Why Does Swimming Make You Tired and Sleepy? 10 Reasons and What to Do

Swimming is renowned for providing an excellent full-body workout. However, many swimmers report feeling tired or sleepy during or after swimming laps. While some post-exercise fatigue is normal, excessive tiredness after swimming can diminish performance gains and enjoyment of the sport.

Read on to understand the causes of swim-induced fatigue and its science, along with actionable tips to help minimize the exhaustion and recover effectively afterward.

Reasons Swimming Makes You Tired

Swimming can induce fatigue through several interconnected physiological, biomechanical, and psychological mechanisms. Let’s break down the primary factors:

Water Temperature Affects Body Systems

According to research, one of the most convincing theories explaining post-swim tiredness relates to the physiological effect of water temperature on the body.

When you swim in colder water (below 75°F or 23°C), your body loses heat rapidly due to the increased conduction property of water compared to air. This causes your core body temperature to drop slightly even when swimming vigorously.

Additionally, your body has to expend extra energy to maintain its core temperature against the cold. This added exertion can lead to more significant fatigue than average.

After exiting the pool, the re-warming process makes you feel sleepy in the same way drinking a hot beverage or sitting near a fireplace does on a chilly day.

So, the cold water itself may not directly cause tiredness – instead, it’s the body’s reheating afterward.

On the flip side, swimming in warmer water can also increase fatigue. Your body’s cooling mechanisms like sweating, must work harder to regulate your core temperature in the heat, depleting energy and fluids.

The ideal water temperature for lap swimming is around 78-80°F (25-26°C) – warm enough to avoid excessive chill but cool enough to prevent overheating.

Full-Body Resistance Training

Swimming engages all the major muscle groups in your body, especially the back, arms, abs, legs, and shoulders.

The constant muscular contraction and relaxation required for propulsion generate significant metabolic demands. Stroke after stroke works your entire body against the natural resistance of water.

Water provides 12 times more resistance than air does. So swimming serves as both an aerobic and anaerobic workout, challenging your different energy systems in a way that tires muscles out.

After a tough swim, your body has to repair damage to muscle fibers throughout all its major muscle groups, not just isolated areas like during running or biking. This whole-body exhaustion can make you feel drained.

Further Reading: The Health Benefits of Swimming for Body and Mind

Dehydration and Mineral Loss

You might be surprised to learn swimming causes significant fluid loss through sweating. Though less noticeable than on land, the constant motion and water temperature make sweating inevitable.

Losing fluids and electrolytes through sweat can lead to dehydration, especially in warmer pools. This causes physical and mental fatigue.

Deficiencies in minerals like magnesium, potassium, and sodium, lost through prolonged sweating, may also contribute to swim fatigue. Research shows athletes need 10-20% increased magnesium uptake.

High Intensity Leads to After-Burn

It may seem counterintuitive, but higher-intensity swims can leave you feeling more energized than lower-intensity ones due to a phenomenon called excess post-exercise oxygen consumption (EPOC) or after-burn effect.

After intense exercise, your body continues expending energy during recovery above resting levels for 30 minutes up to 24 hours. Despite physical tiredness, you’ve likely experienced trouble sleeping after a challenging swim workout or race.

So, higher intensity provides an alertness boost, while easier swims make you sleepy.

Nutritional Timing Matters

Proper nutrition plays a crucial role in preventing post-swim tiredness. Swim workouts often happen early morning after fasting overnight, causing low energy reserves right when you need to perform.

Not refueling correctly after the workout can also deplete you for hours.

When you swim, your body uses significant energy and nutrients to power through the water. Hunger can set in quickly without replenishing these resources at the right time.

Further Reading- From Pool to Plate: Understanding Why Swimming Sparks Hunger

By fueling your body with a balanced meal or snack before and after swimming, you can help maintain optimal energy levels and minimize post-swim exhaustion.

Ensuring you have enough carbohydrates for energy, protein for muscle recovery, and fluids for hydration is key to combating tiredness after your swim sessions.

Poor Swimming Technique

Swimming with poor technique can significantly contribute to feelings of fatigue and tiredness. When your swimming technique is inefficient, you expend more energy than necessary to move through the water.

