Table 3 Studies focused on nutrition topic

Energy expenditure, energy and nutritional intake

da Silva et al. [68]

Energy expenditure, estimated by indirect equations using the total time in each activity, revealed a total energy expenditure during the match of 734 kcal (first half: 374 kcal; second half: 359 kcal)

Nutritional strategies should be adapted to referee activities

Silva et al. [69]

The ingestion of a pre-determined volume of carbohydrates reduced the sweat rate to 0.72 ± 0.12 l h⁻¹ compared to ad libitum (1.16 l min⁻¹). In addition, the time spent in low-intensity activities was also reduced by 69.9% with a carbohydrate solution

Carbohydrate rehydration is an effective solution to decrease the time spent on low-intensity activities

Teixeira et al. [72]

On average, the daily energy intake was 2819 kcal day⁻¹ or 36 kcal day⁻¹. Regarding the macronutrient intake, soccer referees did not fit the recommendations of carbohydrates (4.1 g kg⁻¹). On the other hand, the average intake of protein is near the upper limit of guidelines (1.7 g kg⁻¹). Saturated fat exceeded the recommendation and polyunsaturated fats were below the recommendations. Folate, vitamin A, vitamin C, magnesium and calcium intakes did not meet the recommendations. 78% of participants exceeded the recommendations of sodium intake

The intake of carbohydrates could compromise the preparation and recovery from training sessions and matches. Therefore, referees need nutritional advice

Renon and Collado [73]

The daily energy intake was, on average, 2409 kcal day⁻¹. The intake of carbohydrates was low, while the protein intake was high. No differences in carbohydrate intake were found according to the type of day (rest, training and match), although referees tended to ingest more carbohydrates on match days. The intake of vitamins B1, B2, B6, B12 and minerals (calcium, magnesium, iron) exceeded the guidelines. On the other hand, magnesium intake met the recommendations. No differences in minerals and fibre were found by type of day

Overall, soccer referees ingested limited carbohydrates, while protein intake exceeded the recommendations. The periodization of nutrients needs to be adjusted appropriately for the type of day

Metz et al. [74]

Energy intake was higher during the game day compared to the day off (game day: 2782 kcal; day off 2270 kcal). Considering the two conditions (game day vs day off), differences between macronutrients were significant for carbohydrates, while negligible differences in protein and fat intake were found. Carbohydrate intake tends to increase during breakfast and snacks and, in parallel, decrease during dinner. The stress level before each meal tended to be higher on match day

Soccer referees must adapt their intake according to match demands or recovering days

Paes and Fernandez [70]

Backward movements at velocities similar to jogging and walking showed an energy expenditure of less than 9 kcal. Energy expenditure estimated by mathematical equations overestimated the observed values

Backward movements should not be defined as high-intensity activities, and equations to predict energy expenditure have associated errors related to higher body fat levels found in referees

Malaguti et al. [71]

Using a watch, energy expended during the training sessions (referees: 997 kcal; assistant referees: 701 kcal) was lower than during the matches (referees: 1266 kcal; assistant referees: 994 kcal). Referees from a lower competitive level tended to consume more dietary supplements following a friendly suggestion. 46% of international referees reported that they follow the advice of an expert

Referees did not have adequate knowledge about supplements and their impact on soccer. With this in mind, official federations should promote educational lessons about nutrition

Gacek et al. [75]

Referee experience was positively associated with the frequency of fruit, dairy products, nuts and alcohol consumption. On the other hand, carbohydrate drinks, sea fish and cereals were negatively related to experience. The self-efficacy questionnaire was associated with the frequency of consumption of dairy products with fat content, eggs and mineral water

Overall, the nutritional choices of soccer referees tended to improve with age and experience

Mascherini et al. [76]

Soccer referees ingested 3.1 g kg⁻¹, 1.3 g kg⁻¹ and 1.1 g kg⁻¹ of carbohydrates, fat and protein, respectively. Regarding micronutrients, soccer referees ingested 661 mg day⁻¹, 2929 mg day⁻¹, 794 mg day⁻¹, 10.3 mg day⁻¹, 21.2 μg day⁻¹, 0.3 μg day⁻¹, 381 μg day⁻¹ of calcium, potassium, zinc, magnesium, iodine, vitamin B12 and vitamin B9, respectively

