The Effect of Paddle Stroke Variables Measured by Trainesense SmartPaddle® on the Velocity of the Kayak

This is a sel -a chi ed e sion o an o iginal a icle. This e sion may di e om he o iginal in pagina ion and ypog aphic de ails. Au ho (s): Ti le: Yea : Ve sion: Copy igh : Righ s: Righ s u l: Please ci e he o iginal e sion: CC BY 4.0 h ps://c ea i ecommons.o g/licenses/by/4.0/ The E ec o Paddle S oke Va iables Measu ed by T ainesense Sma Paddle® on he Veloci y o he Kayak © 2022 by he au ho s. Licensee MDPI, Basel, Swi ze land. Published e sion Löppönen, An i; Vän inen, Tomi; Ha e inen, Ma ko; Linnamo, Vesa Löppönen, A., Vän inen, T., Ha e inen, M., & Linnamo, V. (2022). The E ec o Paddle S oke Va iables Measu ed by T ainesense Sma Paddle® on he Veloci y o he Kayak. Senso s, 22(3), A icle 938. h ps://doi.o g/10.3390/s22030938 2022   Ci a ion: Löppönen, A.; Vän inen, T.; Ha e inen, M.; Linnamo, V. The E ec o Paddle S oke Va iables Measu ed by T ainesense Sma Paddle®on he Veloci y o he Kayak. Senso s 2022,22, 938. h ps://doi.o g/10.3390/s22030938 Academic Edi o : Giuseppe Vannozzi Recei ed: 10 No embe 2021 Accep ed: 23 Janua y 2022 Published: 26 Janua y 2022 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2022 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). senso s A icle The E ec o Paddle S oke Va iables Measu ed by T ainesense Sma Paddle®on he Veloci y o he Kayak An i Löppönen 1,2 , Tomi Vän inen 3, Ma ko Ha e inen 1,4 and Vesa Linnamo 1,* 1Facul y o Spo and Heal h Sciences, Uni e si y o Jy äskylä, 40014 Jy äskylä, Finland; [email p o ec ed] (A.L.); [email p o ec ed] (M.H.) 2Physical Ac i i y, Spo s and Heal h Resea ch G oup, Depa men o Mo emen Sciences, KU Leu en, 3000 Leu en, Belgium 3KIHU-Resea ch Ins i u e o Olympic Spo s, 40700 Jy äskylä, Finland; [email p o ec ed] 4Va ala Spo s Ins i u e, 33240 Tampe e, Finland *Co espondence: [email p o ec ed]; Tel.: +358-405044800 Abs ac : (1) Backg ound: This s udy aimed o compa e key a iables o paddle s oke measu ed by a comme cial T ainesense Sma Paddle ® agains he s ain-gauge sha and in es iga e how hese a iables a e associa ed wi h he eloci y o he boa among na ional-le el canoe polo playe s. (2) Me hods: This s udy in ol ed 14 Finnish na ional-le el canoe polo playe s. The measu emen p o ocol consis ed o h ee di e en paddling eloci ies, which we e pe o med in indoo swimming pools. The eloci y o he boa was calcula ed based on he pe o mance ime measu ed wi h he lase pho ocell ga e. Canoe polo equipmen was used in he s udy and a Sma Paddle senso was a ached o he paddle blade. A s ain-gauge paddle sha was used as a e e ence me hod o examine he alidi y o Sma Paddle. (3) Resul s: The s oke a e, o ce p oduc ion ime, mean and maximal o ce measu ed wi h he s ain-gauge paddle sha co ela ed s ongly ( = 0.84–0.95, p< 0.01) wi h Sma Paddle. Howe e , he Sma Paddle o e es ima ed he maximum o ce compa ed o he s ain- gauge sha . S oke a e ( = 0.86, p< 0.01), mean o ce ( = 0.79, p< 0.01), maximal o ce ( = 0.78, p< 0.01) and o al absolu e impulse ( = 0.70, p< 0.01) co ela ed posi i ely and o ce p oduc ion ime nega i ely ( = − 0.76, p< 0.01) wi h he eloci y o he boa . (4) Conclusions: We conclude ha he Sma Paddle p o ides p omising in o ma ion on s oke key a iables when compa ed o he s ain-gauge paddle sha . The Sma Paddle is a new and in e es ing ool o biomechanical esea ch and daily kayaking coaching in eal open wa e condi ions. Howe e , mo e esea ch and algo i hm de elopmen a e needed be o e he Sma Paddle can be used in e e yday coaching sessions in kayaking. Keywo ds: kayaking; biomechanics; canoe polo; ine ial measu emen uni 1. In oduc ion To c ea e a o wa d accele a ion o he boa , he paddle mus win he esis ance o ces o wa e and ai [ 1 – 4 ]. Fo