INTERNATIONAL JOURNAL OF SPORT BIOMECHANICS, 1992,8, 233-250

The Technique of Elite Flatwater Kayak Paddlers Using the Wing Paddle

Selina /. Kendal and Ross H, Sanders

The technique of elite New Zealand kayak paddlers using the Norwegian wing paddle was analyzed to identify factors leading to success. Five male New Zealand kayak paddlers were filmed with two high-speed cinemato- graphic cameras. Paths of the blade tip and joint centers were determined from film data. Velocities ranged from 4.63 to 5.38 mls. Stroke frequency ranged from 1.93 to 2.26 cycles/s. Results indicated that the more successful paddlers, based on previous competitive performances, had similar movement patterns and blade paths and that these differed from those of less successful paddlers. Their blade tip and joint center paths were inore consistent across trials. More successful paddlers entered their blade well forward and closer to the longitudinal axis of the kayak than did less successful paddlers, and moved the blade a large distance laterally from the ly a small distance backward with respect tb the water.

Olympic flatwater kayaking requires a high level of skill to succeed at the international level, and modifications in technique and equipment are made continuously to improve performance. A new type of paddle, termed the wing paddle due to its airfoil shape, has been developed in Sweden and has been credited with improving the performance of its users. Recently the Swedish wing paddle was further modified in Norway, and this new design is now used by international kayak paddlers. Little is known about the factors associated with superior paddling technique with the wing paddle. Several descriptive analyses of the kayak stroke with the standard blade design have been published (Kearney, Klein, & Mann, 1979; Mann & Kearney, 1980; Mann, Kearney, & Kaufmann, 1978; Plagenhoef, 1971,1979), but there have been few scientific reports of wing paddle technique. However, it is clear that the wing paddle technique differs from the standard paddle technique (Thompson, 1985). "

According to Anderson (1988), the blade is moved diagonally away from the kayak, generating a lift propulsive force as the water flows over rhe Swedish wing-shaped blade (Figure 1). Colman, Van Oost, Persyn, and Deldaeti: (1989) compared the technique of one kayaK paddler using both a standard paddle and a wing paddIe. The lateral iiiovement of the wing blade was found to displace a large amount of water a short distance, resulting in the kayak covering a Ionger

The authors are with the School of Physical Education, University Dunedin, New Zealand.

Kendal and Sanders

Figure 1 - The production of lift and drag forces on the wing blade in kayaking. D = drag force on blade; L = lift force on blade; R = resultant force.

distance during the pull with the wing paddle than with the standard paddle. Issourin (1989) studied the movement patterns of a wing blade and found that throughout the stroke the blade was oriented at small angles of attack to the direction of water flow. He concluded that a small angle of attack was important in producing a lift propulsive force.

Sanders and Kendal (in press) studied kayak paddlers ranging in ability from novice to elite to determine the factors associated with superior performance using the Swedish wing. Data obtained from the lateral aspect were supplemented with data from a frontal view to attain a more complete picture of the movement pattern of the body segments and path of the paddle. It was found that good performances were distinguished by a high stroke frequency rather than a great stroke length. Good paddlers achieved higher stroke frequencies by minimizing both pull time and glide time.

The purpose of this study was to identify factors associated with successful kayak paddling technique using the Norwegian wing paddle, and to gather data from elite kayak paddlers, forming a standard to which non-elite paddlers can be compared. In this study we investigated the relationship between stroke frequency, pull time, glide time, stroke length, pull length, glide length, forward reach, backward reach and slip, and the performance criterion, average kayak velocity. The paths of the joint centers were described with respect to the moving kayak center, and the path of the blade tip was described with respect to the moving kayak center and the water. The paths of the blade tip and joint centers have been described by Plagenhoef (1971, 1979) and by Mann and Keamey (1980) for technique using the standard paddle. To the best of our knowledge, these paths have not yet been described for elite paddlers using the Norwegian wing paddle.

Elite Flatwater Kayak Paddlers

Method

Subjects and Kayak Preparation

Five male New Zealand kayak paddlers (S1 to S5) ranging in age from 22 to 37 years (mean = 26 yrs) participated in the study. All had competed at international level. S3 and S5 were the most successful paddlers, based on previous competitive performances. Each subject was filmed while performing a series of five trials in which he accelerated over a self-chosen distance (greater than 50 meters) to reach maximum velocity just prior to moving into the filming area. All subjects used their own kayak and Norwegian wing paddle.

