Canoes and kayaks are two of numerous examples of boats defined as a small water vessel, typically open to the elements, and powered by wind, mechanical, or human power. Both the canoe and the kayak are relatively narrow, hollow shells, pointed at both ends, and propelled by human power over water by means of paddles. For these reasons, canoes and kayaks share similar, but not identical, characteristics in how they move over water. Modern canoe and kayak designs represent thousands of years of the gradual evolution of a craft whose purpose is maximum speed and efficiency across water.

Hydrodynamics is the physical study of the forces created or acted upon by fluids; water is the common fluid studied. The hydrodynamics of a canoe or a kayak will involve an analysis of how the shape of the hull (body of the boat) is impacted as it moves through or over the water. The speed with which a boat can move over water is a function of the power applied to the vessel (in the case of the canoe or kayak, the power of the paddling), and the effect of the "drag" created against the hull of the boat as it passes through the water. Drag is a physical concept, similar to the principle of friction; the drag equation, employed by all designers of boats, will determine how much the flow of water against the hull of a canoe or kayak will impact the speed of the craft. The key relationship in the drag equation is the faster the boat travels, the greater its drag. Water drag increases with the square of the velocity of the boat hull. The greater the drag, the more power is required to move the craft at the same speed.

Three design features of a canoe or kayak will have an impact on its overall hydrodynamics: primary stability, secondary stability, and rocker. Primary stability is a measure of how stable the craft is when the hull is resting flat on the water surface. The flatter the hull, the more stable the craft; boats with excellent primary stability tend to be slower as the flat hull will produce more drag in the water. Secondary stability is the stability gained by a vessel as it heels over on its axis in the water, requiring the side of the hull to bear the weight of the vessel. The more curved the hull, the greater the secondary stability of the vessel, and the less likely it will be to capsize. Rocker is the degree of curvature in the hull from bow to stern along its axis. The greater the degree of rocker, the more maneuverable and generally less stable the boat will be.

As a general proposition, for both canoe and kayak sprint-racing—where there is little impact on the motion of the boat through wind, wave, or opposing currents—the craft will possess a longer and lighter hull. Such construction results in less drag caused by the water, as the longer hull displaces less water, meaning that the craft has less hull below the surface and more hull above. Long, narrow, lightweight hulls, with no stabilizing keel (a main beam that provides stability), are very difficult to paddle in less calm, unsettled water, as waves and wind tend to push the narrower crafts from their intended course.

Current, wave action, and water obstacles all influenced how each type of vessel evolved. The racing versions of both canoes and kayaks reflect this evolution. Both canoe and kayak racing are organized at the international level in three general divisions: short distance sprints, with single-, two-, or four-person classes (described by the short forms C1, K1, C2, K2, etc.). Sprint racing requires paddling over relatively calm water; whitewater races are contested in narrow, fast-flowing, turbulent rivers; long distance racing is generally an open, large water body event. Each racing category involves craft that has been substantially modified by adaptations of the basic form; racing designs are a true reflection of the maxim "function over form."

In sprint racing, the canoes used by elite-level racers bear little resemblance to the craft that are paddled for recreational purposes. These events are conducted on short (500 m [548 yd] or 1,000 m [1,094 yd]), sheltered race courses, with considerable protection from wind and resulting wave action on the boats. The courses are divided into lanes. For example, the C1 version is relatively long (16 ft [5.2 m]) in relation to both weight and width, with no minimum width required. C1 craft are constructed with a minimum weight of only 35 lb (16 kg). The C1 paddler propels this open deck craft from a kneeling position, using a single-blade paddle, controlling the boat through the stroke, as a rudder and a keel are not permitted. Stability is sacrificed in sprint canoe racing for straight-line speed.

Sprint kayaks, when observed from a distance, appear similar in design to that of the sprint canoe. The K1 version is propelled by a paddler who is seated on a fixed chair (as opposed to the boat seats that move with the stroke of the athlete in rowing disciplines). The boat is steered through both the stroke of the double-bladed paddle and a rudder operated by foot action. A K1 has a closed deck, the same 17 ft (5.2 m) maximum length as the C1, but even lighter weight at a minimum 26 lb (12 kg).

Whitewater canoe and kayak racing, referred to in international and Olympic competition as "wild-water," may be organized on either natural river courses or artificial water courses. The courses are configured with artificial gates, through which the paddler must steer the craft, or otherwise sustain a penalty. The race course will also present natural obstructions such as boulders, rock ledges that resemble small waterfalls, and fast currents, all of which are intended to maximize the paddler's difficulty in completing the race course. The whitewater canoes and kayaks must be strong, durable, and highly maneuverable. The athletic qualities required of the paddler in each discipline include muscular power, speed and reaction time, and dexterity. The additional and critical athletic skill demanded in successful whitewater competition is tactical ability: the athlete's choices as to the route from the top of the race course to the bottom will be a significant performance factor.

A whitewater K1 craft imposes the same requirements regarding the position of the paddler as with any type of kayak. This K1 is shorter, at 14 ft (4.5 m), than the sprint version; it weighs a minimum of 24 lb (11 kg) and it has a minimum width of 1.8 ft (0.6 m). The result is a hull not much wider than the paddler's torso, which places the athlete as close to the surface of the water as possible to heighten responsiveness in fast-fowing water.

