Comparative study between fully tethered and free swimming at different paces of swimming in front crawl

Body Composition and Dietary Intake Profiles of Elite Iranian Swimmers and Water Polo Athletes

BACKGROUND

This study aimed to conduct a detailed and comparative analysis of body composition and dietary habits in elite swimming and water polo athletes. Through the examination of these key parameters, this study seeks to compare the dietary intake of these two distinct aquatic sports disciplines.

METHODS

A total of 10 top-level swimmers and 13 water polo athletes participated in anthropometric and body composition assessments, as well as a detailed analysis of nutritional intake. To compare the two groups, an independent samples t-test was used, and variance homogeneity was checked using Levene's test. The effect size of the group differences was evaluated using Hedges' g.

RESULTS

Water polo athletes showed significantly greater height (189.4 ± 2.9 vs. 186.5 ± 2.0 cm, p = 0.013), body mass index (24.3 ± 1.4 vs. 22.1 ± 0.5 kg/m2, p < 0.001), fat-free mass (62.9 ± 1.4 vs. 61.1 ± 1.38 kg, p < 0.001), skeletal muscle mass (47.1 ± 1.3 vs. 43.9 ± 1.6 kg, p < 0.001), and overall weight (86.9 ± 6.9 vs. 76.7 ± 2.2 kg, p < 0.001) in comparison to swimmers. Swimmers consumed greater amounts of mean daily energy (60.0 ± 1.0 vs. 39.0 ± 1.0 kcal/kg, p < 0.001), carbohydrate (7.8 ± 0.3 vs. 4.4 ± 0.5 g/kg, p < 0.001), protein (1.7 ± 0.5 vs. 1.4 ± 0.5 g/kg, p < 0.001), and fat (2.4 ± 0.5 vs. 1.7 ± 0.5 g/kg, p < 0.001) compared to water polo athletes.

CONCLUSION

Our findings highlight the need for differentiated targeted nutritional interventions to enhance athletic performance in different types of water sports. Compared to water polo athletes, swimmers consumed significantly higher amounts of calories, matching their increased calorie demand from their specific training regime. However, this is an observational study and the differential needs of energy and macronutrients in water sports should be confirmed by studies with energy expenditure measurements.

Force production during maximal front crawl tethered swimming: exploring bilateral asymmetries and differences between breathing and non-breathing conditions

The present study focused on propulsive forces applied during tethered swimming. The main aims were to identify asymmetries between dominant and non-dominant arms, quantify the effect of breathing on force application and, explore any association between each variable and swimming performance. Fifteen regional level swimmers completed a maximal front crawl tethered swimming test, with maximal kicking, under four conditions: 1) Dominant arm strokes only, no breathing; 2) non-dominant arm strokes only, no breathing; 3) full stroke, no breathing; 4) full stroke, breathing on the preferred side. The outcome variables were: absolute and normalised (force divided by body mass) minimum, mean and maximum force; stroke cycle time and; impulse. The symmetry index was also calculated, and all variables were correlated with the swimmers' season best times in 50 m front crawl. Some bilateral force asymmetries were found, but they did not always favour the dominant side and were not directly linked with swimming performance. There was no strong evidence that force production is higher on the dominant side or that symmetry in force production affects performance. Despite the longer stroke cycle times when breathing, the breathing actions did not affect force production. Faster swimmers often produced higher maximum force values and, sometimes, higher mean force values.

Which Strength Manifestation Is More Related to Regional Swimmers' Performance and In-Water Forces? Maximal Neuromuscular Capacities Versus Maximal Mechanical Maintenance Capacity

PURPOSE

To explore the association of the load-velocity (L-V) relationship variables and ability to maintain maximal mechanical performance during the prone bench-pull exercise with sprint swimming performance and in-water forces.

METHODS

Eleven competitive adult male swimmers (50-m front crawl World Aquatics points: 488 [66], performance level 4) performed 1 experimental session. The L-V relationship variables (L0 [ie,  maximal theoretical load at 0 velocity]; v0 [ie, maximal theoretical velocity at 0 load], and Aline [ie, area under the L-V relationship]) and maximal mechanical maintenance capacity were assessed at the beginning of the session. Afterward, sprint swimming performance and in-water force production were tested through a 50-m front-crawl all-out trial and 15-s fully-tethered swimming, respectively.