Black circles marked on white tape were placed on the side of the kayak in line with the ends of the cockpit, to serve as a reference for determining the scale factor used in the subsequent analysis. The center of the kayak was regarded as the midpoint of these markers. A wooden T bar with markers at the top, bottom, and both sides was taped in an inverted position on the upper surface of the kayak at a measured distance from the bow. This enabled a scale factor to be determined for the frontal view. The paddle was marked at each end of the shaft, and the distance of the markers from the tip of the blade was measured.

Data Collection

Two phase-locked Photosonics 16-mm high-speed cameras fitted with Angenieux 12-150 mm zoom lenses were used to film the trials. Camera 1 (lateral) was positioned with the lens axis perpendicular to the plane of motion at a distance of approximately 20 m. Camera 2 (frontal) was positioned with the lens axis in the intended plane of motion at a distance from the moving kayak, which varied from approximately 20 m to 10 m during each film trial. The subjects were instructed to paddle directly toward this camera. The cameras operated at a nominal framing rate of 100 fps with a 90' shutter (effective exposure time 11400 s).

Trials in which two consecutive strokes (a right-side stroke followed by a left-side stroke) were not in view of the lateral camera, or in which the kayak was not moving directly toward the frontal camera, were not considered for analysis. Four trials were analyzed for all subjects with the exception of S2, for whom only one trial was analyzed.

A Calcomp 9100 digitizer was used to digitize each trial from 10 frames prior to right-side blade entry to 10 frames following right-side blade re-entry. The following reference points for the lateral view were digitized: external refer- ence point, stern marker, bow marker, right paddle marker, left paddle marker, vertex of the head, 7th cervical vertebrae, right shoulder, right elbow, right wrist, right hand center, left shoulder, left elbow, left wrist, and left hand center. The following reference points for the frontal aspect were digitized: external reference point, top T bar point, bottom T bar point, right T bar point, left T bar point, vertex, lower midline point, right paddle marker, left paddle marker, right shoul- der, elbow, and hand center, left shoulder, elbow, and hand center. The digitized film coordinates were input to a Foman analysis program that calculated the kinematic variables.

Kendal and Sanders

Frames of Reference

The X, Y, and Z coordinate records of each data point were filtered using a second-order Butterworth digital filter employing an optimal frequency cutoff to reduce random error associated with the digitization process. The cutoff frequen- cies were always within the range of 5 to 7 Hz. Data points were then expressed in terms of their displacement along three orthogonal axes:

1. The X axis was the horizontal axis perpendicular to the optical axis of the lateral camera and in the approximate plane of motion of the kayak. X coordinates were expressed in two ways: (a) with respect to the center of the kayak at the beginning of the stroke cycle, termed the external reference frame; (b) with respect to the moving kayak center, termed the internal reference frame.

2. The Y axis was the horizontal axis perpendicular to the kayak's plane of motion. The Y coordinate data were digitized from the film of the frontal camera. The scaling of the Y axis was adjusted throughout the trial for each reference point by taking account of its X displacement (determined from the lateral camera view) from the film plane of the frontal camera. The Y coordinates were expressed with respect to the moving kayak center in the internal reference frame.

3. The Z axis was the vertical axis in the kayak's plane of motion. The Z coordinates were obtained from the digitized film taken from the lateral camera. These were expressed with respect to the moving kayak center in the internal reference frame.

Data Analysis

Variables selected for analysis in this study were average kayak velocity, stroke frequency, pull time, glide time, stroke length, pull length, and glide length for the right and left stroke cycles; forward reach, backward reach, and slip for the right stroke cycle only; right blade tip path and joint center paths for the right shoulder, elbow, and hand. Instantaneous values of velocity of the kayak were derived from the kayak center position data. Maximum velocity, minimum veloc- ity, decrease in velocity, and the time to maximum velocity were determined for the left and right stroke cycles. The decrease in kayak velocity was calculated as the difference between the maximum and minimum velocity values during the stroke cycle. The time to maximum velocity was calculated as the time from blade entry to maximum velocity.

