Education: Box Jumps

One of the ever so popular crossfit movements also happens to be on of my favorite movements…but it can also leave you crippled, injured, or just in a lot of pain if you don’t take care of yourself before and after. So how do we approach these?

Anatomy lesson…Lets look at the lower leg…your “calf muscle” is actually 2 different muscles (soleus and gastrocnemius). Something else you should be aware of is your achilles tendon.

Notice that these muscles are not very big. So it wouldn’t take a lot of reps to cause injury. Therefore proper warm up is crucial.

When you perform a jump (of any kind really) this what happens:

Phase 1 – Adopt a mid-foot balance, lean forward, lengthen spine, begin to swing arms backwards

Phase 2 – Continue the forward bend, storing elastic tension in your posterior chain (glutes and hamstrings), coiling your body down into the earth like a spring ready to jump

Phase 3 – You begin leg drive, pressing feet into the ground/initial surface as arms start to swing forward.

Phase 4 – You extend/open your hips forcefully, allowing knees and ankles to fully extend for extra power generation (think core to extremity).

Phase 5 – You consciously pull yourself to your target through the air. Even after the force generation is complete, you need to actively control your movement.

Phase 6 – You reach for your target with your feet, and ensure good posture for landing.

Phase 7 – (for crossfitters doing box jumps) – for the rep to count you must finish with open hips and straight legs.

How do we speed this up? How can we “land and stand” on top of the box with open hips and straight knees and still make reps count? Easy, we rebound off the ground making our “rest” be on top of the box.

Eccentric & Concentric.

“During an eccentric contraction (lengthening contraction), the muscle elongates while under tension due to an opposing force greater than the muscle generates.” (wikipedia). Think of this as “stretching” the muscle. Specifically to the calf muscles, when you stand on a curb/step and lower your heel past the step/curb. You are stretching your muscles, creating distance between the origin and insertion of muscle. Phases 1-3.

“A concentric contraction or shortening contractionis a type of muscle contraction in which the muscles shorten while generating force. This occurs when the force generated by the muscle exceeds the load opposing its contraction.” (wikipedia) This action allows you to lift weight, or in a box jump case, get off the initial objected (the ground) onto the desired platform, (the box). Phase 4-7.

Safety First.

If “jumping” is new to you, first make sure you have a solid air squat jump. Can you load your posterior chain (glutes and hamstrings) properly? Are you comfortable landing? Practice first by performing a jump from the bottom of your air squat. If that is comfortable, practice jumping over “lines/cracks” on the floor then move into jumping on to objects such as bumper plates on the ground then low boxes working your way up (mentally and physically) to the higher boxes that would be considered “RX”.

If the reps are high then you should make sure your ankles are exceptionally warm. You might even want to consider jumping up on the box and stepping down to prevent injury.

Mobility.

If you look at your WOD…whether it be The Open or just written on your whiteboard in your local box (or home gym)…and you see box jumps, mobilizing your calf/achilles area should be #1 on your list.

Some of my favorite tools to do this are:

Single lacrosse ball on a block