688 research outputs found
Quantifying Added Drag in Swimming With Parachutes: Implications for Resisted Swimming Training
No full textColoretti, V, Fantozzi, S, Gatta, G, Bonifazi, M, Zamparo, P, and Cortesi, M. Quantifying added drag in swimming with parachutes: implications for resisted swimming training. J Strength Cond Res 39(5): e701-e705, 2025-Swimming parachutes are often used during training as resistive equipment, but their added load and the hydrodynamic effects of the swimmer in front have yet to be investigated. This study explores the drag coefficient (k) of 4 commercial parachutes with different sizes under 3 conditions: (a) when towed without a swimmer in front (kpara), (b) pulled by a passive (streamlined) swimmer (kPpara), and (c) pulled by an actively propelling swimmer (kApara). An electromechanical device was used to assess kpara and kPpara as the ratio between towing force and the square of towing velocity during 5 trials at different velocities while kApara was measured based on full-tethered and semi-tethered forces using the residual thrust methods. The values of kpara were as follows: 15.4 ± 0.1, 19.7 ± 0.1, 37.2 ± 0.1, and 73.9 ± 2.8 N·s2·m-2 for parachutes with surfaces of 400, 529, 900, and 1,600 cm2, respectively. Parachute resistance decreased by approximately 21% when pulled by a passive swimmer, whereas it increased by about 15% when pulled by a propelling swimmer. Possible explanations for these differences include drafting and added mass effects. Data reported in this study can assist coaches in quantifying the added load of swimming parachutes during training, by knowing only the parachute size and the swimming velocity
Wearable inertial sensors in swimming kinematics: intra-cyclic analysis of stroke, breath, and kick timing during front-crawl
No full textValidity and reliability of the wireless pressure sensors for aquatic activities and their ecological usefulness for swimming propulsion analysis
No full textINTRODUCTION:
The thrust force (Ft) is only a fraction of the overall force exerted by the swimmer to move his body. In the last decades, the hand pressure measurement technique has been implemented to support the understanding of Ft mechanism. However, because the direct assessment during free swimming remains difficult to quantify, the Ft measurement during tethered swimming was proposed as an alternative method. Furthermore, the advances in wireless technology could help the knowledge about swimming propulsion using an ecological approach and lower interferences with the swimming action than the wired sensors. Thus, the aims of this study were: i) to test the within-sensor, between-sensor and day-by-day reliability of the device, ii) to test the device in terms of accuracy than theoretical static (PRsT) and dynamic (PRdT) pressures, iii) to compared Ft between the differential pressure approach (FtHAND) and the dynamometrical approach (FtTET) during fully-tethered swimming.
METHODS:
Static pressure (PRs) collected by the wearable pressure sensor (SEAL, Platysense) was compared to PRsT (PRsT=Patm+ρgh) through a step static immersion up to 50 cm. Dynamic pressure (PRs) was compared to PRdT (PRdT=0.5ρv2) by towing 4 SEALs using a towing system at constant velocities (V) of 1.0, 1.6, and 1.9 ms-1 and controlling the water depth. The resultant force exerted by each hand to move the water (FHAND) of 15 young swimmers (7 F, 75.5 ± 7.1 % of WR) was the product of differential hand pressure (palmar minus dorsal, PRDIFF) and the hand surface (A). Ft exerted by the hand to propel the body (FtHAND) was the FHAND horizontal component and was estimated as Fhand . sin(α), where α was the underwater angle between trunk and upper arm (assuming circle-shaped hand kinematics). FtTET was the average value of the 10-s maximal effort in front-crawl.
RESULTS:
PRs showed excellent agreement for within-sensor, between-sensor and day-by-day reliability regarding ICC (0.99, 0.99, 0.99) and CV% (<0.1, <0.08, <0.13). Small biases and no-differences (p < 0.05) were detected for PRs vs. PRsT (<0.13 KPa) and for PRd vs. PRdT (-0.11, -0.26, -0.21 KPa, for each V comparison). PRDIFF was 4.678±1.123 Kpa, A was 0.015± 0.001 m2 and stroke frequency was 0.91 ± 0.06 Hz. FtHAND (51.6±17.0 N) was positively correlated (r=0.904, p<0.001) with FtTET (80.4±15.9 N) but significantly lower (p<0.001).
