Sarcomere disruptions of slow fibres resulting from mountain ultramarathon

Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 1 o 7 ORIGINAL INVESTIGATION h p://dx.doi.o g/10.1123/ijspp.2014-0267 Moun ain Ul ama a hon and Sa come e Dis up ions o Slow Fibe s Ge a d Ca mona, Emma Roca, Ma io Gue e o, Rose Cussó, Al edo I u ia, Lexa Nescola de, Daniel B o ons, Josep L. Bedini, and Joan A. Cade au Objec i e: To in es iga e changes a e a moun ain ul ama a hon (MUM) in he se um concen a ion o as (FM) and slow (SM) myosin iso o ms, which a e ibe - ype-speci ic sa come e p o eins. The changes we e compa ed agains c ea ine kinase (CK), a widely used ibe -sa colemma-damage bioma ke , and ca diac oponin I (cTnI), a widely used ca diac bioma ke . Me hods: Obse a ional compa ison o esponse in a single g oup o 8 endu ance- ained ama eu a hle es. Time- ela ed changes in se um le els o CK, cTnI, SM, and FM om compe i o s we e analyzed be o e, 1 h a e he MUM, and 24 and 48 h a e he s a o he MUM by 1-way ANOVA o epea ed measu es o F iedman and Wilcoxon es s. Pea son co ela ion coe icien was employed o examine associa ions be ween a iables. Resul s: While SM was signi ican ly (P = .009) inc eased in se um 24 h a e he beginning o he MUM, FM and cTnI did no change signi ican ly. Se um CK ac i i y peak was obse ed 1 h a e he MUM (P = .002). Mo eo e , se um peaks o CK and SM we e highly co ela ed ( = .884, P = .004). Conclusions: Since he e is e idence o muscle damage a e p olonged moun ain unning, he inc ease in SM se um concen a ion a e a MUM could be indi ec e idence o slow- ( ype I) ibe -speci ic sa come e dis up ions. Keywo ds: eccen ic con ac ion, c ea ine kinase, muscle myosin iso o ms Moun ain ul ama a hons (MUM) a e compe i i e e en s 1 con- sis ing o walking and unning on moun ain ails o e a g ea cumu- la i e ele a ion gain and o e a longe dis ance han he a hle ic ma a- hon (>42.195 km). Dis ance and cumula i e ele a ion gain a e he main de e minan s o MUM di icul y. Long-dis ance ail compe i- ions ha e isen in popula i y o e he las ew yea s.1 Howe e , he acu e physiological esponses o ex eme endu ance e en s s ill e- main unclea . I is known ha MUM compe i ions a e s enuous and gene ally include nega i e slopes, so long dis ances a e un downhill. I has been s a ed ha s enuous exe cise can esul in muscle dam- age,2 which is pa icula ly exace ba ed i eccen ic con ac ions a e pe o med ( o a e iew see P oske and Allen3). Downhill unning inc eases he eccen ic componen because he peak lexion angles a e signi ican ly g ea e , and i is a much s onge s imulus o damage han le el o uphill unning.4 The e o e, i seems easonable o ela e mos o he muscle damage o he nega i e-slope phases o he ail. MUM is a g ea oppo uni y o ield-speci ic assessmen s o a physi- ologically s ess ul compe i i e e en ha induces muscle damage.5,6 Di ec e alua ion o muscle damage in ol es his ological examina ion o muscle issue by biopsy. Howe e , in a spo s con ex , he analysis o exe cise-induced muscle damage is essen ially based on p oxy ma ke s such as measu emen s o enzyme ac i i y in blood, especially he ac i i y o c ea ine kinase (CK). P e ious s udies e alua ed he muscle damage induced by MUMs5,6 and e ealed la ge inc eases in o al CK concen a ions. Howe e , CK is no a speci ic bioma ke o skele al muscle.7 Kolle e al8 used slow ( ype I) myosin hea y-chain (MHC) agmen s, and Melin e al9 used be a MHC as 1 Ca mona, I u ia, and Cade au a e wi h he Na ional Ins o Physical Educa ion o Ca alonia, Ba celona, Spain. Roca is wi h he