The whitewater canoe, referred to as a Canadian canoe in the international rules of the sport, is propelled from a kneeling position using a single-blade paddle. The C1 whitewater version, at 13 ft (4.3 m) long, a weight of 26 lb (12 kg), and a minimum width of 2 ft (0.7 m), is designed to be stable and maneuverable; an expert paddler can spin the craft on its axis to obtain optimum position on the race course.

The canoes used to race over long distances are constructed to be propelled in an efficient, steady state, where competitive success will depend on the ability of the athlete to maintain a consistent paddling rate over time. Long distance racing has two distinct types of competition: marathon canoe racing and dragon boat racing.

The international rules that govern marathon racing events are less structured than those regarding sprint and whitewater competition. A race course must be a minimum length of 12.4 mi (20 km), with no upper limit (races of 31 mi/50 km are relatively common); the course may require portages, which is the crossing of land to avoid a barrier such as waterfall, the racer carrying the canoe, paddles, and any other gear without assistance. The athletes are expected to take the water conditions as they may exist at any given time. C1 marathon canoes are very lightweight for these reasons (22 lb/10 kg is the minimum).

Dragon boat racing originated in Hong Kong, a part of the festivals that pay homage to the dragon, an ancient Chinese symbol. The sport captured international notice in the late 1970s, due in part to the color and the pageantry of the decorated race boats. The sport has grown in popularity throughout the world; in China, there are an estimated 20 million dragon boat participants. A chief spur to the worldwide interest in dragon boating has been the rise of corporate team participation. Companies and charitable groups have adopted dragon boat racing as a powerful tool for building employee morale, participant fitness, and notable charitable fundraising.

Dragon boat racing involves a number of factors not present in other forms of canoe racing. A typical dragon boat has 20 paddlers, a drummer to provide the cadence to assist the paddlers to work in unison, and a steersperson/navigator. Dragon boat races can be many miles in length over open lake or ocean waters, with exposure to wave action. The boat is a heavy, stable craft—by international rule, the dragon boat weighs a minimum of 550 lb (250 kg), with a maximum length of 38 ft (12.48 m).

The successful dragon boat crews function as one; synchronized paddling causes the boat to move with a stable forward motion, parallel to the direction of intended travel. When paddlers fall out of rhythm, they are directing forces with each paddle that are not complimentary to one another. This unsynchronized delivery of power causes the boat to rock along its axis, which moves the boat away from the optimum line of travel. The dragon boat will travel further and require more energy from the paddlers to reach its destination.

Canoeing and kayaking place similar demands on the body in competition. Sprint and whitewater racing require the development of both the aerobic and anaerobic energy systems. The anaerobic system is used by the body in shorter, more intense forms of activity, where energy can be utilized without oxygen; the aerobic system is the primary energy system when the body requires steady amounts of energy to be delivered to its working muscles over a longer period of time. For this reason, both sprint work

A kayak paddled by an expert can be taken through very rough, fast-flowing currents, with the double paddle permitting the hull of the craft to be readily spun in 180° changes of direction where necessary.
and whitewater training must development of both systems. be directed to the development of both systems.

"Dry land training" is the term generally used by water sport athletes such as swimmers and divers to describe a workout regime that is apart from the water. The dry land program of a canoeist or kayaker designed to enhance the development of their energy systems will include aerobic training such as running, cycling, or the use of equipment such as an elliptical trainer. Interval running is a useful anaerobic dry land training method for canoeists.

Both disciplines place a primary emphasis on the athlete's shoulders, arms, and back muscles to drive the paddle quickly and effectively into the water. The kayaker, through the twisting motion required of a double paddle, coupled with the seated position in the boat, places significant stress upon the lumbar (low) back, the abdominal muscles that stabilize the paddler during the extension of the arms in paddling, and the hip flexors, which assist in moving the body forward to make the stroke.

Whitewater canoe and kayak racing places an additional training premium on shoulder strength and quickness. Dry land training for this aspect of performance will include weightlifting, especially those directed to the shoulders and upper arms. Wrist strength is essential to paddling grip. Modified plyometric shoulder and arm exercises are required to build explosive generation of the paddling power required to make sharp turns and the pulling of the craft sideways in the water (known as a "draw stroke").

The muscular requirements placed upon the athlete in the long distance varieties of canoeing and kayaking are more focused on muscle endurance than explosive power and strength. As with all other forms of this sport, the more efficiently the athlete can use the paddle, the faster the boat will travel. Errors or weaknesses in paddling technique cause the craft to move less efficiently, or alternatively, place greater stress on both the muscular capabilities and the energy reserves of the paddler.

Canoe and kayak racing does not involve significant risk of injury by trauma. The combination of explosive power and repetitive movements, especially in the shoulders and arms of the athlete, is the chief cause of injury. Muscle strains through overuse or competitive stresses are common. The paddling mechanism in kayaking, involving the rotation of the shoulders, can lead to rotator cuff injuries

SEE ALSO Canoe/Kayak: Hydrodynamics; Endurance exercise; Plyometrics; Shoulder anatomy and physiology.