Why does my runner's arms pump up and down instead of swinging front to back?
Vertical arms take effort and give nothing back, and the fix is usually in the hands, not the shoulders.
Watch from the side and the arms look like they are working hard: a tight, fast pump straight up and down in front of the chest, almost like a boxer skipping rope. Watch the stopwatch and none of that effort shows up in the splits, because an arm swinging up and down is not swinging in the direction that moves a runner forward.
What the arm is actually for
A running arm swings front to back through the shoulder, roughly in the same plane the leg is driving in, and its job is to balance the opposite leg's rotation so the hips and shoulders don't twist against each other. That only works if the swing has a front-to-back path. Lift the forearm mostly up and down instead and it stops cancelling anything, which means the trunk has to counter-rotate some other way, usually by twisting more than it should.
Where it usually comes from
- Learned on a treadmill, where the belt does the forward work and nothing is pushing the runner to swing the arm back against the ground.
- Gripped fists and tight shoulders, which shorten the swing and push whatever motion is left upward instead of backward.
- Trying to pump harder to go faster, which with a bent, tense elbow has nowhere to go but up.
It is easy to miss from behind, where an up-and-down arm can still look busy, and easy to confuse with an arm swinging too wide, which is a side-to-side fault rather than a vertical one. The two look similar at a glance and call for different fixes.
What usually fixes it
Relaxed hands, a loose fist rather than a clenched one, and a cue to drive the elbow back rather than up, so the hand finishes near the hip pocket instead of near the chin. Seated arm swings, done slowly with no legs involved, let the athlete feel the front-to-back path without the whole-body tension that creeps in at speed.
The Film Room's elbow angle reading is a single number, the bend at the elbow against the roughly 90 degree norm, and it will flag an arm that is too straight or too folded. It will not by itself tell you whether that arm is swinging front to back or up and down. That is a question about the path the hand travels, not the angle at the elbow, and a side-on clip only answers it if you watch where the hand actually goes.
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Related
Should a sprinter run with clenched fists or relaxed hands?
A tight fist locks up the whole arm before it locks anything else, and the fix usually starts at the hand, not the shoulder.
Read →Why does my sprinter's arm swing look so wide?
Wide, flapping arms are usually a symptom of tension somewhere else, and it is a fault a side-on camera is not even positioned to measure.
Read →Why does my distance runner's arm swing get bigger as they fatigue?
Wide, flailing arms late in a race usually mean the legs have stopped producing enough force on their own, and the arms are trying to make up the difference.
Read →