Elite squash players nutrition knowledge and influencing factors

Background There is a reported mismatch between macronutrient consumption and contemporary macronutrient guidelines in elite standard squash players. Suboptimal dietary practices could be due to a lack of nutrition knowledge among players. Subsequently, the purpose of this study was to assess the sports nutrition knowledge of elite squash players through the Nutrition for Sport Knowledge Questionnaire (NSKQ) and provide an indication of whether players require nutrition support to increase their nutrition knowledge. Methods This cross-sectional study assessed the nutrition knowledge of 77 elite squash players via the NSKQ over the period of June 2020 to August 2020. Results Players conveyed average nutrition knowledge with a mean NSKQ score of 48.78 ± 10.06 (56.07% ± 11.56%). There were no significant differences in NSKQ score between male and female players (p = .532). There was found to be a weak positive association between world ranking and NSKQ score (r = .208) and age and NSKQ score (r = .281). Players who had a relevant undergraduate degree (e.g. BSc Sport & Exercise Science) had significantly greater NSKQ score than players with no relevant qualifications (p = .022). Players who consulted a sports nutritionist to obtain their main source of nutrition information were shown to have significantly greater knowledge than those who acquired knowledge from a sports scientist (p = .01) or the internet / social media (p = .007). Conclusions Players should consult with a sports nutritionist to increase their sport nutrition knowledge. Future research should quantify the effectiveness of a nutritional education intervention at increasing nutrition knowledge in players. Supplementary Information The online version contains supplementary material available at 10.1186/s12970-021-00443-3.


Background
Squash is a high intensity intermittent sport [1] which is classified as one of the four major racket sports [2]. Elite male squash players are reported to exhibit a mean energy expenditure of 4933 ± 620 kJ.h − 1 , mean heart rate of 92 ± 3% heart rate maximum and mean respiratory exchange ratio of 0.94 ± 0.06 throughout simulated match play [3], conveying the high intensity nature of the sport [1]. At elite standard, players are reported to train for more than 12 h per week, with squash-specific sessions such as pressure sessions and continuous rallies eliciting heart rates above 90% heart rate maximum [4,5]. Due to the high energetic demands of elite squash, adequate energy intake is required to optimise health and physical performance [6,7]. Subsequently, sports nutritionists have become an integral part of high-performance teams to help promote optimal nutrition practices. Despite this, there is a paucity of information regarding specific nutritional recommendations for squash, unlike in other racket [8] and high intensity intermittent sports [9]. This makes it difficult for practitioners working with elite squash players, as they have to make recommendations based on non-specific guidelines [10].
Ventura-Comes et al., (2019) [11] analysed the food habits of elite Spanish squash players using a food consumption frequency questionnaire and found that players under consumed carbohydrate-rich foods such as bread, potatoes, pasta and rice when compared to contemporary guidelines [10]. Low frequency of carbohydrate rich foods are likely to result in low carbohydrate intakes in relation to guidelines, reducing high intensity intermittent performance [10].
Mismatches between contemporary nutritional recommendations and players habitual nutritional practices suggest that elite squash players might lack the nutrition knowledge to have optimal dietary practices. An athlete's nutrition knowledge is one modifiable determinants of dietary behaviour [12], with a weak positive correlation being reported between an athlete's nutrition knowledge and their diet quality [13,14]. The association between nutrition knowledge and dietary behaviour is multifaceted and influenced by many other individual and environmental factors such as hunger and appetite, taste and food preferences, beliefs, culture, experiences, selfefficacy, financial status, peers, sporting culture, access to food and cooking skills [12][13][14][15]. The evaluation of association between nutrition knowledge and diet quality is also complex due to a plethora of inadequately or partially validated instruments to assess nutrition knowledge [12,13] and inappropriate tools to quantify dietary intake [13], such as 24-h dietary recalls and three-day self-reported food diaries, which have both been shown to poorly estimate micronutrient intake [16,17]. Athletes energy requirements are also highly variable throughout macro-, meso-and microcycles, as many adopt a periodised training approach [18,19] complicating the assessment process [20]. Despite only a weak association between an athlete's nutrition knowledge and their diet quality, nutrition education interventions have been shown to increase athlete's nutrition knowledge and lead to greater dietary behaviours [21], optimising physical performance [22]. Subsequently, increasing an athlete's nutrition knowledge is of interest to sport nutrition practitioners as it might enhance athlete's dietary practices [21] and athletic ability [22].
The final aim of the study was to survey what contemporary sports nutrition research elite squash players would like to see being conducted in the future. There are currently no specific nutritional guidelines for elite squash players. By surveying players, the aim was to ensure that all relevant nutrition research in elite squash is undertaken, specific to player's needs. This data can then be used to create a nutritional education intervention which is bespoke to elite squash players.

