Supplements with good to strong evidence of achieving benefits to performance when used in specific scenarios
| Caffeine | |
| Overview | Caffeine is a stimulant that possesses well-established benefits for athletic performance across endurance-based situations, and short-term, supramaximal and/or repeated sprint tasks. |
| Mechanism | Adenosine receptor antagonism; increased endorphin release; improved neuromuscular function; improved vigilance and alertness; reduced the perception of exertion during exercise29 48 |
| Protocol of use | 3–6 mg/kg of body mass (BM), in the form of anhydrous caffeine (ie, pill or powder form), consumed ~60 min prior to exercise49 Lower caffeine doses (<3 mg/kg BM, ~200 mg), provided both before and during exercise; consumed with a CHO source48 |
| Performance Impact | Improved endurance capacity such as exercise time to fatigue50 and endurance-based time-trial (TT) activities of varying duration (5–150 min), across numerous exercise modalities (ie, cycling, running, rowing and others)49 Low doses of caffeine (100–300 mg) consumed during endurance exercise (after 15–80 min of activity) may enhance cycling TT performance by 3%–7%.51 52 During short-term, supramaximal and repeated sprint tasks, 3–6 mg/kg BM of caffeine taken 50–60 min before exercise results in performance gains of >3% for task completion time, mean power output and peak power output during anaerobic activities of 1–2 min in duration,53 and of 1%–8% for total work output and repeat sprint performances during intermittent team game activity.54 55 |
| Further considerations and potential side effects | Larger caffeine doses (≥9 mg/kg BM) do not appear to increase the performance benefit,56 and are more likely to increase the risk of negative side effects, including nausea, anxiety, insomnia and restlessness.29 Lower caffeine doses, variations in the timing of intake before and/or during exercise, and the need for (or lack thereof) a caffeine withdrawal period should be trialled in training prior to competition use. Caffeine consumption during activity should be considered concurrent with carbohydrate (CHO) intake for improved efficacy.52 Caffeine is a diuretic promoting increased urine flow, but this effect is small at the doses that have been shown to enhance performance.57 |
| Creatine | |
| Overview | Creatine loading can acutely enhance the performance of sports involving repeated high-intensity exercise (eg, team sports), as well as the chronic outcomes of training programmes based on these characteristics (eg, resistance or interval training), leading to greater gains in lean mass and muscular strength and power.58 59 |
| Mechanism | Supplementation increases muscle creatine stores, augmenting the rate of PCr resynthesis, thereby enhancing short-term, high-intensity exercise capacity60 and the ability to perform repeated bouts of high-intensity effort. |
| Protocol of use | Loading phase: ~20 g/day (divided into four equal daily doses), for 5–7 days61 Maintenance phase: 3–5 g/day (single dose) for the duration of the supplementation period62 Note: concurrent consumption with a mixed protein/CHO source (~50 g of protein and CHO) may enhance muscle creatine uptake via insulin stimulation.10 |
| Performance Impact | Enhanced maximum isometric strength63 and the acute performance of single and repeated bouts of high-intensity exercise (<150 s duration); most pronounced effects evident during tasks <30 s13 61 Chronic training adaptations include lean mass gains and improvements to muscular strength and power.58 59 Less common: enhanced endurance performance resulting from increased/improved protein synthesis, glycogen storage and thermoregulation64 65 Potential anti-inflammatory and antioxidant effects are noted.66 |
| Further considerations and potential side effects | No negative health effects are noted with long-term use (up to 4 years) when appropriate loading protocols are followed.67 A potential 1–2 kg BM increase after creatine loading (primarily as a result of water retention66 68) may be detrimental for endurance performance or in events where the BM must be moved against gravity (eg, high jump, pole vault) or where athletes must achieve a specific BM target. |
| Nitrate | |
| Overview | Dietary nitrate (NO3 −) is a popular supplement that has been commonly investigated to assess any benefits for prolonged submaximal exercise69 and high-intensity, intermittent, short-duration efforts.70 71 |
| Mechanism | Enhances nitric oxide (NO) bioavailability via the NO3