Uni e si y o Gi ona, Gi ona, Spain. Gue e o and Cussó a e wi h he Dep o Physiological Sciences I, Uni e si y o Ba celona, Ba celona, Spain. Nescola de is wi h he Poly echnic Uni e si y o Ca alonia, Ba celona, Spain. B o ons is wi h he Ca alan Spo s Council, Go e nmen o Ca alonia, Ba celona, Spain. Bedini is wi h he Hospi al Clinic, Ba celona, Spain. Add ess au ho co espondence o Joan Cade au a jcade au@genca .ca . muscle- ibe -speci ic damage bioma ke s. Those g oups ound inc eases in his p o ein in plasma a e moun ain- unning e en s. Al hough slow ( ype I) MHC agmen s and be a MHC a e common o skele al and ca diac muscle, he damage was mainly ela ed o slow ( ype I) ibe s o skele al muscle. Howe e , he esul s ound by Kolle e al8 and Melin e al9 we e highly unspeci ic, since plasma le els o MHC agmen s we e no compa ed wi h any ca diac- speci ic bioma ke . Since i has been s a ed ha s enuous exe cise could induce a signi ican elease o ca diac p o eins such as oponin in o he bloods eam,10 i seems easonable o assume ha p o eins ound in ca diac and skele al muscle, such as MHC agmen s and be a MHC, could also be eleased om myoca dium o blood. Recen ly, myosin iso o ms ha e been p oposed as ibe - ype- speci ic bioma ke s o muscle damage ha would ep esen indi ec e idence o sa come e dis up ions.11 Howe e , Ca mona e al11 obse ed selec i e elease o as myosin iso o ms (FM) a e high- in ensi y knee-ex enso exe cise, bu no changes in slow-myosin- iso o m (SM) se um concen a ion we e epo ed. SM is ound in bo h ca diac and skele al muscle, and FM is cha ac e is ic o as skele al muscle. Limb skele al muscles a e composed o slow ( ype I) and as ( ype II) ibe s,12 bu adul skele al muscles shows plas ici y and can unde go con e sion be ween di e en ibe ypes in esponse o exe cise.13 Endu ance a hle es end o ha e a p edominance o slow ( ype I) ibe s.14,15 Fo hese easons, we hypo hesized ha se um inc eases in myosin iso o ms, especially in SM, in endu ance- ained pa icipan s a e a MUM could indica e no only he ex en bu also he ype o ibe a ec ed. Fu he mo e, in he cu en s udy, he lack o speci ici y o SM was minimized by analyzing he changes in se um concen a ion o ca diac oponin I (cTnI), a widely used myoca dial-speci ic bioma ke . I has been shown ha cTnI is eleased a e p olonged exe cise. Howe e , in con as o myoca dial in a c ion, in which cTnI is usually o e 0.6 ng/mL and emains s able in blood o a leas 5 days, cTnI elease a e p olonged exe cise does no achie e such high se um le els and e u ns o Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 2 o 7 baseline wi hin 24 o 48 hou s.16 To he bes o ou knowledge, his is he i s ield s udy o use a combina ion o myosin iso o ms and cTnI o assess indi ec ly he muscle damage induced by a MUM. The aim o his s udy was o in es iga e changes in se um concen a ion o myosin iso o ms a e a MUM. SM and FM we e compa ed wi h CK, a widely used bioma ke o exe cise-induced muscle damage. The lack o speci ici y o SM was coun e ed wi h he measu emen o se um cTnI concen a ion. Since he e is e idence o muscle damage a e p olonged moun ain unning,5,6 we hypo hesized ha a speci ic inc ease in SM se um concen a ion a e a MUM would be indi ec e idence o slow ( ype I) - ibe sa come e damage in endu ance- ained moun ain unne s. Me hods Pa icipan s We ini ially ec ui ed 17 endu ance unne s, 14 men and 3 women. Howe e , due o bad wea he condi ions du ing he compe i ion, only 8 subjec s decided o comple e he s udy: 7 men and 1 woman (mean ± SD; men, n = 7, 39.8 ± 3.3 y, 178.7 ± 5.2 