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Hydration, Timing, and Supplements

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CSCS Certified Strength and Conditioning Specialist

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1 Introduction

About the CSCS Exam Structure and Content Breakdown Pass Rates and Scoring How to Use This Guide

2 Exercise Science

Muscular and Neuromuscular Systems Skeletal and Cardiovascular Systems Bioenergetics and Metabolism Biomechanics Physiological Adaptations to Training

3 Sport Psychology & Nutrition

Motivation and Goal Setting Arousal, Anxiety, and Performance Mental Skills and Team Dynamics Macronutrients and Energy Hydration, Timing, and Supplements

4 Exercise Technique

Resistance Training Technique Olympic Lifting Technique Plyometric and Speed Training Flexibility and Warm-up Spotting and Equipment Safety

5 Program Design

Needs Analysis and Training Goals Training Variables Periodization Models Resistance Training Program Design Speed, Agility, and Conditioning Programs

6 Testing, Evaluation & Administration

Pre-Participation Screening Cardiovascular and Body Composition Testing Strength, Power, and Speed Testing Flexibility Assessment Facility Management and Legal Issues

Hydration, Timing, and Supplements

Key Takeaways Explain This Topic AI

Pre-exercise hydration: 5-7 mL/kg body weight 4 hours before; an additional 3-5 mL/kg if urine is dark 2 hours before.

During exercise: 0.4-0.8 L/hour; add sodium (300-600 mg/L) for exercise >1 hour or heavy sweating.

Post-exercise: Replace 150% of body weight lost (1.5 L per kg lost) over 2-4 hours with sodium-containing fluids.

Pre-workout nutrition: 1-4 g/kg carbs 3-4 hours before; post-workout: 1.0-1.2 g/kg carbs plus 20-40g protein within 2 hours.

Evidence-based supplements include creatine (3-5g/day), caffeine (3-6 mg/kg), beta-alanine (3.2-6.4g/day), and sodium bicarbonate (0.3 g/kg).

Last updated: January 2026

Quick Answer: Hydrate with 5-7 mL/kg 4 hours pre-exercise, 0.4-0.8 L/hour during, and replace 150% of weight lost post-exercise. Legal evidence-based supplements include creatine (3-5g/day), caffeine (3-6 mg/kg), beta-alanine (3.2-6.4g/day), and sodium bicarbonate (0.3 g/kg).

Hydration Guidelines

Maintaining proper hydration is critical for performance and safety. Even mild dehydration (2% body weight loss) impairs performance.

Pre-Exercise Hydration

  • Timing Recommendation Purpose
  • 4 hours before 5-7 mL/kg body weight Achieve euhydration
  • 2 hours before 3-5 mL/kg (if urine is dark) Fine-tune hydration status

Example for 70 kg athlete:

  • 4 hours before: 350-490 mL (12-17 oz)
  • 2 hours before: 210-350 mL if needed (7-12 oz)
  • Hydration Status Indicators
  • Indicator Well Hydrated Dehydrated
  • Urine color Pale yellow Dark yellow/amber
  • Urine frequency Regular Infrequent
  • Body weight Stable Decreased
  • Thirst Minimal Strong
  • During Exercise Hydration
  • Condition Fluid Intake Sodium Needs
  • Exercise <1 hour 0.4-0.8 L/hour Usually not needed
  • Exercise >1 hour 0.4-0.8 L/hour 300-600 mg/L (sports drink)
  • Heavy sweating Individualize based on sweat rate 300-600 mg/L
  • Hot environment Higher end of range Essential

Key Point: Don't overdrink! Hyponatremia (low blood sodium from excessive water intake) is dangerous. Match fluid intake to sweat losses.

  • Calculating Sweat Rate
  • Sweat Rate = (Pre-exercise weight - Post-exercise weight + Fluid consumed) / Exercise duration
  • Post-Exercise Rehydration
  • Recommendation Amount Timing
  • Total fluid replacement 150% of weight lost Over 2-4 hours
  • Sodium inclusion Include sodium-containing foods/fluids Essential for retention

Example: If an athlete loses 1 kg during exercise, they should consume 1.5 L of fluid over 2-4 hours post-exercise.

