Athletic Performance: Pre-Workout Evidence Across Ingredients

Evidence-based guide to supplements that enhance athletic performance, strength, endurance, and recovery. Grades for caffeine, creatine, beta-alanine, nitrates, and others based on systematic reviews.

When to see a doctor / red flags

If you are new to intense training, have undiagnosed chest pain, shortness of breath, joint pain, or a history of arrhythmia or cardiac disease, see a doctor before adding supplements or increasing exercise intensity. Similarly, if you take prescription medications, consult your prescriber before adding caffeine, stimulants, or other performance aids—interactions are common.

What's happening: brief overview of athletic performance

Athletic performance depends on a hierarchy: genetics → consistent training → adequate sleep and nutrition → supplements. Most athletes plateau not from lack of pills but from suboptimal sleep, inconsistent training structure, or undereating. That said, evidence-backed supplements can nudge power output, endurance, and recovery at the margins—typically 2–5% gains—which matter in competitive sport.

Performance supplements work through several mechanisms: enhancing energy availability (creatine), improving oxygen delivery (nitrates), buffering acid during high-intensity effort (beta-alanine), or sharpening focus and reducing fatigue perception (caffeine). The strongest evidence clusters around supplements that address specific, measurable domains: power, repeated high-intensity efforts, or aerobic endurance.

Supplement evidence at a glance

Supplements with strongest evidence

Caffeine

What it does: Blocks adenosine receptors in the brain and spinal cord, reducing fatigue perception, enhancing alertness, and increasing adrenaline output. It also improves muscle contractility and fat oxidation.

Evidence base: Over 100 randomized controlled trials (RCTs) across endurance, power, team sports, and cognitive domains. Meta-analyses consistently show a ~3% improvement in work capacity, power output, and time-to-exhaustion. Effects replicate across trained and untrained populations, though habitual users see smaller gains.

Typical dose: 3–6 mg/kg body weight, 30–60 minutes pre-exercise. A 70 kg athlete consumes 210–420 mg (roughly 2–4 cups of strong coffee). Lower doses (3 mg/kg) minimize jitters and GI upset; higher doses don't proportionally improve performance.

Timeline: Peak blood levels at 30–60 minutes; effects last 4–6 hours.

Key cautions: Tolerance develops within 1–2 weeks of daily use; cycling on/off preserves sensitivity. Avoid after 2 PM if you have sleep problems. Anxiety, jitters, and heart palpitations more common at doses >6 mg/kg, especially in caffeine-naive athletes. Monitor for interactions with medications (some antidepressants, beta-blockers, contraceptives potentiate effects).

Creatine Monohydrate

What it does: Increases phosphocreatine (PCr) stores in muscle, buffering ATP depletion during high-intensity efforts lasting 6–30 seconds. Secondarily promotes water retention in muscle, improving protein synthesis and reducing myostatin (a growth-limiting protein).

Evidence base: ~30 years of RCTs, >300 studies. Cochrane and International Society of Sports Nutrition reviews confirm 5–15% improvements in maximum power, repeated effort performance, and lean mass in resistance-trained athletes. Effects strongest in team sports (football, rugby, hockey) requiring repeated sprints. Minimal benefit in single-effort events (100 m sprint) or endurance-only sports.

Typical dose: Loading: 20 g/day (5 g × 4 times) for 5–7 days, then 3–5 g/day maintenance. Or skip loading and consume 3 g/day for 30 days (slower accumulation, same endpoint). Monohydrate is most studied; other forms (ethyl ester, buffered) show no advantage.

Timeline: Loading reaches muscle saturation in 5–7 days; maintenance phase takes 30+ days without a load. Effects persist 4–6 weeks after stopping.

Key cautions: Mild weight gain (1–2 kg) from water retention is expected. Monitor kidney function if you have pre-existing renal disease. No increased injury risk in normal doses. Creatine is contraindicated in dehydration or uncontrolled hypertension. Cost is minimal; monohydrate (not fancy forms) is supported by evidence.

Nitrates (Beetroot, Spinach)

What it does: Dietary nitrates are converted to nitric oxide (NO) in blood vessels, improving vasodilation, oxygen delivery, and mitochondrial efficiency. Endothelium-dependent flow increases by ~10–15%.