The dependent variable, average kayak velocity, is the product of stroke frequency and stroke length. Stroke frequency, the inverse of stroke time, is composed of two components, pull time and glide time. Pull time is the time from blade entry to blade exit on the same side. Glide time is the time from blade exit to opposite-side blade entry. Stroke length is determined as the distance traveled by the kayak center from blade entry to entry of the opposite-side blade and is also composed of two components, pull length and glide length. Pull length is the distance traveled by the kayak center during the period of blade entry to blade exit on the same side. Glide length is the distance traveled by the kayak center during the period from blade exit to opposite-side blade entry. Pull length is composed of three variables: forward reach (the horizontal displacement of the

Elite Flatwater Kayak Paddlers 237

blade tip at entry relative to the center of the kayak), backward reach (the horizontal displacement of the blade tip at exit relative to the center of the kayak), and slip. Slip is the horizontal displacement of the blade tip while in the water along the X axis with respect to the external reference frame.

The blade tip path was regarded as the path of the tip of the right blade with respect to the center of the kayak from the time of right-side blade entry to right-side blade re-entry. The blade tip position was calculated by adding the measured distance between the blade tip and the known paddle reference point to the right-side paddle reference point. Blade tip path was expressed with respect to the internal reference frame for both a lateral (X, Z) view and a plan (X, Y) view (reconstructed from the lateral and frontal camera views), and with respect to the external reference frame for a plan (X, Y) view. Joint center paths for the right shoulder, elbow, and hand were expressed with respect to the internal reference frame for both the lateral (X, Z), and plan (X, Y) views. To facilitate comparisons among subjects, path and velocity values were determined for per- centiles of the stroke by applying an interpolating quintic spline to the real-time data samples.

Means and standard deviations of each subject's set of trials were calculated for all variables. Average kayak velocity was used as a measure of performance and served as the dependent variable in statistical analysis. Simple regression and Pearson product-moment correlation analyses were performed for each indepen- dent variable to indicate its relationship with average kayak velocity.

Results and Discussion

Velocity

Tables I and 2 present average kayak velocity and maximum and minimum velocity during the right-side and left-side stroke cycle, respectively, for each subject. Average kayak velocity ranged from 4.63 m/s (S4) to 5.38 m/s (Sl). Maximum kayak velocity ranged from 4.80 m/s (S4) to 5.55 m/s (Sl). Minimum kayak velocity ranged from 4.41 m/s (S5) to 5.31 m/s (Sl). The subjects with the highest average kayak velocity had greater maximum velocities (-0.92, R2= 0.98, p<0.01) and minimum velocities (-1.04, R2=0.98, ~ ~ 0 . 0 1 ) than those with smaller average kayak velocities. Velocities of the kayak over two consecutive strokes (a right-side stroke followed by a left-side stroke) are shown for all subjects in Figure 2. The most successful paddlers, based on previous competitive performances, did not attain the greatest average kayak velocities. This may have been due to the short distance of the trials in comparison with race distances. Although some paddlers had high average kayak velocities and high stroke frequencies, it is not known whether these could have been maintained throughout a race distance.

Velocity increased during the pull phase of the stroke and decreased prior to blade exit and throughout the glide phase, due to the effect of drag (Figure 2). Maximum velocity was achieved prior to blade exit for all subjects, suggesting a period toward the end of the pull phase when not enough force was produced to maintain kayak velocity during the period preceding blade exit. Minimum velocity occurred near the instant of opposite-side blade re-enhy.

Velocity patterns were asymmetrical for all paddlers over the right and left

Kendal and Sanders

Table 1

Mean Scores for Each Subject's Set of Trials During the Right-Side Stroke Cycle

Av. kayak Max. Min. Decrease Time to max. velocity velocity velocity in velocity velocity

Subject (m/s) @IS) (m/s) @Is) (% cycle)

Table 2

Mean Scores for Each Subject's Set of Trials During the Left-Side Stroke Cycle

Av. kayak Max. Min. Decrease Time to rnax. velocity velocity velocity in velocity velocity

Subject (m/s) (m/s) (m/s) @Is) (% cycle)

stroke cycles (Figure 2). The maximum velocity for each subject and the time taken to reach it differed between right and left stroke cycles. The decrease in velocity also differed between right and left stroke cycles for all subjects. This asymmetry among elite paddlers may be due to differences in strength and coordination between dominant and nondominant sides of the body.

