Alterations of Vertical Jump Mechanics after a Half-Marathon Mountain Running

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1 Journl of Sports Science nd Medicine (6) 5, Reserch rticle Altertions of Verticl Jump Mechnics fter Hlf-Mrthon Mountin Running Rce Elissvet N. Rousnoglou, Konstntinos Noutsos, Achilles Ppps, Gregory Bogdnis 3, Georgios Vgens 4, Ionnis A. Byios nd Konstntinos D. Boudolos Sport Biomechnics Lortory, Deprtment of Sport Medicine & Biology of Exercise; Deprtment of Sport Gmes; 3 Deprtment of Trck & Field; 4 Sttistics Lortory Deprtment of Theoreticl Studies, School of Physicl Eduction & Sport Science, Ntionl & Kpodistrin University of Athens, Greece Astrct The ftiguing effect of long-distnce running hs een exmined in the context of vriety of prmeters. However, there is scrcity of dt regrding its effect on the verticl jump mechnics. The purpose of this study ws to investigte the ltertions of countermovement jump (CMJ) mechnics fter hlfmrthon mountin rce. Twenty-seven runners performed CMJs efore the rce (Pre), immeditely fter the rce (Post ) nd five minutes fter Post (Post ). Instntneous nd ensemle-verge nlysis focused on jump height nd, the mximum peks nd time-to-mximum peks of: Displcement, verticl force (Fz), nterior-posterior force (Fx), Velocity nd Power, in the eccentric (t ECC ) nd concentric (t CON ) phse of the jump, respectively. Repeted mesures ANOVAs were used for sttisticl nlysis (p.5). The jump height decrese ws significnt in Post (-7.9%) ut not in Post (-4.%). Fx nd Velocity decresed significntly in oth Post (only in t ECC ) nd Post (oth t ECC nd t CON ). Α timing shift of the Fz peks (erlier during t ECC nd lter during t CON ) nd ltered reltive pek times (only in t ECC ) were lso oserved. Ensemle-verge nlysis reveled severl time intervls of significnt post-rce ltertions nd timing shift in the Fz-Velocity loop. An overll trend of lowered post-rce jump output nd mechnics ws chrcterised y ltered jump timing, restricted nterior-posterior movement nd ltered force-velocity reltions. The specificity of mountin running ftigue to eccentric muscle work, ppers to e reflected in the different time order of the post-rce reductions, with the eccentric phse reductions preceding those of the concentric one. Thus, those who engge in mountin running should prticulrly consider downhill trining to optimise eccentric musculr ction. Key words: Countermovement jump, post-ctivtion potentition, force-velocity reltionship, ensemle-verge mechnics. Introduction Mrthons nd ultr-mrthons ttrct the interest of reserchers s excellent prdigms of chllenging the limits of humn performnce (Millet nd Millet, ; Vernillo et l., 4). Μountin hlf-mrthons re more populr with recretionl runners (Running USA's Annul Hlf-Mrthon Report, 4), ecuse they comine the chllenge of long-distnce running, while llowing runners to devote shorter periods in trining nd competing. The scrcity of dt regrding the chnges of muscle output following prolonged mountin running (Millet, ) mkes the hlf-mrthon n ttrctive intervention model for studying its ftiguing effects on verticl jump mechnics. This is due to the high running velocity nd rte of energy expenditure ssocited with hlf-mrthons (Sugy et l., 3). In previous long-distnce rod running studies (miniml inclintions) including post-running investigtion of countermovement (CMJ) mechnics, the nlysis ws limited to jump height nd the concentric phse of the jump (Lzzer et l., 4; Lepers et l., ; Millet et l., ; Petersen et l., 7). Considering the complexity of neuromusculr ftigue (Knicker et l., ), these studies my hve underestimted the potentil role of the eccentric phse of musculr ction. However, eccentric musuclr ction, in ddition to constituting fundmentl component of the stretchshortening cycle (Nicol et l., 6), is