Workout Recovery Checklist: Evidence-Based Heat vs. Ice Guidance, Protein Targets, Hydration and Practical Routines

Table of Contents

1. Key Highlights:
2. Introduction
3. How muscles recover: the biology behind soreness and adaptation
4. Cold vs. heat: evidence-based guidance for when to use each
5. Protein and calories: rebuilding tissue and restoring energy
6. Hydration, electrolytes and the role of sodium
7. Sleep, hormonal recovery and scheduling training
8. Active recovery, mobility and low-intensity work
9. Therapies and gadgets: what helps and when
10. Measuring recovery: practical tools and metrics
11. Putting it together: a workout recovery checklist and sample plans
12. Common mistakes and myths
13. Real-world examples: how athletes and teams apply recovery protocols
14. When to seek professional advice and red flags
15. Practical, evidence-based checklist (printable)
16. FAQ

Key Highlights:

• Use cold therapy for acute pain and inflammation control; use heat to relieve stiffness and improve mobility. Timing matters: ice soon after injury, heat before activity or for chronic tightness.
• Prioritize adequate protein (20–40 g per meal; 1.2–2.0 g/kg daily depending on goals), structured carbohydrate intake for glycogen replenishment, and consistent sleep (7–9 hours) to maximize repair and adaptation.
• Combine active recovery, hydration with electrolytes, targeted therapies (massage, compression, contrast baths) and objective monitoring (soreness, sleep, HRV) to make day-to-day decisions about training load.

Introduction

Recovery is the intentional side of training. How you spend the hours and days after a hard workout determines whether the session produces adaptation or only leaves you sore. Athletes who treat recovery like a second workout — planning nutrition, sleep, hydration and targeted therapies — maintain performance, reduce injury risk and accelerate progress. This guide turns the most common advice into a practical, evidence-based checklist: when to use heat versus ice, how much protein and carbohydrate to consume, which recovery modalities deliver measurable benefits, and how to read objective signals to adjust training.

The content synthesizes peer-reviewed evidence, performance-practice norms from professional sport, and practical protocols suitable for gym-goers, weekend warriors and competitive athletes. Each section translates physiological principles into concrete steps you can apply after a run, a heavy lifting session, an interval workout or a match.

How muscles recover: the biology behind soreness and adaptation

Training intentionally breaks down muscle fibers and depletes biochemical stores. That damage and stress trigger inflammation, cellular signaling and protein synthesis — the processes responsible for stronger, better-adapted tissue. Understanding these mechanisms explains why different interventions help at specific times.

• Mechanical stress and microtears. High-tension activities (heavy lifting, eccentric contractions) create structural changes to muscle fibers and the connective tissue surrounding them. The repair process recruits satellite cells and protein synthesis pathways that rebuild and strengthen muscle.
• Metabolic stress and glycogen depletion. Endurance and high-intensity interval workouts reduce muscle glycogen. Restoring glycogen requires carbohydrate and time; without it, performance and recovery suffer.
• Inflammation and soreness. Acute inflammation clears debris and starts repair but feels unpleasant. Delayed onset muscle soreness (DOMS) peaks 24–72 hours after unusual or intense exercise. DOMS reflects healing processes rather than ongoing damage alone.
• Hormonal and neural recovery. Sleep and nutrition influence growth hormone, testosterone, insulin-like growth factor (IGF-1) and neural drive — all of which determine recovery quality and readiness for the next session.

These processes overlap in time. Interventions that blunt early inflammation (e.g., icing, NSAIDs) can reduce soreness and speed short-term return to activity but, if used chronically, may attenuate some training adaptations. The goal is to select tools that relieve symptoms when needed while preserving the stimulus that drives improvement.

Cold vs. heat: evidence-based guidance for when to use each

Cold and heat are the two most familiar thermal therapies, but they serve different purposes. Use them with intent rather than habit.

