We all love a good box jump, the mental challenge of attempting to jump on top of a box that is higher than what we consider is humanly possible is a fantastic exercise for us and our clients in itself let alone the physical benefits. It teaches our clients a lot about mental fortitude and self belief.
The box jump is obviously part of the plyometric family and used as a speed/ power development tool for the legs. We can obtain fantastic improvements through our stretch-reflex cycle primarily in our lower legs and Achilles which transfers to a more rapid force output and therefore making us more powerful.
I don’t mind this so much as for the most part our typical clients aren’t training to become Olympic athletes, however! What I do mind is the lax nature in which personal trainers prescribe box jumps to their clients, whom for the most part are not ready for the complexities of the movement. PT’s don’t really understand these complexities and hence why they throw the movement out there like it’s going out of fashion.
When we run we have on average 2-3x our body weight going through our ankles, knees and hips at the point of contact with the ground. The average person only has around 20cm of lift off the ground, so how much force is generated and travelling though our joints when we jump of a 60cm box? The anecdotal answer is...a shitload!
This wouldn’t be a huge issue if our clients were only performing 3x6 with a 3min break between sets (This would be a typical prescription for power development). Instead we prescribe 15-20 reps during a circuit when our stabilisers are fried from the other 3, 4 or 5 movements included in the circuit. This in turn already puts our clients in a vulnerable position even before they have started their box jumps!
Let’s look at the numbers game a little more closely. So if the client has been prescribed 20 box jumps as part of the circuit and they are going to complete 5 rounds of that circuit, some basic maths tells us that equals 100 jumps or 100 contacts which is how volume is measured with plyometrics. Now what if I told you that in a typical power development session performed by novice athletes sees them perform no more than 60-100 contacts in a typical session!
The two really big considerations here is the fact that one, they’re athletes! Comparatively they have had significantly more training to deal with the stresses compared to the barely trained average Joe that’s rocked up to their first small group PT session in the gym. The second consideration is that all the athletes jumps/reps for the most part are performed in short sharp bursts where they are relatively fresh, not fatigued such as in a typical circuit environment where we find most box jumps performed in a gym. It’s the combination of these two points that sends the injury risk sky-high for our client’s, their ankles, knees, hips and lower back all become vulnerable.
So in conclusion be sure to think twice about who you get to perform a box jump, the environment in which you prescribe them and monitor the volume or reps you prescribe. Our average clients don’t need 15-20 jumps per round in a circuit environment, keep that mark closer to 8-10 and have the focus on quality not quantity. No one likes to see 15-20 jumps where the knees are buckled and the back is flexed forward it makes the movement hard to watch and the joints themselves hate you for it!
Tell us what you think, do you use box jumps with your clients? Leave us a comment below!
Tristan Hill, Masters of Sports Coaching, author of Lifting the Bar and mentor to Personal Trainers.