Inspiratory muscle fatigue after race-paced swimming is not restricted to the front crawl stroke

ABSTRACT: Lomax, M, Iggleden, C, Tourell, A, Castle, S, and Honey, J. Inspiratory muscle fatigue following race-paced swimming is not restricted to the front crawl stroke. J Strength Cond Res 26(10): 2729-2733, 2012-The occurrence of inspiratory muscle fatigue (IMF) has been documented after front crawl (FC) swimming of various distances. Whether IMF occurs after other competitive swimming strokes is not known. The aim of the present study was to assess the impact of all 4 competitive swimming strokes on the occurrence of IMF after race-paced swimming and to determine whether the magnitude of IMF was related to the breathing pattern adopted and hence breathing frequency (fb). Eleven, nationally ranked, youth swimmers completed four 200-m swims (one in each competitive stroke) on separate occasions. The order of the swims, which consisted of FC, backstroke (BK), breaststroke (BR), and butterfly (FLY), was randomized. Maximal inspiratory mouth pressure (MIP) was assessed before (after a swimming and inspiratory muscle warm-up) and after each swim with fb calculated post swim from recorded data. Inspiratory muscle fatigue was evident after each 200-m swim (p < 0.05) but did not differ between the 4 strokes (range 18-21%). No relationship (p > 0.05) was observed between fb and the change in MIP (FC: r = -0.456; BK: r = 0.218; BR: r = 0.218; and FLY: r = 0.312). These results demonstrate that IMF occurs in response to 200-m race-paced swimming in all strokes and that the magnitude of IMF is similar between strokes when breathing is ad libitum occurring no less than 1 breath (inhalation) every third stroke.     

Swimming performance is reduced by reflective markers intended for the analysis of swimming kinematics

The present study aimed to clarify whether swimming performance is affected by reflective markers being attached to the swimmer’s body, as is required for a kinematic analysis of swimming. Fourteen well-trained male swimmers (21.1 ± 1.7 yrs) performed maximal 50 m front crawl swimming with (W) and without (WO) 25 reflective markers attached to their skin and swimwear. This number represents the minimum required to estimate the body’s center of mass. Fifty meter swimming time, mid-pool swimming velocity, stroke rate, and stroke length were determined using video analysis. We found swimming time to be 3.9 ± 1.6% longer for W condition. Swimming velocity (3.3 ± 1.8%), stroke rate (1.2 ± 2.0%), and stroke length (2.1 ± 2.7%) were also significantly lower for W condition. To elucidate whether the observed reduction in performance was potentially owing to an additional drag force induced by the reflective markers, measured swimming velocity under W condition was compared to a predicted velocity that was calculated based on swimming velocity obtained under WO condition and an estimate of the additional drag force induced by the reflective markers. The mean prediction error and ICC (2,1) for this analysis of measured and predicted velocities was 0.014 m s⁻¹ and 0.894, respectively. Reducing the drag force term led to a decrease in the degree of agreement between the velocities. Together, these results suggest that the reduction in swimming performance resulted, at least in part, from an additional drag force produced by the reflective markers.     

The aerobic demand of backstroke swimming, and its relation to body size, stroke technique, and performance

Few studies have examined the aerobic demand of backstroke swimming, and its relation to body morphology, technique, or performance. The aims of this study were thus to: i) describe the aerobic demand of backstroke swimming in proficient swimmers at high velocities; ii) assess the effects of body size and stroke technique on submaximal and maximal O2 costs, and; iii) test for a relationship between submaximal O2 costs and maximal performance. Sixteen male competitive swimmers were tested during backstroke swimming at velocities from 1.0 to 1.4 m.s-1. Results showed that VO2 increased linearly with velocity (m.s-1) following the equation VO2 = 6.28v - 3.81 (r = 0.77, SEE/Y = 14.9%). VO2 was also related to the subjects' body mass, height, and armspan. Longer distances per stroke were associated with lower O2 costs, and better maximal performances. A significant relation was found between VO2 at 1.1 m.s-1, adjusted for body mass, and 400 m performance (r = -0.78). Submaximal VO2 was also related to reported times for 100 m and 200 m races. Multiple correlation analyses indicated that VO2 at 1.1 m.s-1 and VO2max accounted for up to 78% of the variance in maximal performances. These results suggest that the assessment of submaximal and maximal VO2 during backstroke swimming may be of value in the training and testing programs of competitive swimmers.     