DISCUSSION:
PRs and PRd acquired using wireless pressure sensors showed a small amount of error when compared to theoretical pressures (<0.4 %) which represents a maximum error of 7.8 N in FtHAND value. The swimmer’s thrust force estimated using this approach is lower than the force collected by the dynamometrical approach during fully-resisted swimming (-41%). This difference could be partly imputable to the contribution of the forearm
Relationship between propulsion, symmetry, stability, and height in three different static figures of artistic swimming
No full textSYMMETRY OF PROPULSION EXERTED DURING TETHERED- AND FREE-SWIMMING
No full textINTRODUCTION
Swimming is characterized by body propulsion, where the upper limbs play the role of the
main contributor (Zamparo et al., 2020). Recently, the study of the propelling forces involved
during the swimming action has been ecologically allowed using wearable pressure sensors.
Thus, this study analyzed the propelling forces of the two hands during free (Free) and tethered
(Tet) swimming conditions by means of wearable pressure sensors.
METHODS
Eleven regional-level swimmers (age 15.4±0.5y.; body mass 58.0±7.1Kg; stature 168.4±5.0
cm) performed a 10-sec maximal full-tethered test and a 10-sec free-swimming test at front-
crawl only-arms. Two pressure sensors (SEAL, Platysens) were attached to each swimmer’s
hand (dorsal and palmar side) to estimate the propelling forces as the horizontal component of
the product of differential pressure and hand surface. Propelling forces of each hand in terms
of average (FMEAN), impulse (I), peak (FPEAK) and instantaneous (by means of Statistical
Parametric Mapping, SPM) values were analysed as a function of swimming condition and
dominant/non-dominant hand. Furthermore, the symmetry index (SI) of propelling forces was
analysed as a function of swimming condition.
RESULTS
Larger FMEAN, FPEAK, and I were found during Tet compared to Free condition (F>14.29,
p<0.001). SPM highlighted larger FMEAN in Tet condition only at the beginning of the stroke
(from 7 to 28% of stroke cycle duration). Additionally, no significant differences were observed
for FMEAN and FPEAK between the hands (p>.05). SPM and SI confirm non-significant differences
between dominant and non-dominant hands in propelling forces (p>0.05), while larger I was
found in the dominant hand (F=11.11, p<.05).
DISCUSSION
The swimmer appears to exert larger hand propulsion in tethered- than free- swimming. Our
experiments reveal a similar symmetry and hands propelling models in the two analysed
swimming conditions (Tet and Free) despite the fact that the effect of hand kinematic was not
taken into account
A novel method for assessing added mass in front crawl swimming
No full textDuring starts and turns, between and within laps, the swimmer's velocity is not constant; thus, besides the drag force, the swimmer experiences an additional (inertial) force. Some of the water around the swimmer is set in motion and this can be thought of as an added mass (MA,a) the swimmer has to accelerate (in addition to body mass, M0): the higher MA,a, the higher the resistive and inertial forces that oppose the swimmer's motion during acceleration phases. This study introduces a novel method to determine MA,a, consisting of a standing start maximal test. Sixteen male swimmers (526.1 ± 65.8 FINA Points) performed maximal sprints during which their instantaneous speed was assessed using an IMU positioned on their sacrum. The estimation of MA,a was based on the swimmer's maximum velocity (vmax) and acceleration time (τ), as determined using a standing start test, and the active drag coefficient (ka) and mean propulsive force (FP), as determined using the residual thrust method. On average vmax = 1.73 ± 0.11 m.s-1, τ = 1.14 ± 0.11 s, FP = 146.8 ± 20 N and ka = 47.9 ± 5.7 kg.m-1. MA,a in surface swimming (28.7 ± 15.2 % M0) is similar to the added mass that can be determined in passive conditions underwater (MA,p = 25 ± 3 % M0) but presents a larger variability. This variability could not be attributed to the swimmer's technical level, e.g the active to passive drag ratio: ka/kp, where kp = 26.6 ± 3.3 kg.m-1 (determined using passive towing experiments)
