Why Elite Swimmers Train Underwater Kicking More Than Freestyle

This overview reflects widely shared professional practices as of May 2026; verify critical details against current official guidance where applicable. Elite swimmers at the Olympic level spend up to 40% of their training volume on underwater kicking—more than on freestyle swimming itself. This counterintuitive allocation stems from a fundamental truth: races are won and lost in the transitions. The underwater phase off starts and turns accounts for a disproportionate share of race distance, especially in short-course meters where turns occur every 25 meters. Moreover, underwater kicking develops muscular endurance and power in ways that swimming laps cannot replicate. This guide unpacks the biomechanical, physiological, and strategic reasons behind this training emphasis, providing coaches and athletes with actionable frameworks to optimize their own programs.

The Race-Changing Impact of Underwater Phases

In elite competition, the difference between gold and fourth place often comes down to milliseconds. Underwater kicking directly influences those margins. Research in competitive swimming shows that underwater dolphin kicking can produce speeds 10-15% faster than surface swimming due to reduced wave drag. When a swimmer pushes off the wall and submerges, they enter a zone of lower resistance. The body is fully submerged, eliminating the energy cost of creating surface waves. This advantage is so pronounced that FINA regulations limit underwater distance to 15 meters from the wall. Swimmers who maximize that 15-meter zone with powerful, efficient kicks gain a decisive edge.

Quantifying the Advantage

Consider a 100-meter freestyle race in a 50-meter pool. There are three turns and one start, each offering a 15-meter underwater phase. That's 60 meters of underwater kicking—60% of the race distance. In short-course meters (25-meter pool), the underwater proportion jumps to 80%. Swimmers who neglect underwater kicking effectively cede more than half the race. Elite performers like Caeleb Dressel and Sarah Sjöström are known for their explosive underwater kicks, which allow them to surface ahead of competitors even if their surface speed is comparable. The cumulative effect over multiple turns can be a body-length lead by the finish.

Beyond Drag Reduction

The benefits extend beyond hydrodynamics. Underwater kicking engages the core and hip flexors in a unique manner. The undulating motion requires coordinated activation of the rectus abdominis, obliques, and lower back muscles, building a stable platform for efficient swimming. Many coaches observe that swimmers with strong underwater kicks also exhibit better body roll and streamlined positioning on freestyle. This cross-training effect makes underwater kicking a dual-purpose tool: it improves both the kick itself and the overall stroke mechanics.

Another often overlooked factor is the psychological impact. Swimmers who know they have a superior underwater kick gain confidence on starts and turns. They can afford to push harder off the wall, knowing their kick will maintain speed. This mental edge translates to more aggressive racing and better execution under pressure. Conversely, swimmers weak underwater often hesitate on turns, losing momentum before they even begin their breakout stroke. The training emphasis on kicking thus addresses both physical and psychological readiness.

Biomechanical Foundations of the Dolphin Kick

The underwater dolphin kick is not a simple flutter kick performed while submerged. It is a whole-body undulation that begins at the chest and propagates through the hips, legs, and feet. Elite swimmers generate propulsion by creating a wave-like motion that pushes water backward. The key to efficiency lies in the amplitude and frequency of the kick, as well as the stiffness of the body line. A typical elite swimmer performs 2-4 kicks per underwater phase, with some sprinters doing up to 6-8. The kick frequency is higher than surface kicking because the water density is greater, requiring more force per kick.

Core Engagement and Body Line

A common mistake among age-group swimmers is kicking from the knees, which creates drag and reduces propulsion. The dolphin kick should originate from the core, with the legs following passively. Swimmers must maintain a tight streamline—arms extended overhead, hands clasped, biceps squeezing the ears. Any break in streamline increases frontal drag exponentially. Elite swimmers spend hours practicing streamline holds on dry land and in the water, ensuring that their body position remains arrow-straight during the kick. This attention to detail separates good from great underwater performers.

Kick Dynamics: Amplitude vs. Frequency

Two primary variables govern dolphin kick velocity: amplitude (the size of the undulation) and frequency (the number of kicks per second). Research suggests that for most swimmers, a moderate amplitude with high frequency yields the best results. Excessive amplitude creates side-to-side sway and increases drag, while too low amplitude fails to generate sufficient propulsion. Elite swimmers often use a two-beat kick pattern on the first few kicks off the wall, then transition to a six-beat pattern as they approach the surface. This allows them to maximize speed when drag is lowest (deep underwater) and maintain momentum as they prepare to break out.