Tables 1 and 2 show that the mean decrease in kayak velocity from maxi- mum velocity prior to blade exit and throughout the glide phase ranged from 0.25

Elite Flatwater Kayak Paddlers 239

TIME (% s t r o k e c y c l e )

6.50 >

Figure 2 - Velocity of the center of the kayak during right and left stroke cycles. Stick figure sequence indicates phases of stroke cycles from a lateral view. Solid lines represent right side of paddler, dashed lines represent left side.

6.00 - d

I m

m/s for S1 to 0.72 m/s for S3. The decrease in kayak velocity varied among subjects. This may have been due to a number of factors including the timing and magnitude of their maximum velocity, the time the blades were out of the water, the wetted area of the kayak, and the angle of the kayak to the intended line of travel.

Because drag tends to increase in proportion to the square of velocity (Hay, 1985), it would seem that subjects who attained a large velocity during the pull phase would have experienced a large decrease in velocity during the glide phase. However, no relationship was found between the maximum velocity and the amount of decrease during the glide phase. This suggested that factors other than velocity had a substantial influence on the drag experienced during the glide phase.

S l -.-.- 52 . . . . . . . . . . . . 53 - 54 -. 1 . right entry s5

2 - right exit 3 - left entry 4 - left exit

Stroke Frequency

4.0 0 0 10 20 30 40 50 60 70 80 90 100

Stroke frequency ranged from 1.93 cycles/s for S5 to 2.26 cycles/s for S1 (Table 3). Although S1 had the greatest average kayak velocity and also the highest stroke frequency, no relationship was found between stroke frequency and kayak velocity. Anderson (1988, p. 127) stated that "the stroke frequency has decreased with the wing paddle as a longer, slower, more powerful stroke is produced." Although some of the subjects in this study had stroke frequencies with the wing paddle approaching those reported by Plagenhoef (1979) for the standard paddle,

Kendal and Sanders

Table 3

Mean Scores for Each Subject's Set of Trials (averaged over right and left stroke cycles)

Av. kayak Stroke Stroke Pull Glide velocity freq. time timea timeb

Subject (mts) (cyclests) (sec) (set) (set)

a ~ u l l time as a percentage of stroke time in parentheses; b ~ l i d e time as a percentage of stroke time in parentheses.

it is not clear to what extent stroke frequency and kayak velocities can be sustained by the subjects in this study over race distances.

Pull Time and Glide Time 1 I

Pull time varied between 0.30 s for S 1 and 0.37 s for S5 (Table 3). Pull time was expressed as a percentage of stroke time and ranged from 65% for S2 to 72% for S5. These values were similar to the ones reported (Mann & Kearney, 1980; Plagenhoef, 1979) for the standard paddle. Plagenhoef (1979) concluded that the ideal value for pull time with the standard paddle was 69% of the stroke time. This was based on data obtained from elite kayak paddlers competing in major international regattas, including the 1976 Montreal Olympics. Mann and Keamey (1980) studied male and female Olympic-style flatwater kayak paddlers using standard paddles and found their pull times to be between 66 and 80% of the stroke time. The average was 71.5%. Although S l had the greatest average kayak velocity and also the shortest pull time, no relationship was found between pull time and kayak velocity. A relationship was found between pull time and stroke I time (r=1.07, R2=0.84, p=0.018), however, suggesting that reducing pull time reduces stroke time.

The glide time varied between 0.13 s for S 1 and 0.18 s for S2 (Table 3). Glide time as a percentage of stroke time ranged from 28% for S4 and S5 to 35% for S2. No significant relationship was found between glide time and kayak velocity. Similarly, no relationship was found between glide time and stroke time, which indicates that those subjects with longer stroke times did not necessarily have longer glide times.

Elite Flatwater Kayak Paddlers 241

Stroke Length, Pull Length, and Glide Length

Stroke length ranged from 2.32 m for S4 to 2.55 m for S3 (Table 4). No significant relationship was found between stroke length and kayak velocity.

