Differences in Forearm Muscle Activation between Amateurs and Pro's
Today I am going to review a fascinating 2009 article from the American Journal of Sports Medicine that studied forearm muscle activation in amateur versus professional golfers (source at the end).
This study took 20 right-handed male golfer participants and divided them into amateur (10-20 handicap) or professional (handicap <4) groups. 4 forearm muscles were tested using fine-wire electromyography/”EMG,” essentially inserting a small electrode into the muscle belly and recording muscle contraction; this was documented as a percentage of voluntary maximum isometric contraction on manual muscle testing. The 4 muscles tested were the pronator teres (PT) most importantly, as well as 2 wrist flexor muscles and 1 wrist extensor muscle. Forearm muscle activation was reported for each of the 5 swing phases: take-away, forward swing, acceleration, early follow-through, and late follow-through.
The intriguing differences between the amateur and professional golfer groups are below, and these two findings were statistically significant:
There was significantly greater PT activity in the lead arm of the professional golfers compared to the amateur golfers during the acceleration phase (88.1% vs 36.3% max. isometric exertion, p = .03).
There was significantly greater PT activity in the trail arm of the amateur golfers compared to the professional golfers during the forward swing phase (120.9% vs 57.4% max. isometric exertion, p = .04). (It just missed statistical significance but there was a trend toward greater PT activity in the trail arm of the amateur golfers compared to the professional golfers during the acceleration phase as well, 104.8% vs 53.1% max. isometric contraction, p = .08).
Perhaps take a pause here and grab a wedge (please don’t break anything). Take your grip and hold the club in front you. Step away from the lamps. Pick a forearm and rotate in one direction, then the other. Notice how lead arm pronation must occur with trail arm supination, and vice versa lead arm supination must occur with trail arm pronation.
Now back to the article and what I think are the biggest takeaways (no pun intended). Notice how, relative to the professional group, the amateur group over-activated their PT muscle during the forward swing phase, which is the phase at the start of the downswing. (Presumably, since it must occur together though it wasn’t specifically tested in this study, lead arm supination must have been simultaneously occurring). What does this trail arm over-pronation and lead arm over-supination mean for your downswing? It buys you the danger of an over-the-top motion and impending slice. The second takeaway (pun definitely intended) comes from how we saw the professional group showed significantly greater lead arm PT activation in the acceleration phase, which is the swing phase on the downswing from club-horizontal to impact. I think this reflects superior release and timing in the professional group compared to the amateur.
If you struggle with an over-the-top or out-to-in motion on your downswing, then perhaps try slow-motion recording yourself at the range. Watch the rotation of your forearms on the downswing, and see if trail arm pronation is occurring as you initiate your downswing and causing your club angle to steepen. As a swing thought, perhaps try to concentrate on calming your trail arm pronation and/or activating your lead arm pronation on the downswing. Now, relatively excessive trail arm forward swing phase pronation has to be taken into consideration with the rest of your swing, as a swing flaw occurring earlier in the swing may be the cause and is producing this compensation, and later in the swing you face the effect of this muscle activation pattern. Regardless, hopefully you learned something convincing today and that these brave study participants—nay, heroes-- who had their muscles penetrated by small electrode needles for science to bring you this information did not do so in vein.
Some quick limitations and caveats. 20 participants is a relatively small sample size. All participants were men. This study only looked at driver swings off a tee. Lastly, muscle activation was recorded but gross movement was not; hypothetically the PT for example could be active during isometric or eccentric contraction, not just concentric contraction (active pronation).
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Source:
Farber AJ, Smith JS, Kvitne RS, Mohr KJ, Shin SS. Electromyographic analysis of forearm muscles in professional and amateur golfers. Am J Sports Med. 2009;37(2):396-401.