Effects of a 6-week plyometric training program on performances in pubescent swimmers

This study examined in pubescent swimmers the effects on front crawl performances of a 6-week plyometric training (PT) in addition to the habitual swimming program. Swimmers were assigned to a control group (n = 11, age: 14.1 ± 0.2 years; G(CONT)) and a combined swimming and plyometric group (n = 12, age: 14.3 ± 0.2 years; GSP), both groups swimming 5.5 h · wk(-1) during a 6-week preseason training block. In the GSP, PT consisted of long, lateral high and depth jumps before swimming training 2 times per week. Pre and posttests were performed by jump tests (squat jump [SJ], countermovement jump [CMJ]) and swim tests: a gliding task, 400- and 50-m front crawl with a diving start (V400 and V50, m · s(-1)), and 2 tests with a water start without push-off on the wall (25 m in front crawl and 25 m only with kicks). Results showed improvement only for GSP for jump tests (Δ = 4.67 ± 3.49 cm; Δ = 3.24 ± 3.17 cm; for CMJ and SJ, respectively; p < 0.05) and front crawl tests (Δ = 0.04 ± 0.04 m · s(-1); Δ = 0.04 ± 0.05 m · s(-1); for V50 and V400, respectively; p < 0.05). Significant correlations were found for GSP between improvements in SJ and V50 (R = 0.73, p < 0.05). Results suggested a positive effect of PT on specific swimming tasks such as dive or turn but not in kicking propulsion. Because of the practical setup of the PT and the relevancy of successful starts and turns in swimming performances, it is strongly suggested to incorporate PT in pubescent swimmers' training and control it by jump performances.     

Estimation of hand forces and propelling efficiency during front crawl swimming with hand paddles

The aim of the study was to investigate possible modifications caused by hand paddles in the relative contribution of the lift and drag forces of the hand and in the propelling efficiency, during front crawl swimming. Eight female swimmers swam 25 m with maximal intensity without paddles, with small (116 cm(2)) and with large paddles (268 cm(2)). Four cameras operating at 60 Hz were used to record the images and the Ariel Performance Analysis System was used for the digitisation. The results showed that, although during swimming with hand paddles the hand's velocity decreased, the greater propulsive area of the hand paddle caused an increase in the drag, lift, resultant and effective forces of the hand. However, the relative contribution of lift and drag forces on swimming propulsion was not modified, nor was the direction of the resultant force. Hand paddles also increased the propelling efficiency, the stroke length and the swimming velocity, mainly because of the larger propulsive areas of the hand in comparison with free swimming. However, the significant decrease of the stroke rate, might argue the effectiveness of hand paddle training, particularly when large paddles are used in front crawl swimming.     

Rolling rhythms in front crawl swimming with six-beat kick

The purpose of this study was to establish the rhythm characteristics of skilled front crawl swimmers using a six-beat kick. These included the amplitudes of the first three Fourier harmonics (H1, H2, H3) and their percent contributions to power contained in the angular displacement signals of the shoulders, hips, knees, and ankles with respect to the longitudinal axis in line with the swimming direction. Three-dimensional video data of seven national/international level swimmers were collected during simulated 200 m front crawl races in which swimmers maintained six-beat kicking patterns. Swimmers differed in all variables but had small variability across the four 50 m laps. Modest changes occurred during the 200 m, with the exception of shoulder roll, which remained constant and was represented almost entirely by a single sinusoid (H1). Changes across laps reached significance for swimming speed, stroke rate, hip roll, and H3 wave velocity between the knee and ankle. A H3 body wave of moderate and increasing velocity travelled caudally from hip to ankle. In the light of existing knowledge of aquatic locomotion this was compatible with the goal of generating propulsion in an efficient manner.     

Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer.