cm, 76.9 ± 7.9 kg; women, n = 1, 39.1 y, 173.0 cm, 67.0 kg). All o he pa icipan s we e expe ienced whi e nonp o essional a hle es (mean aining egimen, 450.0 ± 210.31 min/wk o endu ance aining) who we e speci ically ained o MUM. All we e heal hy and had incu ed no muscle inju ies in he 6 mon hs be o e he s udy. To a oid bias, no ins uc ions we e gi en abou he ype o aining pe o med he week be o e he compe i ion, bu a hle es we e asked abou i o be e in e p e he baseline se um le els o enzymes and con ac ile p o eins. Physical ac i i y a e he ace was limi ed and massages we e p ohibi ed. The s udy con o med o he Decla a ion o Helsinki o medical esea ch, pa icipan s p o ided w i en in o med consen , and he esea ch was app o ed by he e hics commi ee o he Ca alan Spo s Council (Go e nmen o Ca alonia). Design The s udy design used obse a ional compa ison o esponse in a single g oup o endu ance- ained ama eu a hle es. Me hodology The pa icipan s an in he “Ca alls del Ven ” MUM in 2012, an o icial compe i ion o ganized by Salomon Na u e T ails. I was a ci cula ou e wi h an o icial leng h o 84.84 km (~85 km) and a o al cumula i e ele a ion gain o 12,180 m. The s a o he ace was a 755 m abo e sea le el and he maximum summi achie ed du ing he ail was 2520 m (Figu e 1). Each unne ’s a e age speed was calcula ed acco ding o he o al dis ance un di ided by his o he o icial ime. <<<<<<<<<FIGURE 1>>>>>>>>>>>>> Fou blood samples we e ob ained: 1 day be o e he compe i ion (p e), less han 1 hou a e inishing he compe i ion (pos ), and, because a signi ican deg ee o damage can occu du ing he ace, 24 and 48 hou s a e he beginning o he MUM. A 5-mL blood sample was d awn om an an ecubi al ein. Blood was allowed o clo o 30 minu es in a ube (SST II Ad ance, Bec on Dickinson Vacu aine Sys ems, UK) be o e being cen i uged a 3000 g o 10 minu es a 4°C. Th ee 200- L aliquo s o se um we e s o ed a –80°C un il analysis. CK de e mina ions we e pe o med in an Ad ia 2400 au oma ic de ice (Siemens Medical Solu ions Diagnos ics, Ta y own, NY, USA), and cTnI de e mina ions we e made in a Dimension Clinical Chemis y Sys em au oma ic de ice (Siemens Heal hca e Diagnos ics, Ta y own, NY, USA) wi h an analy ical measu emen ange o 0.017 o 40 ng/mL. To ob ain muscle myosin-iso o m concen a ions in se um, we de eloped an enzyme-linked immunoso ben assay (ELISA-sandwich), which is desc ibed elsewhe e.11 B ie ly, a calib a ion cu e was ob ained by a se ial dilu ion om 0 o 250 ng o pu e myosin om po cine muscle M0273, and he ELISA was comple ed by using monoclonal an imyosin (skele al, as ) clone My-32, monoclonal an imyosin (skele al, slow) clone NOQ7.5.4D, an imyosin polyclonal an ibody M7523, and mouse an i-IGG linked o pe oxidase A6154 (all Sigma Ald ich, Poole, UK). In a-assay coe icien s o a ia ion we e below 8% o FM and below 7.5% o SM. The linea i y o he FM assay esul s was 80%, and i was 90% o he SM assay. S a is ical Analyses The no mali y o each a iable was es ed using he Shapi o-Wilk es . As SM and CK we e asymme ically dis ibu ed, hese a iables we e log- ans o med be o e analysis. One-way epea ed-measu es ANOVA was used o iden i y he e ec o ime on CK ac i i y and SM and FM se um le els. When any signi ican main e ec s we e ound, pai wise - es compa isons wi h a Bon e oni co ec ion we e used. The ime cou se o changes in cTnI se um concen a ion was e alua ed wi h he use o F iedman and Wilcoxon nonpa ame ic es s. E ec sizes (ES) (Cohen d) we e calcula ed o de e mine he p ac ical di e ence be ween baseline alues and se um peaks