4.1 Key Concepts and Evidence Available4.1.1 Macronutrient Requirements for Golf Performance

Golf generally provides moderate aerobic physical activity with an average MET value of 4.5 METs [4]. Golf can also provide low- or high-intensity aerobic exercise depending on age and fitness of participants, the layout of the course, and whether a golf cart is being ridden. The typical distance walked during a round of golf can vary dependent on a number of factors (e.g., number of holes played, length of the course, scoring ability), but it has been reported that golfers can potentially cover in excess of 10 km during a round, with a round typically lasting between 4 and 6 h [16]. Golfers may experience fatigue (both mentally and physically) in the latter stages of a round. The fatigue experienced during a round could be partly attributed to the decline in blood glucose, which has been reported to be as much as 10–30% after an 18-hole game when no nutrition was consumed [17]. Golf-specific carbohydrate research has suggested that the consumption of carbohydrates or carbohydrates with protein, may alleviate perceived levels of fatigue and improve physical performance (assessed via driving accuracy of six amateurs with an average handicap (HCP) index of 8.5 ± 6.72 throughout the first 9 holes) [18]. Although blood glucose was not measured in this study, further research fed 12 competitive amateurs carbohydrate in the form of gummies (30 g/h) throughout 18 holes whilst measuring interstitial glucose concentration and anticipated feelings of fatigue [19]. These authors reported that falls in interstitial glucose and anticipated fatigue were significantly reduced, with main effects for trial and time for interstitial glucose (trial: p < 0.001, time: p < 0.001; interaction: p = 0.923) in the carbohydrate fed group compared with the control group. Interstitial glucose concentrations were significantly higher in the carbohydrate group at the 4th–6th (p = 0.042); 7th–9th (p = 0.046); 10th–12th (p = 0.037); 13th–15th (p = 0.020), and 16th–18th holes (p = 0.023), suggesting that carbohydrate feeding may help maintain performance during golf [19].

In an MSc thesis by Robinson [20], low glycaemic index (LGI) and high glycaemic index (HGI) carbohydrates were provided to six amateur golfers (HCP Index ≤ 15.4) before and throughout competitive golf play. There were no significant differences in blood glucose at any time point between the LGI and HGI groups, with decreases in blood glucose of 0.3 mmol/L observed when measured at the 10th hole, and a similar decrease when measured again at the 18th hole. The total decrease in blood glucose was ~ 10% in both conditions. There was no significant difference in golf-related performance metrics between the two groups, suggesting that the GI of the carbohydrate, when consumed pre and during competition, does not affect golfing performance or blood glucose concentrations [20].

Outside of the on-course golf demands, it is also important to consider the overall carbohydrate requirements of golfers based upon their baseline requirements and additional training demands. It is now widely recognised that increasing muscle strength has the potential to improve golf performance [21,22,23] and therefore many golfers incorporate resistance training into their daily schedule. Whist there are guidelines recommending carbohydrate intakes between 3 and 5 g/kg body mass (BM) a day for low-intensity or skill-based activity [24], to date there are no specific recommendations from peer-reviewed literature in terms of the carbohydrate requirements for amateur or professional golfers taking into consideration the on-course, off-course and, for some, travel demands.

Given the importance of dietary protein in muscle protein synthesis, and the growing interest in increasing muscle size and strength in golfers, it was somewhat surprising that there were no relevant studies on the protein requirements for golf. One study examined the effects of protein ingestion when combined with carbohydrate prior to a 9-hole round on acute performance by assessing driving distance, and accuracy of driving, iron shots, chipping and putting [18]. There were significantly lower perceived levels of fatigue when consuming the combined protein and carbohydrate feeding compared with both the placebo and carbohydrate alone, highlighting that a mixed meal may be more beneficial consumed together during golfing performance. Future research must now address the protein requirements for golfers in terms of the timing, type and total amounts required for the long-term development of the golfer especially considering that golfers often play on consecutive days and increasing dietary protein may support muscle recovery and repair.

There were no published studies on the effects of fat consumption on either acute golf performance or long-term health. Considering a round of golf can last anywhere from 4 to 6 h, and is generally of moderate intensity for amateurs and low intensity for professionals (who are typically younger and do not carry their own bags), golf may be a sport where it is possible to fuel the performance using fat as a fuel source [25]. Future research should attempt to identify if it is possible to become fat adapted for golf and if this is an optimal strategy to fuel on-course performance and support improvements in long term health.