  • Exercise Nutrition Timing
  • Pre-Exercise Nutrition
  • Timing Carbohydrate Protein Fat Fiber
  • 3-4 hours before 1-4 g/kg 20-30g Moderate Moderate
  • 1-2 hours before 1 g/kg 10-20g Low Low
  • <1 hour before 0.5 g/kg (liquid) Optional Avoid Avoid

Key Point: Reduce fat and fiber closer to exercise to prevent GI distress.

During Exercise Nutrition

  • Duration Carbohydrate Needs Source
  • <45 minutes Not needed Water only
  • 45-75 minutes Small amounts or mouth rinse Sports drink
  • 1-2.5 hours 30-60 g/hour Sports drinks, gels
  • >2.5 hours Up to 90 g/hour Multiple carb sources (glucose + fructose)
  • Post-Exercise Nutrition
  • Nutrient Amount Timing Purpose
  • Carbohydrate 1.0-1.2 g/kg Within 30-60 min, continue for 4-6 hours Glycogen resynthesis
  • Protein 20-40g (0.3 g/kg) Within 2 hours Muscle protein synthesis
  • Fluid 150% of weight lost Over 2-4 hours Rehydration

Glycogen Resynthesis: Rate is highest immediately post-exercise. Consuming carbs within 30-60 minutes takes advantage of this "glycogen window."

Evidence-Based Supplements

Only a small number of supplements have strong evidence supporting their ergogenic effects. Always verify supplements are third-party tested for banned substances.

Tier 1: Strong Evidence

Supplement Dose Loading Benefit Best For

Creatine Monohydrate 3-5 g/day Optional: 20g/day for 5-7 days Increased strength, power, muscle mass Strength/power sports

  • Caffeine 3-6 mg/kg 30-60 min before exercise Increased endurance, reduced perceived exertion All sports
  • Beta-Alanine 3.2-6.4 g/day Divide into 0.8-1.6g doses Increased high-intensity capacity 1-10 minute efforts
  • Sodium Bicarbonate 0.3 g/kg 60-90 min before exercise Buffer lactic acid 1-7 minute high-intensity
  • Creatine Details
  • Aspect Information
  • Mechanism Increases phosphocreatine stores for ATP regeneration
  • Loading protocol 20g/day (4 x 5g) for 5-7 days, then 3-5g/day
  • No-loading protocol 3-5g/day (takes 3-4 weeks to saturate)
  • Best form Creatine monohydrate (most studied, effective)
  • Side effects Initial weight gain (water retention), generally safe
  • Caffeine Details
  • Aspect Information
  • Mechanism Adenosine receptor antagonist; reduces perceived exertion
  • Dose 3-6 mg/kg (low doses still effective)
  • Timing 30-60 minutes pre-exercise
  • Forms Coffee, pills, gum, energy drinks
  • Considerations Tolerance develops; may disrupt sleep
  • Beta-Alanine Details
  • Aspect Information
  • Mechanism Increases muscle carnosine, buffers H+ ions
  • Loading Takes 2-4 weeks of daily use to saturate
  • Side effect Paresthesia (tingling)—harmless, reduce dose if bothersome
  • Best for Repeated high-intensity efforts lasting 1-10 minutes
  • Sodium Bicarbonate Details
  • Aspect Information
  • Mechanism Extracellular buffer, delays fatigue from acidosis
  • Protocol 0.3 g/kg, 60-90 minutes before exercise
  • Side effects GI distress common—practice in training
  • Alternative Sodium citrate (fewer GI issues)
  • Third-Party Testing

Athletes should only use supplements verified by third-party testing programs:

  • Program Description
  • NSF Certified for Sport Tests for banned substances and label accuracy
  • Informed Sport Banned substance testing program
  • BSCG (Banned Substances Control Group) Independent testing for banned substances

Warning: Many supplements are contaminated with banned substances or don't contain what the label claims. ALWAYS use third-party tested products.

Supplements with Limited or No Evidence

  • Supplement Status
  • BCAAs Limited evidence; adequate protein intake sufficient
  • Glutamine No ergogenic benefit for healthy athletes
  • HMB May help untrained individuals; limited benefit for trained
  • Tribulus No evidence for testosterone or performance enhancement
  • Most "testosterone boosters" No evidence; may contain banned substances