Evidence base: 50+ RCTs, predominantly in cycling and running. Meta-analyses show ~2–3% improvements in VO₂ max, time-to-exhaustion, and power output at lactate threshold. Effects strongest in endurance athletes with lower baseline fitness and those with lower dietary nitrate intake (Western diets). Some studies report null findings; response variability is high (~30% of athletes are "non-responders").

Typical dose: Beetroot juice: 500 mL (6–8 mmol nitrate) consumed 2–3 hours pre-exercise. Concentrated beetroot shots (70 mL) provide equivalent nitrate. Spinach, arugula, and lettuce also work but are less practical acutely.

Timeline: Onset 2–3 hours; peak at 4–6 hours. Effects diminish 24 hours post-consumption.

Key cautions: Beetroot juice can stain teeth and urine red (harmless). Some athletes report GI upset or bloating. If you have hypotension or take phosphodiesterase-5 inhibitors (sildenafil), use caution—NO amplifies those effects. High dietary nitrate may theoretically increase endogenous nitrosamine formation, but evidence in athletes is lacking. Safe for most; contraindicated if you have hyperthyroidism (high iodine content in some preparations).

Supplements with moderate evidence

Beta-Alanine

What it does: Precursor to carnosine, which buffers hydrogen ions (acid) in muscle during high-intensity effort. Higher muscle carnosine → greater acid buffering → improved performance in the 30-second to 10-minute effort window.

Evidence base: 50+ RCTs. Meta-analyses show ~2–3% improvements in repeated sprint performance, 1–4 minute time trials, and resistance training volume (reps to failure). Effects strongest in repeated efforts; minimal gain in single maximal efforts. Most robust in trained athletes; untrained populations show variable response.

Typical dose: 3–6 g/day in divided doses (0.75–1.5 g per dose) for 4–6 weeks to accumulate muscle carnosine. Loading faster (~6–8 weeks) with higher doses; low dose (~3 g/day) takes 10+ weeks. Duration matters more than high single doses.

Timeline: No acute effect; carnosine accumulates over weeks. Benefits persist 2–4 weeks after discontinuation.

Key cautions: Paresthesia (tingling in face, hands, feet) is common at doses >3 g/day—harmless but annoying. Divide into small doses to minimize. Long-term safety (>1 year) is limited. Vegetarians often have lower baseline muscle carnosine; they may see larger relative gains.

Sodium Bicarbonate (Baking Soda)

What it does: Alkalizes extracellular pH, increasing the buffering gradient for acid (hydrogen ions) exiting muscle. Similar mechanism to beta-alanine but acute (works the day-of).

Evidence base: 40+ RCTs. Cochrane review found ~1–3% improvements in repeated sprint performance and high-intensity efforts lasting 1–10 minutes. Strongest evidence in combat sports (boxing, judo) and repeated sprints. Less consistent in endurance or single-effort power.

Typical dose: 0.3 g/kg body weight, 60–90 minutes pre-exercise. A 70 kg athlete consumes ~21 g (roughly 5 teaspoons mixed in water or a slurry). Timing matters; earlier consumption reduces GI side effects but blunts efficacy.

Timeline: Onset 60–90 minutes; peak 2–3 hours; duration ~4 hours.

Key cautions: GI distress (cramping, diarrhea, nausea) is the main side effect in ~30% of users. Dose-dependent; start low and titrate. Not recommended if you have hypertension or kidney disease. High sodium load; monitor if sodium-restricted.

Branched-Chain Amino Acids (BCAAs)

What it does: Leucine, isoleucine, and valine compete with tryptophan for brain uptake, potentially reducing serotonin-mediated fatigue. Also provide substrates for protein synthesis if carbohydrate/overall protein intake is low.

Evidence base: 30+ RCTs with mixed results. Small studies report reduced perceived exertion and fatigue in endurance athletes; however, meta-analyses show no consistent advantage in power, strength, or endurance when total protein intake is adequate (1.6+ g/kg/day). Benefits may be limited to athletes with very low protein intake (<0.8 g/kg/day) or extreme endurance events (ultra-marathons, multi-day efforts).

Typical dose: 5–10 g, 1–2 hours pre-exercise or post-exercise. Often combined with carbohydrate or protein shakes.

Timeline: Acute effect (within hours); peaks at 1–2 hours.

Key cautions: Redundant if you consume whey, casein, or a complete protein meal. May increase ammonia (from leucine catabolism) in those with liver disease. Safe for most; prioritize whole protein sources first.