4.1.2 Hydration and Golf

Hydration on the golf course can be affected by several factors including participant demographics, fluid intake, exercise intensity, sweat rate, competition climate and the type of clothing worn. Dehydration is associated with poorer cognitive function, raised core body temperature, increased glycogen utilisation, and increased sensation of fatigue, which may all lead to a negative effect on golf performance [5, 26]. It was therefore of no surprise that hydration and the golfer was one of the more researched areas of performance nutrition for golf. For example, the hydration status of 15 elite collegiate golfers (mean HCP + 1.1) was monitored using their urine specific gravity (USG) status immediately pre and post an 18-hole round [27]. For context a USG > 1.020 was considered dehydrated [28]. The mean number of shots taken were significantly higher (p = 0.049) in the players who began the round dehydrated (79.5 ± 2.1 strokes) when compared with the euhydrated group (75.7 ± 3.9 strokes). It was noted that all the dehydrated players (n = 6) failed to consume sufficient fluids throughout the 18 holes to reach a euhydrated state indicating an immediate target for golfer education. In support of this suggestion, the authors asked the golfers to complete the fluid section of a nutrition knowledge questionnaire, and it was reported that the golfers who started the round dehydrated displayed less knowledge on hydration compared with players in the euhydrated state. In a similar study using seven amateur golfers (HCP 3.0 ± 1.2), it was reported that cognitive tasks, including the golfers’ overall distance and accuracy judgements were impaired when even mildly dehydrated [5]. The dehydrated athletes experienced a body weight (BW) loss of just 1.1 kg, supporting previous suggestions that even modest levels of dehydration may be associated with performance decrements [26], in particular cognitive function [29].

There was limited research identified examining the composition of fluids provided during golfing performance. Thompsett et al. [18] investigated the effect of a zero-calorie drink (330 mL Gatorade Zero Sugar Orange Thirst Quencher) with or without 30 g carbohydrates or 15 g carbohydrates plus 15 g protein on fatigue levels and performance across 9 holes with feedings administered at holes 1, 4 and 7. In all conditions, the amateur golfers commenced the round somewhat dehydrated (USG of 1.021–1.023). The authors reported no effects of the drinks on golf performance or alertness but did suggest decreased levels of self-reported fatigue in the two carbohydrate conditions compared with the zero-calorie condition. This suggests that providing some nutrition with the fluid is better than fluid alone. However, it was not assessed if fluid alone was better than no fluid at all. It should also be noted that sweat rate during play was low (0.17–0.22 L/h) and therefore these data may not be applicable to golf in warmer climates where sweat rates may be significantly higher. Research on specific oral rehydration solutions and the specific composition of the drinks in golf is lacking, and it is therefore not possible to make definitive recommendations as to the ideal drinks to consume during competition. Future research should explore the composition of the drinks examining if electrolytes and/or carbohydrate solutions would be beneficial for golfing performance, and explore this in differing environmental conditions.

4.1.3 Energy Requirements of Golf

Studies on the energy expenditure of golf were the second-most prevalent topic of research reviewed with the prevailing view that golf provides moderate intensity exercise, while this varies within the round and between subjects and conditions (Table 2). However, it was apparent that due to a wide array of methodologies employed, combined with a wide range of playing standards, the range of reported energy expenditures was vast, ranging from 663 kcal to 1,954 kcal per round equating 3.2–11.8 kcal/min [30, 31]. Whilst the total amount of energy expended can depend on numerous factors including the individual, the method of transporting the clubs, climatic conditions, and course terrain, it appears the major discrepancy was related to the equipment employed to collect the energy expenditure data, which therefore must be taken into consideration when reviewing the data. For context, 11.8 kcal/min is greater than typically reported when running a marathon [32], which seems excessive for a sport whose primary activity is walking. Moreover, not all studies differentiated between the total energy expenditure of golf (total energy expended during the round) and activity energy expenditure of golf (total energy expended minus resting metabolic rate), which also may contribute to the variability reported.

Table 2 Energy expenditure (EE)/activity energy expenditure (AEE) over the course of 9 and 18 holes for various golfing abilities

Kasper et al. [31] used Actiheart® Monitors to measure the activity energy expenditure of golf over 18 holes in high-level golfers (HCP: 1.5 ± 2.4). The Actiheart® Monitor has been validated against doubly labelled water (DLW) in free-living conditions [33] and may therefore provide a more reliable assessment of the activity energy expenditure of golf. Using Actiheart® Monitors, some of the lowest energy expenditure values were reported (3.2 kcal/min, approximately 768 kcal/round) suggesting that the major contributor to the activity energy expenditure of golf is the walking between shots. Despite using validated equipment, the study was not without its limitations, which consisted of a higher percentage of males than females and the total walking distance covered during the rounds not being measured. This is important as it could be argued that higher standard golfers cover less distance than lower standard players as there may have been less searching for golf balls resulting in a more direct route being walked.