o enzymes and p o eins. ES alues o abo e 0.8, 0.8 o 0.5, 0.5 o 0.2, and lowe han 0.2 we e conside ed la ge, mode a e, small, and i ial, espec i ely. Pea son co ela ion coe icien was employed o e alua e he associa ion be ween he a iables o in e es . Da a a e p esen ed as mean ± s anda d e o o he mean unless o he wise s a ed. The le el o signi icance was se a P < .01. All s a is ical analyses we e conduc ed using SPSS e sion 20.0 s a is ical-analysis so wa e (SPSS S a is ics, IBM Co p, A monk, NY). Resul s The week be o e he compe i ion, pa icipan s epo ed he use o simila aining s a egies, based on a dec ease in aining olume (km/wk) and an inc ease in in ensi y ( unning a e age eloci y). A he compe i ion, only 1 pa icipan inished he MUM (~85 km). The es o he pa icipan s le he compe i ion a di e en poin s along he ail due o bad wea he condi ions: empe a u e, ange 0.9°C o 13.1°C; ain, ange 0 o 6.1 mm/h; humidi y, ange 90% o 97%; and wind speed (eas -sou heas ), ange 1.1 o 5 m/s. The o al dis ance (km) co e ed and o icial ime (h:min:s) o each pa icipan who decided o ca y on wi h he s udy p o ocol we e de e mined by he las o icial con ol poin passed jus be o e lea ing he MUM. Indi idual a e age speed (km/h) was calcula ed acco ding o hese esul s (Table 1). Wi h espec o biochemical ma ke s, he a e age se um CK ac i i y a baseline was in he clinically no mal ange (35– 175 U/L) and ose signi ican ly om 132 ± 22 U/L (p e) o a peak o 2052 ± 860 U/L (ES = 3.02) less han 1 hou a e inishing he MUM. A e age CK se um ac i i y emained signi ican ly ele a ed 24 hou s (1345 ± 651 U/L) (ES = 2.59) a e he beginning o he compe i ion, bu a clea dec easing end was obse ed (Figu e 2). The only woman who pa icipa ed in he s udy un il he end and also comple ed he whole long-dis ance ail (pa icipan numbe 7) had he highes alues o CK in se um in all samples (Table 1). Almos all pa icipan s we e in he clinically no mal ange o cTnI (<0.017– 0.050 ng/mL), o sligh ly abo e, in all analyzed samples (Table 1). No signi ican inc ease was seen in a e age cTnI se um concen a ions 1 hou a e he MUM ( om 0.018 ± 0.001 ng/mL o Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 3 o 7 0.067 ± 0.028 ng/mL), and alues e u ned o baseline 1 day a e he ail (Figu e 2). Howe e , he a e age alues o cTnI we e highly biased, because pa icipan numbe 7 showed an almos 10- old inc ease in cTnI se um concen a ion 1 hou a e he compe i ion, which emained a ound 4- old ele a ed 24 and 48 hou s a e he s a o he MUM (Table 1). A nonsigni ican sligh inc ease in a e age FM se um concen a ion was obse ed 1 hou a e he compe i ion ( om 1508 ± 222 g/L o 1731 ± 204 g/L), which emained s able un il 24 hou s a e he beginning o he compe i ion (1744 ± 250 g/L) and e u ned o baseline alues a 48 hou s (1520 ± 318 g/L) (Figu e 1). A e age FM se um alues o all ime poin s analyzed we e in he p e iously es ablished no mal ange (> 1000 g/L).11 Finally, no changes in SM we e ound un il 24 hou s a e he s a o he MUM, when SM se um concen a ion ose signi ican ly om 1443 ± 390 g/L o 3743 ± 1110 g/L (ES = 1.34). SM se um ac i i y emained nonsigni ican ly ele a ed 48 hou s a e he ini ia ion o he compe i ion (2828 ± 762 g/L). A e age baseline SM se um le els we e in he no mal ange (> 2000 g/L).11 (Figu e 2). The SM se um peak a 24 hou s a e he s a o he MUM was also highly co ela ed wi h he CK se um peak ound 1 hou a e he compe i ion ( = .884; P = .004) (Figu e 3). Finally, SM was no co ela ed wi h cTnI. <<<<<<<<<TABLE 1>>>>>>>>>>>>> <<<<<<<<<FIGURE 2>>>>>>>>>>>>> <<<<<<<<<FIGURE 