Participants
The research was approved by an institutional ethics committee (ER23597808). All participants who volunteered provided informed consent with the study being conducted according to the principles of the 7th revision of the Declaration of Helsinki [58].
A convenience sample of prospective participants were contacted through the Professional Squash Association (PSA) on two separate occasions (June 2020 and August 2020) and were provided with information about the study. Players were required to be a member of the PSA to take part in the study, with this forming the inclusion criteria for the study. Seventy-seven elite squash players took part in the study, 37 were male, and 40 were female. Responses were received from a global sample of the population (North America = 5; South America = 2; Europe = 55; Africa = 5; Asia = 6; and Oceania = 4). The mean average (± standard deviation) age and world ranking of the participants was 24 ± 5 and 190 ± 167 respectively. World rankings were taken from the PSA September rankings upon termination of the data collection period. Figure 1 details the distribution of the players world ranking.
The NSKQ was written in English and was distributed online via Qualtrics (Washington, USA). Players were informed that the questionnaire would take approximately 25 min to complete [23] and instructed to complete the questionnaire in their own time without the use of resources (peers, books, internet etc.).
Two additional questions were asked upon completion of the NSKQ to quantify some of the factors influencing nutrition knowledge. Players were asked to 'detail any relevant qualifications which are specific to nutrition' (e.g. A-Level biology, BSc sport and exercise science etc.), as standard of education has been shown to positively influence nutrition knowledge [25][26][27][28][29][30]. These were subsequently ordered into four groups, taking the participants highest standard of relevant education (no qualification, A-Level [physical education / sport, biology, chemistry etc.] undergraduate degree [sport and exercise science, nutrition or equivalent] and postgraduate degree [sport and exercise science, nutrition or equivalent]). Players were also asked 'where they obtained their main source of nutritional information from' to gain an understanding of how many players currently consult with a sport nutritionist. Athletes have been shown to gain their nutrition information from a variety of sources including nutritionists, strength and conditioning coaches, sport specific coaches, peers, the internet etc. [29,40,48,[61][62][63][64][65][66][67][68]. Players were provided six options, with them selecting the most relevant (sports nutritionist; conditioning coach or sport scientist; squash coach; peer review journal articles; internet or social media; and other).
Finally, players were asked to share what squash nutrition research they would like to see in the near future. This was split into six options with players able to select their top three (quantification of energy expenditure throughout training periods in elite squash players to create specific nutritional training guidelines; quantification of energy expenditure throughout competition periods in elite squash players to create specific nutritional competition guidelines; quantification of sweat sodium losses in elite squash players to create specific hydration guidelines; nutrition to support immune function in elite squash players; efficacy of ergogenic aids in elite squash; other). These options were devised as they underpin the relevant knowledge to create specific nutritional recommendations  was performed to calculate any significant differences between NSKQ score or section scores against standard of relevant education and main source of nutrition information. Where a significant main effect was observed, the Hochberg Post-Hoc pairwise comparison was used to determine which groups were statistically significant.

NSKQ score, subsection scores and individual question responses
The mean NSKQ score was 48.78 ± 10.06 (56.07% ± 11.56%), defined as "average" nutrition knowledge. Figure 2 details players grand mean subsection scores. The highest scoring section was alcohol, with players demonstrating "good" knowledge. Players had "average" macronutrient, weight management and sports nutrition knowledge. Supplements was the lowest scoring section with players exhibiting "poor" nutrition knowledge. Players also had "poor" knowledge of micronutrients. An additional file details individual question scores (see Supplementary  Tables 1-87 for Individual Question Scores).
Differences between male and female players in NSKQ score and subsection scores  and female players in NSKQ score or subsection scores (p > 0.05).
Effects of standard of relevant education on NSKQ score Effects of Main source of nutrition information on NSKQ score Figure 6 details the effects of main source of nutrition information on NSKQ and subsection scores. Players main source of nutrition information had a significant positive effect on NSKQ score (p = .000). Hochberg Post-Hoc pairwise comparison showed that players who received their main source of nutrition information from a sport nutritionist, nutritionist, registered dietitian or equivalent scored significantly higher than players who received their main source of nutrition information from a sport scientist (p = .010; d = 1.2; CI = 1.61-18.62) or the internet / social media (p = .007; d = 0.96; CI = 1. 57-15.62). No other significant differences were observed across any of the groups when compared against each other. throughout competition periods to create specific nutritional competition guidelines was the second most popular (n = 34; 44.16%). Seventeen players stated they would like to see research regarding nutrition to support immune function (22.08%), with 16 players specifying they would like to see a quantification of ergogenic aids in squash (20.78%). The lowest scoring area of interest was the quantification of sweat sodium losses in squash to create specific nutritional guidelines (n = 10; 12.99%). Two players selected the 'other' suggesting "how to get everything into your diet while choosing plant based" and "the sustainability of a ketogenic diet for high performance in squash".