There have been suggestions that the energetic cost of golf differs in male versus female amateur golfers [34]. Using a BioHarness 3 Zephry-wireless monitor, Ilhan Odabas and Gercek reported that the female golfers had significantly higher energy expenditure (1823 ± 304 kcal; n = 11) than their male counterparts (1440 ± 611 kcal; n = 14), although both groups reported similar ratings of perceived exertion. The authors suggested that the difference in energy expenditure between the female participants and their male counterparts could be explained by the higher physiologic load, physiologic intensity, higher training load, and training intensity experienced by the females. The energetic costs were almost double that reported by Kasper et al. [31]. Future studies should further address this hypothesis in male and female golfers using the most appropriate techniques including DLW for the assessment of total daily energy expenditure, alongside ActiHeart® Monitors to determine the energy expenditure of the individual components of golf play and practice (e.g., driving range, chipping, putting) and the playing round itself.

In terms of professional golf, the activity energy expenditure of 20 professional male golfers was measured over the course of four tournaments on The Challenge Tour and The Alps Tour using commercially available technology (WHOOP Strap 2.0) [35]. The Whoop Strap uses light-emitting diodes and photoplethysmography (PPG) to gather metrics such as heart rate and estimated basal metabolic rate (BMR) to assess activity energy expenditure [36]. Mean activity energy expenditure was 1555 ± 158 kcal per round, which also seems at the higher end for a low- to moderate-intensity sport [4]. It has been previously suggested [37] that using wearable technology to measure heart rate and then using this to estimate activity energy expenditure over 18 holes of golf overestimates energy expenditure (1609 kcal) given that heart rate may be affected by sensor movement, environment, and fitness [38, 39]. This may somewhat account for the high energy expenditures reported in golf when using heart rate technology. With such variability in the range of energy expenditure reported in the published golf literature, it is now essential to determine an accurate benchmark of the energy expenditure of golf play to ensure that golfers are fuelling themselves adequately for both their on-course performance and long-term health [40].

The method of transportation of clubs may also affect the energy expenditure of the round, especially when riding a golf cart. Research investigated the effects of one amateur subject riding a golf cart (1303 kcal) in comparison with using a caddy (1527 kcal) and carrying their own bag (1954 kcal) over 18 holes [30]. However, data may not be accurate as this was a case study on one amateur golfer and therefore requires replicating with a larger cohort of male and female golfers.

4.1.4 Nutrition and Cognitive Performance

Success in golf requires fine movement patterns and motor skills that require immense concentration. Due to the typical time taken to play a round of golf, there are many opportunities for a momentary lapse in concentration to occur and impact upon golf performance [41]. For example, cognitive anxiety, which is linked to negative self-talk, was shown to correlate with golf putting performance [42]. Participants reported that rational self-talk was more helpful for their putting performance when compared with irrational self-talk (mean difference = 16.49, SD = 28.38, p < 0.01). Furthermore, rational self-talk improved putting scores by 66% from baseline, in comparison with a 33% improvement when utilising irrational self-talk. Moreover, there have been suggestions of a link between elevated plasma cortisol concentrations and attentional bias towards negative self-talk, although there was no observed decrement in performance [43]. To our knowledge no study has assessed if nutrition can influence cortisol concentrations during a round of golf, which could have an impact on concentration and performance. However, the effects of 6 weeks of supplementation with 200 mg oral phosphatidylserine supplementation on perceived stress was investigated [44]. The authors reported a trend, albeit not statistically significant, for phosphatidylserine to reduce stress alongside a significant increase in ball flight accuracy. It should be stressed, however, that these data were collected on 20 mid-high HCP golfers and therefore should be translated to other standards of golfers with caution [45]. Future research should assess if nutritional strategies can reduce cognitive anxiety and improve aspects of golf mental performance. Such research should not only assess if nutritional supplements may help but also assess the impacts of maintaining euhydration and optimised on-course fuelling strategies. There are suggestions that hydration may impact cognitive performance (through misjudgement of distance) when dehydrated [5], and this should be further explored.

4.2 Dietary Supplements and Golf Performance

Whilst it is important that athletes, including golfers, should adhere to a food-first strategy, there are a number of situations where performance supplements may be considered using a food-first but not always food-only approach [46]. It is strongly advised that golfers, especially those competing at a high level (e.g., national squads, professional), only consider use of supplements with caution due to the risk of potential anti-doping rule violations [52]. To mitigate these risks, it is advised players consult with qualified professionals to ensure that comprehensive risk-mitigation strategies are employed including batch testing by a reputable third-party organisation. This scoping review identified a small number of studies on performance supplements for golf, although the research was somewhat limited when compared with supplement research in other sports.