Pull length ranged from 1.61 m for S4 to 1.8 1 m for S3 (Table 4). There was no relationship between pull length and kayak velocity. Although subjects with a long pull length tended to have a long stroke length, no relationship was found between pull length and stroke length. Although it is desirable to increase pull length, increasing it beyond a certain subject-specific optimum would be counterproductive, as this would reduce stroke frequency.

Glide length ranged from 0.67 m for S5 to 0.88 m for S2 (Table 4). There was no relationship between glide length and kayak velocity.

Forward Reach and Backward Reach

Forward reach varied between 0.92 m for S1 and 1.08 m for S3 (Table 4). No relationship was found between forward reach and kayak velocity. There is no benefit to be gained by attempting to increase forward reach, as this would decrease stroke frequency. Subjects should limit forward reach to that where they can apply large propulsive forces immediately following blade entry.

Backward reach varied between 0.75 m for S1 and S2 and 0.93 m for S5 (Table 4). No relationship was found between backward reach and kayak velocity. Because the kayak velocity was decreasing during the last part of the pull phase in which the blade was behind the kayak center, a longer backward reach did not result in a greater kayak velocity but contributed to a longer pull time. Those subjects with the longest pull time as a percentage of the stroke time also had the longest backward reach (e.g., S5). Subjects with a short backward reach had a more effective stroke technique because they minimized stroke time by reducing time spent in an ineffective part of the pull phase.

Table 4

Mean Scores for Each Subject's Set of Trials

Stroke Glide Pull Fomard Backward length length length reach reach Slip

Subject (m) (m) (m) (m) (m) (m)

242 Kendal and Sanders

Slip

Slip ranged from -0.07 m for S2 to -0.22 m for S5 (Table 4). Although no significant relationship was found between slip andkay* velocity, those subjects with the highest kayak velocity also had the smallest slip (S1 and S2). It is likely that the successful paddlers obtained lift from the lateral movement of their blade, minimizing the need for backward movement. It may be expected that minimizing slip would increase pull length (because the kayak has moved further before the blade is withdrawn) withom increasing pull time.

Blade Tip and Joint Center Paths

Plan (X, Y) and lateral (X, Z) views of the blade tip and joint center paths for a representative trial of S3 and S4 are presented in Figures 3 and 4, respectively, These subjects were selected for illustrative purposes because they highlight differences between the most successful paddler, S3, and the least successful paddler, S4, based on previous competitive performances. These show the path of the right blade tip and joint centers with respect to the internal reference frame. It should be noted that some of the variance in the instant of entry from one stroke to the next may have been due to perspective error. This is because all parts of the paddler and kayak are assumed to be the same distance from the film plane of the lateral camera. Hdwever, because the camera was approximately 20 m away from the plane of motion, this perspective error was small (<3%). While it is important to recognize the existence of the small perspective error, it does not unduly affect the ability to compare among trials and among subjects.

Blade Path. The position of the blade during "the pull phase with respect to the external reference frame is given for all subjects in Table 5. In the X, Y (plan) view, shown in Figure 3a, it was evident that subjects entered their blade

I

Table 5

Blade Position With Respect to X and Y Axes During Pull Phase of the Right-Side Stroke Cycle

Entry Exit Displacement

X Y X Y X Y Subject (m) (m) (m) (m) (m) (m)

well forward and close to the longitudinal axis of the kayak. The position of the blade at entry in the X direction ranged between 0.92 m for S 1 and 1.07 m for S3 (Table 5). The entry position in the Y direction ranged from 0.44 m (S3) to 0.63 m (S4). After right-side blade entry, the blade was moved in a lateral direction (positive Y direction) and backward (negative X direction) relative to the internal reference frame until the instant of blade exit (see Figure 3a). The displacement of the blade in the X direction ranged from -0.07 m for S2 to -0.22 m for S5.

According to Anderson (1988), the lateral component of the wing blade's motion develops lift in the forward direction. The displacement of the blade in the Y direction ranged between 0.37 m (S4) and 0.70 m (S2) (Table 5). The position of the blade in the X direction at exit relative to the external reference frame ranged from 0.81 m for S5 to 0.94 m for 53. The exit position in the Y direction relative to the external reference frame ranged between 0.97 m (S5) and 1.24 m (S2).