lso seen s criticl determinnt of downhill mountin running performnce (Millet, ). Much of the ftigue generted in prolonged mountin running is specific to eccentric muscle work (Millet, ; Temesi et l., 4). This specificity is expected to reflect differently on the eccentric nd concentric mechnics of verticl jump fter rce. To dte, CMJ nlysis hs focused on instntneous mechnics nd entire-curve profiles (i.e. ensemle verging). Cormie et l. (9; ) explored CMJ mechnics y exmining pek displcement, force, velocity nd power estimtes, long with time-curve ssessments. Gthercole et l. (5) quntified ftigueinduced ltertions in CMJ mechnics y estimting effect sizes, coefficients of vrition or res under forcevelocity curves, wheres Gollhofer et l. (99) nd McBride et l. (8) exmined verticl displcement loops s lternte mens of ssessing typicl work-energy potentil. Given the scrcity of dt regrding the potentil ltertions in the mechnics of jumping fter longdistnce mountin running, the purpose of this study ws to exmine the ltertions induced in CMJ mechnics fter hlf-mrthon mountin running rce. The ojective ws to use instntneous nd ensemle-verged curve mechnics to identify post-rce ltertions seprtely for the eccentric nd the concentric phse of the verticl jump. Methods Prticipnts Received: 5 Ferury 6 / Accepted: 6 Mrch 6 / Pulished (online): 3 My 6

2 78 Verticl jump fter mountin hlf-mrthon The study orgniser informed the prticipnts (n = 7 men; Tle ) of the elements of the study. Prior to the rce, the sujects provided informed consent nd completed questionnires on their helth sttus nd trining history. The study dhered to the reserch policy of the Ntionl nd Kpodistrin University of Athens. Rce chrcteristics The rce ( In the pth of Deuklion, 7//4, Prnssus Mountin, Delphi, Greece, egn nd completed outside the Museum of Delphi (544 m ltitude, 5 C nd 7% humidity). The ltitude profile of the 3.5 km rce distnce (8 m totl positive elevtion) (Figure ), included n initil 5. km uphill (+.3%), followed y.5 km of lternting downhill nd uphill prts (, 7,,, nd 43 m t ground slopes of 5.8, +4.9,.9, +.4, -3.4 nd +4.7%, respectively) nd finl downhill of 8 km ( 9.9%). Testing procedures Running speed, hert rte nd perceived exertion To ssess the physiologicl effort of the runners during the rce, running speed (km hour - ) nd hert rte (HR) (ets minute - ) dt were collected from 9 prticipnts (Grmin Forerunner 3ΧΤ Grmin Ltd., Hz smpling rte), uploded to the Grmin Connect wesite ( nd then verged t every m. The Grmin 3XT Forerunner relies on Glol Positioning System (GPS) ltimeter, with GPS ccurcy within ± 9 ft (equivlent to ± 5.79 m) (Forerunner 3XT owner s mnul, 3). It is consistent commercil device with.9% vriility of the totl elevtion gin (the sum of the verticl distnce trvelled during uphills nd downhills) (Menspà et l. 4). Also, ech runner s perceived overll effort ws ssessed using the 6 to Borg Scle. CMJ testing nd nlysis Verticl jump testing included CMJs performed on force Tle. Chrcteristics of the prticipnts (n=7 men). Men (SD) Rnge Age (y) 4.3 (3.8) Body height (m).79 (.7) Body mss (kg) 8. (8.9) Mountin rcing experience (y) 5.6 (5.4) -9 Finish time (h:m:s) 3::3 (:35:8) :4:3-4::3 Pre-rce vlue. yr: n=8, -5yrs: n=8, 6-8y: n=6, -5yrs: n=3, 9-yrs: n= n=7 from st to 97 th (:4:8 to 3::4) nd n= from 5 th to 5 th (3:8: to 4::8). Altitude (m) Altitude Speed Running Distnce (Km) Speed (Km. h - ) Altitude (m) Altitude Hert Rte Running Distnce (km) Hert rte (ets. min - ) Figure. The ltitude profile of the hlf-mrthon rce (lck solid line). Men (lck dotted line) nd SD (grey verticl rs) of running speed (Km h - ) (top), nd hert rte (ets/min) (ottom), superimposed on the ltitude profile, for 9 of the 7 prticipnts. Ech running speed nd hert rte vlue represents its verge every m of the running distnce.