ce, powe , and s oke a e a e he mos impo an ac o s in luencing he eloci y o he boa [ 5 – 9 ]. In addi ion, i is impo an o p oduce a “bell- shaped” o ce p o ile, which leads o a bigge impulse [ 6 , 10 , 11 ]. The paddle s oke is mos e ec i e when he blade is pe pendicula o he wa e su ace [ 2 , 12 ] and he maximum o ce is eached jus be o e his [ 13 , 14 ]. S udies ocused on he paddle ajec o y ha e shown ha mo e expe ienced paddle s a e capable o mo e symme ical paddling pe o mance [ 15 – 17 ] and ha e wide ajec o ies han inexpe ienced paddle s [16]. T adi ionally, he di ec ion o he paddle s oke is pa allel o he kayak’s cen e line, bu on a wing paddle, he ajec o y is sligh ly di e en because he blade’s wing shape p oduces buoyancy compa ed o a adi ional paddle [ 11 , 12 , 15 ]. When he paddle is using he wing paddle, he ajec o y should be on a sligh ly mo e cu ed line, mo ing beyond Senso s 2022,22, 938. h ps://doi.o g/10.3390/s22030938 h ps://www.mdpi.com/jou nal/senso s Senso s 2022,22, 938 2 o 12 he cen e line o he boa [ 15 ]. This has been ound o p olong he op imal du a ion o he p opulsion gene a ion posi ion [ 11 ]. The s oke ajec o y is hus one o he key ac o s ela ed o paddling pe o mance and a ies be ween di e en ypes o paddling such as canoe polo and sp in kayaking. Al hough he canoe polo is paddled wi h a adi ional paddle ( la -blade) and should ollow he same p inciples as o he kayak spo s using a adi ional paddle, he ac ual esea ch e idence on canoe polo is s ill limi ed. Mos o he biomechanical kayaking s udies ha e been conduc ed h ough mo ion analysis and di ec o ce measu emen s. S udies ha e been made by e gome e s in labo a- o y condi ions [ 8 , 18 – 20 ] and open wa e en i onmen s [ 7 , 10 , 12 , 21 – 23 ]. S udies in an open wa e en i onmen o en use a s ain-gauge paddle sha [ 6 , 21 , 23 ] o measu e he bending o he sha and he eby he a iables o he s oke. This me hod has also been ound o be a eliable analyze on-wa e owing pe o mance [ 24 ]. Paddle blade ajec o y- ela ed s udies ha e p e iously been done wi h an e gome e in labo a o y condi ions [ 20 , 25 ] and open wa e using cinema og aphic came as [12,26]. Howe e , he limi a ion o hese me hods is ha hey canno be used o s udy he di ec- ion o he paddle s oke o he ajec o y o he paddle blade when paddling in open wa e condi ions o long dis ances (compe i i e analyzes). Mo eo e , many me hods such as 3D- mo ion analysis a e no sui able o di ec ans e o an open wa e en i onmen especially o daily ( echnical) coaching sessions, whe e a s and-alone sys em is o en equi ed. The new compac senso echnology could o e new oppo uni ies o biomechanical esea ch and daily coaching in wa e spo s. The small-sized ine ial measu emen uni s allow hese de ices o be used in eal condi ions [ 27 – 29 ]. Ine ial measu emen uni s a e capable o measu ing, p ocessing, and s o ing da a in a compac size and a e also e y ligh and a e hus possible o in eg a e in o equipmen [ 27 ]. Ine ial measu emen uni s ha e been used in wa e spo s especially in swimming [ 30 , 31 ] bu also in kayaking o measu e kayak mo emen s [ 32 , 33 ]. I is also no ewo hy ha he de elopmen o algo i hms plays a key ole as senso echnology is a g owing me hod in he biomechanical measu emen o spo s. Fo example in swimming, s oke a e, swimming eloci y, and s oke phases ha e been he mos impo an a iables in algo i hm de elopmen [ 34 ]. Howe e , o ou knowledge, he ine ial measu emen uni s ha e no been used o measu e simila kayaking s oke a iables such as o ce, s oke, o o ce p oduc ion ime. The ine ia measu emen uni could p o ide a ool o es ima e he di ec ion o paddle s oke unde eal condi ions because he da a measu ed by i s senso s can be used o de e mine ajec o ies. In his s udy, we use he T ainesense