The successful paddlers (S3 and S5) were very consistent in the path of their blade in the X, Y, and Z directions, while the blade paths of less successful subjects (e.g., S4) varied across trials, particularly in the recovery phase. There were differences among subjects in the distance the blade moved with respect to the kayak center in the X and Y directions. Successful paddlers (e.g., S3) entered their blade further forward and closer to the longitudinal axis of the kayak than did less successful paddlers (e.g., S4), and moved it further from the kayak in the lateral direction (positive Y direction) during the pull phase.

During the pull phase S3 moved his blade a greater distance laterally (positive Y direction) away from the kayak compared to S4 (see Figure 3a). The X, Z (lateral) view, shown in Figure 4a, indicated that during the recovery phase the blade was brought forward to a position in front of the entry point and then back to the point of entry. In Figure 4a it was evident that S3 did not pull his blade to as great a depth (negative Z direction) or recover his blade as high (positive Z direction) as S4 during the recovery phase. At the time of left-side blade exit, S3's blade was lower than S4's, closer to the point of entry.

An X, Y (plan) view of the path of the blade tip with respect to the external reference frame for a representative trial of S3 and S4 is shown in Figure 5. During the pull phase, S3's blade traveled further in the positive Y direction from the longitudinal axis of the kayak than did S4's (Figure 5). It is likely that the greater lateral movement of S3's blade generated more lift in the forward direction (positive X direction), producing a higher kayak velocity than for S4. Less successful paddlers (e.g., S4) moved the blade farther backward (negative X direction) through the water during the pull phase. Results shown in Tables 4 and 5 indicated that differences in the amount of slip were related to differences in the path of the blade tip during the pull phase.

Subjects with a small slip (e.g., S1 and S2) moved their blades a large distance in the positive Y direction from the longitudinal axis of the kayak during the pull phase. Subjects with a large slip (e.g., S4 and S5) did not move their blades as far from the longitudinal axis of the kayak as other subjects. It appears that if subjects did not continue the lateral (positive Y direction) movement of their blade, it moved backward (negative X direction) through the water, producing a large amount of slip. This may have resulted from the blade not finding "still" water during the pull phase. It is likely that during this part of the stroke these

Kendal and Sanders

Y POSITION (in)

Y POSITION (m)

Figure 3 - Plan view of path of right blade tip (a), and right hand center (b), for Subject 3 (S3) and Subject 4 (S4) for the right-side stroke cycle. (cont.)

Elite Flatwater Kayak Paddlers

Y POSITION (m)

S3 d 54 ,,------.

1 - rlght entry 2 - right exlt 3 - left entry 4 - left exlt

Y POSITION (mf

Figure 3 (cont.) - Plan view of path of right elbow (c), and right shoulder (d), for Subject 3 (S3) and Subject 4 (54) for the right-side stroke cycle.

Kendal and Sanders

_--- ___--------__ --

2 - right exit

4 - left exit

-. --- ----_---- +-.-

X POSITION (m)

X POSITION (m)

Figure 4 - Latefal view of path M @fit blade 9ip ,(a), hnd qight hand venter (b); for Subject 3 (S3) aild'SaBject 4 (S4) during th6 right-side stroke cycle. Cont.)

Elite Flatwater Kayak Paddlers

1.0 0 - C

S3 S4 ----------,--.

1 - rlght entry 2 - rlght exit 3 - left entry 4 - left exlt

0 -60 -.40 -20 0 .2 0 -4 0

X POSITION (m)

X POSITION (m)

.70 .. z o H

I- H ~n .60 0 a N

.!iO

ure 4 (cont.) - Lateral view of path of right elbow (c), and right shoulder (dl, Subject 3 (S3) and Subject 4 (S4) during the right-side stroke cycle.

___-----------__ 2---3*" --_ -_ .. **-.. -. Q ---._ C----___

----*- -.. i*' ---___----- 1 - right entry

.. 2 - right exit 3 - left entry

.. 4 - left exlt

Kendal and 3anders

1.20 I I - rlght emry 2 - rlght exit

6 0 .4 0 6 0 .8 0 1.0 0 120 140

Y POSITION (ml

Figure 5 - Plan view of path of right blade tip with respect to the external reference frame for Subject 3 (S3) and Subject 4 (S4) during the right-side pull phase. Circles indicate fifth percentiles of stroke cycle.

subjects were relying on a greater proportion of drag than lift for forward propul- sion.