Discussion
The main aim of this study was to assess the nutrition knowledge of elite squash players. This study also aimed to quantify the factors which may influence an elite squash players nutrition knowledge. The final aim of the study was to survey what contemporary sports nutrition research elite squash players would like to see being conducted in the future.
The main findings of this study were (1) elite squash players had average nutrition knowledge, (2) there were no differences in nutrition knowledge between male and female players, (3) age and world ranking had a weak positive association with nutrition knowledge, (4) players who had a relevant undergraduate degree were found to have better nutrition knowledge than those who had no relevant qualification, (5) players who obtained their main source of nutrition knowledge from a sports nutritionist were shown to have better nutrition knowledge than players who obtained from a sports scientist or the internet, and (6) players valued quantifying the energetic demands throughout a training period as the research they would like to see undertaken in the future.

Overall nutrition knowledge
Players nutrition knowledge was average (56%). Consequently, elite squash players should aim to increase their nutrition knowledge, as this may lead to greater dietary behaviours [21] and athletic ability [22]. Sport nutrition practitioners implement a variety of techniques to promote positive dietary behaviours, increasing nutrition knowledge in adolescent [47,55,[71][72][73][74][75][76], collegiate [21,22,77,78] and elite athletes [79]. Future research should aim to quantify the effectiveness of a nutritional education intervention at increasing elite squash players nutrition knowledge.
Evaluations of players nutrition knowledge in comparison to other athletes is difficult, due to the heterogeneity of tools used to assess nutrition knowledge [12,80]. The NSKQ was devised as a universal tool to quantify athlete's nutrition knowledge and make comparisons among different sports [23]. However, there are many other factors such as sex, playing ability, age, standard of education and main source of nutrition knowledge which influence an athlete's nutrition knowledge [12] making comparisons challenging. To date, three previous studies [30,65,81] have used the NSKQ to assess sports nutrition knowledge. All three studies found athletes' sports nutrition knowledge to be poor (Jenner et [81]) in contrast to the present findings. A plausible explanation for this is that the standard of athlete was higher in the present study in relation to the aforementioned studies [30,65,81]. This study featured six of the world's top twenty squash players, and as a result these athletes may have greater access to resources (nutritionist, funding etc.) which may increase levels of nutrition knowledge [12]. Individual athletes such as elite squash players may also obtain personalised nutrition support which isn't available to team sport athletes due to time and cost limitations. This personalised support can focus on the key concepts which need to be addressed specific to the athlete's needs.