Training the dolphin kick requires specific drills. One effective method is vertical kicking: swimmers tread water using only a dolphin kick, arms crossed or holding a float. This drill builds explosive power and teaches the swimmer to maintain a tight core. Another drill is the underwater kick set, where swimmers push off the wall and kick as far as possible on a single breath, measuring distance. Progressive overload involves increasing the number of kicks per push-off or adding resistance with fins or a drag parachute. Coaches should emphasize technique over distance initially to ingrain proper movement patterns.

Periodizing Underwater Kick Training

Elite swimmers do not train underwater kicking year-round at the same intensity. Periodization is crucial to avoid overtraining and to peak at the right time. In the general preparation phase (off-season), the focus is on building a foundation: developing core strength, flexibility in the ankles, and endurance for sustained kicking. Swimmers may perform 3-4 sessions per week of underwater kicking, with sets totaling 1,000-2,000 meters. Drills include using fins to increase resistance and build leg strength, and kickboards to isolate the legs for flutter kick technique.

Pre-Competition Phase

As competition approaches, the volume decreases but intensity increases. Swimmers shift to high-quality, low-volume sets that mimic race conditions. For a sprinter, this might involve 10-15 push-offs with maximal effort, each followed by a 15-meter underwater kick, with 45 seconds rest. The goal is to simulate the explosive demand of a race start or turn. Coaches also incorporate race-pace kicking: the swimmer kicks at the same speed they would during a race, often using a tempo trainer to regulate kick frequency. This phase typically lasts 4-6 weeks and includes 2-3 underwater kick sessions per week.

Peaking and Taper

During the taper period (1-2 weeks before a major meet), underwater kick volume drops to 1-2 sessions per week, with very low volume but high intensity. Swimmers perform just enough to maintain neuromuscular adaptation without fatiguing. A typical taper set might be 4-6 explosive push-offs with a 15-meter kick, followed by easy swimming. The emphasis is on freshness and mental sharpness. Coaches must resist the urge to add extra kick sets during taper, as this can blunt race-day explosiveness. The goal is to enter competition with a well-rested central nervous system and primed fast-twitch fibers.

An often-neglected aspect of periodization is ankle flexibility. The dolphin kick requires a high degree of plantar flexion (pointed toes). Swimmers with limited ankle range of motion struggle to generate propulsion. A periodized flexibility program should include daily ankle stretches, such as sitting on the heels or using a stretch band to pull the toes into a point. Some elite swimmers perform 10-15 minutes of ankle mobility work before every practice. This investment pays dividends in kick efficiency and reduces the risk of foot cramps during high-intensity sets.

Tools and Technology for Kick Optimization

Modern training tools have revolutionized underwater kick development. The most fundamental tool is the monofin, which forces the swimmer to use a dolphin kick and provides instant feedback on body position. Monofin sets are common in national team camps, where swimmers perform 50-100 meter underwater kicks with the fin, focusing on maintaining a steady undulation. Another tool is the underwater camera, which allows coaches to analyze kick amplitude and body line frame by frame. Many elite programs use GoPro housings or pool-side video systems to record kick sets, then review footage immediately to correct errors.

Resistance and Assistance Training

Resistance training includes drag socks, parachutes, or power towers. Drag socks increase surface area on the feet, making each kick harder. Swimmers use them in short bursts (15-25 meters) to build explosive power. Parachutes create resistance during the entire underwater phase, simulating the feeling of pushing off the wall against water pressure. Assistance training, such as using a bungee system that pulls the swimmer forward, helps develop high-frequency kicking. The swimmer kicks at a faster rate than normal, training the nervous system to recruit motor units quickly.

Recovery and Maintenance

Underwater kicking places high stress on the hip flexors and lower back. Without proper recovery, swimmers risk developing hip impingement or lower back strain. Tools like foam rollers, massage guns, and percussion therapy are used daily by elite athletes. Many teams schedule active recovery sessions that include light kicking with a snorkel and fins, focusing on technique rather than power. Cold water immersion and contrast baths are also common to reduce inflammation. Nutrition plays a role too: adequate protein intake supports muscle repair, and hydration helps maintain joint lubrication. Coaches should monitor swimmer fatigue levels and adjust kick volume accordingly, especially during heavy training blocks.