RESULTS

Only v0 presented high positive associations with 50-m time and swimming kinematics (r > .532; P < .046). The L0, v0, and Aline showed very high positive associations with the in-water forces during tethered swimming (r > .523; P < .049). However, the ability to maintain maximal mechanical performance, assessed by the mean velocity decline during the prone bench pull, was only significantly correlated with stroke rate (r = -.647; P = .016) and stroke index (r = .614; P = .022).

CONCLUSIONS

These findings indicate that maximal neuromuscular capacities, especially v0, have a stronger correlation with swimming performance and in-water force production than the ability to maintain maximal mechanical performance in level 4 swimmers.

Estimating Active Drag Based on Full and Semi-Tethered Swimming Tests

During full tethered swimming no hydrodynamic resistance is generated (since v = 0) and all the swimmer's propulsive force (FP) is utilized to exert force on the tether (FT = FP). During semi-tethered swimming FP can be made useful to one of two ends: exerting force on the tether (FST) or overcoming drag in the water (active drag: Da). At constant stroke rate, the mean propulsive force (FP) is constant and the quantity FP - FST (the "residual thrust") corresponds to Da. In this study we explored the possibility to estimate Da based on this method ("residual thrust method") and we compared these values with passive drag values (Dp) and with values of active drag estimated by means of the "planimetric method". Based on data obtained from resisted swimming (full and semi-tethered tests at 100% and 35, 50, 60, 75, 85% of the individual FT), active drag was calculated as: DaST = kaST.vST2 = FP - FST ("residual thrust method"). Passive drag (Dp) was calculated based on data obtained from passive towing tests and active drag ("planimetric method") was estimated as: DaPL = Dp.1.5. Speed-specific drag (k = D/v2) in passive conditions (kp) was )25 kg.m-1 and in active conditions (ka) )38 kg.m-1 (with either method); thus, DaST > Dp and DaST > DaPL. In human swimming active drag is, thus, about 1.5 times larger than passive drag. These experiments can be conducted in an ecological setting (in the swimming pool) by using basic instrumentation and a simple set of calculations.

Lower and upper extremity contributions to propulsion and resistance during semi-tethered load-velocity profiling in front crawl swimming

The study estimated lower and upper extremity contributions to whole-body front crawl swimming using semi-tethered load-velocity profiling. Nine female and 11 male (inter)national-level swimmers performed 20 m semi-tethered sprints, each with five progressive loads for lower (leg kicking), upper (arm stroke), and whole-body front crawl movements. The theoretical maximal speed (v0) and load (L0), and active drag (Da) were expressed as a percentage of the sum of both extremities for the movements of each extremity to calculate their contributions. The difference of whole-body values minus the sum of both extremities was used to estimate whole-body reserves. Lower (upper) body contributions were 43.8 ± 2.8% (56.2%) for v0, 37.3 ± 7.1% (62.7%) for L0, and 39.6 ± 5.6% (60.4%) for Da. Statistically significant whole-body reserves were found for v0 (-30.9 ± 3.9%, p < 0.001) and Da (-5.7 ± 11.7%, p = 0.04). V0 reserves correlated very highly with whole-body v0 in males (r = 0.71, p = 0.014) and moderately in females (r = 0.47, p = 0.21). The lower extremities contribute substantially to front crawl load-velocity profiles of highly trained swimmers. Higher sprint swimming speeds are associated with an efficient speed transfer from lower- and upper- to whole-body movement.

Effects of exceeding stroke frequency of maximal effort on hand kinematics and hand propulsive force in front crawl

This study aimed to assess kinematic and kinetic changes in front crawl with various stroke frequency (SF) conditions to investigate why swimming velocity (SV) does not increase above a certain SF (SFmax). Eight male swimmers performed 20 m front crawl four times. The first trial involved maximal effort, whereas SF was controlled during the next three trials. The instructed SFs were 100 (T100%), 110 (T110%), and 120% (T120%) of the SFmax. Through pressure measurement and underwater motion analysis, hand propulsive force (calculated by the difference between the palm and dorsal pressure value and the hand area) and the angle of attack of the hand were quantified, and differences between trials were assessed by a repeated-measures ANOVA. There was no difference in SV between the conditions, while the angle of attack during the latter half of the underwater stroke at T120% was smaller by 25.7% compared with T100% (p = 0.007). The lower angle of attack induced a lower pressure value on the palm that consequently caused a smaller hand propulsive force at T120% than T100% (p = 0.026). Therefore, the decrease in the angle of attack must be minimised to maintain the hand propulsive force.