Cold (cryotherapy)

• Best for: acute injuries (sprains, strains, contusions), reducing pain and local swelling, and short-term symptom relief when you need to perform again soon (e.g., between tournament games).
• Mechanism: vasoconstriction reduces blood flow to injured tissue, limits edema and slows metabolic processes that drive pain. Cooling also reduces nerve conduction velocity, which lowers pain sensation.
• Evidence and caveats: Cold immersion and ice can reduce subjective soreness and speed perceived recovery between repeated events. However, repeated cold exposure immediately after strength training may blunt anabolic signaling and reduce muscle hypertrophy gains if used chronically. Limit routine cold use after every strength session if hypertrophy is a primary goal.
• Practical use: Apply ice or cold packs for 10–20 minutes to the affected area in the first 48 hours after an acute injury or after competition when you must recover quickly. For full-body cooling (ice baths), 10–12 minutes at ~10–15°C is common among athletes; longer or colder exposures are not necessary and may be counterproductive.

Heat (thermotherapy)

• Best for: chronic tightness or stiffness, increasing mobility before activity, and improving tissue extensibility after the acute swelling phase has passed.
• Mechanism: Heat promotes vasodilation, increases tissue temperature and elasticity, improves blood flow, and stimulates heat-shock proteins that can aid cellular recovery.
• Evidence and caveats: Heat applied before exercise increases range of motion and may reduce the risk of muscle tears when used as part of a warm-up. Sauna exposure following exercise has been associated with cardiovascular benefits and improved endurance adaptations in some studies. Avoid applying heat immediately to actively bleeding or acutely swollen tissue.
• Practical use: Use moist heat packs or a 10–20 minute hot shower before an activity to loosen muscles. Saunas (15–30 minutes at appropriate temperatures) can be integrated after training on non-injury days to support recovery and vascular conditioning.

Contrast therapy and when to combine Alternating cold and heat (contrast baths) can create vascular pumping, promoting circulation and faster clearance of metabolic byproducts. Athletes use contrast therapy between repeated sessions or during tournaments, but the evidence for superior long-term adaptation is mixed. The most practical role is symptom-focused: contrast baths reduce soreness and the sensation of fatigue when recovery time is scarce.

When to prioritize one over the other

• Acute injury (0–48 hours): prioritize cold to control swelling and pain.
• Chronic stiffness or persistent tightness: prioritize heat before activity or therapy.
• Post-competition same-day recovery: short cold exposure for pain relief and contrast therapy if tolerated.
• Long-term adaptation (strength/hypertrophy): avoid routine cold after every training session to preserve anabolic signaling.

Protein and calories: rebuilding tissue and restoring energy

Nutrition is the foundation of recovery. Meals supply the amino acids, glycogen and cellular energy required for repair and future performance. Precision matters less for casual exercisers and more for athletes chasing performance adaptations.

Daily protein targets

• For general fitness: 1.2–1.6 g/kg body weight per day supports recovery and body composition.
• For strength athletes or those in caloric deficit: 1.6–2.0 g/kg daily preserves muscle mass and supports hypertrophy.
• For older adults: lean toward the higher end of the range because of anabolic resistance.

Per-meal protein and leucine trigger

• Aim for 20–40 g of high-quality protein per meal, depending on body size. Each meal should supply ~2.5–3 g of leucine to maximally stimulate muscle protein synthesis. Lean meats, dairy, eggs and whey are efficient sources.
• Distribute protein evenly across 3–4 meals rather than loading most protein in a single evening meal. Even distribution sustains muscle protein synthesis across the day.

Protein timing

• Immediate post-workout protein is helpful, especially when sessions are long, glycogen-depleting or performed in a fasted state. A 20–40 g dose of whey or a mixed meal within 60–120 minutes supports repair.
• If your next meal falls within 1–2 hours after training, the urgency is lower. The overall daily protein amount and per-meal distribution matter more than a single post-workout window.

Carbohydrate for glycogen

• Strength sessions rely mostly on intramuscular energy, so carbohydrate needs are modest unless training volume is high.
• Endurance sessions and interval workouts require more glycogen replenishment. Consume 1.0–1.2 g/kg carbohydrate in the first 4 hours for rapid glycogen resynthesis after prolonged, glycogen-depleting exercise. When events are repeated within 24 hours, prioritize higher immediate carbohydrate intake.
• Combine protein with carbohydrate (e.g., yogurt with fruit, chocolate milk, rice and chicken) to support both glycogen recovery and protein synthesis.

Calories and energy balance

• Chronic under-eating impairs recovery and compromises immune function. Match calorie intake to training demands. During heavy training blocks, increase calories progressively to support repair and adaptation.
• Short-term caloric deficits can be used for body composition goals, but expect slower recovery and adjust training intensity and recovery strategies accordingly.