This can increase oxygen consumption, muscle fatigue, and lactic acid buildup. Additionally, poor technique may lead to improper body alignment and excessive drag in the water, making it harder for you to maintain a steady pace and causing unnecessary strain on your muscles.

To prevent excessive tiredness after swimming, improving your stroke mechanics and body position in the water is essential.

Improving your swimming efficiency allows you to conserve energy and swim faster with less effort.

Mental Focus and Motivation

The mental challenge of swimming can augment physical tiredness. Having to monitor technique and breathing closely is mentally taxing.

The pressure to perform at the same level as others can also cause mental fatigue, leaving you physically and mentally drained. Instead, focus on your own performance goals.

Low motivation and lack of mental stimulus on long, monotonous swims contribute to mental fatigue, which compounds physical tiredness.

Swim Gear & Attire

The kind of swim gear or attire you wear and how you use it can also contribute to fatigue. While some swim gear is purposefully created to increase resistance, making you work harder, resulting in more strength and endurance, other items unintentionally create drag, making you tired easily.

For instance, while warming up with swim hand paddles and gloves correctly and at a leisurely pace can significantly improve arm and shoulder strength while developing a better feel for the water, misusing them at an intense pace can drain you quickly.

While they eventually make you faster and more powerful, swim power training tools such as parachutes, drag sox, swim tethers and power towers create more drag, leaving you exhausted.

Properly-fitting goggles that don’t leak are essential for clear underwater vision and allow you to swim efficiently. Poorly fitted goggles require frequent adjustment and hinder technique.

Attire

• Choose performance swimsuits made with smooth, quick-drying material that provides flexibility without drag. Avoid baggy shorts.
• Wear a well-fitted swim cap to increase hydrodynamics. Long hair creates significant drag without a cap. Silicone or latex caps stay put best.
•  For women, one-piece performance swimsuits are less prone to drag, risk of dislodging, and loss of hydrodynamic shape compared to bikinis.

Effects of Sunshine

Outdoor swimming on hot sunny days can lead to overheating, dehydration, and a natural increase in melatonin levels, which induces sleepiness. Direct sun exposure causes some people to feel drained.

Pre-Existing Medical Conditions

•  Thyroid disorders like hypothyroidism or hyperthyroidism can cause persistent tiredness unrelated to swimming exertion. Get evaluated if you suspect thyroid issues.
• Iron deficiency anemia, common in athletes, reduces oxygen and the oxygen-carrying capacity of the blood, contributing to rapid fatigue with exertion.
• Asthma-related breathing difficulties worsen with vigorous exercise like swimming. The use of inhalers pre-swim can alleviate airway limitations and shortness of breath.
• Underlying cardiac or pulmonary disease can hamper cardiovascular conditioning and induce fatigue with exertion disproportionate to your fitness. Seek medical guidance.
• Diabetes, especially when poorly controlled, can lead to chronically low energy levels and impact performance during exercise like swimming.

Lack of Adequate Sleep

Multiple studies have consistently demonstrated that fatigue primarily arises due to the physiological effects of insufficient sleep.

Not getting sufficient sleep (7-9 hours for adults) impairs muscle recovery from training, leading to accumulated fatigue.

Poor sleep quality reduces sleep’s therapeutic benefits. Sleep apnea, frequent waking, and insomnia disrupt sleep architecture and deep sleep stages.

Late training sessions within 1-2 hours of bedtime may negatively impact sleep. Caffeine after 2 p.m. also hinders sleep at night for some people.

Scientific Explanations Behind Swimming Fatigue

Now that we’ve covered the primary factors causing tiredness in swimming, let’s dig into the physiology and science behind them:

Muscular Fatigue Limits Performance

The continuous muscular work involved in swimming leads to a depletion of stored energy sources like ATP and glycogen inside muscle cells.

As muscles become fatigued, their ability to generate forceful contractions declines. This manifests as reduced power output and slower swim times.

Fatigued muscles also lose coordination and efficiency. The stroke technique begins deteriorating when muscles lack energy.

Cardiovascular Demands

During swimming, your cardiovascular system works harder to deliver oxygenated blood to working muscles while removing metabolic waste products like lactic acid.

