Erratum: Hołub et al. Predicting Breaststroke and Butterfly Stroke Results in Swimming Based on Olympics History. Int. J. Environ. Res. Public Health 2021, 18, 6621

In the original article [...]

Phi-Bonacci Butterfly Stroke Numbers to Assess Self-Similarity in Elite Swimmers

A harmonically self-similar temporal partition, which turns out to be subtly exhibited by elite swimmers at middle distance pace, is formally defined for one of the most technically advanced swimming strokes—the butterfly. This partition relies on the generalized Fibonacci sequence and the golden ratio. Quantitative indices, named ϕ-bonacci butterfly stroke numbers, are proposed to assess such an aforementioned hidden time-harmonic and self-similar structure. An experimental validation on seven international-level swimmers and two national-level swimmers was included. The results of this paper accordingly extend the previous findings in the literature regarding human walking and running at a comfortable speed and front crawl swimming strokes at a middle/long distance pace.

Predicting Breaststroke and Butterfly Stroke Results in Swimming Based on Olympics History

Here we describe historic variations in Olympic breaststroke and butterfly performance and predict swimming results for the 2021 Olympic Games in Tokyo. The results of the finalists, winners, and last participants in the women’s and men’s finals were analyzed, and a mathematical predictive model was created. The predicted times for the future Olympics were presented. Swimming performance among Olympians has been steadily improving, with record times of 18.51 s for female finalists in the 100 m butterfly (a 24.63% improvement) and 31.33 s for male finalists in the 200 m butterfly (21.44%). The results in all analyzed groups showed improvement in athletic performance, and the gap between the finalists has narrowed. Women Olympians’ performances have improved faster than men’s, reducing the gap between genders. We conclude that swimming performance among Olympians is continuing to improve.

Propulsive Force of Upper Limbs and its Relationship to Swim Velocity in the Butterfly Stroke

The aims of this study were to: (1) verify the sex effect; (2) assess upper limb asymmetry in anthropometrics and propulsive force variables; and (3) identify the main determinants of butterfly swim velocity based on a set of anthropometrics, kinematics, and propulsive force variables. Twenty swimmers (10 males: 15.40±0.30 years; 10 females: 14.43±0.23 years) at the national level were recruited for analysis. A set of anthropometrics, kinematics, and propulsive force variables were measured. Overall, a significant sex effect was verified (p≤0.05). Non-significant differences between upper-limbs were noted for males and females in all variables, except for the dF in males (t=−2.66, p=0.026, d=0.66). Stroke frequency presented the highest contribution, where a one unit increase in the stroke frequency imposed an increase of 0.375 m·s-1 (95CI: 0.105;0.645, p=0.010) in the swim velocity. The swim velocity was predicted by the mean propulsive force, intra-cyclic variation of the swim velocity, and stroke frequency. Overall, swimmers exhibit non-significant differences in the variables assessed. Swim velocity in the butterfly stroke was determined by an interaction of propulsive force and kinematic variables in young swimmers.

How Should the Transition from Underwater to Surface Swimming Be Performed by Competitive Swimmers?

Despite the increasing importance of the underwater segment of start and turns in competition and its positive influence on the subsequent surface swimming, there is no evidence on how the transition from underwater to surface swimming should be performed. Therefore, the aim of the present study was to examine the role of segmental, kinematic and coordinative parameters on the swimming velocity during the pre-transition and transition phases. A total of 30 national male swimmers performed 4 × 25 m (one each stroke) from a push start at maximum velocity while recorded from a lateral view by two sequential cameras (50 Hz), and their kinematic and coordinative swimming parameters were calculated by means of two-dimensional direct linear transformation (DLT) algorithms. Unlike pre-transition, backward regression analysis of transition significantly predicted swimming velocity in all strokes except breaststroke (R2 ranging from 0.263 in front crawl to 0.364 in butterfly). The inter-limb coordination was a predictor in butterfly stroke (p = 0.006), whereas the body depth and inclination were predictors in the alternate strokes (front crawl (p = 0.05) and backstroke (p = 0.04)). These results suggest that the body position and coordinative swimming parameters (apart from kicking or stroking rate and length) have an important influence on the transition performance, which depends on the swimming strokes.