Reliability of a semi-tethered front crawl sprint performance test in adolescent swimmers

This study aimed to evaluate the test-retest reliability of a sprint performance test with semi-tethered front crawl swimming to indirectly assess the current potential to perform at maximal anaerobic effort in adolescent swimmers. Eight adolescent swimmers participated in this study (gender: females (n = 4) aged 13.0 ± 0.8 years, body height 1.6 ± 0.0 m, body mass 50.1 ± 4.5 kg; and males (n = 4) aged 13.3 ± 1.3 years, body height 1.7 ± 0.1 m, body mass 59.0 ± 8.2 kg. The testing protocol consisted of two trials of 25 m semi-tethered front crawl swimming with maximal effort and with 1 kg resisted isotonic load. Velocity data were recorded automatically by the 1080 Sprint device for 15 m (between 3 m and 18 m). The Fast Fourier Transform algorithm filtered raw instantaneous swimming velocity data in distance (time) function. A third-degree polynomial was used to extract the individual velocity profile, from which the following variables were chosen for test-retest reliability and the assessment of sprint performance: ttrial15, vmax, vmin, tvto max, tvat max, Dto vmax, Dat vmax, fatigue index. Parameters such as vmax, vmin, and ttrial15 were estimated from swimming velocity profiles and considered as reliable. The CV showed low variance <5%; while ICC2,1 demonstrated respectively good (ICC2,1: 0.88), very good (ICC2,1: 0.95), and excellent (ICC2,1: 0.98) rate of relative reliability; and the Bland-Altman index revealed an acceptable agreement (LoA ≤5%) between two measurements. The sprint performance test based on semi-tethered front crawl swimming confirmed that ttrial15, vmax, and vmin were reliable variables to indirectly indicate a potential to perform the maximal anaerobic effort among adolescent swimmers. The evaluation of the swimming velocity profiles allows coaches to monitor the adaptive changes of performance during the training process.

How do swimmers control their front crawl swimming velocity? Current knowledge and gaps from hydrodynamic perspectives

The aim of this study was to review the literature on front crawl swimming biomechanics, focusing on propulsive and resistive forces at different swimming velocities. Recent studies show that the resistive force increases in proportion to the cube of the velocity, which implies that a proficient technique to miminise the resistive (and maximise the propulsive) force is particularly important in sprinters. To increase the velocity in races, swimmers increase their stroke frequency. However, experimental and simulation studies have revealed that there is a maximum frequency beyond which swimmers cannot further increase swimming velocity due to a change in the angle of attack of the hand that reduces its propulsive force. While the results of experimental and simulation studies are consistent regarding the effect of the arm actions on propulsion, the findings of investigations into the effect of the kicking motion are conflicting. Some studies have indicated a positive effect of kicking on propulsion at high swimming velocities while the others have yielded the opposite result. Therefore, this review contributes to knowledge of how the upper-limb propulsion can be optimised and indicates a need for further investigation to understand how the kicking action can be optimised in front crawl swimming.Abbreviations: C: Energy cost [kJ/m]; Ė: Metabolic power [W, kJ/s]; Fhand: Fluid resultant force exerted by the hand [N]; Ftotal: Total resultant force [N] (See Appendix A); Fnormal: The sum of the fluid forces acting on body segments toward directions perpendicular to the segmental long axis, which is proportional to the square of the segmental velocity. [N] (See Appendix A); Ftangent: The sum of the fluid forces acting on body segments along the direction parallel to the segmental long axis, which is proportional to the square of the segmental velocity. [N] (See Appendix A); Faddmass: The sum of the inertial force acting on the body segments due to the acceleration of a mass of water [N] (See Appendix A); Fbuoyant: The sum of the buoyant forces acting on the body segments [N] (See Appendix A); D: Fluid resistive force acting on a swimmer's body (active drag) [N]; T: Thrust (propulsive) force acting in the swimming direction in reaction to the swimmer's actions [N]; Thand: Thrust force produced in reaction to the actions of the hand [N]; Tupper_limb: Thrust force produced in reaction to the actions of the upper limbs [N]; Tlower_limb: Thrust force produced in reaction to the actions of the lower limbs [N]; Mbody: Whole-body mass of the swimmer [kg]; SF: Stroke frequency (stroke number per second) [Hz]; SL: Stroke length (distance travelled per stroke) [m]; v: Instantaneous centre of mass velocity of the swimmer [m/s]; V - : Mean of the instantaneous centre of mass velocities in the swimming direction over the period of the stroke cycle [m/s]; a: Centre of mass acceleration of the swimmer [m/s2]; V - hand: Mean of the instantaneous magnitudes of hand velocity over a period of time [m/s]; Ẇtot: Total mechanical power [W]; Ẇext: External mechanical power [W]; Ẇd: Drag power (mechanical power needed to overcome drag) [W, Nm/s]; α: Angle of attack of the palm plane with respect to the velocity vector of the hand [deg]; ηo: Overall efficiency [%]; ηp: Propelling efficiency [%]; MAD-system: Measuring Active Drag system; MRT method: Measuring Residual Thrust method.