At high swimming intensities, your heart has to pump more blood per minute to meet the muscles’ demand for oxygen. This increased cardiovascular workload leads to fatigue over time.

As muscle glycogen stores deplete during long or intense swims, less oxygen is available for energy production inside muscle cells. This oxygen debt contributes to muscular fatigue.

Elevated Body Temperature

The increased metabolic activity and muscular work of swimming raise your core body temperature. This heat buildup causes your blood vessels to dilate near the skin surface to dissipate heat.

But this diversion of blood flow from working muscles to the skin means less oxygen and nutrient delivery to where they are needed. The cardiovascular system cannot cool the body, resulting in impaired muscle function adequately.

Higher temperatures also hinder your body’s ability to sweat, which is the primary heat-loss mechanism. This compounds heat buildup and hastens fatigue.

Lactic Acid Buildup

During high-intensity exercise, your muscles rely more on anaerobic metabolism for energy production. This incomplete breakdown of glucose causes lactic acid to accumulate.

Lactic acid lowers the pH inside muscle cells, making them more acidic. This interferes with muscle contraction and the ability to produce force.

Lactic acid buildup also reduces oxygen supply to working muscles by promoting vasoconstriction of local blood vessels.

So, lactic acid has dual fatigue-inducing effects, inhibiting muscular contractions and limiting oxygen delivery.

Oxygen Consumption Ramps Up

The metabolic demands of swimming require your muscles to consume oxygen at high rates to meet energy needs. Oxygen consumption increases proportional to swimming intensity.

At a certain point, your cardiovascular system cannot deliver enough oxygen to working muscles, forcing increased reliance on anaerobic metabolism. This accelerates glycogen depletion.

Without adequate oxygen to facilitate energy production, your muscles quickly fatigue. You have to slow down as your muscles become unable to generate power.

Mental Focus Wanes

Mental fatigue impairs your ability to maintain concentration, motivation, and proper technique during swimming:

• Reduced motivation makes it harder to push yourself to complete strenuous sets.
• Increased anxiety and muscle tension interfere with stroke coordination.
• Declining focus leads to inefficient stroke execution.
• Impaired technique increases exertion requirements.

Together, these effects of mental tiredness magnify physical fatigue. Managing mental energy is as important as physical conditioning for optimal swimming performance.

Dehydration Hampers Performance

Because water conducts heat away from your body so effectively, swimming causes heavy sweating and fluid loss.

When you become dehydrated, less blood circulates through your blood vessels. This decreases the amount of oxygen muscles receive.

Dehydration also makes it harder for your cardiovascular system to remove waste products like lactic acid, contributing to fatigue.

Additionally, fluid loss leads to electrolyte imbalances that disrupt muscle contraction and energy production.

Proper hydration is critical for maintaining muscle function, temperature regulation, and cardiovascular performance when swimming.

Actionable Tips to Reduce Swimming Fatigue

Now that you understand the science behind swim fatigue, here are some tips to help minimize tiredness and swim more efficiently:

Choose the Ideal Water Temperature

• Find a pool that maintains a temperature of around 78-80°F (25-26°C) for optimal performance and comfort. This is the ideal temperature used in Olympic competitions.
• Avoid swimming in outdoor pools during the hottest parts of the day when water temperature rises significantly. Schedule workouts in the early morning or evening instead.
• If training in a colder pool, schedule a short 15-20 minute run or cycling session right after to boost core temperature back up and avoid the re-warming fatigue.
• Invest in a well-fitted suit for open-water swimming. Where wetsuits are allowed, use them to stay warmer in cooler conditions. Look for thick neoprene construction of at least 3/2 mm thickness.

Streamline Your Technique

• Take swim lessons from a certified coach to improve your stroke efficiency, kicking, and breathing technique. They can provide expert feedback.
• Focus on proper streamlined body alignment at the water surface and when submerged. Keep your head in line with the spine. Engage core muscles.
• Avoid overexerting your kick, which can waste energy – let your buoyant legs trail behind you. Emphasize propulsion from your upper body.
• Master an optimal rhythmic breathing pattern that seamlessly integrates with your overall stroke cycle. This reduces energy wasted on suboptimal breathing.
• Learn proper sighting techniques to swim straight and conserve energy in open water. Lift your head briefly without over-rotating your body.
• Practice pacing yourself and conserve energy during demanding workouts by mixing up intensities. Don’t try to maintain maximum effort the entire time.