Return to Sport After Arthroscopic Rotator Cuff Repair in Middle-Aged and Elderly Swimmers

Background: No reports have been published on the clinical outcomes, including return to sport, after rotator cuff repair in middle-aged and elderly swimmers with rotator cuff tears. Purpose: To retrospectively investigate clinical outcomes and return to sport after arthroscopic rotator cuff repair in middle-aged and elderly swimmers. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent arthroscopic rotator cuff repair and met the following criteria were included: (1) age older than 45 years, (2) rotator cuff tears confirmed during surgery, (3) arthroscopic suture bridge rotator cuff repair, (4) primary surgery, and (5) swam more than once a week before surgery. The exclusion criteria were as follows: (1) irreparable large and massive tears, (2) shoulder instability, (3) arthritis or rheumatic disorders, or (4) less than 2-year follow-up. We investigated functional outcomes including range of motion; the University of California, Los Angeles (UCLA) score; the American Shoulder and Elbow Surgeons (ASES) score; return to swimming; and the return rates for each style of swimming. In addition, the functional outcomes and findings of magnetic resonance imaging were compared between the group with complete return and the group with incomplete or failed return. Results: A total of 32 shoulders in 31 middle-aged and elderly swimmers (5 males, 26 females) were included. The mean age was 65 years (range, 47-78 years), and the mean follow-up was 47 months (range, 24-86 months). Return to swimming was achieved in 31 (97%) shoulders at a mean of 8 months (range, 3-24 months), and complete return was achieved in 18 (56%) shoulders at a mean of 12 months (range, 3-24 months). The return rate was 97% for freestyle, 83% for breaststroke, 74% for backstroke, and 44% for butterfly stroke. Postoperative UCLA and ASES scores were significantly higher in the group with complete return than in the group with incomplete or failed return ( P = .001 and .01, respectively). Postoperative forward elevation was significantly better in the complete return group ( P = .01). Conclusion: This study demonstrated that 97% of elderly swimmers who underwent arthroscopic rotator cuff repair could return to swimming. The complete return rate was 56%; however, the group with incomplete or failed return showed poorer active forward elevation. Freestyle had the highest complete return rate, whereas the butterfly stroke had the lowest return rate. It may be important to achieve good active forward elevation postoperatively to return to swimming.

KONTRIBUSI KELENTUKAN BAHU SERTA DAYA LEDAK OTOT TUNGKAI TERHADAP KETERAMPILAN BERENANG BUTERFLY STROKE MAHASISWA PROGRAM STUDI PJKR-FKIP UNSYIAH

The aim of this study is to looking the contribution of flexibility shoulder muscle as well as the muscular power of the hands in relation to the skill of butterfly stroke. The population or research subjects used are students of study Program PJKR FKIP Unsyiah 2015 number of 132 MHS. Sample or data source selected using Purposive Sampling technique with consideration of value for MK TP. Renang Lanjutan Category A is B a number of 25 people. Data collection is carried out using the Flexibility shoulder test and measurement approach, the leg muscle explosive power, and the butterfly swimming ability test. The collected data is processed using the mean statistical approach, deviation standard, regression analysis, as well as test F. Data processing results obtained score rx1y worth 0.91 contribution worth 82.81%, rx2y worth of 0.87 contributed worth 75.69%, and Rx1x2y Worth 0.86 But the value of Fcount is greater than that of Ftabel with significance worth. Abstrak Tujuan dari penelitian yang dilakukan ini adalah untuk mengetahui kontribusi flexibilitas otot bahu serta daya ledak otot tungkai dalam kaitannya dengan keterampilan berenang gaya kupu atau butterfly stroke. Populasi atau subjek penelitian yang digunakan yaitu Mahasiswa Program Studi PJKR FKIP Unsyiah angkatan 2015 sejumlah 132 Mhs. Sampel atau sumber data dipilih dengan menggunakan teknik Purposive Sampling dengan pertimbagan nilai untuk MK Renang Lanjutan kategori A samapi B sejumlah 25 orang. Pengumpulan data dilakukan menggunakan pendekatan tes dan pengukuran kelentukan bahu, daya ledak otot tungkai, serta tes kemampuan renang gaya kupu. Data yang terkumpul diolah mengunakan pendekatan statistik mean, standar deviasi, analisis regresi, serta uji F. Hasil pengolahan data diperoleh score rx1y senilai 0,91 berkontribusi senilai 82,81%, rx2y senilai 0,87 berkontribusi senilai 75,69%, dan Rx1x2y senilai 0,86 namun nilai Fhitung lebih besar dari pada Ftabel dengan signifikansi senilai 95% (db= n-k-1) yaitu= 25 – 2 – 1 = 22, oleh sebab itu didapati Ftabel=3.54, serta Fhitung=36. Sehubungan dengan itu dapat digambarkan bahwa kelentukan bahu dan daya ledak otot tungkai berkontribusi signifikan terhadap kemampuan renang gaya kupu-kupu. Kata Kunci: Kelentukan, Power, Gaya Kupu-kupu