The purpose of this investigation was to test whether the concept of critical power used in previous studies could be applied to the field of competitive swimming as critical swimming velocity (vcrit). The vcrit, defined as the swimming velocity over a very long period of time without exhaustion, was expressed as the slope of a straight line between swimming distance (dlim) at each speed (with six predetermined speeds) and the duration (tlim). Nine trained college swimmers underwent tests in a swimming flume to measure vcrit at those velocities until the onset of fatigue. A regression analysis of dlim on tlim calculated for each swimmer showed linear relationships (r2 greater than 0.998, P less than 0.01), and the slope coefficient signifying vcrit ranged from 1.062 to 1.262 m.s-1 with a mean of 1.166 (SD 0.052) m.s-1. Maximal oxygen consumption (VO2max), oxygen consumption (VO2) at anaerobic threshold, and the swimming also velocity at the onset of blood lactate accumulation (vOBLA) were also determined during the incremental swimming test. The vcrit showed significant positive correlations with VO2 at anaerobic threshold (r = 0.818, P less than 0.01), vOBLA (r = 0.949, P less than 0.01) and mean velocity of 400 m freestyle (r = 0.864, P less than 0.01). These data suggested that vcrit could be adopted as an index of endurance performance in competitive swimmers.     

Blood lactate and stroke parameters during front crawl in elite swimmers with disability

The purpose of this investigation was to compare the blood lactate concentration ([La]), stroke distance (D(s)), and swim index (SI) during an incremental swim test (IST) in elite swimmers who had a loss in mobility (LM) (n = 6) or who had full mobility (FM) (n = 5) of the lower limbs. The IST consisted of 5 repeats of either 100 or 200 m front crawl depending upon the ability level of the swimmer. The [La] and heart rate measured during the IST showed no significant differences (p > 0.05). However, velocity (V(s)) and D(s) were all significantly lower (p < 0.01) during the IST. SI was significantly (p < 0.01) lower during repeats 1 to 3 and 5, but not repeat 4. These data indicate that the [La] response to incremental exercise is similar during incremental front crawl activity in swimmers suffering from loss of lower limb mobility. However, a critical V(s) is reached in LM swimmers where swimming efficiency is optimal compared with FM swimmers.     

Dynamic Resistance Parameters of Arm Stroke during Swimming

Swimming, as a sport beneficial to body and mind, also has a place in international sports. For swimmers and coaches, it is always the most important to improve the propulsion and reduce the resistance during swimming. This paper briefly introduced the resistance of human body in swimming, described the dynamic resistance of human body in arm stroke, and then introduced the principle of micro disturbance method which was used for measuring the dynamic resistance in swimming. Finally, ten swimmers from school team and ten beginners were tested for the dynamic resistance in freestyle, backstroke and breaststroke when they swam with arm stroke only. After adding micro resistance, the swimming speed of the subjects decreased when they swam with all their strength; the speed of freestyle swimming was the largest, followed by backstroke and breaststroke before and after loading, and the swimming speed of school team members was larger than that of beginners; the dynamic resistance and dynamic resistance coefficient of breaststroke were the largest, backstroke was the second, freestyle was the smallest, and the dynamic resistance and dynamic resistance coefficient of school team members were always smaller than those of beginners no matter the swimmer took which swimming style.     

KINEMATIC VARIABLES AND BLOOD ACID-BASE STATUS IN THE ANALYSIS OF COLLEGIATE SWIMMERS’ ANAEROBIC CAPACITY

Short duration repeated maximal efforts are often used in swimming training to improve lactate tolerance, which gives swimmers the ability to maintain a high work rate for a longer period of time. The aim of the study was to examine the kinematics of swimming and its relation to the changes in blood acid-base status and potassium level. Seven collegiate swimmers, with at least 6 years of training experience, volunteered to participate in the study. The test consisted of 8 x 25 m front crawl performed with maximum effort. The rest period between repetitions was set to five seconds. Blood samples were taken from the fingertip at rest, after warm-up and in the 3rd minute after completion of the test. The swimming was recorded with a video recorder, for later analysis of time, velocity and technique (stroke index). Based on the swimming velocity results, the obtained curve can be divided into rapid decrease of velocity and relatively stable velocities. The breaking point of repetition in swimming velocity was assumed as the swimming velocity threshold and it was highly correlated with the decrease of the blood acid-base status (pH r=0.82, BE r=0.87, HCO₃ ^- r=0.76; p<0.05 in all cases). There was no correlation between stroke index or fatigue index and blood acid-base status. Analysis of the swimming speed in the 8 x 25 m test seems to be helpful in evaluation of lactate tolerance (anaerobic capacity) in collegiate swimmers.     