Fuel Properly

• Ingest a mix of carbohydrates, proteins, and fats before and after swimming to provide quick and sustained energy.
• Have a small meal containing complex carbs, lean protein, and healthy fats roughly 60 minutes before exercise. This gives you energy and avoids stomach issues.
• Consume portable snacks like energy bars, gels, bananas or mixed nuts during lengthy swim practices to maintain blood glucose levels.
• Replenish calories burned by eating a carb-protein meal within 30 minutes after finishing swimming to kickstart recovery. Chocolate milk is a convenient option.
• While caffeine can boost alertness when used strategically, don’t rely on it as your sole pre-swim energy source. Develop overall healthy nutritional habits.

Hydrate Adequately

• Drink plenty of cool water and sports drinks containing electrolytes before, during, and after swimming to replace fluids and minerals lost through sweat.
• Consume around 0.5-1 ounce of water per pound of body weight daily as a general hydration guideline. Needs will vary based on sweat rate, intensity, environment, etc.
• Use your urine color as a quick indicator of hydration status. Pale yellow = well hydrated. Dark yellow = dehydrated.
• For workouts over 60 minutes, use portable water bottles to regularly ingest 3-5 oz of fluid every 15-20 minutes during rest intervals.

Develop Good Sleep Habits

• Get at least 7 hours of quality sleep nightly to allow optimal physical and mental recovery between swimming sessions.
• Keep a consistent bedtime/wake-up schedule, including weekends, limit electronics before bed, and sleep in a cool/dark room.
• Take occasional 20-30 minute power naps during the day if needed.
•  If poor sleep persists despite a good sleep routine, get medically evaluated to identify and treat any underlying issues hindering high-quality sleep.

Monitor Intensity

Do sprint, interval, and race pace workouts when you feel most alert and energetic, typically earlier in the day or after adequate rest.

Schedule longer endurance and technique-focused practices for the evening when feeling more fatigued. Lower intensity allows recovery from high-intensity sessions.

Take short breaks every 15-25 minutes during demanding swim practices to drink fluids, stretch briefly, and give your body intermittent rest.

Avoid overexertion by listening to your body’s signals. Adjust intensity if feeling excessive fatigue or muscle pain during a session.

While friendly competition can be motivating, avoid expending unnecessary energy obsessively trying to beat others during training. Stay focused on your individual performance goals.

Avoid Sun Exposure

Swim in the morning or late afternoon when sunlight is less direct overhead. Hydrate well and use sunscreen. Consider wearing a visor cap for added sun protection if swimming midday.

Swimming Fatigue Recovery Techniques

Implementing certain active and passive recovery techniques can help overcome post-swim tiredness faster:

Engage in light aerobic activities like jogging, cycling, or using an elliptical machine, which boosts circulation without further fatiguing muscles.

Perform gentle static and dynamic stretching, which enhances the range of motion, reduces muscle soreness, and promotes tissue repair after intense swimming.

Use compression garments, contrast water therapy, or massage techniques like foam rolling to accelerate lactic acid clearance following demanding practices.

Reduce life stresses through relaxation techniques like meditation, deep breathing exercises, yoga, and music therapy, which alleviate mental fatigue.

Have enough sleep.

If fatigue persists, seek help from coaches, sports medicine professionals, or dietitians if fatigue is hampering your performance. They can assess your training load, identify issues, and prescribe appropriate solutions.

Frequently Asked Questions

Still, have questions about why swimming makes you tired? Here are answers to some commonly asked questions:

Conclusion

Swimming can spur profound feelings of tiredness through a variety of interlinking physical and mental pathways. But with the right preparation and recovery strategies, you can minimize fatigue and achieve your peak swimming potential.

Pay close attention to your body’s signals, swim smart, fuel well, recover thoroughly, and incorporate periodic rest to sustain your vitality in and out of the water.

While swimming will always require significant exertion, you can learn to harness your energy so that rather than limiting you, it propels you to new heights in the water.