Today was a recovery focused day. 8 miles in the morning then 5 miles this evening all at a very relaxed and easy effort. After my evening run I jumped rope for 5:00- 100 single leg jumps on each leg, then 75/ 50/ 25/4 /4 /4 /4 all at a fast cadence. This is possibly, in my opinion, the single best exercise a jogger can perform. If you look at the mechanics of single leg jump rope you will realize that your foot plant is (needs to be) perfectly mid-foot.. it's not possible to heal strike. Your body has got to be perfectly balanced over your foot. The action of the single leg jumps is quite difficult and has potential to injure anyone, which is why it has such benefit. The foot strike, then rebound and toe off in jogging requires a very explosive and dynamic action in order to produce speed and efficiency. A balanced body that is efficiently placed over the foot strike, a mid foot plant and less time on the ground is where we all want to go! I feel that single leg jump rope is an opportunity for anyone that doesn't have perfect biomechanics to work towards possibly changing them. Not many other exercises will allow this !And I do believe that biomechanics can be changed using muscle balance and strength and good old fashioned will.
For example: If your hands are too low (down by your waist) when your arms swing you will expend more energy.. it's physics. If you don't believe me here is an equation that will prove me right:
θ'' = − g⁄R sin θ
I haven't got a clue what the hell that means but it is an actual equation to help calculate the energy required to swing a pendulum of varying length. For a real world example.. hold a 5# dumbell (and I know what you're thinking.. and I weigh 145#) straight down by your thigh on either side of your body, then swing your arm without bending it.. swing it quite far out in front and behind... you will feel torque through your core and your arm (if it's weak like mine) will feel the effort. Now: bend your arm all the way and bring the dumbell up to your deltoid/ chest.. now swing your elbow in a wide arc... not much energy is required to do that! Now think about swinging both your arms a gazillion times during a marathon.
Now, I know exactly what some of you are thinking.. you need your arm swing to balance and counter act the movements of the legs. Which is partly true. You do need some balance.. but if your core is reasonably strong there will not be as much need for the counter balance, the swing of your arms (elbows) while your hands are up near your chest will still be plenty. I should say too though that on the back swing, your arms and hands should be relaxed which will drop them some.. the idea is to simply eliminate the weight of your hands and forearms as much as possible.