Participant characteristics

Out of ten articles, four studies focused on male golfers [12,19,28,31], one study focused on a female golfer [30], and three studies investigated mixed-gender populations [19,32,34]. Additionally, two studies did not specify the gender of the golfers [33,35]. Furthermore, MF effects varied across age groups: five studies involved participants aged 18–22 [28,29,33–35], three studies included golfers aged 22–30 [19,30,32], and two studies focused on golfers aged 30–50 [12,31]. The literature includes four studies involving beginner golfers [29,30,33,34], three studies focused on sub-professional golfers [12,19,31], and three studies on well-trained golfers [28,32,35].

MF-inducing interventions

This systematic review included ten studies covering various MF interventions, including measures to induce MF and measures to recover from MF. As measures to induce MF, Shin et al. [30] required participants to transcribe a neutral text at their fastest speed participants in the experimental group had to omit all letters "e" and "t", inducing MF by violating habitual writing practices. Doan et al. [28] used a continuous 36-hole official competition and Runswick et al. [33] used a pressure competition scenario, simulating actual competition pressure to induce MF. Measures to recover from MF mainly included nutritional supplements and psychological strategies, such as Stevenson et al. [19] and Mumford et al.’s [12] caffeine-containing drinks and supplements, as well as Nagashima et al.’s [35] carbohydrate supplement gummies, aimed to alleviate MF, increase alertness, and reduce fatigue to improve performance. Psychological strategies aimed to improve performance by adjusting the athletes’ psychological state, such as Lam et al. [29] preparation and execution following a successful putt and Galanis et al. [34] self-talk strategy.

The MF intervention scenarios included a laboratory scenario, a simulated match scenario, and an actual match scenario. Three studies focused on match scenarios [12,28,35], one study investigated simulated match scenarios [19], and six studies investigated laboratory scenarios that focused on technique/skill, specifically putting performance [29,30,31,32,33,34] The short-duration studies are all from the laboratory, while the long durations are all based on competition scenarios. For example, six studies examined activities lasting 1–30 minutes [29,30,31,32,33,34], three studies investigated activities lasting 120–240 minutes [12,19,35] and one study explored activities lasting over 240 minutes [28].

Because of the different research scenarios, the tools for detecting MF are categorized in two ways. Five out of ten studies detected MF through subjective measures of Visual Analogue Scales [19,28,35] and Questionnaire [30,34]. The other five studies identified the effects of MF through Cognitive Performance [12,29,31,32,33].

Effects of MF on golf performance

Doan et al. [28] demonstrated in their study that physical fatigue and MF significantly increased as the number of holes played in a 36-hole golf tournament progressed, leading to a decline in overall golf scores. Shin et al. [30] supported this observation in a laboratory setting, showing that MF significantly impacts putting performance. Campbell et al. [31] and Carnegie et al. [32] explored the potential moderating effects of different skill levels of golfers on intervention outcomes. While their study designs varied, their results indicated potential differences between high and low-level golfers in response to MF and performance.

Galanis et al. [34] found that self-talk strategies significantly reduced the occurrence of MF and markedly improved golf putting performance. This suggests that cognitive interventions can enhance athletes’ focus and performance levels.

On the other hand, Mumford et al. [12] highlighted the benefits of caffeine supplementation in enhancing alertness, confidence, and attention during golf competition, while reducing the experience of MF. Nagashima et al. [35] further supported this finding, showing that continuous ingestion of carbohydrate supplements lowered perceived fatigue levels and increased attention and relaxation. Stevenson et al. [19] confirmed that using carbohydrate-electrolyte formulations containing caffeine significantly improved golf putting accuracy.

Participant characteristics

Only two studies focused on high-level athletes [12,28], and even four studies had participants who were beginners who had never been exposed to golf [29,30,33,34]. Because high-level athletes and beginners may exhibit significant differences in their responses to MF, intervention effects, and golf performance, results from studies on beginners cannot be directly generalized to high-level athletes. This limitation may restrict the generalizability of study findings. Focusing excessively on beginners or individuals who have never been exposed to golf may lead to gaps and shortcomings in theoretical development, intervention design, and practical application. To comprehensively understand the role of MF in golf, future research should prioritize investigating high-level athletes and conducting comparative analyses across different levels of athletes.