A comparison of load cell and pressure sensors to measure in-water force in young competitive swimmers

The purpose of this study was to compare the in-water force of young competitive swimmers using tethered swimming and differential pressure sensors. Thirty-one swimmers (16 girls and 15 boys) were randomly assigned to perform two in-water tests. Swimmers completed two maximum bouts of 25 m front crawl with a differential pressure system and a 30 s maximum bout with an attached load cell (tethered-swimming). The peak force (FPEAK, in N) of dominant and non-dominant upper limbs was retrieved for further analysis. Comparison between methods revealed significant differences in all force variables (p ≤ 0.05) and the biases (mean differences) were large in girls (FPEAK dominant, 45.89 N; FPEAK non-dominant, 43.79 N) and boys (FPEAK dominant, 67.26 N; FPEAK non-dominant, 61.78 N). Despite that, simple linear regression models between the two methods showed significant relationships with a moderate effect in all variables for girls, whereas in boys a high and moderate effect was verified for FPEAK of dominant and non-dominant limbs (respectively). It seems that using pressure sensors and tethered swimming leads to different FPEAK values in young competitive, where correction factors are needed to compare data between both methods.

Oxygen Uptake Kinetics and Time Limit at Maximal Aerobic Workload in Tethered Swimming

This study aimed to apply an incremental tethered swimming test (ITT) with workloads (WL) based on individual rates of front crawl mean tethered force (Fmean) for the identification of the upper boundary of heavy exercise (by means of respiratory compensation point, RCP), and therefore to describe oxygen uptake kinetics (VO₂k) and time limit (t_Lim) responses to WL corresponding to peak oxygen uptake (WLVO_2peak). Sixteen swimmers of both sexes (17.6 ± 3.8 years old, 175.8 ± 9.2 cm, and 68.5 ± 10.6 kg) performed the ITT until exhaustion, attached to a weight-bearing pulley-rope system for the measurements of gas exchange threshold (GET), RCP, and VO_2peak. The WL was increased by 5% from 30 to 70% of Fmean at every minute, with Fmean being measured by a load cell attached to the swimmers during an all-out 30 s front crawl bout. The pulmonary gas exchange was sampled breath by breath, and the mathematical description of VO₂k used a first-order exponential with time delay (TD) on the average of two rest-to-work transitions at WLVO_2peak. The mean VO_2peak approached 50.2 ± 6.2 mL·kg^-1·min^-1 and GET and RCP attained (respectively) 67.4 ± 7.3% and 87.4 ± 3.4% VO_2peak. The average t_Lim was 329.5 ± 63.6 s for both sexes, and all swimmers attained VO_2peak (100.4 ± 3.8%) when considering the primary response of VO₂ (A_1' = 91.8 ± 6.7%VO_2peak) associated with the VO₂ slow component (SC) of 10.7 ± 6.7% of end-exercise VO₂, with time constants of 24.4 ± 9.8 s for A_1' and 149.3 ± 29.1 s for SC. Negative correlations were observed for t_Lim to VO_2peak, WLVO_2peak, GET, RCP, and EEVO₂ (r = -0.55, -0.59, -0.58, -0.53, and -0.50). Thus, the VO₂k during tethered swimming at WLVO_2peak reproduced the physiological responses corresponding to a severe domain. The findings also demonstrated that t_Lim was inversely related to aerobic conditioning indexes and to the ability to adjust oxidative metabolism to match target VO₂ demand during exercise.