Key concepts from individual questions
Players in the present study had poor knowledge of the contemporary carbohydrate and protein guidelines (see supplementary Tables 13 and 33 [10,82]). This is consistent with findings from Ventura-Comes et al., (2019) [11] that elite Spanish squash players under consume carbohydrate in comparison to contemporary guidelines [10], with players rarely consuming foods which have a high carbohydrate content such as bread, potatoes, pasta and rice. Despite having poor knowledge of contemporary guidelines, players were able to identify the carbohydrate (see supplementary Tables 14-18) and protein (see  supplementary Tables 32 and 42) content of foods, as well as appropriate protein sources to promote muscle growth post resistance training (see supplementary  Tables 34-37). Players were also aware of what macronutrients to consume pre (see supplementary Table 59), during (see supplementary Table 64) and post exercise (see supplementary Table 66), as well as a suitable fuelling strategy (see supplementary Table 61) and snack during a 60-90-min session (see supplementary Table 65). This suggests that players may have greater procedural knowledge than declarative knowledge [83] and indicates that while players are unaware of contemporary nutrition guidelines, they understand the nutritional composition of foods along with the appropriate time to consume them, enabling them to follow optimal fuelling and recovery strategies. Many of the carbohydrate sources Ventura-Comes et al., (2019) [11] were reporting players to under consume were low glycemic index carbohydrates. It could be possible that squash players have a higher intake of high glycemic index carbohydrates. These are recommended around training sessions [10]. Future research should aim to quantify the training loads and energy expenditures of elite squash players to determine the nutritional requirements of the sport, as reported in other racket [8] and high intensity intermittent sports [9]. This would convey whether contemporary non-specific nutrition guidelines [10] are relevant to elite squash players, with this data informing any nutrition education intervention undertaken with elite squash players. Fifty five players (71%) surveyed in the present study conveyed that they would like to see this research undertaken. Players' dietary intakes should also be quantified alongside training loads, as reported in other high intensity intermittent sports [84,85]. This would give an insight into whether players' dietary intake is optimal in relation to their training load [18,19]. Food consumption frequency questionnaires, as reported by Venutra-Comes et al., (2019) [11] have been shown to display poor validity and reliability [86] in comparison to other methods such as weighed food diaries, snap 'N' send and 24-h dietary recall [17,87]. Subsequently, more valid and reliable methods need to be employed to assess the energy intake and nutritional habits of elite squash players to obtain a better understanding of their dietary practices. Players had poor micronutrient knowledge (45%). Quantifying players dietary intakes in future research would also provide an understanding of whether this lack of knowledge translates to poor diet quality. Tam et al., (2019) [80] reported that only 38% of nutritional education interventions include information regarding micronutrients. It is feasible that sport nutritionists focus on educating athletes to achieve an optimal diet specific to their needs, rather than educating athletes about micronutrient roles and requirements.
Players also had poor supplementation knowledge (45%). This is consistent with findings from Ventura-Comes et al., (2018) [88] who reported that elite Spanish squash players consumed ergogenic aids which had a lower efficacy such as glutamine, branch chain amino acids and flaxseed oil, rather than ones which had higher efficacy such as beta-alanine, creatine and sodium bicarbonate [89]. Players in the present study were unable to identify the rationale for use of beta-alanine supplementation (see supplementary Table 77). Beta-Alanine could enhance squash performance by increasing muscle carnosine stores and subsequent buffering capacity of the muscle [90]. Tam et al., (2019) [80] reported that supplementation was the least frequent topic of nutrition education interventions (34%). It is plausible that athletes may only take supplements recommended by their sports nutritionist, with nutritionists prioritising achieving an optimal energy intake and greater diet quality, rather than a supplementation strategy. There is also a paucity of research on the efficacy of supplements on squash-specific performance. Therefore, sports nutritionists may not recommend supplements to elite squash players due to a lack of sport-specific evidence. Future research should aim to quantify the efficacy of ergogenic aids which have been shown to augment high intensity intermittent exercise (e.g. beta-alanine, sodium bicarbonate, creatine, caffeine and nitrates) [91] in elite squash to establish a supplementation strategy specific to the sport.