3 Rousnoglou et l. 79 plte positioned t 5 m distnce from the finish line (Kistler 986AA, smpling rte t 75 Hz, Kistler Bio- Wre Dt Acquisition nd Anlysis Softwre, version 3..6). The CMJ testing took plce efore the rce (Pre: individul wrm up of out 5 minutes) nd t two time points fter the rce: immeditely fter (Post ) nd five minutes fter Post (Post ). Due to the logistics of the testing protocol, the Post nd Post time points vried mong prticipnts (Post : 4.5 ±.5 minutes; Post :.7 ±.5 minutes). Ech prticipnt performed three consecutive trils of their highest nd most powerful CMJ (with their hnds t mid wist) t Pre, Post nd Post, respectively. Between Post nd Post, the prticipnts kept wrm y wering thletic grments nd moving continuously. All CMJ trils were videotped to llow for offline inspection of proper CMJ execution. The est trils (those with the gretest jump height) in Pre, Post nd Post, respectively, were used for further nlysis. The durtions of the eccentric phse (t ECC ) (from ody weight seline minus 4 stndrd devitions to mximum downwrds displcement) nd the concentric phse (t CON ) (from mximum downwrds displcement to tkeoff) were expressed in solute (s) nd reltive (percentge of totl contct durtion: % t CONTACT ), time units. Instntneous CMJ mechnics The instntneous CMJ mechnics for t ECC nd t CON included the mximum peks of Displcement, verticl force (Fz), nterior posterior force, Velocity, nd Power (Kistler BioWre Dt Acquisition nd Anlysis Softwre, version 3..6). Fz nd Power were normlised to ody weight due to its significnt reduction (-.4%) fter the rce (Pre rce: ± 87.9 N; Post rce: ± 84.7 N, p =.). Τime-to-mximum peks estimtes were derived for Displcement, Fz, Fx, Velocity nd Power nd, they were expressed in solute (s) nd reltive (percentge of totl contct durtion: % t CONTACT ) time units. Ensemle-verged CMJ mechnics The ensemle verged time-curves (Displcement-time, Fz-time, Fx-time, Velocity-time nd Power-time) were derived fter resmpling ll individul CMJ trils (Cormie et l., 9; ; Gthercole et l. 5). Resmpling ws decided so tht 4 time points represented the reltive time from % to % of t CONTACT. The numer of 4 time points ws sed on the tril with the minimum t CONTACT (which ws determined fter inspecting ll trils of Pre, Post nd Post, respectively). The resmpled signls were used to normlise ech individul time curve to t CONTACT. In ddition, the verging of the ensemle curve for ech prticipnt (men time curves) llowed for oth entire nd piecewise pre- to post-rce curve comprisons. The verged Displcement loops (Fz-, Fx-, Velocity- nd Power-Displcement loops) (Gollhofer et l., 99; McBride et l., 8) nd the verged Fz-Velocity loops were plotted to compre the totl loop res (Cormie et l., 9; ; Gthercole et l., 5). In the cse of multiple crossings etween pre- nd post-rce curves, n dditionl comprison of the piecewise loop re ws completed sed on the time intervls defined y these loop crossings. Sttisticl nlysis A series of one-wy repeted mesures ANOVAs were performed to identify the potentil differences of the instntneous CMJ mechnics mong Pre, Post nd Post. In the cse of significnt lck of sphericity (Muchly s W), the ANOVA sttistics were ssocited with proper correction of errors degrees of freedom with either the Greenhouse-Geisser or the Huynd-Feldt fctor (ε) using ε <.75 or >.75, respectively. Significnt F-tests were followed y three Bonferroni-djusted pirwise comprisons (α =.667). The Cohen s d sttistic ws clculted to estimte the effect size (ES) for ech pirwise difference. For ech ensemle-verged curve, the differences etween Pre, Post nd Post were tested for sttisticl significnce using series of repeted mesures ΑNOVAs tht were trgeted to distinct intervls visully identified on ech time curve or loop. To mintin the fmily-wise error rte for ech intervl of