Swimming turns reduce energy demands of the aerobic performance in front crawl
No full textPurpose Performances in short-course (SC, 25 m) are typically faster than in long-course (LC, 50 m), largely due to the greater number of turns, but the specific energetic contribution of turns has not yet been quantified. This study tested the hypothesis that turns reduce the overall energy cost (C) in swimming, providing an energetic advantage in SC over LC. Methods Eleven male swimmers completed two randomized sessions in SC and LC pools, each consisting of five 400-m front crawl trials at submaximal intensity (70-86% of race velocity) paced by an underwater light system. Turn and clean swimming velocities were standardized between conditions to isolate the effect of turn number. Oxygen uptake, blood lactate, heart rate, perceived exertion, and stroke frequency were assessed, and metabolic power, total energy expenditure (E-tot), and C (E-tot/distance) were calculated. Results When analyzed at equivalent intensity (e.g. in trials corresponding to the same % of race velocity) mean velocity was higher in SC than LC across all intensities (+ 0.07 +/- 0.003 ms(-)(1), + 5.2%) while kinematic, physiological, and energetic parameters showed no significant differences (p > 0.05). When analyzed at paired (absolute) speeds, C values were about 4% higher il LC than in SC, indicating that swimming in short course is more economical, as hypothesized. Conclusions Turns reduce the overall energy cost of 400-m front crawl performance enabling swimmers to sustain higher mean velocities in SC. This highlights the importance of considering pool length when evaluating performance and prescribing training intensities
RESISTED SWIMMING: COMPARISON BETWEEN THRUST FORCE EXERTED BY THE HAND AND APPLIED TO THE TETHERED DEVICE
No full textPERFORMANCE DESCRIPTORS IN ARTISTIC SWIMMING TECHNIQUE: THE RELATIONSHIP BETWEEN PROPULSION, SYMMETRY,STABILITY, AND HEIGHT IN DIFFERENT STATIC FIGURES
No full textFlat-Back vs. Arched-Back Bench Press: Examining the Different Techniques Performed by Power Athletes
No full textThe International Powerlifting Federation recently changed the regulations concerning the bench press (BP) technique, not allowing an accentuated dorsal arch anymore. We investigated the difference between the flat-back vs. arched-back BP performed by competitive powerlifters as concerns the following parameters: (a) 1 repetition maximum (1RM) and barbell displacement; (b) mean and peak barbell velocity and power, and (c) the excitation of the prime movers. Fifteen highly resistance trained individuals (BP 1RM/body mass ratio: 1.38 ± 0.18) performed the flat-back and arched-back BP at their 50, 70, and 90% of the respective 1RM and performed each lift with the intent to maximally accelerate the barbell. Barbell displacement and velocity, power, and the excitation of the upper and lower pectoralis and triceps brachii were assessed. The 1RM was greater with the arched-back BP (+4.2 Kg, 95% confidence intervals + 0.0/+8.4, effect size [ES]: 0.22), whereas the barbell displacement was greater with the flat-back BP for all loads (ES from 0.40 to 0.61). Greater mean (+0.052 m·s-1, 0.016/0.088, ES: 0.42) and peak barbell velocity (+0.068 m·s-1, +0.026/0.110, ES: 0.27) were observed in the flat-back BP, whereas power did not differ. The excitation of upper and lower pectoralis was similar, while an overall trend for an increased activation of triceps brachii was noted in the arched-back vs. flat-back BP. Interestingly, no between-load difference in the excitation of upper and lower pectoralis was observed (p > 0.05). Depending on the training purposes, both flat-back and arched-back BP may be used. The present outcomes may assist practitioners and competitive powerlifters to inform training session
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