One emerging technology is the use of wearable sensors that measure kick force and frequency. These devices attach to the ankle or foot and transmit data to a tablet in real time. Coaches can see exactly how much force each kick generates and whether the swimmer's frequency drops off over a set. While still expensive, these tools are becoming more accessible and provide objective metrics that complement video analysis. For programs without such technology, simple lap counting and subjective observation remain effective—provided the coach has a trained eye for technique.

Growth Mechanics: From Age-Group to Elite

The progression from age-group to elite swimming requires a deliberate focus on underwater kicking. At the novice level, the priority is comfort: learning to hold the streamline, kick from the core, and maintain breath control. Age-group swimmers should practice underwater kicking in a safe environment, with a coach or lifeguard present. A common progression is to start with 5-meter kicks, then gradually increase to 10 and 15 meters. The goal is to build confidence and technique before adding speed.

Junior National Level

At the junior national level, swimmers begin to specialize. Sprinters will emphasize explosive kicks with high frequency, while distance swimmers focus on efficiency and maintaining speed over longer underwater phases. Coaches should tailor kick sets to the swimmer's event. For example, a 50-meter freestyler might do 6-8 kicks per push-off, while a 1500-meter freestyler might do only 2-3 kicks before surfacing. The key is to match the kick count to the race strategy. Many junior swimmers over-kick off turns, burning oxygen and compromising the subsequent swim. A periodized approach with race simulation helps correct this.

Senior and International Level

At the elite senior level, underwater kicking becomes a differentiator. Swimmers like Michael Phelps and Katie Ledecky are known for their underwater prowess. Their training includes specialized sets that combine underwater kicking with surface swimming in a single rep. For instance, a set might be: push off and kick 15 meters underwater, then swim 35 meters freestyle at race pace. This trains the transition from underwater to surface, which is often where swimmers lose momentum if they surface too early or too late. The breakout stroke—the first stroke after surfacing—must be timed perfectly. Some swimmers prefer a single dolphin kick followed by a freestyle pull, while others use two kicks. Coaches experiment with different breakout patterns to find what works for each athlete.

Another growth mechanic is mental rehearsal. Swimmers visualize their underwater kick sequence before races, imagining the feel of the water and the rhythm of the kicks. This primes the nervous system and reduces anxiety. Many elite athletes use visualization as a regular part of their training, often combining it with breathing exercises. The combination of physical and mental preparation creates a holistic approach that yields consistent performance under pressure. Coaches should integrate visualization into practice, asking swimmers to close their eyes and rehearse a perfect start and turn before executing it physically.

Risks, Pitfalls, and Mitigations in Underwater Kick Training

Despite its benefits, underwater kicking carries risks. The most common is overtraining the hip flexors, leading to tendonitis or impingement. Swimmers who perform excessive kick sets without adequate recovery often develop a dull ache in the front of the hip. This can be mitigated by varying kick styles (flutter kick vs. dolphin kick) and incorporating rest days. Another risk is lower back strain from the undulating motion, especially if the swimmer lacks core strength. A prehabilitation program that includes planks, bird dogs, and dead bugs is essential for injury prevention.

Breath-Hold Dangers

Hypoxic training—deliberately holding the breath during underwater kicks—can be dangerous if not supervised. Swimmers may black out due to low oxygen, especially if they hyperventilate before submerging. Coaches must enforce strict safety protocols: never allow solo hypoxic sets, always have a lifeguard on deck, and ensure swimmers surface before exhaustion. A safer alternative is to use a snorkel that allows breathing while the swimmer practices the kick motion on the surface, then gradually increase underwater distance with a spotter. Many elite programs avoid hypoxic sets altogether, relying instead on high-intensity intervals with full recovery to achieve the same physiological adaptations.

Technique Drift

As swimmers fatigue, their underwater kick technique often deteriorates. They may start kicking from the knees, lose streamline, or increase amplitude excessively. This reinforces bad habits that become ingrained. Coaches should film kick sets regularly and provide immediate feedback. A useful drill is the 25-meter kick with a focus on maintaining perfect form for the entire distance. If the swimmer's form breaks down, they stop and reset. Quality over quantity is the mantra for elite kick training. It is better to do 10 perfect kicks than 50 sloppy ones.