4.2.1 Caffeine

Caffeine is one of the most widely studied ergogenic aids, with research suggesting that it can support cognitive performance [47] and enhance endurance exercise [48] and improve team-sport performance [49]. An effective dose of caffeine ranges from 3 to 6 mg/kg BM [47], with a typical 250 mg oral dose of caffeine achieving peak plasma concentrations within 45–60 min post consumption [48]. While multiple studies have explored the effects of caffeine on endurance capacity during extended exercise, to date there has been limited research on golf performance. As a full round of golf typically lasts 4–6 h, and can also be played over consecutive days, caffeine consumed before or during a round may help to maintain plasma caffeine concentrations and alleviate symptoms of fatigue. As some tee times occur later in the day, golfers need to be cautious when using caffeine, as this may negatively impact sleep quality, leading to impaired performance in the following days.

Mumford et al. [50] examined the effect of a caffeine-containing supplement on golf-specific performance and fatigue throughout a 36-hole competitive tournament. In a double-blind, placebo-controlled study, 12 male golfers (HCP 3–10) consumed either a 155 mg caffeine supplement or a placebo 25–35 min before and after each 9 holes over two consecutive days. Caffeine intake led to significantly better total scores (76.9 ± 8.1 vs. 79.4 ± 9.1, p = 0.039), a greater number of ‘greens in regulation’ (8.6 ± 3.3 vs. 6.9 ± 4.6, p = 0.035), and increased drive distance (239.9 ± 33.8 vs. 233.2 ± 32.4 yards, p = 0.047). The caffeine group also reported greater feelings of energy mid round (p = 0.025).

Stevenson et al. examined the effects of a combined (commercially available) caffeine and carbohydrate sport drink on golf putting performance in 20 male amateur golfers (HCP 15 ± 4) during a laboratory-based simulated golf round [6]. The authors reported that the caffeine-containing carbohydrate drink (1.6 mg/kg BM caffeine with 0.64 g/kg carbohydrate) consumed before and during a round of golf led to improved putting performance and increased alertness. Across all 18 holes, the caffeine-containing carbohydrate drink resulted in a significantly higher number of successful putts and significantly lower number of putts falling short of the hole. There was also a main effect of drink on self-rated scores for alertness and relaxation. It should be stressed, however, that the study was not able to differentiate between the effects of caffeine and carbohydrate on golf performance. Not all studies have reported improvements in golf performance following caffeine supplementation. Bristow [51] reported that there was no significant difference between 11 male golfers (HCP: 4.8 ± 3.7) in any performance variables over the course of an 18-hole round between caffeine (3 mg/kg) and a placebo. However, when ten drives were hit on a golf simulator, the caffeine group demonstrated significant improvements in ball speed and total distance. Taken together, there are suggestions that caffeine may enhance aspects of golf performance when taken in the 1.5–3 mg/kg dose range, although more research is needed to explore this as well as assess if doses can be detrimental to golf performance, particularly in caffeine-naïve players. The effects of subsequent days’ performance given potential impact on sleep also needs to be considered.

4.2.2 Creatine

Although in theory creatine monohydrate supplementation could be useful for golfing physical and mental performance [52, 53], golf-specific research on creatine supplementation is limited. The only study identified in the present scoping review used a multi-ingredient commercially available supplement containing 5 g creatine along with 50 mg coffee extract, calcium fructoborate and vitamin D, and compared this to an isocaloric placebo control. In male golfers (5–15 HCP), following 30 days of supplementation the mean driving distance in the experimental group increased (from 270 ± 19 to 284 ± 23 yards) alongside improvements in BM and peak power and velocity during bench press throws [54]. Although the product was a multi-ingredient drink containing caffeine, the actual caffeine dose was low and as such it is likely that the improvement was a result of the creatine, although this suggestion remains speculative. Given the potential for creatine to aid golfing performance, future research should explore this hypothesis investigating the effects of creatine supplementation on both the physical and cognitive aspects of golfing performance.