Sma Paddle ® which is an ad anced comme cial wea able unde wa e senso . I has been widely used in swimming o examine echnique ( ajec o y, eloci y, and o ien a ion o he hand) and he applied o ces du ing a swimming s oke [ 35 ]. This s udy aimed o compa e key a iables o paddle s oke measu ed by a Sma Paddle agains he s ain-gauge paddle sha . In addi ion, we in es iga e how hese key a iables a e associa ed wi h he eloci y o he boa among na ional-le el canoe polo playe s. 2. Ma e ials and Me hods 2.1. S udy Design and Pa icipan s This c oss-sec ional s udy consis ed o wo da ase s. The i s da ase (n= 6, all we e men) compa ed he esul s o he Sma Paddle and a s ain-gauge paddle sha in key paddle s oke a iables. The second s udy ( o al n= 14, men n= 12, women n= 2) in es iga ed he e ec o key paddle s oke a iables measu ed on a Sma Paddle on he eloci y o a boa . The pa icipan s o his s udy we e Finnish na ional-le el canoe polo playe s (Table 1). The a e age age o he da ase one pa icipan s (n= 6) was 39.3 ± 10.1 yea s, heigh 183.3 ±10.6 cm , and weigh 81.3 ± 13.0 kg. The a e age angle o he blade was 80.0 ± 0.0 ◦ and he paddle leng h was 206.0 ± 0.0 cm. The a e age age o he da ase wo pa icipan s (n= 14) was 40.8 ± 17.2 yea s, heigh 182.3 ± 7.6 cm, and weigh 81.2 ± 11.6 kg. The a e age angle o he blade was 69.1 ±17.9◦and he paddle leng h was 206.4 ±0.9 cm. Senso s 2022,22, 938 3 o 12 Table 1. The desc ip i e in o ma ion o he s udy pa icipan s. Mean (SD) 1s Da ase (n= 6) 12nd Da ase (n= 14) 1 Age [yea s] 39.3 ±10.1 40.8 ±17.2 Heigh [cm] 183.3 ±10.6 182.3 ±7.6 Weigh [kg] 81.3 ±12.9 81.2 ±11.6 Blade angle [deg] 80.0 ±0.0 269.1 ±17.9 Paddle leng h [cm] 206.0 ±0.0 2206.4 ±0.9 SD = S anda d De ia ion, 1 Desc ip i e able is missing da a om i e pa icipan s because hey did no eply o he ques ionnai e sen a e wa d (1s da ase = 2 pa icipan s, 2nd da ase = 3 pa icipan s). 2no adjus able. The inclusion c i e ion o he pa icipan s we e: (1) a leas h ee yea s o expe ience o compe i ion kayaking, (2) basic heal h, and (3) we e no allowed o ha e any inju ies o o he p oblems ha in e e ed wi h hei kayaking pe o mance. The s udy p o ocol ollowed he p inciples o he Decla a ion o Helsinki. The s udy was app o ed by he Human Sciences E hics Commi ee o he Uni e si y o Jy äskylä. All pa icipan s signed w i en in o med consen be o e pa icipa ing in he s udy. 2.2. Measu emen Measu emen s we e pe o med in h ee di e en indoo swimming pools, in wo loca ions in Finland. All pa icipan s in da ase one we e measu ed in a 25-m pool wi h a measu emen dis ance o 15 m. Fou pa icipan s o da ase wo we e measu ed in a 50-m pool (measu ing dis ance 30 m) and he emaining 10 pa icipan s we e measu ed in a 25-m pool (measu ing dis ance 15 m). Based on he paddling eloci ies, he measu emen dis ance did no a ec he esul s o he analysis. A a 30-m analysis dis ance (50-m pool), mean (SD) 13.9 ± 1.7 s okes pe side we e included in he analysis a eloci y one, 14.6 ±2.4 s okes a eloci y wo, and 15.5 ± 2.1 s okes a eloci y h ee. A a 15-m analysis dis ance (25-m pool), 6.4 ± 0.8 s okes we e included in he analysis a eloci y one, 6.9 ± 1.0 s okes a eloci y wo, and 7.1 ± 0.9 s okes a eloci y h ee. The eloci y o he canoe was calcula ed based on he pe o mance ime measu ed wi h he lase pho ocell ga es placed on he edges o he pool. The dis ance be ween he pho ocells was measu ed and he a e age eloci y was calcula ed by di iding he paddled dis ance by he pe o mance ime ( = s/ , whe e = eloci y , s = dis ance, and = ime). The pho ocells we e placed in he pools so ha he boa could be accele a ed (accele a ion dis ance was 5 m) o he c uising eloci y be o e he i s pho ocell ga e s a ed he iming. The measu emen p o ocol o da ase one (Sma Paddle & s ain-gauge sha compa - ison) consis ed o h ee di e en eloci ies o paddling pe o mances. Fi s pa icipan s we e ins uc ed o paddle a a basic endu ance pace ( eloci y 1), which was desc ibed as a slow and calm bu s ong pace ha can be main ained o a long ime. The second eloci y was clea ly ( eloci y 2) as e paddling, which was desc ibed as s ong, bu echnically pu e, paddling. This eloci y was pe o med wi h h ee di e en echniques (no mal, ene ge ic bea ing s oke, delayed long and ligh s oke) o add he e ogenei y o he da a used in he alidi y analysis. The las was maximum eloci y ( eloci y 3), which was desc ibed as a nea maximum pe o mance, whe e he pace is almos a maximum, bu he paddling echnique emains high quali y. In o al, da ase one con ained a o al o 60 da a poin s (=6 pa icipan s × 5 di e en pe o mances/pa icipan × 2 sides (le and igh ). The eloci ies one (1.95 ± 0.22 m/s) wo (2.20 ± 0.21 m/s) and h ee (2.50 ± 0.20 m/s) di - e ed signi ican ly (p< 0.05) as planned. The eloci ies o he wo di e en echnical s yles (ene ge ic bea ing s oke 2.36 ± 0.26 m/s & delayed long and ligh s oke 2.25 ±0.21 m/s ) we e he same as no mal s yle o eloci y wo (p= 0.313, p= 0.563. espec i ely) as planned. Da ase wo consis ed o he h ee di e en eloci ies wi h no mal paddling pe o - mances men ioned abo e ( eloci y 1, 2 & 3), o s udy he e ec o key paddle s oke a iables measu ed on a Sma Paddle on he eloci y o a boa . Da ase wo con ained a o al o 84 da a poin s (=14 pa icipan s ×3 di e en eloci y pe o mances/pa icipan ×2 sides Senso s 2022,22, 938 4 o 12 (le and igh )). The eloci y o he boa di e ed signi ican ly be ween di e en eloci ies (p< 0.001) as planned. 2.3. Ins umen a ion The comme cial Sma Paddle (T ainesense Oy, Tampe e, Finland) was used as a measu ing uni (9-axis IMU + p essu e senso ). The de ice uses a sampling equency o 100 Hz and he da a was s o ed in he T ainesense Analysis Cen e cloud se ice. The da a was uploaded o he mobile phone and onwa d Analysis Cen e ia a Blue oo h connec ion. The Sma Paddle was moun ed on he back o he blade (B aca-Spo Polo Kine ic max, adjus able sha , ze o-leng h 205 cm) using silicone s aps, and a 15 mm diame e hole was d illed in he paddle blade o he p essu e senso (Figu e 1). Senso s 2022, 22, x FOR PEER REVIEW 5 o 13 Figu e 1. (A) Sma Paddle place on he blade, (B) S ain-gauge sha in calib a ion boa d (wi hou IMU a ached), (C) Sma Paddle a ached o he blade, (D) s uc u e o he s ain-gauge senso s. 2.4. Da a P ocessing The Sma Paddle calcula ion algo i hm has no been published. The Sma Paddle gene a es he p ocessed da a ia he closed Ma lab GUI (G aphical Use In e ace) (Tam- pe e, Finland) de eloped by he T ainesense Oy (Tampe e, Finland) meaning ha he e is no access o Sma Paddle aw da a and he algo i hm calcula ion cons an s can no be adjus ed. This was also he eason why he compa isons be ween he s ain-gauge sha and he Sma Paddle used a e aged a iables as i was no possible o pe o m he ac ual s oke (Sma Paddle)-s oke (s ain-gauge sha ) synch oniza ion due o lack o he aw da a om he Sma Paddle. In he p esen s udy, he Sma Paddle a iables we e no mal- ized o paddle blade (B acsa polo kine ic max, 735 cm 2 ) a ea and he da a we e p ocessed sepa a ely o he igh and le blades. The mean o ce was he a e age o al o ce o ha ime when he blade is in he wa e . The maximum o ce was he highes o al (all di ec ions) o ce ha he Sma Paddle egis e ed du ing he en i e pe o mance. The o ce p oduc ion ime was de ined as he du a ion du ing which he blade p oduced o ce a mo e han 30% o he s oke maximum o ce. The absolu e o al impulse was o al o ce mul iplied by he whole ime when he blade was unde he wa e su ace [35]. The Sma Paddle analysis consis ed o only he c uising phase o he pe o mances wi hou he accele a ion and b aking