The Machine vs The Sand Bag

In the fitness industry today we see many professionals trying to lead their audience into a belief that different forms of movement are “functional”. Or different objects and exercises are more “functional” than others. Firstly, lets define functional. ‘Something that is made to do a specific job” - simple. A muscle is functional because it is designed to move a lever in one way, and apply force to the insertion point to create movement of a specific bodily segment, or multiple bodily segments (this is how we move). We have different axis’ which we can translate or rotate around (coronal axis, vertical axis and the anteroposterior axis) and 3 different planes of motion, which you are probably more aware of; sagittal, frontal and transverse planes. Our body, its anatomy and its muscles are ‘designed’ in a certain way, so that some have mechanical advantages to create movement in some planes, and other muscles are designed to move in other planes.

Force is force. All exercise, resistance training, even walking applies force. It applies a force that us as a human have to deal with. The quadriceps for example will not understand the different between walking, or a leg extension. Albeit walking will probably create less of a challenge to the quads, thus less force to be dealt with, whereas the leg extension will put a lot more torque demand at the knee and thus more of a quadricep challenge. For all the quadriceps know, its the same force, just of a different magnitude (less magnitude via walking)

Essentially the exercise selection does not make a workout more or less functional, exercise selection will just apply different forces to the same muscles/joints. As I have mentioned, a muscle has one job - create tension to apply a force to the attachment site where the tendon meets the bone. If you were to pick up a sandbag, or do a hack squat, the quad will do the same thing, the adductors will do the same thing, the glutes will do the same thing. They will all create tension so that the specific muscle can apply force to the corresponding attachment site. In the sandbag pick up, because you are moving in potentially a multitude of planes and around different axis’, there will be a much greater amount of muscles called upon to apply force to multiple segments. The quads will apply force to the tibial tuberosity to extend the knee, the qluteus maximus will apply force to the gluteal tuberosity to extend the hip, as well as the biceps will be applying force to the radius to flex the elbow. They will be doing their individual jobs. What makes anyone think that a muscle, with a specific job, will be asked to do something different just because someone is picking up an odd object, because it’s ‘functional’ bro. Muscles will not understand that you are picking up a sandbag, or doing a hack squat. The sandbag will ask for recruitment of more muscles in a dissipated fashion to allow movements at multiple joints to all combine together to pick the object up. The hack squat will mainly be asking for the quads to extend the knee as this is where the greatest torque demand is. Maybe 80% of the external load is challenging the knee (quadriceps), and the remaining 20% is being dissipated through all other muscles in the body. Whereas 50% the sandbag pickup may be challenging the one extensors, 20% the hip extensors, 10% the spinal extensors, 5% the elbow flexors and 1% from about 100 other muscles. These individual muscle do not understand anything but force production, they are just doing their job.

Then it comes down to application, and the considerations that need to be made upon choosing exercises. Many people will not have the available range, the load tolerance or the co-ordination to pick up a heavy object from the floor. If they fo not have the pre-requisites to perform a movement under load, this doesn’t mean the more they do it, the better they will get at it. You will be asking the body to do something it simply cannot do, and possibly create injury and dysfunction. Is that sandbag now less functional that a machine? Probably, because it’s actually now a risk for injury. If we look back to our earlier definition of ‘functional’ it is something that is made to do a specific job. This brings us to the question, is a machine, that is designed to challenge a muscle in a certain way (control for people available ranges, load tolerances and skill), actually more functional than common ‘functional’ pieces of equipment; like sandbags, medicine balls, KBs etc, that may create dysfunction due to the extremely high skill and mechanical ability needed to perform such lifts. Its not something that I am telling, its simply a thought that everyone should probably consider when it comes to understanding ‘functional training’

Muscles contract, they apply force to bone, and they produce movement or tension. They have no idea about the object they are picking up, or the handle they are pulling. Like I said, the quadriceps job in a sandbag squat, compared to a hack squat is exactly the same. They will apply as much force as needed to the tibia to produce knee extension. THAT IS IT. However the challenge to multiple other tissues, in different planes and around different axis’ that the sandbag pick up and squat will expose the body to may bring us into a position that we cannot tolerate, and thus cause injury, and like I mentioned, doing something that you cannot do will not eventually mean you can do it. Applying the same force, to the same muscle, in a safer environment, like the hack squat will probably be a safer option (and more functional)

But rotation is functional isn’t it?

Just because it is a different plane of motion around a different axis, this doesn’t change the role of a muscle tissue. A muscle, that is designed to create rotation will still apply force, to a bone, and produce movement. Whether the muscle is isometrically contacted during sagittal plane movement, or isotonically contracting during movement of the transverse plane, it will be still applying force to the same bone. Doing a single leg, single arm, contralateral medicine ball Russian Twist will not make that muscle (lets say external obliques) work in a different way. A restrained, supported torso rotation, on a cable machine will probably be a safer environment, allow you to put more of the external load through the desired tissue, and actually get more out of the exercise, and target muscle.


There is no functional way to exercise, nor is there more functional exercises than others. Creating functional, injury free, pain free movement will mean performing exercises and challenging tissues appropriately in whatever way necessary. Sometimes a leg extension will have much more benefit than a squat for a whole multitude of reasons, and WILL be more ‘functional’ considering the ability to handle forces, skill level, range of motion, injury status, load tolerance and so many more. The individual that steps off the leg extension having appropriately challenged their quads, built strength and resilience in the tissues surrounding the knee and finishes with zero pain, will definitely be more functional than someone who has performed a ‘functional’ front squat who has finished their 4th set with a niggling lower back and shoulder pain, because they don’t have the tolerance to load the spine, or load the shoulder in the extreme position that is required for front squatting.

Question your thoughts when it comes to ‘functional training’. Don’t get pulled into the bullshit.

Luke French, Health & Physique Coach | Published 3rd September, 2020

Personal training services in Tunbridge Wells, Sevenoaks, Tonbridge and Hildenborough. Local personal trainer.

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