Soccer is a high intensity intermittent sport, featuring critical events completed at high/maximal intensity which is superimposed onto an aerobic base of lower intensity activities and rest. Due to these varying energic demands and the duration of competition the need for optimal nutritional strategies to offset and delay fatigue are paramount. Over the last 50 years, several investigations have been reported on aspects of soccer be they nutrition-focused or those concerning the demands of the sport. Emanating from these scientific papers, observations have been made on the likely factors which result in the fatigue during match-play. Factors such as muscle glycogen depletion and hypoglycaemia are discussed. Studies on the energy demands of soccer have employed a variety of methodologies which are briefly reviewed and vary between the use of heart rate telemetry to the use of global positioning systems (GPS). Moving on from observations of the energy demands of the sport leads to the major focus of this review which highlights key nutritional strategies to support the preparation and recovery of male soccer players to enhance performance, or at least to enable players to perform adequately. This review examines relevant methodologies in assessing training and competitive energy costs as well as the concomitant energy intakes demanded for successful performance outcomes. In order to bring an applied aspect to the overall findings from areas discussed, some practical ideas of feeding strategies are presented.

Energy Expenditure was measured with doubly labelled water technique during heavy sustained exercise with an official finishing team in the Race Across America. Energy Intake was also calculated to produce an energy balance for the race. A team of 4 cyclists (Mean ±SD age: 37+4 yr; body height: 182+8 cm; body mass: 80.8+6.6 kg) completed the race in a relay fashion. The team completed the race in 6 days 10 h and 51 min. Total mean energy expenditure was found to be 43 401 kcals (181 711 kJ) with a mean daily energy expenditure of 6 420 kcals (26 879 kJ). Total mean energy intake from all food and drink consumed was calculated at 29 506 kcals (123 536 kJ) with a mean daily energy intake of 4 918 kcals (20 591 kJ). This resulted in a total mean energy deficit of 13 878 kcals (58 104 kJ) with a mean daily energy deficit of 1 503 kcals (6 293 kJ). The high energy expenditure highlights the need for correct and practical dietary strategies and challenges nutritionists to devise high energy diets that not only contain the correct macronutrient balance, but are also palatable to the cyclists, thus encouraging a high energy intake.

Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg⁻¹ BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg⁻¹ BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg⁻¹ BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg⁻¹ BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.

Pre-exercise meals or single foods containing low glycaemic index (LGI) carbohydrates (CHO) have been shown to enhance performance prior to prolonged steady state exercise compared to high glycaemic index (HGI) CHO. This study investigated the impact of HGI and LGI pre-exercise meals on intermittent high intensity exercise. Nine male recreational football players performed a football specific protocol followed by a 1 km time trial 3.5 h after ingesting 1 of 2 isoenergetic test meals (HGI: 870.3 kcal, LGI: 889.5 kcal), which were either HGI (GI: 80) or LGI (GI: 44). Blood glucose, fatty acids (FA), glycerol, β-hydroxybutyrate, lactate and insulin were assessed before, during, and after the exercise bout, whilst rates of CHO and fat oxidation were determined at 4 time points during the protocol. No significant differences were found for the 1 km time trial (LGI: 210.2±19.1 s: HGI: 215.8±22.6 s) (mean±SD), nor for any of the other variables measured (P>0.05) apart from a significant condition effect with FA and significant interaction effects observed for glucose, β-hydroxybutyrate and lactate (P<0.05). These findings suggest that the type of CHO ingested in a pre-match meal has no significant impact on performance or metabolic responses during 90 min of intermittent high intensity exercise.

Purpose: Variations in substrate metabolism have been identified in women during continuous steady-state aerobic exercise performed at the same relative intensity throughout discrete phases of the menstrual cycle, although some evidence exists that this is abolished when carbohydrate is ingested. This investigation examined the effects of a supraphysiologic exogenous glucose infusion protocol, administered during two phases of the menstrual cycle (follicular and luteal) in eumenorrheic women to identify differences between metabolic, hormonal and substrate oxidative responses. Methods: During the experimental conditions, blood glucose was infused intravenously at rates to “clamp” blood glucose at 10 mM in seven healthy females (age 20 ± 1 y, mass 55.0 ± 4.1 kg, $$\dot V{O_{2peak}}$$V ˙ O 2 p e a k 40.0 ± 1.8 ml/kg/min). Following 30 min of seated rest, participants exercised on a cycle ergometer for 90 min at 60% $$\dot V{O_{2peak}}$$V ˙ O 2 p e a k . During the rest period and throughout exercise, blood metabolites and hormones were collected at regular intervals, in addition to expired air for the measurement of substrate oxidation. Results: Significant differences between ovarian hormones and menstrual phase were identified, with estrogen significantly higher during the luteal phase compared to the follicular phase (213.28 ± 30.70 pmol/l vs 103.86 ± 13.85 pmol/l; p = 0.016), and for progesterone (14.23 ± 4.88 vs 2.11 ± 0.36 nmol/l; p = 0.042). However, no further significance was identified in any of the hormonal, metabolite or substrate utilisation patterns between phases. Conclusion: These data demonstrate that the infusion of a supraphysiological glucose dose curtails any likely metabolic influence employed by the fluctuation of ovarian hormones in eumenorrheic women during moderate exercise.