phases. All a - iables excep maximum o ce we e a e ages o he s okes included in he analysis. The Figu e 1. ( A ) Sma Paddle place on he blade, ( B ) S ain-gauge sha in calib a ion boa d (wi hou IMU a ached), (C) Sma Paddle a ached o he blade, (D) s uc u e o he s ain-gauge senso s. A s ain-gauge paddle sha (sel -manu ac u ed, Uni e si y o Jy äskylä, Finland) [ 9 ] was used o he compa ison o he Sma Paddle (Figu e 1D). This same s ain-gauge equipmen has also been used in p e ious esea ch when examining he ela ionships Senso s 2022,22, 938 5 o 12 be ween o ce- ime pa ame e s and kayak eloci y [ 9 ]. The da a p oduced by he s ain- gauge senso s we e ampli ied wi h sepa a e ampli ie s (TR es i Oy, Jy äskylä Finland) and s o ed on a eco dable AD con e e (sel -manu ac u ed “LIIKE ca d”, Spo s Technology, Uni e si y o Jy äskylä, Vuoka i, Finland) a a equency o 250 Hz. The gauge paddle sha was calib a ed using 0 kg, 4 kg, and 10 kg weigh s o calcula e he linea gain ac o . Du ing he calib a ion p ocess, he s ain gauge sha was a ached o he calib a ion able wi h he clamps and he ulc um poin was a he edge o he able (Figu e 1B). The linea gain ac o de e mined om he calib a ion was en e ed in o he eco dable AD Con e e analysis so wa e. 2.4. Da a P ocessing The Sma Paddle calcula ion algo i hm has no been published. The Sma Paddle gene a es he p ocessed da a ia he closed Ma lab GUI (G aphical Use In e ace) (Tampe e, Finland) de eloped by he T ainesense Oy (Tampe e, Finland) meaning ha he e is no access o Sma Paddle aw da a and he algo i hm calcula ion cons an s can no be adjus ed. This was also he eason why he compa isons be ween he s ain-gauge sha and he Sma Paddle used a e aged a iables as i was no possible o pe o m he ac ual s oke (Sma Paddle)-s oke (s ain-gauge sha ) synch oniza ion due o lack o he aw da a om he Sma Paddle. In he p esen s udy, he Sma Paddle a iables we e no malized o paddle blade (B acsa polo kine ic max, 735 cm 2 ) a ea and he da a we e p ocessed sepa a ely o he igh and le blades. The mean o ce was he a e age o al o ce o ha ime when he blade is in he wa e . The maximum o ce was he highes o al (all di ec ions) o ce ha he Sma Paddle egis e ed du ing he en i e pe o mance. The o ce p oduc ion ime was de ined as he du a ion du ing which he blade p oduced o ce a mo e han 30% o he s oke maximum o ce. The absolu e o al impulse was o al o ce mul iplied by he whole ime when he blade was unde he wa e su ace [ 35 ]. The Sma Paddle analysis consis ed o only he c uising phase o he pe o mances wi hou he accele a ion and b aking phases. All a iables excep maximum o ce we e a e ages o he s okes included in he analysis. The ela i e o wa d, la e al and e ical impulses es ima ed by he Sma Paddle we e calcula ed in line wi h kayaking di ec ion. The da a s o ed om he s ain-gauge paddle sha was p ocessed using Ma lab (R2020b, The Ma hWo ks Inc., Na ick, MA, USA). Fi s , he aw da a we e il e ed us- ing a mo ing-a e age il e (mo mean unc ion) wi h a alue o 10 da a poin s ( il e window) [ 36 ], o a enua e he la ges in e e ence peaks. Then he maximum o ce (max– unc ion) o he paddle s oke was de e mined om he il e ed da a by iden i ying a peak o ce alue (highes o ce) o he en i e pe o mance (c uising phase). Finally, mean s oke o ce and o ce p oduc ion ime we e calcula ed using he same 30% o ce limi as he Sma Paddle algo i hm in o de o make he analysis compa able. This was done by de e mining a le el o 30% o he maximum o ce. The du a ion and mean o he o ce p oduc ion ime we e de e mined om he o ce ec o abo e his le el. The le and igh sides we e p ocessed sepa a ely in he analysis, wi h bo h sides o ming hei own da a poin s in he s a is ical analysis. Mean alues (excep maximum o ce) o o al kayaking pe o mances (c uising phase) we e used in his s ain-gauge paddle sha analysis o make i compa able wi h he Sma Paddle analysis. 