The influence of anthropometrical and flexibility parameters on the results of breaststroke swimming

The aim of this investigation was to study the possible relationships between anthropometry, flexibility and specific swimming results in female breaststroke swimmers. Subjects were 125 female breaststroke swimmers in age of 11-18 years. Body height and mass were measured and BMI (kg/m2 ) and Broca index (body height in cm - 100 = weight in kg) were calculated. The flexibility of hip external rotation, knee external rotation, ankle dorsal flexion and ankle supination were measured with plastic goniometer. 100 m breaststroke swimming using kickboard and legs only was used as a swimming performance parameter. The number of kicks was also fixed. Horizontal jumping ability was measured using a simple standing broad jump (cm) minus body height (cm). As a rule, flexibility in different joints did not depend on anthropometrical parameters. Only knee external rotation and ankle dorsal flexion correlated significantly with body mass (r = -0.221 and r = -0.210, respectively) and BMI (r = 0.242 and r = 0.204, respectively). The relationship between flexibility in different joints, as a rule, was not significant. Stepwise multiple regression analysis indicated that from the used anthropometrical parameters the most important was the body height, which explained 11.1% (R2 x 100) of the 100 m breaststroke swim results using legs only. The most important parameter from the measured flexibility indices was knee external rotation (11.1%, R2 x 100). Combination of knee external rotation and ankle supination increased the determination coefficient to 24.4%. Finally, three flexibility measures (knee external rotation, ankle supination, hip external rotation) explained the swimming results by 28.2% (R2 x 100). It was concluded that the good flexibility is more important than single anthropometrical parameters when explaining the breaststroke swimming results using kickboard and legs only.     

Phase-dependence of elbow muscle coactivation in front crawl swimming

Propulsion in swimming is achieved by complex sculling movements with elbow quasi-fixed on the antero-posterior axis to transmit forces from the hand and the forearm to the body. The purpose of this study was to investigate how elbow muscle coactivation was influenced by the front crawl stroke phases. Ten international level male swimmers performed a 200-m front crawl race-pace bout. Sagittal views were digitized frame by frame to determine the stroke phases (aquatic elbow flexion and extension, aerial elbow flexion and extension). Surface electromyograms (EMG) of the right biceps brachii and triceps brachii were recorded and processed using the integrated EMG to calculate a coactivation index (CI) for each phase. A significant effect of the phases on the CI was revealed with highest levels of coactivation during the aquatic elbow flexion and the aerial elbow extension. Swimmers stabilize the elbow joint to overcome drag during the aquatic phase, and act as a brake at the end of the recovery to replace the arm for the next stroke. The CI can provide insight into the magnitude of mechanical constraints supported by a given joint, in particular during a complex movement.     

Dry-land strength training vs. electrical stimulation in sprint swimming performance

This study was undertaken to compare the effects of dry-land strength training vs. an electrical stimulation program on swimmers. Twenty-four national-level swimmers were randomly assigned to 3 groups: the dry-land strength training program (S), the electrical stimulation training program (ES), and the control (C) group. The training program lasted 4 weeks. The subjects were evaluated before the training, at the end of the training program, and 4 weeks later. The outcome values ascertained were peak torque during arm extension at different velocities (from -60 to 180°·s(-1)) using an isokinetic dynamometer and performance, stroke rate, and stroke length during a 50-m front crawl. A significant increase in swimming velocity and peak torque was observed for both S and ES at the end of the training and 4 weeks later. Stroke length increased in the S group but not in the ES group. However, no significant differences in swimming velocity between S and ES groups were observed. No significant changes occurred in the C group. Programs combining swimming training with dry-land strength or electrical stimulation programs led to a similar gain in sprint performance and were more efficient than swimming alone.     