interest t the α FW =.5 level, ech ANOVA ws tested. A Bonferoni djustment ws pplied to keep the per-comprison lph level of α = -(.5) /k, with k representing the numer of F-tests pplied to ech seprte intervl. Dt re summrized nd reported s mens nd stndrd devitions (SD). All sttisticl nlyses were completed using the IBM SPSS. (Armonk, NY: IBM Corp.). Sttisticl significnce ws tested t nominl fmily-wise error rte of α =.5. Results Running speed, hert rte nd perceived exertion Running speed ws estimted t 9.7 ±.3 km hour - (rnge: 4.5 to 4 km hour - ) nd hert rte t 63 ± 4 ets minute - (rnge: to 68 ets minute - ) (Figure ). The perceived exertion reched.6 ±.6 units on the 6 to Borg Scle. CMJ testing Jump height decresed fter the rce in oth Post nd Post, ut the difference ws significnt only in Post (p.5) (Tle ). There were no significnt post rce differences in Displcement, neither in t ECC nor in t CON (p >.5) (Tle ). The solute durtions of t CONTACT, t ECC nd t CON did not chnge significntly (Tle ). The reltive durtions of t ECC nd t CON lso did not chnge significntly (t ECC : 65.6 ±.8, 66.4 ± 3.4 nd 65.4 ±.9% t CON- TACT, F =.56, p =., η =.6 nd t CON : 34.4 ±.8%, 33.6 ± 3.4% nd 34.6 ±.9% t CONTACT, F =.56, p =., η =.6, for Pre, Post nd Post, respectively). Instntneous CMJ mechnics As shown in Tle, significnt Pre to Post differences were found for Fx nd Velocity in t ECC, with significnt Post differences of Fx nd Velocity, in oth t ECC nd t CON. Power in t CON ws the only vrile displying significnt difference in oth Post nd Post. Regrding the solute time vriles, the only significnt difference ws identified in the lte pek of Fz during t CON in Post

4 8 Verticl jump fter mountin hlf-mrthon Tle. Men (SD) of jump height nd the dynmic vriles during the eccentric (t ECC ) nd the concentric (t CON ) contct phses, in Pre, Post nd Post. The sttistics of the univrite repeted mesures ANOVAs nd the concomitnt pirwise comprisons re lso noted. Pirwise Comprisons Men (SD) ANOVA Cohen s d effect size (% of difference) Vriles Pre vs Pre vs Post vs Pre Post Post F p vlue η Post Post Post Jump height (cm) *.* 7.94.*.3 (4.7) (4.7) (4.6) (-4.) (-4.) (-8.) DECC (cm) (5.3) (6.5) (5.8) (-5.9) (-.) (-6.8) DCON (cm) (7.) (5.5) (4.63) (-.7) (-.4) (-4.) FzECC (BW) (.4) (.) (.7) (-3.8) (+9.8) (+5.7) FzCON (BW) (.4) (.4) (.3) (.6) (-.3) (-.8) FxECC (N) *.55* *.4 (36.) (4.4) (37.5) (-8.3) (-5.9) (-3.) FxCON (N) * *. (48.) (5.8) (4.5) (-.8) (-4.6) (-4.9) VECC (m s-) *.34* *.3 (.6) (.) (.9) (-.9) (+5.6) (-5.9) VCON (m s-) *.*..*.8 (.9) (.9) (.9) (-.) (-.7) (-3.7) PECCst (W BW-) (.3) (.8) (.9) (-9.) (+3.3) (+3.) PECCnd (W BW-) (.) (.) (.) (-7.) PCON *.4 (W BW-) (.47) (.44) (.45) (+8.8) *significnce of ANOVA nd pirwise comprisons t p.5. D = Displcement, V = Velocity, P = Power st nd nd: the st nd nd, respectively, peks of the Power time curve during the eccentric contct phse. (+.4). (-4.) (-8.8).* (+4.4) tfzecc ECC tfχecc tfy ECC tvecc ECC tpecc tp tpecc tfz CON tfzcon tfy CON tfχcon tv CON tvcon tp tp CON tpcon t contct (%) *Pre *Pre - - Post Post *Pre Pre - - Post Post *Pre - - Post *Pre Pre - - Post *Pre - - Post Pre Post Post *Pre - - Post *Pre Pre - - Post *Post - - Post Figure. Men (SD) of the reltive time vriles (% t CON- TACT) in the eccentric (ECC) nd concentric (ECC) contct phses. The significnt pirwise differences (* p.5) mong Pre (lck rs), Post (light grey rs) nd Post (drk grey rs) re noted. (Tle 3). The reltive time vriles (Figure ) indicte significntly erlier time to pek the eccentric Fz in Post (-.8%) (Pre to Post, p =.5, ES =.48) nd Velocity (Pre to Post : -3.