2.5. S a is ical Analysis Resul s a e epo ed as mean and s anda d de ia ion (SD). Shapi o-Wilk no mali y es and his og ams isual e alua ion (no mal dis ibu ion cu e and dis ibu ion skewness and ku osis) we e used o check he no mali y o he da a. The Shapi o-Wilk es indica ed ha some o he a iables we e no no mally dis ibu ed (s oke a e, boa eloci y, la e al and e ical ela i e impulse). Simila ly, he isual in e p e a ion o he his og ams and he small sample size (n=6&n= 14) suppo ed he selec ion o non-pa ame ic es s. Associa ions be ween he da a measu ed by he Sma Paddle and he s ain-gauge paddle Senso s 2022,22, 938 6 o 12 sha we e es ed wi h he Spea man co ela ion coe icien . The co espondence be ween he da a measu ed by he Sma Paddle and he gauge-paddle sha was e alua ed wi h wo-way andom (absolu e ag eemen ), single measu e in a-class co ela ion coe icien s (ICC) [ 37 ], and isualized wi h Bland-Al man plo s [ 38 ]. ICC was used o cha ac e ize he co espondence as poo (<0.40), ai (0.40 o <0.60), good (0.60 o <0.75), o excellen ( ≥ 0.75) [ 39 ]. The ela ionship be ween eloci y and key paddle a iables measu ed wi h he Sma Paddle was also s udied by he Spea man co ela ion coe icien s ( wo- ailed). Di e ences be ween eloci ies g oups and s ain-gauge paddle sha and he Sma Paddle we e es ed using ela ed–samples Wilcoxon signed- ank es . S a is ical signi icance was se a p ≤ 0.05 ( wo- ailed) and analyses we e pe o med wi h he R s a is ical compu ing so wa e ( e sion 4.0.3) [40]. 3. Resul s 3.1. S ain-Gauge Sha Compa ison The Sma Paddle measu ed highe maximum o ce alues han he s ain-gauge paddle sha (p< 0.001) (Table 2). The s ain-gauge paddle sha maximum o ce was 125.4 ±34.2 N , while he mean o he maximum o ce o he Sma Paddle was 152.1 ±57.4 N . Howe e , he co ela ion be ween Sma Paddle and s ain-gauge paddle sha was s ong 0.84 (p< 0.001), and he ICC was classi ied o be good 0.64 (Con idence In e al CI 95% 0.21, 0.82) (p= 0.003). The s ain-gauge paddle sha mean o ce was 85.4 ± 25.3 N and he Sma Paddle 83.3 ± 30.3 N, wi h a s ong co ela ion o 0.88 (p< 0.001) and an excellen ICC o 0.86 (CI, 0.78, 0.92) (p< 0.001). This di e ence in mean o ce was no s a is ically signi ican be ween hese wo me hods (p= 0.083). Table 2. Compa ison be ween he s ain-gauge paddle sha and he Sma Paddle (9-axis IMU+ p essu e senso ) in key paddle s oke a iables (n= 6). Mean (SD) S ain-Gauge Sma Paddle p-Value 1 2ICC 3 Maximal o ce [N] 125.4 ±34.2 152.1 ±57.4 <0.001 0.84 ** 0.64 *** Mean o ce [N] 85.4 ±25.3 83.3 ±30.3 =0.083 0.88 ** 0.86 *** Fo ce p od. ime [s] 0.43 ±0.08 0.44 ±0.10 =0.472 0.88 ** 0.81 *** S oke a e [1/min] 84.8 ±25.6 80.7 ±21.0 =0.199 0.95 ** 0.95 *** SD = S anda d de ia ion, 1 Wilcoxon signed ank es , 2 Spea man’s ank co ela ion coe icien , 3 ICC = In aclass Co ela ion Coe icien , ** Co ela ion is s a is ically signi ican 0.01 le el (2- ailed), *** p< 0.001. The o ce p oduc ion ime s ongly co ela ed be ween he s ain-gauge paddle sha and he Sma Paddle (0.88, p< 0.01) and he a e age di e ence was only 0.01 s (p= 0.472) The ICC was classi ied o be excellen 0.81 (CI, 0.70, 0.88) (p< 0.001). O all he a iables, he s onges co ela ion was ound in he s oke a e 0.95 (p< 0.01) and i did no di e s a is ically (p= 0.199), and he ICC was excellen a 0.95 (CI, 0.89, 0.98) (p< 0.001) (Table 2). Sca e plo s and R 2 alues be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables a e p esen ed in Figu e 2. The Bland-Al man analysis (Figu e 3) showed ha he e we e only a ew cases ou side he conco dance limi s (95%) and no sys ema ic e o di e ence was no iceable, as he measu emen esul s we e e enly dis ibu ed on bo h