Swimming Warm-Up and Beyond: Dryland Protocols and Their Related Mechanisms—A Scoping Review

In swimming, the beneficial effects of the in-water warm-up are often undermined by the long transition periods before competition (≥ 20 min). For that reason, studies comparing the effects of in-water warm-ups followed by dryland activities have been conducted in the swimming literature. This has brought conflicting evidence due to large combinations of supervised and unsupervised warm-up procedures used. Therefore, a scoping review was performed to discuss (1) why warm-up strategies are important for competitive swimming; to identify (2) what are the different warm-up approaches available in the literature, and; to establish (3) what are the main conclusions, considerations and gaps that should be addressed in further research to provide clearer guidance for interventions. The search was conducted on PubMed, Web of Science, Scopus, and SPORTDiscus databases. To be considered eligible, studies must have assessed acute short-term responses of warm-up procedures in swimmers by using randomized controlled trials or pre-post study designs. A total of 42 articles were included in this review. The effectiveness of warm-up responses was evaluated based on the inclusion or not of warm-up, the type of conditioning activity (in-water exercise, in-water exercise combined with dryland or dryland exercise only), its duration, and intensity. (1) Warm-up mechanisms have been mainly related to temperature changes associated to cardiovascular adaptations and short-term specific neuromuscular adaptations. Thus, maintaining muscle activity and body temperature during the transition phase immediately prior to competition could help swimmers' performance; (2) the most common approach before a race usually included a moderate mileage of in-water warm-up (~ 1000 m) performed at an intensity of ≤ 60% of the maximal oxygen consumption, followed by dryland protocols to keep the muscle activity and body temperature raised during the transition phase. Dryland activities could only optimize performance in sprint swimming if performed after the in-water warm-up, especially if heated clothing elements are worn. Using tethered swimming and hand-paddles during warm-ups does not provide superior muscular responses to those achieved by traditional in-water warm-ups, possibly because of acute alterations in swimming technique. In contrast, semi-tethered resisted swimming may be considered as an appropriate stimulus to generate post-activation performance enhancements; (3) nothing has yet been investigated in backstroke, butterfly or individual medley, and there is a paucity of research on the effects of experimental warm-ups over distances greater than 100 m. Women are very under-represented in warm-up research, which prevents conclusions about possible sex-regulated effects on specific responses to the warm-up procedures.

Quantification of swimmers' ability to apply force in the water: the potential role of two new variables during tethered swimming

This study aimed 1) to examine variables that may quantify the ability to apply force in the water and 2) to test their relationship with free swimming performance. Sixteen regional-level swimmers participated in this study. Average (Favg) and maximum (Fmax) forces were measured for 30 s arm stroke tethered swimming in a flume at zero and 1.389 m/s water flow speeds. The maximum and average force's relative changes (ΔFmax and ΔFavg, respectively) were calculated between tethered swimming at zero and 1.389 m/s water flow speeds. Free swimming speeds were obtained from 25, 50, and 100 m front crawl trials, and were correlated with ΔFmax and ΔFavg. A negative correlation was found between ΔFmax and 25, 50 and 100 m speeds (r =  -0.84, r = -0.74, r = -0.55; p < 0.05, respectively) and ΔFavg correlated negatively with 25 and 50 m speeds (r = -0.63, r = -0.54; p < 0.05, respectively), but it did not correlate with 100 m swimming speed. The relative change in force could be used to quantify the ability to apply force in the water. This could aid coaches to understand if changes in swimmers' ability to apply force in the water contribute to improvements in performance.

Propulsive forces in human competitive swimming: a systematic review on direct assessment methods

Human propulsive forces are a key-factor to enhance swimming performance, but there is scarce knowledge when using direct assessments. The aim of this review was to analyse the evidence about human propulsive forces in competitive swimming measured by direct assessment methods. A search up to 30 June 2020 was performed in Web of Science, PubMed, and Scopus databases. The Downs and Black Quality Assessment Checklist was used to assess the quality index (QI) of the included studies. Out of 2530 screened records, 35 articles met the inclusion criteria. Tethered-swimming and differential pressure sensors allow directly measure propulsive forces. Cross-sectional designs measured peak and mean propulsive force during the front crawl stroke and including men/boys (≥15 years-old) at different competitive levels were mostly reported. Men are more able to show higher propulsive forces than women counterparts. Short- and long-term effects were observed while using dry-land and in-water training programmes. The magnitude of propulsive force is dependent on the type of assessment method, swimming stroke, number of body limbs and gender. While the short-term effects supporting the different training programmes lead to an increase in propulsive force, there is a lack of long-term evidence.