3>>>>>>>>>>>>> Discussion To ou knowledge, his is he i s s udy o assess he u ili y o he myosin iso o ms SM and FM as se um biochemical ma ke s o ibe - speci ic muscle damage induced by a MUM in expe ienced endu ance unne s. SM and FM we e compa ed agains CK, a widely used bioma ke o exe cise-induced muscle damage, and cTnI, a speci ic bioma ke o ca diac damage. The no el inding o he cu en s udy was ha only SM se um le els we e signi ican ly aised, while FM se um le els emained almos unal e ed a e he MUM compe i ion. Ano he ema kable inding was ha CK and SM se um peaks we e highly co ela ed. In he absence o myoca dial in a c ion, muscle inju y, o disease, la ge and ime-sus ained inc eases in blood CK ac i i y ha e been widely accep ed as a bioma ke o muscle damage.17 As expec ed, he MUM induced la ge inc eases in CK se um le els, up o an almos 16- old ise 1 hou a e he compe i ion. Signi ican CK se um inc eases in heal hy and well- ained pa icipan s ha e been p e iously documen ed a e MUM compe i ions.5 La ge a iabili y in se um CK concen a ions among pa icipan s is common and has been p e iously desc ibed in expe ienced ul ama a hone s a e 24 hou s o eadmill unning18 and a e a 166-km MUM.6 The eason o his a iabili y s ill emains unclea , bu i has been sugges ed ha suscep ibili y is mainly ela ed o geno ype cha ac e is ics.19 The CK se um peak 1 hou a e he MUM and i s eco e y o e he ollowing 48 hou s we e also consis en wi h p e ious s udies.6 Howe e , CK le els p o ide a g oss indica ion o muscle- ibe damage, because hey canno iden i y he magni ude o damage20 o he ype o ibe s a ec ed.7 Al hough di ec e idence o muscle damage is his ological, o ce-gene a ing capaci y is conside ed a eliable and alid ma ke o muscle damage.21 I has mo eo e been demons a ed ha unning a MUM induces la ge dec eases in he knee-ex enso o ce-gene a ing capaci y (a 35% dec ease a e a 166-km MUM), which a e ela ed o a igue and muscle damage.6 Fu he mo e, di e en s udies ha e ecen ly p oposed sa come e p o eins such as oponin as p oxy ibe - ype-speci ic bioma ke s o muscle damage.7,22 Acco ding o he obse ed ime cou se, molecula mass, and ibe compa men in which hese p o eins a e loca ed, hei ele a ion in se um sugges s mo e se e e damage, signi ying sa come e damage.22 As ibe - ype- speci ic sa come e p o eins, SM and FM could allow o indi ec diagnosis o sa come e damage and he ype o ibe a ec ed.11 Because MUM unning has been demons a ed o induce muscle damage,6 he signi ican inc eases in SM se um concen a ion seen 24 hou s a e he s a o he MUM sugges ed selec i e slow ( ype I) ibe damage, and due o i s ele a ed molecula weigh (493 kDa) and i s ibe in asa come ic compa men aliza ion, inc eased se um SM could indica e sa come e dis up ions o hose ibe s. Mo eo e , since cTnI showed a nonsigni ican se um inc ease 1 hou a e he compe i ion and e u ned o almos baseline alues 24 hou s a e he beginning o he MUM, SM se um inc eases in heal hy indi iduals can be mainly ela ed o skele al-muscle slow- ibe damage, a he han myoca dial damage. Fu he mo e, he e was no s a is ical ela ionship be ween SM and cTnI. Howe e , u he esea ch is needed on cTnI and he dis ance o ul aendu ance e en s, because he only pa icipan who comple ed he whole MUM (pa icipan numbe 7) showed he highes inc eases in cTnI in e e y sample analyzed a e he compe i ion. No changes in FM se um concen a ion we e seen a e he MUM, which indica es ha he as ibe s su e ed no damage o , a leas , less damage han he slow ibe s. Ce ainly, i has been p o ed by his ology