Regarding the nutritional intake of soccer, referees did not follow the guidelines proposed for soccer players

Body size and composition

Krustrup et al. [13]

Assistant referees loss on average 0.8 kg, which corresponds to 1.0% of body mass. They ingested 0.36 l of fluids thereby, estimated sweat rate was 1.17 l

(see Table 2)

Silva et al. [61]

The mean age of present sample was 33.7 years. Mean value of fat mass percentage was 18.5%. Younger referees (20.0–29.9 years) showed lower values of fat mass percentage in comparison to the other age-groups (30–39.9 years; ≥ 40 years). No differences were found between national and regional referees

Referees presented higher values of fat mass than soccer players and, consequently, nutritional interventions should be implemented

Stulp et al. [59]

Referees were on average taller 4 cm than assistant referees. Height was associated with authority and effectiveness on the match. Taller players compared shorter referees mark less fouls

Taller referees maintained the control of the match once mark less fouls

Casajus et al. [62]

Referees had lower values of fat mass percentage than assistant referees. Age comparisons indicated that younger referees had lower fat mass percentage than older referees

Values of fat mass percentage were within the normal range of healthy population. Body composition assessment should be part of FIFA fitness evaluation

Casajus et al. [63]

Body fat was significantly lower in referees (1st, 2nd and 2nb B division) than assistant referees (1st and 2nd divisions). Comparisons between age groups showed that older referees had, on average, higher values of fat mass percentage than younger referees. A trend towards the stabilization of fat mass across 1-year among referees was noted—the values ranged 8–14%

The stabilization of fat mass percentage between 8 and 14% is particular important to achieve the standards required to be a referee. Monitorization of fat mass should be considered across the season

Bozdogan et al. [77]

Among referees, body fat had impact on YOYO distance covered and repeated sprint ability test (total time). Among assistant referees, body fat was associated with repeated sprint ability test

Given the negative impact of fat mass on running performance, appropriate training programs and nutrition interventions should be considered

Banda et al. [60]

Referees were 4.5 cm than assistant referees. Differences by between competitive level suggested that FIFA referees had, on average, lower values of fat mass percentage and sum of six skinfolds in comparison to ZIFA referees

Age is an important parameter to attain refereeing elite and body composition should be monitored, particularly at older ages

Casajus et al. [64]

Variables of body composition extracted from bioimpedance and dual-energy X-ray absorptiometry showed significant differences. Assistant referees had higher values of fat mass than referees (assistant referees: 17.8% with dual-energy X-ray absorptiometry, 13.9% with bioimpedance; referees: 15.6% with dual-energy X-ray absorptiometry; 11.7 with bioimpedance). In general, and considering all sample (referees and assistant referees), bioimpedance underestimated 3.87% fat mass and overestimated 3.56 kg fat-free mass compared with dual-energy X-ray absorptiometry

Optimal body composition is required to promote referees to elite level. In this context, general equations based on bioimpedance should not be used among soccer referees. In contrast, specific equations need to be developed

Castillo et al. [40]

10-week competitive period at end of the season noted a significant decrement on skinfold thickness and, in opposition, lean body mass increased 1.1 kg

Intense competition at the end of the season caused changes in skinfolds, estimated fat mass and lean body mass

McCarrick et al. [24]

The present study suggested that height was related to the number of yellow, red cards and penalties registered by match in lower competitive leagues. Contrasting results were obtained to higher competitive leagues

The impact of height on punitive actions is dependent of the competitive context

Petri et al. [66]

Correlation coefficients between fat mass percentage derived from dual-energy X-ray absorptiometry and anthropometry varied between moderate to very large (the only exception was the sum of anterior and medial calf). The current study presented a skinfold model to estimate fat mass percentage derived from dual-energy X-ray absorptiometry: %FM = 8.386 + (0.478 × iliac crest skinfold) + (0.395 × abdominal skinfold (r = 0.781; R² = 0.610; SEE = 2.62%)

National and international referees should assess body composition based on the proposed anthropometric equation

Lopez-Garcia et al. [67]

Assistant referees presented, on average, higher body fat mass percentage than referees based on anthropometry (referees: 21.3%; assistant referees: 22.7%) and dual-energy X-ray absorptiometry (referees: 20.9%; assistant referees: 21.5%)

Differences between groups were partially explained by the physical demands of soccer matches