Supplements with weak or insufficient evidence

Citrulline Malate

What it does: Precursor to arginine; boosts nitric oxide production, improving blood flow, reducing fatigue, and enhancing the "pump."

Evidence base: 15+ small RCTs. Some show modest (~3%) gains in bench press reps and leg press volume; others report null findings. Meta-analyses suggest small, inconsistent effect sizes. Variability high; individual response unpredictable. Studies are often industry-sponsored and small (n < 30).

Typical dose: 6–8 g, 60–90 minutes pre-exercise.

Key cautions: Safe; well-tolerated. But evidence is weaker than caffeine or creatine, and cost–benefit is questionable for most.

Beta-Hydroxy-Beta-Methylbutyrate (HMB)

What it does: Metabolite of leucine; promotes protein synthesis and reduces proteolysis (muscle breakdown), theoretically preserving muscle during caloric deficit or intense training.

Evidence base: 20+ RCTs. Small gains (1–2 kg lean mass) in untrained or sedentary individuals; minimal benefit in resistance-trained athletes eating adequate protein. Most studies are 4–12 weeks; long-term data lacking. Effect sizes often small and offset by cost.

Typical dose: 3 g/day in divided doses.

Key cautions: Safe; no known toxicity. Expensive relative to evidence; prioritize adequate protein intake first.

Cordyceps

What it does: Fungal-derived compound traditionally used in Chinese medicine for energy and stamina. Proposed mechanisms: ATP production, mitochondrial function, oxygen utilization.

Evidence base: <10 small, mostly open-label or quasi-randomized trials. No robust Cochrane review. Most studies in Asian populations with doses and formulations poorly standardized. No clear advantage over placebo in published RCTs; effect sizes unclear.

Typical dose: Highly variable; 1–3 g/day common.

Key cautions: Safety data limited. Allergic reactions reported in susceptible individuals. Insufficient evidence to recommend; avoid if pregnant or immunocompromised.

Lifestyle factors that often outperform supplements

• Sleep: 7–9 hours nightly is non-negotiable. Sleep deprivation halves power output and VO₂ max gains. More powerful than any supplement.
• Periodized training: Progressive overload, deload weeks, and sport-specific programming drive 10–30% gains. Haphazard training + supplements = mediocre results.
• Nutrition (whole-food priority): Adequate protein (1.6–2.2 g/kg), carbohydrate timing, and micronutrient-rich foods (iron, zinc, B vitamins) are foundational. Most athletes underfuel; fixing this alone beats most supplements.
• Hydration: Even 2% dehydration drops power output ~8%. Water is free and underrated.
• Recovery modalities: Stretching, foam rolling, active recovery days, and stress management reduce injury risk and improve adaptations more reliably than pills.

Putting it together: a starter framework

For strength and power athletes (weightlifting, rugby, team sports):

• Prioritize: creatine monohydrate (5 g/day, indefinitely) and caffeine (3–5 mg/kg pre-competition). Both have strong evidence and low cost.
• Consider adding: beta-alanine (3 g/day for 6 weeks) if repeated sprints are game-critical.
• Ensure: adequate protein (1.8–2.2 g/kg/day), sleep, and periodized training. Skip citrulline malate unless money is no object.

For endurance athletes (cycling, running, triathlon):

• Prioritize: caffeine (3–6 mg/kg 30–60 min pre-exercise) and dietary nitrates (beetroot juice 500 mL 2–3 hours pre-race). Evidence is strong to moderate; cost-effective.
• Consider: creatine (3 g/day) if your sport has short, intense intervals (e.g., triathlon run finish).
• Assess your baseline: nitrates work better if you're not already a high-vegetable eater. If you are, gains are smaller.
• Avoid: BCAAs and cordyceps unless you're underfed (fix nutrition first).

For all athletes:

• Start with one supplement: Add one at a time so you can assess personal response. Stacking five supplements makes it impossible to know what works.
• Test during training, not competition: Your first creatine loading, beta-alanine tingle, or beetroot juice GI surprise should not occur on race day.
• Track objectively: Power output (via power meter or app), time-to-exhaustion, reps, or race time. "Feels better" is placebo; numbers don't lie.
• Re-assess every 4–8 weeks: If no objective gain, discontinue. Supplements that don't work for you aren't worth the money.
• Consult an anti-doping authority: If you compete in tested sports, verify supplement legality (especially pre-workout mixes, which sometimes contain banned stimulants).