Supplements with practical support

• Creatine monohydrate: consistent evidence supports improved recovery of power and performance and faster gains in strength when used with resistance training.
• Omega-3 fatty acids: may reduce exercise-induced muscle soreness and inflammation modestly while offering cardiovascular and joint benefits.
• Beta-alanine: supports high-intensity endurance and may indirectly reduce perceived fatigue.
• Protein powders: convenient for meeting per-meal protein targets when whole-food meals are delayed.

Use supplements as adjuncts, not replacements for a balanced diet. Check ingredients and dosing; consult a clinician if you use medications or have health conditions.

Hydration, electrolytes and the role of sodium

Fluid balance matters for cognitive function, thermoregulation and muscle performance. Rehydration strategy depends on how much you sweat and the duration and intensity of the exercise.

Assess fluid loss

• Weigh yourself immediately before and after exercise. Each kilogram (~2.2 lb) lost represents roughly one liter of sweat. Replace 150% of fluid losses over the next several hours to account for continued losses and urinary excretion (e.g., if you lost 1 kg, drink ~1.5 L).
• Thirst alone is an imperfect cue, especially after prolonged exercise. Use weight changes and urine color as practical guides.

Electrolytes

• Sodium is the key electrolyte to replace after long sessions, heavy sweat losses, or multi-hour events. Sports drinks that contain 300–700 mg sodium per liter support faster rehydration.
• Potassium, magnesium and calcium also matter but are typically restored through food (bananas, leafy greens, dairy, nuts).
• For shorter workouts (<60 minutes) with minimal sweat, water is often sufficient. For sessions longer than 60–90 minutes, include carbohydrate–electrolyte solutions.

Caffeine and recovery

• Caffeine in moderate doses (3–6 mg/kg) before training improves performance; after exercise it may aid glycogen resynthesis when combined with carbohydrate in some contexts. Avoid excessive late-evening caffeine that disrupts sleep.

Practical hydration protocol

• Pre-exercise: drink 400–600 mL of fluid 2–3 hours before; top off with 150–250 mL 15–30 minutes pre-workout if needed.
• During exercise: aim for 150–300 mL every 15–20 minutes for moderate sessions; tailor to sweat rate.
• Post-exercise: follow weight-based replacement and include sodium in fluids or food. A recovery drink like chocolate milk provides a convenient carbohydrate-protein-electrolyte mix for many athletes.

Sleep, hormonal recovery and scheduling training

Sleep is the most potent recovery tool available. It regulates hormonal cycles, memory consolidation for motor skill learning, immune function and metabolic repair.

How much sleep?

• Most adults require 7–9 hours nightly. Athletes involved in high training loads often benefit from 8–10 hours including naps.
• Prioritize consistent bed and wake times to strengthen circadian rhythm and improve sleep quality.

Why sleep matters for training adaptation

• Growth hormone and tissue repair mechanisms are activated during slow-wave sleep.
• Sleep deprivation reduces insulin sensitivity, increases markers of inflammation, and lowers motor skill retention.
• Short naps (20–90 minutes depending on timing) can boost alertness and occasionally offset partial sleep loss, but they do not replace a full night’s recovery.

Schedule training around sleep

• Avoid high-intensity sessions late at night if they impair sleep onset. If evening training is unavoidable, incorporate a wind-down routine: light stretching, dim lights, and avoidance of screens 30–60 minutes before bed.
• Use travel and time-zone considerations (jet lag) when planning competition blocks; prioritize sleep strategy on travel days to reduce performance disruption.

Active recovery, mobility and low-intensity work

Rest does not always mean total inactivity. Active recovery refers to low-intensity movement intended to maintain blood flow, accelerate metabolic clearance and maintain joint mobility without creating additional significant fatigue.

Forms of active recovery

• Low-intensity cycling, walking, swimming or elliptical work for 10–30 minutes.
• Mobility drills and dynamic stretching to maintain range of motion.
• Light skill work that emphasizes technique without heavy loading.

Benefits and practical use

• Active recovery accelerates lactate clearance and reduces perceived soreness compared with complete rest.
• Use active sessions 24–48 hours after intense bouts when DOMS is present but no acute injury exists.
• Keep intensity below 50–60% of maximal efforts to avoid interfering with adaptation.