The path of the blade with respect to the external reference frame (Figure 5) indicated that for all subjects the blade moved initially slightly forward (positive X direction) after entry before it moved backward (negative X direction). Depending on the lift force gained by the lateral (positive Y direction) movement of the paddle blade, the forward (positive X direction) movement of the paddle as it was being immersed may indicate that the paddle was producing an additional drag force rather than a propulsive force at this time. It appears that this part of the stroke was ineffective. The delay in increasing velocity during this period supports this possibility, In Figure 5 it is evident that the blade also moved forward (positive X direction) immediately prior to blade exit. An additional drag force may also have been produced prior to--blade exit, The decrease in velocity prior to blade exit suggests that this is also an ineffective part of the stroke.

Hand Center Path. The X , Y (plan9 view, shown in Figure 3b, indicated that the hand at blade entry was approximately in line with the longitudinal axis of the kayak. After blade entry, the hand moved backward (negative X direction) and laterally (positive Y direction) away from the kayak. The position of the hand at the end of the pull phase was behind the center of the kayak. The hand was then recovered forward (positive X direction), crossed the longitudinal axis of the kayak, and was returned to the blade entry position. The X, Z (lateral) view, shown in Figure 4b, indicated that the hand was lowered (negative Z direction) as the blade was immersed, pulled back (negative X direction) during the pull phase, and raised (positive Z direction) as the blade was removed from the water. Duringlrecovefy the hand wa's~raise'd above the shouldef and puSWCd' foY\hr-ard, then lowered to the entry position. 7 I , 1 f a $L , b ? 5 t . i

Elite Flatwater Kayak Paddlers 249

This general pattern was common to all subjects. With the exception of S 1 and S4, subjects were consistent across trials with respect to the path of their hand. While the basic pattern was similar, there was some variation in the hand center path among subjects. The X, Y (plan) view of the hand center path, shown in Figure 3b, indicated that the successful paddler (S3) positioned his hand closer to the longitudinal axis of the kayak at blade entry than the less successful paddler (S4), and moved his hand a greater distance laterally away from the kayak (positive Y direction). Figure 3b shows that during recovery the best paddler (S3) moved his hand initially further forward in the positive X direction than S4, then moved it in the negative Y direction across the longitudinal axis of the kayak. S3 recovered his hand in the negative Y direction to a position further across the longitudinal axis of the kayak than S4. The X, Z (lateral) view, shown in Figure 4b, indicated that the successful paddler, S3, did not recover his hand as high as the less successful paddler, S4. At the time of left-side blade exit, S3's hand was lower than S4's, closer to its blade entry position.

Elbow Path. The X , Y (plan) view (Figure 3c) indicated that at blade entry the elbow was positioned in front of the center of the kayak. It was moved initially in the positive Y direction away from the longitudinal axis of the kayak, and then in the negative X direction toward the rear of the kayak. During recovery it moved initially in the positive Y direction away from the kayak and in the positive X direction, and then in the negative Y direction across to the center of the kayak before returning in the positive Y direction to its position at blade entry. Both the X, Y (plan) view, shown in Figure 3c, and the X, Z (lateral) view, shown in Figure 4c, highlight differences between the elbow paths of S3 and S4. The elbow of the successful paddler (S3) was positioned closer to the longitudinal axis of the kayak at blade entry, compared with the less successful paddler (S4). At blade exit, the elbow of the successful paddler was positioned further from the longitudinal axis of the kayak in the positive Y direction than was that of the less successful paddler. 53 recovered his elbow further in the positive X direction than S4 before returning it toward the longitudinal axis of the kayak. Figure 4c indicates that S3 did not recover his elbow as high as S4. At the time of left-side blade exit, S3's elbow was lower than S4's, just above its position at blade entry.