sides o he ze o le el. 3.2. Key Va iables o Veloci y S oke a e ( = 0.86, p< 0.001) and mean o ce ( = 0.79, p< 0.001) we e mos s ongly ela ed o boa eloci y and di e ed be ween all kayaking eloci ies (p< 0.001) (Tables 3and 4) . The absolu e impulse ( = 0.70, p< 0.001) was also posi i ely ela ed o he eloci y o he boa and di e ed signi ican ly (p< 0.001) be ween he eloci ies while he o ce p oduc ion- ime was nega i ely ela ed ( = − 0.76, p< 0.001) o he eloci y o he boa . Senso s 2022,22, 938 7 o 12 Senso s 2022, 22, x FOR PEER REVIEW 7 o 13 2). Sca e plo s and R2 alues be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables a e p esen ed in Figu e 2. Table 2. Compa ison be ween he s ain-gauge paddle sha and he Sma Paddle (9-axis IMU+ p essu e senso ) in key paddle s oke a iables (n = 6). Mean (SD) S ain-Gauge Sma Paddle p-Value 1 2 ICC 3 Maximal o ce [N] 125.4 ± 34.2 152.1 ± 57.4 <0.001 0.84 ** 0.64 *** Mean o ce [N] 85.4 ± 25.3 83.3 ± 30.3 =0.083 0.88 ** 0.86 *** Fo ce p od. ime [s] 0.43 ± 0.08 0.44 ± 0.10 =0.472 0.88 ** 0.81 *** S oke a e [1/min] 84.8 ± 25.6 80.7 ± 21.0 =0.199 0.95 ** 0.95 *** SD = S anda d de ia ion, 1 Wilcoxon signed ank es , 2 Spea man’s ank co ela ion coe icien , 3 ICC = In aclass Co ela ion Coe icien , ** Co ela ion is s a is ically signi ican 0.01 le el (2- ailed), *** p < 0.001. Figu e 2. Sca e plo s and R2 alues be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables (n = 6) (R2 = coe icien o de e mina ion showing how close he da a a e o he i ed eg ession line). The Bland-Al man analysis (Figu e 3) showed ha he e we e only a ew cases ou - side he conco dance limi s (95%) and no sys ema ic e o di e ence was no iceable, as he measu emen esul s we e e enly dis ibu ed on bo h sides o he ze o le el. Figu e 2. Sca e plo s and R 2 alues be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables (n= 6) (R 2 = coe icien o de e mina ion showing how close he da a a e o he i ed eg ession line). Senso s 2022, 22, x FOR PEER REVIEW 8 o 13 Figu e 3. Bland–Al man analysis be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables (n = 6). 3.2. Key Va iables o Veloci y S oke a e ( = 0.86, p < 0.001) and mean o ce ( = 0.79, p < 0.001) we e mos s ongly ela ed o boa eloci y and di e ed be ween all kayaking eloci ies (p < 0.001) (Tables 3 and 4). The absolu e impulse ( = 0.70, p < 0.001) was also posi i ely ela ed o he eloci y o he boa and di e ed signi ican ly (p < 0.001) be ween he eloci ies while he o ce p oduc ion- ime was nega i ely ela ed ( = −0.76, p < 0.001) o he eloci y o he boa . Table 3. Desc ip i e cha ac e is ics o he pa icipan s and esul s o he es ing eloci ies (n = 14). Mean (SD) Veloci y 1 Veloci y 2 Di V1–V2 1 Veloci y 3 Di V2–V3 1 Veloci y [m/s] 2.1 ± 0.2 2.4 ± 0.1 <0.001 2.7 ± 0.3 <0.001 Maximal o ce [N] 112.6 ± 38.4 145.1 ± 40.1 <0.001 224.9 ± 67.8 <0.001 Mean o ce [N] 61.6 ± 17.9 83.6 ± 21.8 <0.001 115.8 ± 32.2 <0.001 Fo ce p od. ime [s] 0.46 ± 0.06 0.40 ± 0.06 <0.001 0.34 ± 0.07 <0.001 S oke a e [1/min] 75.7 ± 14.3 93.5 ± 13.4 <0.001 119.3 ± 19.7 <0.001 To al impulse abs [Ns] 58.6 ± 16.8 69.2 ± 15.8 <0.001 90.1 ± 22.8 <0.001 Impulse o wa d [%] 2 49.50 ± 4.29 50.36 ± 4.23 0.387 49.75 ± 4.05 0.770 Impulse la e al [%] 2 28.81 ± 4.90 29.60 ± 5.10 0.058 32.08 ± 5.14 0.036 Impulse e ical [%] 2 21.69 ± 4.45 20.04 ± 3.81 0.002 18.17 ± 4.24 0.009 SD = S anda d de ia ion, 1 Rela ed-samples Wilcoxon signed- ank es , 2 Po ion o o al impulse. The ela i e la e al impulse was posi i ely and mode a ely ela ed o boa eloci y ( = 0.42, p < 0.001) while he e ical impulse was nega i ely and mode a ely ela ed o e- loci y ( = −0.42, p < 0.001). The e was no change in he o wa d impulse as he eloci y inc eased and i did no co ela e signi ican ly wi h he eloci y ( = −0.09, p = 