Strength training: trunk exercises to improve core stability

One of the key messages that appears regularly in PP is that training methods and exercises must be specific if you want to improve your performance. This is especially true for strength training. For example, for many athletes one-legged squats are more specific than knee extensions. One-leg squats are performed one side at a time, in a standing position, with the ankle, knee and hip joints all working together in a similar way to running and jumping, while a certain degree of stability and balance is trained during the exercise.

The one-leg squat movement is related in function to natural athletic movements such as running and jumping, whereas the knee extension is related only to kicking in a seated position. As a consequence, athletes who spend time on the knee-extension machine will see fewer improvements than those who spend time performing one-legged squats. It’s not that knee-extension exercise will not strengthen the quadriceps; it’s rather that, for improved performance, we are not interested in training ’muscles’ the way a body builder wishes to. Instead, we want to improve the strength and power of ’movements’. If we focus our attention on successfully developing movements, then our time spent in the gym will have a greater positive effect when it comes to competitions.

In this article, drawing on a recent piece by Allen Hedrick (Strength and Conditioning Journal, vol 22⁽³⁾, pp. 50-61), I want to apply the principles of functional training to the trunk muscles. As Hedrick argues, many strength movements focus on legs and arms since these are the parts that perform the movements. However, the prioritisation of extremities over trunk fails to recognise that the majority of powerful athletic movements are either initiated or linked through the trunk area. Consider, as an example, a tackle in rugby. To perform a quality tackle, the driving force comes from the legs and the grasp is performed by the arms. However, the trunk ensures that the leg power can be transferred through to the grasp, thus delivering the tackle’s impact with little energy dissipation and less injury risk. A chain is only as strong as its weakest link; our aim is to ensure that there are no weak links in the core.

Hedrick’s key criticism of common practice is that many programmes neglect functional exercises in favour of those that develop ’six-pack abs’, in other words, focusing on muscles and not movements. To create a strength programme for the trunk that is functional and will thus have some positive effect on athletic performance, and not just how you look in the mirror, Hedrick suggests the following goals.

1. Exercises should be performed in a standing position
Ideally, most of your trunk exercises should be performed standing up, since this is the position of most athletic movements. In addition, while you’re standing the exercises involve all the trunk- and hip-stabiliser muscles and not just the abdominals or low back in isolation.

2. Training should target endurance, strength and power
The trunk muscles are important for maintaining good posture and spinal alignment. This is a 24-7 task - in other words, the trunk muscles have to perform this function all day every day and thus must have good endurance. The trunk muscles are also integral in power movements, e.g., throwing, jumping and hitting, and so strength and power must be developed. Thus, a trunk programme should contain a mix of low intensity/high repetition exercises with high-intensity and plyometric-type movements.

3. Exercises must be multi-directional
The trunk can ⁽¹⁾ flex forward and extend back, ⁽²⁾ flex to the left and right side, ⁽³⁾ rotate about its centre, and ⁽⁴⁾ perform any combination of the above movements in three planes. Exercises that integrate these three planes will provide the biggest challenge and benefits to an athlete looking to develop functional core strength.

4. Trunk exercise programmes must be progressive
Start with simple movements and progress to multi-plane movements when the basics are secure. Start with low-intensity exercises and add resistance to the movements once the technique is mastered and strength is improved. Progress your positions: from lying to sitting, to kneeling to standing, to standing on one leg, to standing on one leg on an unstable base. Start with slow and static exercises and progress to power exercises. To achieve these goals, Hedrick has separated trunk exercises into various categories, and scaled each exercise for difficulty within each category. By selecting exercises from each category you should train each kind of movement the trunk performs, and by starting with the easier exercises in each category you will progress safely and effectively. Here are some examples from each category.

Crunches

1. Ab crunch. Lie on back, knees bent, head off the floor, lower back flat on floor. Curl up shoulders and return.
2. Weighted crunch. Same as 1, but holding a weight disk behind your head for added resistance. Ensure you don’t pull on the head/neck.
3. Medicine-ball crunch throw. Sit on floor, knees bent. A partner throws a ball above your head; you catch the ball and return to a crunch position. Crunch up and simultaneously throw the ball back; receive the ball again at the top of the crunch.

Chops

1. Wood chop. Hold a medicine ball with arms extended above your head. Keeping your arms extended, bend down from the waist, touching the ball between your feet; return up to the top and repeat, just as if you were bringing down an axe.
2. Disk/wobble board one-leg ankle chop. Stand on one leg on a wobble board or inflatable disk. Perform the chop movement down to the left ankle, back up, and then down to the right ankle.
3. Disk/wobble board chop/throw. Stand on one leg on a wobble board or inflatable disk. Perform the chop movement down vigorously, throwing the ball to the floor. Catch the ball, return to the start and repeat.

Twists

1. Medicine-ball seated twist. Sit on the floor, knees bent. Lean back slightly, holding a medicine ball at arms length. Twist to one side and then back to the other side. Do not use your arms; initiate the movement from your trunk only.
2. Kneeling ball twist throw. Perform the above ball twist movement, kneeling, with knees shoulder-width apart. This time, as you twist, throw the ball to a partner 10m to your side.
3. Disk/wobble board one-leg twist throw. Stand on one leg on a wobble board or inflatable disk. Perform the twist-and-throw movement in this position.
4. One-leg speed rotation. Stand on one leg. Turn and look over your left shoulder with your arms extended out to the side. Your partner throws the ball over your left shoulder; you catch it and immediately rotate to your right and throw the ball back. Stay looking over your left shoulder, receive the ball again and rotate to your left, etc.

Pushes

1. Medicine-ball push down. Perform the crunch movement, holding a ball directly above your head. As you reach the top of the crunch, your partner pushes you back down to the floor. Resist the push but let your shoulders return, and then repeat.
2. Leg pushes. Lie on your back with your legs straight. Hands behind your head, hold on to your partner’s ankles for stability. Raise your legs so your ankles are above your hips; at the top, your partner pushes your legs back to the floor. Resist the push but let the legs return and repeat.

Raises

1. Back extensions. Lie in the back-extension bench holding a weight plate to your chest. Lower down 45 deg. and then raise back up to the straight position.
2. Reverse extensions. Lie the wrong way round in the back extension bench - head where your feet should go. Keep both legs straight, lower your feet to the floor and then raise back up.
3. One-leg back extension with a twist. Perform the back extension as in 1 above but with only one leg locked in the bench and add a twist to each raise so that first your left shoulder is pointing up and then on the next rep your right shoulder is pointing up.

I think you’ll be able to see from this varied selection of exercises that you can train all the muscles in the trunk area and perform movements in different planes and positions. This diversity should increase the functional improvements from the training programme. You will also be able to see that, with a little thought, it is possible to progress the exercises in terms of resistance, speed and complexity.

This isn’t an exhaustive list of trunk exercises, as there are other categories that can be trained - for instance, Pilates type, static bridging exercises and Swiss-ball movements. These can also be included in your programme to improve postural control and trunk coordination. The aim of this article is to set you thinking about how much time in your training programmes is spent developing the trunk, and how much thought is put into the exercises you use to train this very important area of the body.

Raphael Brandon