned slightly to the right of the middle of the ball. Perform half of your reps with your body offset to each of the right and left sides.
1. Use your abdominals to lift your chest up and forward in a crunching motion.
2. Stop when you feel the tension in your abdominals decrease or when your range of motion is complete.
3. Slowly return to the starting position.

Performance Tips: You should still perform a straight crunch, moving your torso just as you would if you didn’t have your body shifted slightly out to one side. Keep your hips and shoulders as square as possible. A small amount of rotation is unavoidable, because you have shifted your torso away from the middle of the ball, thereby increasing the balance challenge. As you perform the crunch, keep your torso slightly open to prevent excessive spine flexion and to keep your inner abdominals engaged.

Now You Know
It should be clear that crunches are neither to be absolutely avoided or used with abandon. Extreme positions grab headlines, but aren’t very useful in the real world. Like other muscles, the abdominals need to provide both stability and mobility at various times and to various degrees. Having a more complete understanding of when and how to use different types of abdominal exercises will enable you to discern the best possible training approach for each of your clients.

Contreras, B. and Schoenfeld, B. (2011). To crunch or not to crunch: An evidence-based examination of spinal flexion exercises, their potential risks, and their applicability to program design. Strength and Conditioning Journal, 33, 4, 8–18.

Escamilla, R.F. et al. (2011). Core muscle activation during swiss ball and traditional abdominal exercises. Journal of Orthopedic & Sports Physical Therapy, 40, 5, 265–276.


rossJonathan Ross, a long-time leader in the fitness industry, is the author of Abs Revealed, a modern, intelligent approach to abdominal training. He was awarded the 2006 ACE Personal Trainer of the Year and 2010 IDEA Personal Trainer of the Year, and is the host of the Discovery Fit & Health series Everyday Fitness. He can be reached at and

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