0.429). Figu e 3. Bland–Al man analysis be ween Sma Paddle and s ain-gauge sha in key paddle s oke a iables (n= 6). Senso s 2022,22, 938 8 o 12 Table 3. Desc ip i e cha ac e is ics o he pa icipan s and esul s o he es ing eloci ies (n= 14). Mean (SD) Veloci y 1 Veloci y 2 Di V1–V2 1Veloci y 3 Di V2–V3 1 Veloci y [m/s] 2.1 ±0.2 2.4 ±0.1 <0.001 2.7 ±0.3 <0.001 Maximal o ce [N] 112.6 ±38.4 145.1 ±40.1 <0.001 224.9 ±67.8 <0.001 Mean o ce [N] 61.6 ±17.9 83.6 ±21.8 <0.001 115.8 ±32.2 <0.001 Fo ce p od. ime [s] 0.46 ±0.06 0.40 ±0.06 <0.001 0.34 ±0.07 <0.001 S oke a e [1/min] 75.7 ±14.3 93.5 ±13.4 <0.001 119.3 ±19.7 <0.001 To al impulse abs [Ns] 58.6 ±16.8 69.2 ±15.8 <0.001 90.1 ±22.8 <0.001 Impulse o wa d [%] 249.50 ±4.29 50.36 ±4.23 0.387 49.75 ±4.05 0.770 Impulse la e al [%] 228.81 ±4.90 29.60 ±5.10 0.058 32.08 ±5.14 0.036 Impulse e ical [%] 221.69 ±4.45 20.04 ±3.81 0.002 18.17 ±4.24 0.009 SD = S anda d de ia ion, 1Rela ed-samples Wilcoxon signed- ank es , 2Po ion o o al impulse. Table 4. The Spea man’s ank co ela ion coe icien by eloci y g oups (n= 14). Veloci y 1 Veloci y 2 Veloci y 3 All Veloci y Maximal o ce [N] 0.60 ** 0.56 ** 0.74 ** 0.78 ** Mean o ce [N] 0.61 ** 0.47 * 0.73 ** 0.79 ** Fo ce p od. ime [s] −0.54 ** −0.40 * −0.56 ** −0.76 ** S oke a e [1/min] 0.82 ** 0.34 0.76 ** 0.86 ** To al impulse abs [Ns] 0.43 * 0.52 ** 0.74 ** 0.70 ** Impulse o wa d [%] −0.15 −0.01 −0.18 −0.09 Impulse la e al [%] 0.45 * 0.11 0.58 ** 0.42 ** Impulse e ical [%] −0.27 −0.07 −0.46 * −0.42 ** *p< 0.05, ** p< 0.01 ( wo- ailed). The ela i e la e al impulse was posi i ely and mode a ely ela ed o boa eloci y ( = 0.42, p< 0.001) while he e ical impulse was nega i ely and mode a ely ela ed o eloci y ( = − 0.42, p< 0.001). The e was no change in he o wa d impulse as he eloci y inc eased and i did no co ela e signi ican ly wi h he eloci y ( = −0.09, p= 0.429). 4. Discussion The p esen s udy sugges s ha he T ainesense Sma Paddle ® o e s p omising op- po uni ies o measu e paddle s oke key a iables acknowledging ha he calcula ion algo i hms and de ice moun ing need o be u he de eloped mo e sui able o kayaking in he u u e. The s oke a e, o ce, o ce- ime, and o al absolu e impulse we e ound o be key a iables a ec ing he eloci y o he boa among canoe polo playe s and hese esul s we e also well in line wi h p e ious s udies wi h sp in kayake s [ 5 , 8 ]. Mo eo e , he T ainesense Sma Paddle ® made i possible o s udy he di ec ion o he s oke, and in his s udy, when he eloci y o he boa inc eased, he ela i e amoun o he la e al impulse o he paddle s oke inc eased, while he e ical dec eased. The T ainesense Sma Paddle can p o ide new insigh s o echnical coaching in kayaking in eal open wa e condi ions. In his s udy, good o excellen ag eemen was ound be ween he Sma Paddle and he s ain-gauge sha in key a iables o paddle s oke (0.64–0.95, p< 0.001). The absolu e di e ences be ween he Sma Paddle and he e e ence me hod in o ce p oduc ion ime, mean o ce, and s oke a e we e small. The Sma Paddle o e es ima ed maximum o ce compa ed o a s ain-gauge sha (p> 0.001) and he ag eemen was also lowes in his a iable (0.64, p< 0.001). This may be due o di e ences in da a p ocessing, especially da a il e ing. We used a mo ing a e age (mo mean) il e o analyze he s ain-gauge sha da a, which may cu he highes o ce peaks mo e han he il e ing algo i hm used by he Sma Paddle. Howe e , i was mo e likely ha he Sma Paddle o e es ima ed he highes alues such as maximum o ce and absolu e impulse due o issues ela ed o hei ha dwa e and algo i hms. This was indica ed by he sensi i i y analysis be ween he le and igh sides which sugges ed ha i was indeed he Sma Paddle ha o e es ima ed he maximum o ce compa ed o he s ain-gauge sha (Supplemen a y Table S1). Un o una ely, his