Relationships between coordination, active drag and propelling efficiency in crawl.

This study examines the relationships between the index of coordination (IdC) and active drag (D) assuming that at constant average speed, average drag equals average propulsion. The relationship between IdC and propulsive efficiency (ep) was also investigated at maximal speed. Twenty national swimmers completed two incremental speed tests swimming front crawl with arms only in free condition and using a measurement of active drag system. Each test was composed of eight 25-m bouts from 60% to 100% of maximal intensity whereby each lap was swum at constant speed. Different regression models were tested to analyse IdC-D relationship. Correlation between IdC and ep was calculated. IdC was linked to D by linear regression (IdC=0.246·D-27.06; R(2)=0.88, P<.05); swimmers switched from catch-up to superposition coordination mode at a speed of ∼1.55ms(-1) where average D is ∼110N. No correlation between IdC and ep at maximal speed was found. The intra-individual analysis revealed that coordination plays an important role in scaling propulsive forces with higher speed levels such that these are adapted to aquatic resistance. Inter-individual analysis showed that high IdC did not relate to a high ep suggesting an individual optimization of force and power generation is at play to reach high speeds.

Influence of kick frequency on metabolic efficiency and performance at a severe intensity in international monofin-swimmers.

The aim of this study was to examine the effect of kick frequency on metabolic efficiency and performance in elite monofin-swimmers at the surface. Seven participants of international calibre were requested to perform three separate time limit exercises conducted at an intensity corresponding to 97.5% of the velocity at the maximal oxygen uptake. The first Time Limit exercise was systematically conducted at a freely chosen kick frequency (FCK(F)) and the other Time Limit exercises were performed in random order at FCK(F)-10% and FCK(F) + 10%. The slow component of oxygen uptake (VO2sc) was identified independently of the Time Limit exercise (ranging from 180 to 243 ml · min(-1), P < 0.05). No significant change in energy cost of aquatic locomotion (ranging from 565 to (596 J · m(-1)) and [VO2sc) responses was observed between the three Time Limit exercises. An increase or decrease of 10% of the FCK(F) was associated with a significant reduction in Time Limit of -47.3% and -49.1%, respectively (P < 0.05). The analysis of the Time Limit exercise indicates that the selection of kick frequency other than FCK(F) is detrimental to overall monofin-swimming performance. Furthermore, the study results showed that the indicators of metabolic efficiency such as energy cost or [VO2sc) do not determine the performance response in elite monofin-swimmers at a severe intensity.

Effect of stroke rate reduction on swimming technique during paced exercise.

The purpose of this study is to analyze the acute adaptations of motor organization subsequent to a reduction in spontaneous stroke rate (SR) at different swimming speeds, a task constraint that is currently used by trainers to improve stroke technique. Ten well-trained swimmers (8 males and 2 females, whose mean swimming speed on a 400-m front crawl stroke represents 76.8 ± 3.7% and 73.3 ± 2.7% of the mean speed of the short-course pool world record, respectively) performed 3 sets of 3 time to exhaustion trials in front crawl at paces corresponding to 95%, 100%, and 110% of the mean speed measured in a 400-m race. During the first set, individual SR was continuously recorded and averaged. During the second set (Fixed), participants were constrained to swim at their individual corresponding SR. For the third set (Lowered), an individual corresponding SR value lowered by 5% was imposed. Durations of trials and arm stroke phases durations were analyzed. The results showed that the durations of the whole trials declined significantly from the Fixed set to the Lowered set (p < 0.05). Swimmers spent more time in the nonpropulsive phases (increases ranged from 8.6-13.2%; p < 0.05), and the duration of the propulsive phases did not differ significantly in the lowered set. The significant decline in exercise durations might have been caused by an unusual muscular solicitation. Swimming technique changes during trials in the Fixed set suggest an increase in magnitude and efficiency in the propulsive force and a better body streamlining to limit an increase of the resistive impulse in between arm propelling actions. In conclusion, these results should be taken into account to better define training-set technical benefits and better include the impact of such task constraints into the training schedule.

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.

Kick frequency affects the energy cost of aquatic locomotion in elite monofin swimmers.