−-nitrite-NO pathway, playing an important role in the modulation of skeletal muscle function72 Nitrate augments exercise performance via an enhanced function of type II muscle fibres73; a reduced ATP cost of muscle force production; an increased efficiency of mitochondrial respiration; an increased blood flow to the muscle; and a decrease in blood flow to VO2 heterogeneities.74 |
| Protocol of use | High nitrate-containing foods include leafy green and root vegetables, including spinach, rocket salad, celery and beetroot. Acute performance benefits are generally seen within 2–3 hours following an NO3 − bolus of 5–9 mmol (310–560 mg).75 Prolonged periods of NO3 − intake (>3 days) also appear beneficial to performance70 76 and may be a positive strategy for highly trained athletes, where performance gains from NO3 − supplementation appear harder to obtain.77 |
| Performance impact | Supplementation has been associated with improvements of 4%–25% in exercise time to exhaustion and of 1%–3% in sport-specific TT performances lasting <40 min in duration.73 78 Supplementation is proposed to enhance type II muscle fibre function,73 resulting in the improvement (3%–5%) of high-intensity, intermittent, team-sport exercise of 12–40 min in duration.70 71 Evidence is equivocal for any benefit to exercise tasks lasting <12 min.76 79 |
| Further considerations and potential side effects | The available evidence suggests there appear to be few side effects or limitations to nitrate supplementation. There may exist the potential for GI upset in susceptible athletes, and should therefore be thoroughly trialled in training. There appears to be an upper limit to the benefits of consumption (ie, no greater benefit from 16.8 mmol (1041 mg) vs 8.4 mmol (521 mg)).80 Performance gains appear harder to obtain in highly trained athletes.77 |
| Beta-alanine | |
| Overview | Beta-alanine augments intracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance. |
| Mechanism | A rate-limiting precursor to the endogenous intracellular (muscle) buffer, carnosine; the immediate defence against proton accumulation in the contracting musculature during exercise81 Chronic, daily supplementation of Beta-alanine increases skeletal muscle carnosine content.82 |
| Protocol of use | Daily consumption of ~65 mg/kg BM, ingested via a split-dose regimen (ie, 0.8–1.6 g every 3–4 hours) over an extended supplement time frame of 10–12 weeks82 |
| Performance impact | Small, but potentially meaningful performance benefits (~0.2%–3%) during both continuous and intermittent exercise tasks of 30 s to 10 min in duration82–84 |
| Further considerations and potential side effects | A positive correlation between the magnitude of muscle carnosine change and performance benefit remains to be established.82 Large interindividual variations in muscle carnosine synthesis have been reported.85 The supplement effectiveness appears harder to realise in well-trained athletes.86 There is a need for further investigation to establish the practical use in various sport-specific situations.82 87 Possible negative side effects include skin rashes and/or transient paraesthesia. |
| Sodium bicarbonate | |
| Overview | Sodium bicarbonate augments extracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance. |
| Mechanism | Acts as an extracellular (blood) buffer, aiding intracellular pH regulation by raising the extracellular pH, and HCO3− concentrations81 88 The resultant pH gradient between the intracellular and extracellular environments leads to efflux of H+ and La− from the exercising muscle.88 89 |
| Protocol of use | Single acute NaHCO3 dose of 0.2–0.4 g/kg BM, consumed 60–150 min prior to exercise90 91 Alternative strategies include the following: Split doses (ie, several smaller doses giving the same total intake) taken over a time period of 30–180 min92 Serial loading with 3–4 smaller doses per day for 2–4 consecutive days prior to an event93–95 |
| Performance impact | Enhanced performance (~2%) of short-term, high-intensity sprints lasting ~60 s in duration, with a reduced efficacy as the effort duration exceeds 10 min90 |
| Further considerations and potential side effects | Well-established GI distress may be associated with this supplement. Strategies to minimise GI upset include the following: Coingestion with a small, carbohydrate-rich meal (~1.5 g/kg BM carbohydrates)96 Use of sodium citrate as an alternative97 Split dose or stacking strategies93–95 Given the high potential for GI distress, thorough investigation into the best individualised strategy is recommended prior to use in a competition setting. |