ha as ibe s a e mos suscep ible o eccen ic con ac ions,23 and downhill unning, which is a mainly eccen ic ac i i y, induces muscle damage.4 Howe e , since endu ance unne s ha e g ea e le els o slow ( ype I) ibe s,14,15 i is easonable o assume ha slow ( ype I) ibe s a e p edominan ly ec ui ed and damaged du ing a MUM. Howe e , he hypo hesis ha a MUM also induces as ( ype II) - ibe damage canno be comple ely uled ou because CK is non– ibe - ype-speci ic. Mo eo e , baseline FM se um le els we e o e he p e iously desc ibed no mal ange,11 a phenomenon ha can be a ibu ed o he ype o aining (highe in ensi y and less olume) pe o med by he unne s he week be o e he ace, bu his is only specula ion. Fu u e s udies in his a ea should ca e ully analyze he aining s a egies used he week be o e he compe i ion. Due o i s mainly sa coplasmic loca ion, CK is hough o indica e inc eased memb ane pe meabili y a e memb ane dis up ions a ea ly ime poin s24 and he pe oxida ion o memb ane lipids caused by an inc ease in eac i e oxygen species and he ac i a ion o ion (Na+ and Ca2+) channels o se e al days a e exe cise.25 The peak alue o CK se um was ound 1 hou a e he MUM. This could be explained by he long du a ion o he compe i ion, causing a signi ican deg ee o memb ane damage du ing he un.26 I has been demons a ed ha he esealing o a i icially p oduced memb ane dis up ions occu s in less han a minu e,27 bu CK e lux may occu du ing he un due o a con inuous p ocess o memb ane dis up ion ollowed by apid esealing. The CK se um peak pos -MUM and i s eco e y kine ics o e he ollowing 2 days we e consis en wi h p e ious s udies.6 Ne e heless, he a e age 1-hou pos -MUM CK se um peak was lowe han ha ound a e longe dis ance aces.28 In his espec , and acco ding o Waskiewicz e al,28 since he olume o exe cise inc eases he me abolic demands o in acellula Ca2+,26 and i is associa ed wi h muscle-damage indices, i seems easonable o assume ha augmen ed memb ane pe meabili y is ela ed o he dis ance co e ed, as can be seen in Table 1. While pa icipan s 2 and 3, who comple ed 26 km, showed mild inc eases in se um CK ac i i y pos -MUM, pa icipan 7, he only one who comple ed he whole MUM (~85 km), p esen ed he g ea es inc eases in CK se um ac i i y a e he compe i ion. In con as , Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 4 o 7 exe cise in ensi y, exp essed as a e age speed (km/h) a which he pa icipan s an he MUM, showed no end, since pa icipan s le he compe i ion a di e en poin s along he ou e (see Table 1). Fu he esea ch wi h a la ge sample is he e o e needed in his a ea o cla i y he ela ionship be ween biochemical ma ke s o muscle damage and bo h dis ance (km) and a e age speed (km/h). Myosin iso o ms ha e a di e en se um ime cou se han CK.11 Sa come e-p o ein u no e is longe han ha o sa coplasm p o eins,29 so he SM se um peak 1 day a e he MUM can be explained by he inc eased ac i i y o calpain 2 days a e exe cise.30 Calpain is a Ca+2-dependen p o ease. The long du a ion o he MUM may ha e led o la ge inc eases in in acellula Ca+2 du ing he un, which would accele a e calpain deg ada ion and lead o he signi ican inc eases in SM se um 1 day a e he MUM. Calpain emo es myosin om he ilamen ous s uc u e o he sa come e.31 A his ime, inc eased memb ane pe meabili y due o he ac i a ion o s e ch-ac i a ed ion channels25 could lead o a elease o la ge p o eins in o he in e s i ium. Once in he in e s i ial space, p o eins a e mainly anspo ed ia he lympha ic sys em in o he bloods eam, because he capilla y memb anes in skele al muscle a e