Influencing factors of nutrition knowledge
Sex was shown to have no significant differences on overall nutrition knowledge or any subsections (Figs. 3  and 4). Sex is reported to have an equivocal influence on nutrition knowledge with some studies reporting female athletes to have greater nutrition knowledge than male counterparts [26,27,31,32,37,39,46,49], whereas other studies convey no differences between sexes [33-36, 38, 40-45, 47, 48]. Assuming appropriate energy availability [6], aside from iron intake in regularly menstruating females [92], the main determinants of a player's nutritional requirements are based on their training load, regardless of sex [93]. Therefore, nutritional education requirements or nutrition knowledge shouldn't differ between sexes in elite squash players.
World ranking was shown to have a weak positive association with nutrition knowledge (r = .208). The influence of athlete ability on nutrition knowledge is equivocal with some studies showing a greater standard of athlete to possess greater nutrition knowledge [39,46,50], some studies conveying no differences [28,44,[51][52][53][54] and others reporting non-elite Australian Football athletes to have greater nutrition knowledge than elite counterparts [30]. Differences in athlete ability and nutrition knowledge may be confounded by influencing factors. Many studies quantifying the nutrition knowledge of athletes are undertaken in tertiary educated individuals (e.g. collegiate athletes), with this level of education being shown to positively influence nutrition knowledge [12]. Sub-elite and recreational individuals are also anticipated to spend less time training than elite counterparts, potentially having more time for educational purposes.
Age was also shown to have a weak positive association with nutrition knowledge (r = .281) The influence of age on nutrition knowledge is equivocal with some studies reporting older athletes to display greater nutrition knowledge [46,55,57] and others reporting no differences [27,41,44,56]. Older athletes may have greater nutrition knowledge as time is required to be able to progress to higher levels of education (e.g. tertiary). Players may also not have access to a sports nutritionist in the early years of their career, as national governing bodies prioritise senior players who have a greater likelihood of achieving success, reducing the opportunity to increase their nutrition knowledge.
Players that had a relevant undergraduate degree reported higher nutrition knowledge than those that had no relevant qualifications (Fig. 5). This is to be expected given that undergraduate degrees (e.g. BSc Sport & Exercise Science) are designed to increase knowledge in a subject specific area, and many players cited that they had completed a nutrition module as part of their course. This is consistent with previous research which reports athletes who study or have studied at tertiary level have greater nutrition knowledge than those who have not [25][26][27][28][29][30].
Players who received their main source of nutrition information from a sport nutritionist were shown to score significantly higher than players who received their main source of nutrition information from a sport scientist, or the internet / social media (Fig. 5). This is in contrast to findings from Trakman et al., (2019) [54] who found no differences in athlete's nutrition knowledge and main source of nutrition information. It should be noted that athletes in the aforementioned study were non-elite [54]. The level of nutrition support may vary between elite and non-elite athletes and may influence nutrition knowledge scores. Consequently, players should look to consult with a sports nutritionist to obtain nutrition information and be discouraged from using the internet / social media to increase their nutrition knowledge. Surprisingly, players who obtained their main source of nutrition information from a sports scientist were shown to have poor nutrition knowledge (44%). Sport scientists might be able to understand and communicate mechanistic underpinning. However, they may lack the ability to translate this into practical nutrition recommendations and coherent strategies for athletes.

Limitations
A limitation of the study is that it is impossible to know whether players cheated throughout completion of the NSKQ. Players were asked to complete the NSKQ without the use of resources (peers, books, internet etc.). No member of the research team was supervising players when they completed the questionnaire due to the universal nature of the study. Therefore, it is impossible to know whether players completed NSKQ with or without the use of resources. If players were to complete the NSKQ with resources this could influence their score and provide a false result. However, the lead author would expect scored to be greater than 'average' if players cheated. Another limitation of the study is that the NSKQ is not specific to an individual or sport. Therefore, while players may have poor nutrition knowledge, they may have a good understanding of nutrition in relation to their sport and this is not reflected in their score. A final limitation of the study is that despite responses from a global sample of the population, the questionnaire was only distributed in English. Consequently, some players may not have been able to understand questions or may have been deterred from completing the NSKQ.

Conclusions and future directions
This was the first study to quantify the nutrition knowledge of elite squash players. Players were found to have average nutrition knowledge (56%). Sex was shown to have no effect on players nutrition knowledge. Age and world ranking were shown to have a weak positive effect on nutrition knowledge. Players who had a relevant undergraduate degree had better nutrition knowledge than those who had no relevant education. Players who consulted with a sports nutritionist were shown to have better nutrition knowledge than those who obtained nutrition information from the internet or a sport scientist. Consequently, based on data from this study, elite squash players should aim to increase their nutrition knowledge by consulting with a sports nutritionist. Future research should aim to quantify the effectiveness of a nutrition education intervention at increasing the nutrition knowledge of elite squash players.
Players had poor knowledge of contemporary carbohydrate and protein guidelines with previous research reporting mismatches between guidelines and dietary intakes [11]. However, it is plausible that these guidelines are not specific to elite squash players and do not translate into poor dietary practices. Future research should quantify the training load and dietary practices of elite squash players to create specific nutritional recommendations for the sport. This will provide information on whether players dietary practices are optimal in relation to their training load and will create specific nutrition recommendations for elite squash players as exhibited in other racket [8] and high intensity intermittent sports [9]. This data can also be used to inform nutritional education interventions in elite squash players.

Funding
No funding sources were required.

Availability of data and materials
Most of the data generated or analysed during this study are included in this published article [and its supplementary information files] such as overall RNSKQ scores and subsection scores as well as individual RNSKQ question scores (ST1-ST87). Individual players scores cannot be request due to identification of players.

Declarations
Ethics approval and consent to participate The research was approved by Sheffield Hallam University's ethics committee (ER23597808). All players provided informed consent prior to participating in the research.

Consent for publication
All participants gave consent for publication.