4.3 Body Composition, Anthropometric Profiles and Golf Performance

Several studies identified in the present scoping review investigated the body composition of golfers across various skill levels [16, 21]. Golfers tended to have higher body fat compared with athletes in more aerobically demanding sports, such as football [55, 56] and rugby [57]. However, within the golfing population, lower HCP players (who tend to perform better) were reported to have lower body fat percentages alongside greater lean BM compared with higher HCP players [55, 58] suggesting that body composition may be important to golfing performance. Kawashima et al. [55] compared the body composition of professional and amateur Japanese male golfers, showing that professional players had significantly lower body fat percentages (12.8 vs. 19.8%) and higher lean BM than amateur players. It must be stressed that body fat was measured using skinfold callipers, which has limitations when translating from a skinfold thickness to a body fat percentage [59]. Previous work [58] suggested that college female golfers had an average body fat percentage of 28 ± 6%, whilst male golfers had an average body fat percentage of 19 ± 7%, although this again involved skinfold thickness and prediction equations.

More recently, the fat-free mass index (a height-adjusted measure of fat-free mass) of collegiate golfers was investigated [60]; this index is calculated by dividing an individual’s fat-free mass by their height squared [61]. The mean fat-free mass index for male collegiate golfers was 21 ± 1.5 kg·m2, which was lower than that of collegiate rugby and football players. A higher fat-free mass index indicates a higher relative muscularity, which may be beneficial for golfers as higher muscle mass is associated with increased strength, power and driving distance [60, 62]. There was insufficient literature to conclude on an ideal or preferred body composition for golf, and therefore additional research is needed to help with talent identification and to direct the off-course training requirements of golfers. Future studies should attempt to assess this, ideally using a combination of techniques including dual-energy X-ray absorptiometry (DXA) scan technology in a wide range of male and female golfers.

4.4 Travel and Golf

Golfers of all levels frequently travel domestically and internationally for tournaments and training, which can lead to additional unwanted stress on the body, travel fatigue, jet lag, dehydration and gastrointestinal (GI) issues that may negatively impact health and performance [63]. Golfers can utilise individualised nutrition strategies to manage travel fatigue, jet lag and illness when travelling for competitions and training. No studies were identified that looked specifically at the effects of nutrition and travel for golfers, but literature focusing on various other sports and strategies for travel has been explored.

Despite there being no studies specifically focusing on the effects of probiotics and golf, there is available evidence that suggests positive associations with probiotics decreasing upper respiratory tract infections (URTIs) and GI distress, especially when travelling [64]. With the significant travel and competition demands in competitive golf, probiotic supplementation and/or probiotic-containing foods could decrease the risk of illness, although golf-specific studies are now required to explore this. Moreover, despite a recent meta-analysis demonstrating that zinc acetate lozenges may decrease the duration and symptoms of URTIs [65], again there are no golf-specific studies examining this. Given the lack of specific research in this area, the suggested nutrition strategies to reduce the stress burden for golfers documented in a golf text book [66] and a narrative review [63] were forced to utilise best practice guidance from other sports.

General recommendations to help reduce travel fatigue and jet lag suggest that golfers should maintain hydration on the plane, with the possible use of electrolytes, adjust meal timing to the destination, and consider the strategic use of caffeine [66] whilst preventing any nutrient deficiencies such as low vitamin D [63]. Moreover, nutrition suggestions that help to overcome jet-lag symptoms may also aid with day-to-day performance situations given the highly variable tee times players can experience (e.g., waking up at 5 a.m. for an early tee time one day, and then having an afternoon tee time the following day). These suggestions now must be explored in golf-specific research to see if there are any definitive suggestions that can be applied in the sport as most literature has been conducted on sedentary individuals or the general population and not elite athletes.

4.5 Future Research Priorities

This scoping review has identified areas of research that should be focussed on in the future and which are summarised in Table 3. Immediate areas to address include clarification of the confusion with regards to the energetic demands of the sport using techniques such as DLW [67], followed by better understanding of the dietary carbohydrate, protein and fat requirements of elite and recreational players. Despite body composition being the most frequently researched topic in golf, we also suggest that future research should aim to clarify the body composition and anthropometric characteristics of male and female players using improved methodologies such as DXA. To our knowledge, most golf research has been conducted using males, with limited high-quality research on female golfers, and therefore future research should focus on studying larger cohorts of female players of all abilities using accurate methodologies. Given the lack of literature regarding the efficacy of dietary supplements (including caffeine, creatine, electrolytes and supplements reported to enhance cognitive function), there is a need for studies to thoroughly examine such supplements within the context of golf and investigate if any of these nutritional strategies may provide benefits to the golfer. It has been suggested that recovery is a key consideration for the modern golfer given their intense playing schedule, prolonged season and high travel demands [66]. Despite the importance of recovery, it was surprising to note there was no research on nutritional strategies to assist recovery from intense playing schedules, and future research should attempt to address this gap in the literature. Finally, research regarding the nutrition knowledge of golfers would be informative to help understand the barriers to implementing targeted sport nutrition support within golf.