MF-inducing interventions

Prolonged engagement in competitive golf, with its unique demands, may induce hormonal changes that impact immune function and influence overall performance on the course. Doan et al. [28] shed light on the potential consequences of extended golfing on hormonal balance, particularly the delicate interplay between testosterone and cortisol levels. Elevated testosterone levels, often associated with aggressive moods, might not align with the requirements for optimal golf performance. Interestingly, the study by Filaire et al. [36] found essential connections among cortisol levels, physical state anxiety, and cognitive state anxiety. Considering the complex relationship between MF and hormonal fluctuations [28], understanding these physiological mechanisms remains a research gap, which will be a feasible direction for future research, such as how changes in hormone levels affect specific golf performance and how interventions can optimize these effects.

According to Doan et al. [28], during a continuous 36-hole golf competition, golfers experienced an increase in MF with each successive hole, with significant increases in MF observed between holes 25–30 and 31–36. A possible reason for this is that a golf competition lasting over 5 hours requires athletes to engage in complex strategic thinking and decision-making. For instance, selecting the right club, deciding on shot strategies, and adjusting swing angles all demand high levels of cognitive load. Prolonged high cognitive load can lead to MF [37]. Furthermore, unlike sports such as basketball, soccer, and volleyball, which are played on standardized fields, golf courses are designed in vast natural environments [16]. Golfers must operate like snipers, facing challenges from nature and constantly adjusting their play based on factors such as the slope of the fairway, grass length, temperature, humidity, wind speed, and direction. This interesting phenomenon suggests that the competitive golf task in an outdoor setting can itself be a trigger for MF.

Effects of MF on golf performance

This review demonstrates that MF directly affects golf performance, including the overall score for 18 holes, iron club accuracy, drive distance, and especially impacts putting performance. Among the ten articles included in this review, seven studies only involved testing of golf putting [19,29–34]. As a result, the findings are limited and one-sided. The other three studies focused on 18-hole scores [12,28,25], with two of these studies examining driving performance [12,35], and only one study involving iron club tests [35]. These studies were conducted during outdoor 18-hole competitions, making it impossible to rule out various confounding factors of the outdoor environment. For example, Doan et al. [28] found that both physical fatigue and MF were significantly affected by the number of holes played and the duration of time, indicating that as a golf competition progresses, both physical fatigue and MF gradually increase, leading to a decline in golf performance. However, due to the difficulty in clearly distinguishing between physical fatigue and MF in this context, it is challenging to demonstrate that MF is the direct cause of the decline in golf performance. Based on the study designs included in this review, an effective method to avoid confounding factors is to induce MF in a controlled practice range or laboratory setting using specific tasks or tests and then accurately assess golf performance through golf-specific tests. Unfortunately, the results of this review show that the only golf-specific skill tested in such a controlled environment is putting, which is only 1 of 14 clubs in a professional golfer’s bag. This represents a significant research gap, and future studies must test more clubs and techniques.

On the other hand, various studies suggest that the beneficial effects of caffeine can enhance cognitive function in tasks with high mental and physical demands, indicating that its effects are not limited to physical performance enhancement [12,38]. Stevenson et al. [19] found that dietary interventions, such as consuming sports drinks containing carbohydrates and caffeine, can positively impact mental function levels during golf activities, especially in putting. Ataka et al. [39] supported Stevenson et al.’s [19] findings, pointing out that caffeine intake can improve work performance by stimulating the central nervous system without increasing fatigue. For example, Judelson et al. [40] suggested that 100-mg caffeine significantly decreased lethargy/fatigue and increased vigor. Lorenzo Calvo et al. [41] indicated that coffee might improve attention. This highlights the potential impact of nutrition on mental function during golf competitions, warranting further exploration of nutritional interventions in the future.