Shoulder Path. In general, the X, Y (plan) view, shown in Figure 3d, indicates that the shoulder was moved backward (negative X direction) initially during the pull phase, and then in the negative Y direction toward the longitudinal axis of the kayak as the trunk rotated prior to blade exit. The shoulder then moved in the positive Y direction away from the longitudinal axis of the kayak, and forward (positive X direction) throughout the recovery. In the X, Z (lateral) view (Figure 4d) it was evident that the shoulder was moved back (negative X direction) and upward (positive Z direction) during the pull phase, and forward (positive X direction) and down (negative Z direction) during recovery. A similar shoulder path was followed by all subjects. The successful paddler (S3) did not move his shoulder as far backward (negative X direction) as the less successful paddler (S4) during the recovery phase, nor did he raise his shoulder as high.

Summary

Kayak paddlers' average kayak velocities using the wing paddle ranged from 4.63 to 5.38 m/s. Successful kayak paddlers (based on previous competitive

250 Kendal and Sanders

performances) attained higher average kayak velocities than less successful paddlers. Velocity patterns were asymmetrical for all paddlers over the right and left stroke cycles. Stroke frequency ranged from 1.93 to 2.26 cyclesfs. There was a period preceding blade exit in which the paddle did not produce enough force to maintain or increase kayak velocity, thus the kayak decelerated. Stroke length ranged from 2.32 to 2.55 m.

Successful paddlers had consistent blade tip and joint center paths across trials that were similar to each other but different from the less successful subjects in several ways. First, the more successful paddlers entered their blade well forward and closer to the longitudinal axis of the kayak than less successful paddlers. Second, they moved the blade a large distance laterally from the kayak and had less backward movement of the blade with respect to the external reference frame (slip). Because the better paddlers minimized slip and maximized the lateral displacement of the blade, it was thought that better paddlers gained forward propulsion using lift forces generated from the lateral movement in preference to drag forces generated by backward movement. Third, during the recovery phase, the more successful paddlers moved their blades initially a greater distance in the forward direction before moving them toward the longitudinal axis of the kayak to the blade entry position.

References

Anderson, F. (1988, Dee.) Winging it: A revolution in kayak paddles. Canoe, p. 127. Colman, V., Van Oost, F., Persyn, U., & Deldaele, D. (1989). Practical applications of PC

software in kayak. In J. Vrijens, J. Verstnyft, & D. deClercq (Eds.), Intertiationcrl Seminar- 0 1 7 Kayak-Canoe Coac,hing and Sciences (pp. 93-99). Budapest, Hungary: International Canoe Federation.

Hay, J.G. (1 985). T/7e hionrrr~hat~ir~s c?f.~pot./.s t'c~hrriques. Englewood Clifl's, N J : Prentice Hall.

Issourin, V. (1989). Biomechanical aspects of kayak related to strength. In J . Vri.jens, J. Verstnyft, & D. declercq (Eds.), Inteuiatiot~al Sc~nlitr~~r on Kcrycrk-Cotioc Coui~lritlg and Sciences (pp. 83-91). Budapest. Hungary: International Canoe Federation.

Kearney, J.T., Klein, L., & Mann, R. (1979). The elements of style: An analysis of the flatwater canoe and kayak stroke. Canoe, 7(3), 18-20.

Mann, R.V., & Kearney, J.T. (1980). A biomechanical analysis of the Olympic-style flatwater kayak stroke. Mcciic,it~e and Science it1 S11ort.s utrcl E.1-c>rc.i.sc~, 12(3), 183- 188.

Mann, R.V., Kearney, J.T., & Kaufniann, D.A. (1978). A bio~nechanical analysis of Oly~npic flatwater kayak paddlers. Medicit7e ntlcl Scietice h Sport, 10(1), 63.

Plagenhoef, S. (1971). Pcrrtertrs qf hlrnlat~ alotiot~. Englewood Cliffs, NJ: Prentice Hall. Plagenhoef, S. (1979). Biornechanical analysis of Olylnpic tlatwater kayaking and canoe-

ing. Researc.11 Quat.tet.ly, 50, 443-459. Sanders, R.H., & Kendal, S.J. (in press). A description of Olympic tlatwater kayak stroke

technique. A~rstraliat~ .lo11r11uI of SCI'CII(.CJ utld Medic.itle iti Spot./. Thompson, A. (1985). Flat~~utet. kayak rucing. Unpublished manuscript.