The Relationship Between Selected Load-Velocity Profile Parameters and 50 m Front Crawl Swimming Performance

The purpose of the present study was to establish relationships between sprint front crawl performance and a swimming load-velocity profile. Fourteen male national-level swimmers performed 50 m front crawl and semi-tethered swimming with three progressive loads. The 50 m performance was recorded with a multi-camera system, with which two-dimensional head displacement and the beginning of each arm-stroke motion were quantified. Forward velocity (V_50m), stroke length (SL) and frequency (SF) were quantified for each cycle, and the mean value of all cycles, excluding the first and last cycles, was used for the analysis. From the semi-tethered swimming test, the mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load, and a linear regression line expressing the relationship between the load and velocity was established for each swimmer. The intercepts between the established line and the axes of the plot were defined as theoretical maximum velocity (V₀) and load (L₀). Large to very large correlations were observed between V_50m and all variables derived from the load-velocity profiling; L₀ (R = 0.632, p = 0.015), L₀ normalized by body mass (R = 0.743, p = 0.002), V₀ (R = 0.698, p = 0.006), and the slope (R = 0.541, p < 0.046). No significant relationships of SL and SL with V_50m and the load-velocity variables were observed, suggesting that each swimmer has his own strategy to achieve the highest swimming velocity. The findings suggest that load-velocity profiling can be used to assess swimming-specific strength and velocity capabilities related to sprint front crawl performance.

SwimOne. New Device for Determining Instantaneous Power and Propulsive Forces in Swimming

The propulsive forces and instantaneous power that are generated by a swimmer have a great influence on the swimming performance. This works presents a new device, called SwimOne, for measuring propulsive force and estimating the instantaneous power of the swimmer. In addition, the detailed prototype is able to exert a customizable opposition force to the swimmer for training purpose. The conceptual idea is presented by describing the differential equation of the swimmer and the protocol for a factible estimation of the instantaneous power. The variables that are to be measured and estimated are identified and, consequently, the sensor and actuator systems can be selected. The high-level and detailed designs of the prototype are presented together with the protocol that is carried out in order to validate the sensor and actuation systems. The device is able to monitor the variables of interest of the swimmer together with the propulsive force and instant power. Finally, some experiments are carried out providing the results of several participants swimming in crawl, backstroke, butterfly, and breaststroke styles in the presence of different opposition force. The preliminary results show that SwimOne is valid for measuring instantaneous force and power with different loads in swimming.

Maximal Fully Tethered Swim Performance in Para Swimmers With Physical Impairment

The assessment of swimming propulsion should be a cornerstone of Paralympic swimming classification. However, current methods do not objectively account for this component.

PURPOSE

To evaluate the swimming propulsion of swimmers with and without physical impairment using a 30-second maximal fully tethered freestyle swim test.

METHODS

Tethered forces were recorded during maximal fully tethered swimming in 80 competitive swimmers with (n = 70) and without (n = 10) physical impairment. The relationships between absolute and normalized tether forces and maximal freestyle swim speed were established using general additive models.

RESULTS

Para swimmers with physical impairment had lower absolute and normalized tether forces than able-bodied swimmers, and there were moderate positive correlations found between tether forces and sport class (τ = .52-.55, P < .001). There was a nonlinear relationship between tether force and maximal freestyle swim speed in the participant cohort (adjusted R2 = .78-.80, P < .001). Para swimmers with limb deficiency showed stronger relationships between tether force and maximal freestyle swim speed (adjusted R2 = .78-.82, P < .001) than did Para swimmers with hypertonia (adjusted R2 = .54-.73, P < .001) and impaired muscle power (adjusted R2 = .61-.70, P < .001).

CONCLUSIONS

Physical impairments affect Para swimmers' tether forces during maximal fully tethered freestyle swimming, explaining a significant proportion of their activity limitation. It is recommended that maximal fully tethered swimming be included in Paralympic swimming classification as an objective assessment of swimming propulsion.