Assisted and resisted sprint training in swimming

This study was undertaken to determine whether the resisted-sprint in overstrength (OSt) or the assisted-sprint in overspeed (OSp) could be efficient training methods to increase 100-m front crawl performance. Thirty-seven (16 men, 21 women) competition-level swimmers (mean +/- SD: age 17.5 +/- 3.5 years, height 173 +/- 14 cm, weight 63 +/- 14 kg) were randomly divided into 3 groups: OSt, OSp, and control (C). All swimmers trained 6 days per week for 3 weeks, including 3 resisted or assisted training sessions per week for the groups OSt and OSp respectively. Elastic tubes were used to generate swimming overstrength and overspeed. Three 100-m events were performed before, during, and after the training period. Before each 100-m event, strength of the elbow flexors and extensors was measured with an isokinetic dynamometer. Stroke rate and stroke length were evaluated using the video-recorded 100-m events. In the OSt group, elbow extensor strength, swimming velocity, and stroke rate significantly increased (p < 0.05), while stroke length remained unchanged after the 3-week training period. In the OSp group, stroke rate significantly increased (p < 0.05) and stroke length significantly decreased (p < 0.05) without changes in swimming velocity. No significant variations in the C group were observed. Both OSt and OSp proved to be more efficient than the traditional training program. However, the OSt training program had a larger impact on muscle strength, swimming performance, and stroke technique than the OSp program.     

Effect of propelling surface size on the mechanics and energetics of front crawl swimming

In swimming the propulsive force is generated by giving a velocity change to masses of water. In this process energy is transferred from the swimmer to the water, which cannot be used to propel the swimmer. Theoretical considerations indicated that an increase of the propelling surface size should lead to a reduced loss of energy to the water. Thus, in this study, the effect of artificially enlarging the propelling surface of the hand was examined. The effect was examined in terms of the propelling efficiency during front crawl swimming using the arms alone. The legs were floated with a small buoy as previously described (Toussaint et al., J. appl. Physiol. 65, 2506-2512, 1988a). In ten competitive swimmers (six male, four female) the rate of energy expenditure (power input, Pi), power output (Po), work per stroke cycle (As), distance per stroke cycle (d), work per unit distance (Ad), and propelling efficiency (ep) were determined at various swimming speeds once with and once swimming without paddles. At the same average velocity the effect of swimming with paddles was to reduce Pi, Po, and Ad by 6, 7.6, and 7.5% respectively, but to increase ep and As by 7.8 and 7%. The increase in distance per stroke cycle and the decrease in stroke cycle frequency matched the predicted values based on the theoretical considerations in which the actual increase in propelling surface size was taken into account.     

Analysis of selected kinematic and physiological performance determinants during incremental testing in elite swimmers

This study examined the relationships between selected kinematic and physiological parameters and their influence on performance during incremental exercise in elite swimmers competing at the international level. Eleven men and ten women (all specialized in 200-m events) performed an incremental 7 x 200-m test in their specialized stroke. Stroke rate (SR), stroke length (SL), velocity (V), and blood lactate concentration (BLa) were measured for each 200 m. In addition to the cross-sectional group design, the longitudinal performance of a male swimmer was evaluated by 4 tests during a period of 20 weeks. Stroke rate increased and SL decreased with V, regardless of the age, stroke, or gender of the swimmer. Statistically significant correlations were found between SR and V (p < 0.01; r = 0.66 to 0.99), SR and SL (p < 0.01; r = -0.78 to -0.99), SL and V (except for women's freestyle and breaststroke) (p < 0.01; r = -0.67 to -0.98), and BLa and V (p < 0.01; r = 0.7 to 0.96). Changes in SR and SL were not affected by changes in BLa. Similar velocities were produced with different combinations of SR and SL. The fastest times reached in the test were generally slower than expected, and the performance in the test was not associated with competition performance. The case study revealed similar results to those of the group. The test used in this study was informative with respect to identifying the most economical and effective stroke kinematics combination for slow to submaximal velocities. It is possible that the swimming speeds were not maximal in the final 200-m swim because of cumulative fatigue, which is a major limitation for assessing race pace. An additional test that produces velocities similar to those used in competitions would be more useful for the purpose of providing optimal kinematic information specific to racing speeds, which would facilitate performance improvement through regular monitoring in training.     