The aim of this study was to evaluate the influence of kick frequency (K(F)) on the energy cost of aquatic locomotion in elite monofin (Mf) swimmers at the surface. Eight subjects of international calibre (4 females, 4 males) were requested to perform in a 50-m outdoor swimming pool: (1) a continuous multi-stage incremental test to determine maximal physiological responses and (2) a submaximal exercise composed of five constant Mf-swimming tests (600-m exercise, 5-min rest) at an intensity corresponding to 90% of the velocity at the maximal oxygen uptake (VO2max). The first submaximal Mf-swimming test was systematically conducted at a freely chosen K(F) (FCK(F)) and the other tests were performed at FCK(F) - 15%, FCK(F) - 10%, FCK(F) + 10% and FCK(F) + 20% in a random order. No significant effect of K(F) on ventilation, heart rate and blood lactate concentration was observed throughout the submaximal Mf-swimming tests. However, mean values in Ec or fraction of VO2max were significantly lower during the FCK(F) + 10% condition as compared to those observed during the FCK(F) - 15% (-11.5 and -9.6%, respectively, P < 0.05) and FCK(F) - 10% (-10.4 and -9.3%, respectively, P < 0.05) conditions. In conclusion, the lack of significant differences between FCK(F) + 10% and FCK(F) or FCK(F) + 20% does not allow to identify a specific trend, but suggests the occurrence of an energetically optimal K(F) close to that freely chosen by the Mf swimmers. Variations in muscle activity level and active drag have been hypothesized to explain the observed differences in Ec consecutive to the selection of various K(F).

Validity of a nomogram to predict long distance running performance.

The purpose was to test the validity of a nomogram to predict performance at distances ranging from the 10 km to the marathon. Official running rankings of the French Athletics Federation for the men's 10 km, 20 km, and marathon were scrutinized from 2002 to 2006. Performances of runners who competed in the 3 distances during the same year were noted (n = 330). Predicted performance by the nomogram was obtained for each distance from the performance at 2 other distances. Actual and predicted performances were compared by a Wilcoxon matched pairs test. The magnitude of the difference was assessed by the effect size (ES). Correlation and Bland-Altman plots were used to evaluate the association and the level of agreement between actual and predicted performances. The nomogram overestimated performance at the 10-km distance (13 seconds; p = 0.03) and underestimated performance at the 20-km distance (27 seconds; p < 0.01). The overestimation for the marathon was not significant (85 seconds; p = 0.06). Whatever the distance, ES were trivial (-0.04 < ES < 0.05). Correlations were 0.89 for the 10 km and the marathon and 0.97 for the 20 km. The limits of agreement represented 10.2, 6.1, and 13.2% of the mean of actual and predicted performances in 10 km, 20 km, and marathon, respectively. These results support the validity of the nomogram to predict performance on 10 km, 20 km, and marathon from the performance at 2 other distances. The accuracy of predictions is better when performance is interpolated. Given their validity and accuracy, interpolated predictions of the nomogram may be used to prescribe realistic training intensities during tempo runs, but also to determine the optimal strategy during the race.

Stroking characteristics during time to exhaustion tests.

PURPOSE: Race analyses during swimming reveal how exercise duration affects both clean swimming speed (v), stroke rate (SR), and stroke length (SL). The aim of this study is to provide an explanation for the change of SL and SR during paced exercise swimming the front crawl through an analysis of intracycle changes in motor organization. METHODS: Trained swimmers (N = 10) swam three times to exhaustion (TTE in seconds) at predetermined velocities corresponding to 95%, 100%, and 110% of the mean speed attained in a 400-m race (V 400). During TTE tests, SR, SL, durations of the glide + catch, pull, push, and recovery phases (s) were measured. Assessment of arm coordination was made through the calculation of the index of coordination (IdC). The time allotted to propulsion per distance unit was estimated (T prop). RESULTS: For all tested speeds, fatigue development induced a gradual increase of SR with concomitant decrease of SL. The duration of the nonpropulsive phases decreased, whereas the duration of the propulsive phases per stroke remained constant. The IdC increased reflecting a reduction of the lag time between two consecutive propulsive actions. Consequently, T prop increased. CONCLUSION: Fatigue development induced an increase of the SR to compensate for the reduced capacity to generate a propulsive impulse per stroke. The change in arm coordination allows a better chain of the propulsive actions and leads to a greater time allotted to propulsion per distance unit. Such motor adaptation ensures that the overall propulsive impulse remained constant whereas average propulsive force per arm stroke is reduced.

Comparison of maximal and spontaneous speeds during walking on dry land and water.