When to avoid active recovery

• If an acute injury causes swelling, pain, or reduced function, prioritize immobilization and professional assessment instead of movement that could worsen tissue damage.

Therapies and gadgets: what helps and when

The market offers many recovery tools. Some have robust evidence; others provide subjective benefits without clear physiological effects. Choose tools that target your specific goals.

Massage

• Effect: reduces soreness and perceived fatigue, improves range of motion, and promotes relaxation.
• Evidence: systematic reviews show massage reduces DOMS and improves subjective recovery; effects on objective performance are modest.
• Practical use: 10–20 minutes of soft tissue work post-exercise or on rest days. Self-massage tools like foam rollers and massage guns are practical for everyday use.

Compression garments

• Effect: may reduce muscle soreness and perceived fatigue, and could marginally speed recovery when worn after exercise.
• Evidence: small-to-moderate benefits for DOMS and subjective recovery; inconsistent for objective performance improvements.
• Practical use: wear compression tights or sleeves immediately post-exercise or overnight after heavy sessions or competition.

Cryotherapy chambers and cold water immersion

• Effect: reduce pain and inflammation acutely.
• Evidence: cold water immersion helps short-term recovery between repeated bouts (e.g., multi-day events). Routine whole-body cryotherapy has limited independent evidence for adaptation benefits and is costly.
• Practical use: prioritize cold baths and localized ice for acute pain and rapid tournament recovery; avoid frequent cold baths immediately after resistance training if hypertrophy is a priority.

Sauna and heat exposure

• Effect: supports relaxation, circulatory stress and heat-shock protein production; some evidence links sauna use to improved endurance and cardiovascular markers.
• Evidence: athletes who add post-training sauna sessions show improved endurance adaptations in some controlled studies.
• Practical use: 15–30 minutes after training, 2–3 times weekly, can be a useful adjunct for endurance athletes or during deload weeks.

Electrical stimulation and PEMF

• Evidence is mixed. Some athletes use neuromuscular electrical stimulation (NMES) for recovery of muscle activation and to prevent atrophy during immobilization. Pulsed electromagnetic field (PEMF) therapy has limited strong evidence in healthy athletes.

High-tech wearables

• Devices that measure HRV, sleep quality, and movement provide actionable data if interpreted correctly. HRV trends, sleep duration and resting heart rate can flag accumulated fatigue and guide training adjustments.

Cost-benefit approach

• Prioritize low-cost, proven interventions first: sleep, nutrition, hydration, active recovery and targeted cold/heat use. Add massage, compression or sauna based on budget and specific needs.

Measuring recovery: practical tools and metrics

Objective and subjective measures guide decisions about training load. Use multiple signals rather than a single metric.

Subjective measures

• Perceived soreness: simple 0–10 scale each morning.
• Readiness scores: how ready do you feel for an intense session? Combine with mood and energy levels.
• Sleep quality and stress: track nightly sleep and daytime stressors.

Objective measures

• Resting heart rate (RHR): acute increases above baseline can indicate fatigue or illness.
• Heart rate variability (HRV): trending decreases may indicate residual fatigue or stress. Interpret these trends across days, not absolute values.
• Body weight changes: significant overnight weight loss signals fluid deficit; consistent losses suggest energy deficit.
• Strength or power testing: simple daily or weekly tests (vertical jump, barbell velocity, 1–3 rep max probes) indicate neuromuscular readiness.

Decision rules

• If several measures align (e.g., elevated RHR, lower HRV, poor sleep, marked soreness), reduce intensity or volume for that day.
• If objective metrics are near baseline and subjective readiness is good, proceed with planned training.
• Use a two-day look-back: one bad night or one high metric alone is not automatically a reason to stop training, but consistent deviation for 48–72 hours may require a change.

Putting it together: a workout recovery checklist and sample plans

This checklist turns the science into daily routines. Adjust for training type, fitness level and schedule.

Immediate post-workout (0–2 hours)

• Cool down: 5–10 minutes of low-intensity movement to aid circulation.
• Nutrition: consume 20–40 g of protein and 0.5–1.2 g/kg carbohydrate depending on session duration and intensity. Example: Greek yogurt + banana, chicken rice bowl, or a 30 g whey shake with fruit.
• Hydration: weigh-in pre/post to assess sweat loss; drink ~1.5 L per kg of body mass lost and include sodium if sweat loss was high.
• Pain control: apply ice for localized acute injuries or significant swelling. Avoid routine whole-body cold after all strength sessions if hypertrophy is the goal.