Another pitfall is neglecting the flutter kick for freestyle. While dolphin kick is crucial for underwater phases, the flutter kick remains essential for surface swimming. Some swimmers become so focused on dolphin kick that their flutter kick weakens, causing their freestyle stroke to lose propulsion. A balanced training plan includes both kicks, with specific sets for each. For example, a session might start with 400 meters of flutter kick with a board, then transition to 200 meters of underwater dolphin kick off walls. This ensures that neither kick is neglected and that the swimmer develops a well-rounded skill set.

Frequently Asked Questions About Underwater Kick Training

Q: How many underwater kicks should I do per turn? A: It depends on your event. Sprinters (50-100m) often use 6-8 kicks, while distance swimmers (200m+) use 2-4 kicks. The optimal number is the one that allows you to maintain speed without compromising your breakout. A good rule of thumb is to surface when your underwater speed drops below your surface swimming speed. This can be measured by timing a 15-meter underwater kick and comparing it to a 15-meter surface swim.

Q: Can I train underwater kicking every day? A: Not at high intensity. Two to three sessions per week of high-intensity underwater kicking is sufficient for most swimmers. Daily practice should include technique work or low-intensity kicking (e.g., with a snorkel) to reinforce patterns without fatiguing the muscles. Listen to your body; if you feel hip or back pain, reduce volume.

Q: What is the best drill for improving dolphin kick? A: Vertical kicking is highly effective. Stand in deep water, cross your arms over your chest, and kick using only a dolphin motion. Try to keep your head above water. Start with 15-second intervals and build to 60 seconds. Another drill is the underwater kick set: push off the wall and kick as far as possible on one breath, focusing on streamline and kick rhythm. Measure your distance and try to beat it each session.

Q: Should I use fins for underwater kick training? A: Yes, fins are excellent for building leg strength and teaching the correct undulation. However, do not become dependent on them. Alternate between fin and no-fin sets to ensure your kick remains effective without assistance. Fins can also help stretch the ankles, which improves kick efficiency.

Q: How do I know if my kick is efficient? A: One indicator is how far you travel per kick. Have a coach or friend count your kicks over a 15-meter underwater push-off. If you take more than 8-10 kicks to cover 15 meters, your efficiency likely needs improvement. Work on reducing kick count while maintaining speed by focusing on a tighter streamline and more powerful undulation.

Q: What is the biggest mistake swimmers make in underwater kicking? A: The most common mistake is breaking streamline. Many swimmers drop their head or separate their hands during the kick, creating drag. Practice streamline holds on land and in the water until it becomes automatic. Another mistake is kicking from the knees rather than the core. Remember: the kick starts at the chest, not the hips or knees.

Synthesis and Next Actions for Integrating Underwater Kick Training

Underwater kicking is not a supplementary skill—it is a core competency that separates elite swimmers from the rest. The evidence is clear: races are won in the underwater phases, and training volume should reflect that reality. Swimmers and coaches must prioritize kick technique, periodize training to avoid overuse injuries, and use the right tools to measure progress. The path to improvement starts with an honest assessment of your current underwater kick. Time your 15-meter push-off, count your kicks, and compare to benchmarks. If you are slower than 2.5 seconds per 15 meters (for males) or 3.0 seconds (for females), there is significant room for improvement.

Immediate Steps to Take

First, schedule two dedicated underwater kick sessions per week for the next 4 weeks. Each session should include a warm-up of 200 meters easy swimming, followed by 8-10 x 15-meter underwater kicks with 30 seconds rest. Focus on technique: streamline, core engagement, and kick count. Record your best distance and time each session. Second, incorporate vertical kicking 3 times per week for 3 sets of 30 seconds. Third, add ankle flexibility work to your daily routine—5 minutes of stretching before practice. Finally, review race footage of your starts and turns. Identify if you are surfacing too early or losing speed underwater. Adjust your kick count accordingly.

Remember that improvement takes time. Elite swimmers spend years refining their underwater kick. Be patient, stay consistent, and prioritize quality over quantity. The rewards—faster times, better race execution, and reduced drag—are worth the effort. As you progress, revisit your training plan every 4-6 weeks to adjust volume and intensity based on your performance and recovery status. With deliberate practice and a strategic approach, you can transform your underwater kicking from a weakness into a race-winning weapon.