almos impe meable o p o eins.7–32 The muscle- ibe compa men in which SM is loca ed and i s complex deg ada ion p ocess could explain he delayed inc eases in se um o SM. Finally, CK and SM se um peaks occu ed wi h 1-day di e ence bu we e s ongly co ela ed. Memb ane damage could accompany sa come e dis up ions, due o he igh connec ion be ween myo ib ils, cy oskele on, and memb anes.33 The e o e, i seems ha memb ane damage could be ela ed o subsequen ibe sa come e dis up ion o slow ibe s. P ac ical Implica ions The cu en s udy shows ha SM could p o ide indi ec in o ma ion abou ibe - ype-speci ic sa come e damage 1 day a e a MUM, and since he se um peak o myosin iso o ms is no eached un il 1 day a e a MUM, hey could be used in diagnoses ha a e no made immedia ely a e he compe i ion. Al hough ibe speci ici y canno be de e mined by CK, i s se um ac i i y 1 hou a e a MUM seems o be ela ed o he subsequen SM se um esponse. MUM aine s and unne s should be awa e ha he o al dis ance co e ed could be ela ed o muscle damage, and sha p SM se um inc eases sugges ha a longe eco e y may be needed. Fu he esea ch ega ding MUM dis ance co e ed, aining and pe o mance a iables, and damage deg ee in lic ed o skele al-muscle slow ( ype I) ibe s is needed. Conclusions In summa y, since he e is e idence o muscle damage a e p olonged moun ain unning, an inc ease in SM se um concen a ion a e a MUM could be indi ec e idence o selec i e slow ( ype I) - ibe -speci ic sa come e dis up ions. 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Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 6 o 7 Figu e 2 — Changes in (a) se um concen a ion o c ea ine kinase (CK) (n = 8), (b) slow myosin (SM) (n = 8), and (c) skele al-muscle as myosin (FM) (n = 7) 1 day be o e he compe i ion (p e), less han 1 hou a e inishing he compe i ion (pos ), and 1 and 2 days a e he moun ain ul ama a hon. Da a a e no malized (mean ± s anda d e o o he mean) o p e-moun ain-ul ama a hon alues (100%). **Signi ican ly di e en om p eexe cise alue a P < .01. Figu e 3 — Associa ion be ween se um c ea ine kinase (CK) (na u al log) peak ac i i y 1 hou a e inishing he long-dis ance ail compe i ion (pos ) and slow myosin (SM) (na u al log) peak concen a ion 24 hou s a e he s a o he moun ain ul ama a hon (n = 8). , Pea son co ela ion coe icien . Ca mona e al Moun ain Ul ama a hon and Sa come e Dis up ion Page 7 o 7 Table 1 Concen a ions o Se um C ea ine Kinase, Slow Myosin, and Ca diac T oponin I 1 Day Be o e he Compe i ion (P e), Less Than 1 Hou A e Finishing he Compe i ion (Pos ), and 24 and 48 Hou s A e he Beginning o he Moun ain Ul ama a hon o Each Pa icipan C ea ine Kinase (U/L) Slow Myosin ( g/L) Ca diac T oponin I (ng/mL) Pa icipan Gende km Time (h:min:s) A speed (km/h) P e Pos 24 h 48 h P e Pos 24 h 48 h P e Pos 24 h 48 h 1 M 41 09:39:18 4.25 70 793 933 611 856 703 1674 1333 0.017 0.029 0.017 0.017 2 M 26 06:47:33 3.83 108 363 356 214 811 920 1741 1832 0.017 0.022 0.017 0.017 3 M 26 06:47:16 3.83 156 350 196 126 628 505 1233 963 0.017 0.040 0.017 0,017 4 M 41 09:10:12 4.47 74 2691 1118 468 3097 3159 9812 5543 0.018 0.034 0.017 0.018 5 M 53 10:26:24 5.08 173 856 553 259 842 1225 1928 1162 0.017 0.029 0.017 0.017 6 M 53 12:09:28 4.36 179 2542 1156 531 3338 3205 4553 3979 0.017 0.079 0.017 0.017 7 F 85 11:48:48 7.26 233 7643 5819 2722 988 1404 6999 6361 0.027 0.260 0.115 0.101 8 M 53 12:09:32 4.36 59 1175 626 288 984 1400 2007 1454 0.017 0.043 0.017 0.017 Abb e ia ions: M, male; F, emale; km, kilome e s o moun ain ul ama a hon comple ed; A , a e age.