Short-term recovery (2–48 hours)

• Sleep: aim for 7–9 hours; schedule naps (20–90 minutes) if sleep debt is present.
• Active recovery: 20–30 minutes of low-intensity aerobic work, mobility drills, or light yoga.
• Compression or massage: consider brief massage or self-myofascial release on sore areas.
• Monitor: log soreness, mood and HRV.

72+ hours and programming decisions

• If soreness and fatigue resolve, return to planned sessions.
• If persistent pain, decreased strength, or joint swelling exists, reduce volume/intensity and seek assessment if symptoms do not improve.
• Use deload weeks (reduced volume by 40–60% for a week) every 3–6 weeks depending on training load.

Sample routines

• Weekend warrior (run on Saturday): Post-run 20–30 g protein + carb snack, 30 minutes easy walk Sunday, gentle mobility Monday, strength session Tuesday.
• Strength trainee (3× week): Heavy days Mon/Thu/Sat. After heavy sessions: protein within 1 hour, 10–15 minute cool-down, light walking the next day. Avoid routine cold baths immediately post-heavy session; use contrast baths or compression instead if needed for competition scheduling.
• Endurance athlete (multiple hours training): Immediate carbohydrate priority: 0.7–1.0 g/kg in first hour plus 20–30 g protein. Use cold water immersion after multi-day competitions; integrate sauna sessions on easy days to support heat acclimation and cardiovascular conditioning.

Common mistakes and myths

Myth: Ice always speeds healing.

• Reality: Ice reduces pain and swelling acutely, but routine use after resistance training can blunt beneficial inflammation and adaptation. Use cold selectively for pain control and rapid tournament recovery.

Myth: You must drink sports drinks for every workout.

• Reality: For short, low-intensity workouts, plain water and a balanced meal are sufficient. Reserve carbohydrate–electrolyte drinks for sessions over 60–90 minutes, in hot conditions or when rapid rehydration is needed.

Myth: No pain, no gain — push through all soreness.

• Reality: Distinguish between soreness (normal) and sharp pain or loss of function (injury). Training through mild DOMS is acceptable; training through acute joint pain is not.

Mistake: Prioritizing gadgets over basics.

• Reality: Massage guns, cryotherapy, and compression can help subjectively, but sleep, nutrition and progressive programming produce the largest, most consistent returns.

Mistake: Ignoring sleep quality.

• Reality: Poor sleep undermines recovery even if nutrition and therapy are ideal. Address sleep hygiene before adding expensive recovery modalities.

Real-world examples: how athletes and teams apply recovery protocols

• Professional cyclists during stage races routinely use cold water immersion between stages to reduce soreness and maintain performance on consecutive days. The short-term analgesic effect enables consistent high output.
• Strength and power athletes often avoid frequent cold baths after hypertrophy-focused training blocks. They prefer contrast therapy or active recovery when multiple intense sessions are scheduled in a day.
• Soccer teams combine compression garments, scheduled massages, and targeted cold therapy to maintain player availability across congested fixture schedules. Data from wearables and perceived readiness inform individual recovery prescriptions.
• Endurance athletes incorporate post-training carbohydrate–protein beverages immediately after long rides or runs when whole-food meals are delayed; they also use sauna sessions on recovery days to stimulate heat-related adaptations.

These examples demonstrate tailoring: the same tools are used differently depending on the sport, training frequency and the specific goal for the training cycle.

When to seek professional advice and red flags

Recovery plans serve performance and safety. Know when symptoms require evaluation:

• Rapid swelling, deformity, or inability to bear weight after an injury.
• Sharp, localized pain that worsens with rest or activity.
• Persistent loss of range of motion or strength beyond normal DOMS timelines (greater than 7–10 days without improvement).
• Signs of systemic illness: fever, significant fatigue, or persistent elevated resting heart rate even at rest.

A sports medicine clinician, physical therapist or qualified physiotherapist can assess tissue damage, prescribe targeted rehabilitation, and advise on return-to-play protocols.