The aim of this study was to quantify spontaneous and maximal speeds on dry land and in water, in four modalities of walking [forward (F), backward (B) and lateral walking (L)], with chest immersion level. Lateral walking was studied with the upper limbs of the subject alongside the body with hands placed on the lateral face of the thighs (L1) and upper limbs tightened behind the back with the hands joined (L2). 16 males (age 22.8+/-1.8 years, height 178.1+/-6.1cm, body mass 73.5+/-6.6 kg) and 15 females (age 22.8+/-2.1 years, height 171.5+/-5.8 cm, body mass 69.2+/-9.3 kg) were evaluated using the four modalities of walking on dry land and in water. The speed increments between spontaneous and maximal speeds on dry land for F, B and L1 and L2 were 60.2%, 60.9%, 64.3% and 65.3% for males and 47.3%, 48.3%, 44.5% and 53.1% for females. In the water, these variation values for F, B, L1 and L2 for males were 44.6%, 26.1%, 48.8%, and 42.1%. The values for females were 31.7%, 21.6%, 32.8%, and 34.6%. Spontaneous and maximal speeds of walking were substantially reduced in water with the chest immersed, compared to speeds on dry land for the four modalities and the two genders. These findings may be used by therapists who utilize the various modalities of walking in aquatherapy.

Changes in swimming technique during time to exhaustion at freely chosen and controlled stroke rates.

The aim of this study was to assess technical changes during constrained swimming in time-to-exhaustion tests. Ten swimmers of national standard performed a maximal 400-m front crawl and two sets of exhaustion tests at 95%, 100%, and 110% of mean 400-m speed. In the first set (free), swimmers had to maintain their speeds until exhaustion and mean stroke rate was recorded for each test. In the second set (controlled), the same speed and individual corresponding stroke rate were imposed. The durations of the exhaustion tests, relative durations of the stroke phases, and arm coordination were analysed. For each speed in the "controlled" set, the exhaustion tests were shorter. Moreover, variables were consistent, suggesting a stabilization of stroke technique. Under the free condition, stroke rate increased to compensate for the decrease in stroke length. At the same time, swimmers reduced the relative duration of their non-propulsive phases in favour of the propulsive phases. Thus, swimmers changed their arm coordination, which came close to an opposition mode. These two constraints enable swimmers both to maintain their stroking characteristics and develop compensatory mechanisms to maintain speed. Moreover, stroke rate can be seen as a useful tool for controlling arm technique during paced exercise.

Aerobic potential, stroke parameters, and coordination in swimming front-crawl performance.

The purposes of this review were (1) to review the recent studies conducted in swimming on the assessment of aerobic potential and establishment of exercise-intensity domains (it is important that exercise-intensity domains be accurately defined and their physiological underpinnings well understood to optimize and evaluate training programs); (2) to analyze changes in traditionally measured stroke rate and stroke length during exhaustive swims, particularly in relation to the predetermined intensity domains (introduction of an "optimal swimming technique speed"); and (3) to introduce the latest swimming research on arm coordination that might help us better understand the technical adaptations of swimmers under physical stress.

Variations of stroking parameters associated with 200 m competitive performance improvement in top-standard front crawl swimmers.

The aim of this study was to analyse the variations of stroking parameters (speed, stroke length, stroke rate, and stroke index) associated with the 200 m front crawl competitive performance improvement. Two races completed by 17 top swimmers were analysed in the 200 m freestyle final of French or European championships, each final being separated by two years. All the swimmers' performances were bettered in the second race (mean +/- SD: 113.44 +/- 2.50 vs 111.78 +/- 2.71 s; p < 0.01) and were associated with a significant increase of stroke rate without variation of average stroke length and stroke index values (p > 0.05). Swimmers emphasized the first part of the race, with higher speed in the first three lengths, higher stroke rate in the first two lengths and lower stroke length in the first one. Stroke length and stroke rate variations were highly correlated (r = 0.98; p < 0.05). In 11 of the 17 swimmers, the improvement was concomitant with a decrease in stroke length and an increase in stroke rate. Only one swimmer's improvement was associated with a substantial increase in stroke length. These results highlighted that stroke length and stroke index cannot be considered as the only parameters linked to improvement in a 200 m crawl in adult swimmers competing at high standard. Moreover, an increase in stroke rate associated with a slight decrease in stroke length should not be considered as ineffective, especially at top standard.