Intra-Individual Variability of Surface Electromyography in Front Crawl Swimming

The variability of electromyographic (EMG) recordings between and within participants is a complex problem, rarely studied in swimming. The importance of signal normalization has long been recognized, but the method used might influence variability. The aims of this study were to: (i) assess the intra-individual variability of the EMG signal in highly skilled front crawl swimmers, (ii) determine the influence of two methods of both amplitude and time normalization of the EMG signal on intra-individual variability and of time normalization on muscle activity level and (iii) describe the muscle activity, normalized using MVIC, in relation to upper limb crawl stroke movements. Muscle activity of rectus abdominis and deltoideus medialis was recorded using wireless surface EMG in 15 adult male competitive swimmers during three trials of 12.5 m front crawl at maximal speed without breathing. Two full upper limb cycles were analyzed from each of the swimming trials, resulting in six full cycles used for the intra-individual variability assessment, quantified with the coefficient of variation (CV), coefficient of quartile variation (CQV) and the variance ratio (VR). The results of this study support previous findings on EMG patterns of deltoideus medialis and rectus abdominis as prime mover during the recovery (45% activity relative to MVIC), and stabilizer of the trunk during the pull (14.5% activity) respectively. The intra-individual variability was lower (VR of 0.34–0.47) when compared to other cyclic movements. No meaningful differences were found between variability measures CV or VR when applying either of the amplitude or the time normalization methods. In addition to reporting the mean amplitude and standard deviation, future EMG studies in swimming should also report the intra-individual variability, preferably using VR as it is independent of peak amplitude, provides a good measure of repeatability and is insensitive to mean EMG amplitude and the degree of smoothing applied.     

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming.

The purpose of this study was to investigate the validity of heart rate (fc) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10-12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10-20 min until they had returned to their resting fc level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO2) and 30 s of fc were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise. The individual relationships between fc and VO2, and percentage maximal oxygen consumption (%VO2max) were linear with a high correlation r = 0.962-0.996 and r = 0.962-0.996, respectively. Therefore, it was concluded that fc was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's fc were 8.3-26.9 beats.min-1 higher than those of the adults at the given %VO2max. The present study showed two different patterns in the relationship between VO2 and RPE in individuals. In two subjects the RPE increased linearly with VO2 while in the other four subjects the increase was discontinuous. If fc and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that fc would be a more useful guide than RPE for some children.     

Relationship between tethered forces and the four swimming techniques performance

The purpose of the current study was to identify the relationships between competitive performance and tether forces according to distance swam, in the four strokes, and to analyze if relative values of force production are better determinants of swimming performance than absolute values. The subjects (n = 32) performed a 30 s tethered swimming all-out effort. The competitive swimming velocities were obtained in the distances 50, 100 and 200 m using official chronometric values of competitions within 25 days after testing protocol. Mean force and velocity (50 m event) show significant correlations for front crawl (r = .92, p < .01), backstroke (r = .81, p < .05), breaststroke (r = .94, p < .01) and butterfly (r = .92, p < .01). The data suggests that absolute values of force production are more associated to competitive performance than relative values (normalized to body mass). Tethered swimming test seems to be a reliable protocol to evaluate the swimmer stroking force production and a helpful estimator of competitive performance in short distance competitive events.     

Active drag, useful mechanical power output and hydrodynamic force coefficient in different swimming strokes at maximal velocity.

By comparing the time of the same distance swum with and without an added resistance, under the assumption of an equal power output in both cases, the drag of 73 top swimmers was estimated. The active drag Fr(a.d.) at maximal swimming velocities varied considerably across strokes and individuals. In the females Fr(a.d.) ranged from 69.78 to 31.16 N in the front-crawl, from 83.04 to 37.78 N in dolphin, from 93.56 to 45.19 N in breaststroke, and from 65.51 to 37.79 N in back-stroke. In the males Fr(a.d.) ranged from 167.11 to 42.23 N in front-crawl, from 156.09 to 46.95 N in dolphin, from 176.87 to 55.61 N in breaststroke, and from 146.28 to 46.36 N in back-stroke. Also, the ratio of Fr(a.d.) to the passive drag Fr(a.d.) as determined for the analogical velocity in a tugging condition (in standard body position-front gliding) shows considerable individual variations. In the female swimmers variations in Fr(a.d.)/Fr(p.d.) ranged from 145.17 to 59.94% in front-crawl, from 192.39 to 85.57% in dolphin, from 298.03 to 124.50% in breaststroke, and from 162.87 to 85.61% in back-stroke. In the male swimmers variations in Fr(a.d.)/Fr(p.d.) ranged from 162.24 to 62.39% in front-crawl, from 191.70 to 70.38% in dolphin, from 295.57 to 102.83% in breaststroke, and from 198.82 to 74.48% in back-stroke. The main reason for such variations is found in the individual features of swimming technique and can be quantitatively estimated with the hydrodynamic force coefficient, which thus provides an adequate index of technique.