Practical, evidence-based checklist (printable)

Use this daily checklist to guide recovery decisions after moderate to intense training:

Immediate (0–2 hours)

• 5–10 min cool down (easy movement)
• 20–40 g protein within 2 hours
• Carbohydrate: 0.3–1.2 g/kg based on duration/intensity
• Rehydrate: weigh-in; replace 1.5 L per kg lost; include sodium if needed
• Apply ice if acute swelling/pain is present; limit 10–20 min

Next day (24–48 hours)

• Sleep: 7–9 hours (plus naps as needed)
• Active recovery: 20–30 min low-intensity movement
• Mobility: targeted stretching and joint drills
• Self-massage/foam roll as needed
• Monitor soreness, resting HR, HRV and mood

72+ hours

• Reassess readiness using objective testing (jump, sprint, lifting probe)
• Plan deload if training fatigue accumulates every 3–6 weeks
• Seek clinician assessment for persistent sharp pain or swelling

Add-ons (use selectively)

• Compression for overnight wear after very heavy sessions
• Sauna 2–3× weekly on easy days
• Contrast baths for quick tournament recovery
• Massage as a subjective recovery and relaxation tool

FAQ

Q: Should I ice every workout to reduce soreness? A: No. Ice helps with acute pain and swelling and can speed short-term recovery between events. Routine cold exposure immediately after resistance training may blunt adaptive signaling and limit hypertrophy. Reserve ice for acute injuries, notable swelling, or when you must recover quickly for another performance that day.

Q: How much protein do I need after a workout? A: Aim for 20–40 g of high-quality protein per meal, with at least one dose after training if your next meal is more than 1–2 hours away. Total daily intake matters: 1.2–1.6 g/kg for general recovery, 1.6–2.0 g/kg for heavy strength training or during caloric restriction.

Q: Is an ice bath better than a massage? A: They target different aspects. Ice baths offer quick pain relief and reduce inflammation; massage reduces perceived soreness and improves mobility. Choose based on symptoms and goals. For tournament-style repeats, ice baths may be practical; for long-term soft-tissue management, regular massage or self-myofascial work can be more useful.

Q: Can I take ibuprofen to help recovery? A: Short-term NSAID use can reduce pain and swelling. However, repeated or chronic NSAID use around training may interfere with adaptation and has potential side effects (gastrointestinal, renal). Use sparingly and consult a healthcare provider for recurrent pain or use beyond short-term management.

Q: How should I hydrate after a long run? A: Weigh before and after; for each kilogram lost, drink about 1.5 L of fluid over the next several hours, including some sodium (300–700 mg/L) to aid absorption and maintain plasma volume. Include carbohydrate if the workout depleted glycogen and you need to recover quickly.

Q: Are saunas helpful for recovery? A: Post-exercise sauna exposure supports relaxation, cardiovascular stimulus and heat-shock protein production. Some research links regular sauna use to improved endurance adaptations. Use safetly: hydrate before and after, limit sessions to recommended durations, and avoid immediately after acute injury or heavy alcohol consumption.

Q: What’s the best indicator I should skip a session? A: A combination of elevated resting heart rate, significantly reduced HRV trend, poor sleep, high perceived fatigue and marked soreness suggests accumulated fatigue. One anomalous metric alone is not definitive. If multiple signals are negative, reduce intensity or take a rest day.

Q: How do recovery needs differ between endurance and strength athletes? A: Endurance athletes prioritize carbohydrate replenishment and fluid-electrolyte balance due to glycogen depletion and thermoregulatory stress. Strength athletes prioritize protein intake, neuromuscular recovery and careful use of cold therapies to avoid blunting hypertrophy. Both groups benefit from sleep, mobility work and monitoring.

Q: How often should I use active recovery? A: Incorporate active recovery after hard sessions or on planned easy days. For most athletes, 1–3 active recovery sessions per week suffice, with duration 20–45 minutes at low intensity. Adjust based on weekly training volume and how you feel.

Q: When should I see a specialist for persistent soreness? A: If soreness is accompanied by swelling, reduced range of motion, persistent sharp pain, or symptoms that do not improve after 7–10 days of conservative care, seek evaluation by a sports medicine specialist or physical therapist.

This checklist and guidance will help you move beyond guesswork. Align thermal therapy, nutrition, hydration and sleep with training objectives and timing. Use objective metrics to steer day-to-day choices and remember that small, consistent recovery practices compound into sustained performance improvements.