This article examined the effect of caffeine supplementation throughout a 36-hole golf study over the course of 2-days (18 holes each day). As an incentive for performance a $1000 purse was divided to the top finishers. 12 male golfers with a USPGA handicap between 3-10 and an average age of 34 (+/- 14yrs) were recruited as subjects. The study design was a simple yet well-respected randomized double-blind cross-over study. Breaking this down: First, the researchers randomly divided the 12 golfers into two 6-man groups, and what makes it double-blind is that the researchers didn’t know which golfer was assigned to which group. This is essential to remove the researcher bias of wanting the experiment to succeed. Lastly, “cross-over study” means that on day 1 let’s say “group A” receives the caffeine supplement while “group B” receives the placebo. On day two, it switches with group A now receiving the placebo, and group B receiving the caffeine supplement. This protocol eliminates the chance of one group being significantly more sensitive to the caffeine supplement.

The researchers did the correct statistical analysis for the data which was a multiple t-test analysis with Bonferroni corrections. What’s important here is that Bonferroni corrections are needed when sampling a large list of performance variables, such as the ones listed above. The more performance variables collected, the greater the chance of one of those variables being significant by random chance. Therefore, with the increasing number of performance variables observed, the significance threshold (p-value) is lower, and more difficult to achieve.  

Significant – Performance significantly increased with caffeine supplement *All moderate level of significance (< .05)

• Total score
• Greens in regulation (GIR)
• Drive distance
• Questionnaire-> energy and fatigue      

Not Significant – Caffeine performance doesn’t differ from placebo •    

• HR
• Breathing rate
• Peak trunk acceleration
• Putt posture

First, I wanted to note that it is interesting that the caffeine didn’t affect HR or breathing rate because in high enough doses caffeine typically stimulates the sympathetic nervous system, which includes hormones such as adrenaline. This shows that the caffeine dose was low enough not to elicit a significant sympathetic nervous system response. A major consideration to note, is that the study didn’t control against most subjects having an existing caffeine tolerance in the range of 35-300 mg per day. Since the control group wasn’t permitted any form of caffeine on one of the two days, some of the effect seen in the data could come from the negative withdrawal effects of not getting their normal dose of caffeine. A possible solution would have been to include a washout period, where none of the subjects would be allowed caffeine for multiple days prior to the study, to minimize withdrawal effects.

Secondly, the technology they used to collect biomechanics data has large sources of error due to its portability. So, it’s possible that the reason peak swing velocity isn’t significant is because the error is larger than the subtle change that occurred from the caffeine. That said, the biomechanics metrics should be considered inconclusive.

The most important metric to consider in this study is total score because for golf, this is the only variable that matters in determining a winner and a loser. All the other performance variables examined in this study can be considered sub-variables for researchers to try to create a detailed understanding of which specific part of their golf game is improving from caffeine supplementation. Looking at the full picture, I would conclude that caffeine has both a psychological and physical effect on one’s golf game. Drive distance and GIR significance reveal that the golfers are striking the ball more consistently and possibly with more power. On the psychological end, the questionnaire revealed that the golfers subjectively felt more energetic and less fatigued throughout the day, even though the energy expenditure was unchanged. Extrapolating this data to other sports, I believe that caffeine can provide benefit to anaerobic sports by increasing precision and power production, and benefits to aerobic sports by increasing overall time-to-exhaustion. In addition, caffeine has also been shown to attenuate negative short-term effects of sleep deprivation including reaction time and decision-making ability (1).

Other Citations:

1. Lieberman, Harris R., et al. "Effects of caffeine, sleep loss, and stress on cognitive performance and mood during US Navy SEAL training." Psychopharmacology 164.3 (2002): 250-261.