% erlier, p =., ES =.6 nd Pre to Post : = -3.3% erlier, p =., ES =.6). The reltive times to pek the concentric Fz indicte significntly delyed pek in Post (+8.3%, p =., ES =.3) nd in Post (+4.9% lter, p =., ES =.64), with Fz peking significntly erlier in Post thn Post (-3%, p =., ES =.35). Ensemle-verged time curves Figure 3 depicts the ensemle-verged time curves. Time intervls of significnt reductions were identified for Fx (Pre to Post : %; Pre to Post : % nd %), Velocity (Pre to Post : 4 58% nd 75 9%; Pre to Post : % nd %) nd Power (Pre to Post : 33.4% nd %; Pre to Post : %) (Figure. 3). Time intervls of significnt increses nd decreses were indentified for Fz (Pre to Post : %, % nd 85 9%; Pre to Post : %) nd Power (Pre to Post : 3 4.3% nd %; Pre to Post : 3 4.3% nd 58-6%) (Figure 3). Ensemle-verged displcement loops There were no significnt differences in the totl loop re (Figure 4) of the Fz-Displcement loop (F =.84, p =.44, η =.3), the Velocity-Displcement loop (F =

5 Rousnoglou et l. 8 Tle 3. Men (SD) of the time vriles during the eccentric (t ECC ) nd the concentric (t CON ) contct phses, in Pre, Post nd Post. The sttistics of the univrite repeted mesures ANOVAs nd the concomitnt pirwise comprisons re lso noted. Pirwise Comprisons Men (SD) ANOVA Cohen s d effect size (% of difference) Vriles Pre vs Pre vs Post vs Pre Post Post F p vlue η Post Post Post tcontact (ms) () (69) (48) (+.3) (-.4) (-.6) tecc (ms) (89) (33) (8) (+3.4) (-.) (-4.4) tcon (ms) (34) (44) (49) (-.5) (+.) (+.) tfzecc (ms) * *.4 (63) (55) (37) (-.) (-6.3) (-5.7) tfzcon (ms) * *.5 (5) (86) (63) (+4.7) (7.) (-6.6) tfxecc (ms) (4) (57) (3) (-.6) (-3.7) (-.3) tfxcon (ms) (6) (7) (49) (+.5) (-.4) (-.8) tvecc (ms) (73) (97) (65) (-5.) (-8.7) (-3.7) tvcon (ms) () (67) (46) (.) (-.9) (-.8) tpeccst (ms) (7) (77) (49) (-9.6) (-.4) (-3.) tpeccnd (ms) (86) () (8) (-.) tpcon (ms) (5) (7) (5) (+.4) *significnce of ANOVA nd pirwise comprisons t p.5. V = Velocity, P = Power st nd nd: the st nd nd, respectively, peks of the Power time curve during the eccentric contct phse. (-.).3 (-.5) (-.).4 (-.8).9, p =.6, η =.7) nd the Power-Displcement loop (F = 4.55, p =., η =.9). The Fx-Displcement loop totl re (Fig. 4) ws significntly reduced fter the rce (F = 3.6, p =., η =.9 with Pre to Post : p =., ES =.48, Pre to Post : p =., ES =.9 nd Post to Post : p =., ES =.5). The Fz- nd Power- Displcement loops presented multiple crossings (Figure 4), with corresponding time intervls of significnt postrce difference. In the Fz-Displcement loops, these time intervls were identified t % t CONTACT (p =.) nd t % t CONTACT (p =.) for Pre compred to Post nd, t ll time intervls for Pre compred to Post (p =. for ll). In the Power-Displcement loops, the time intervls ssocited with significnt differences were indentified t % t CONTACT (p =.) for Pre compred to Post nd, t % t CONTACT (p =.) nd % t CONTACT (p =.) for Pre compred to Post. Fz-Velocity loops The Fz-Velocity loops presented multiple crossings (Figure 5), with corresponding time intervls of significnt pre to post-rce differences nd reduced loop res during t ECC nd erly t CON (Pre to Post : % t CONTACT, p =., Pre to Post : % t CONTACT, p =.). The loop re incresed towrds the end of t CON (Pre to Post : 94.5 %, p =., Pre to Post : % t CONTACT, p =.). Discussion The min findings of the study were s follows: ) significnt jump height reduction in Post ut not in Post, ) significnt timing ltertions in t ECC s opposed to t CON, c) ltered timing in Fz CON (though its mgnitude did not chnge), d) more pronounced pek mgnitude ltertion in Fx thn in Fz (instntneous mechnics nd ensemle verged curves) nd e) force-velocity nd force-length ltertions, s indicted y the Fz-Velocity nd Fz- Displcement loops, respectively. Τhe running speed (9.7 ±.3 km hour - ) cnnot e compred with previous studies due the lck of mountin hlf-mrthon dt. The men running speed of the present mountin hlf-mrthon is higher thn the men speeds of 5.4 km hour - (Temesi et l., 4), 4. km hour - (Morin et l., ) nd.7 km hour - (Vernillo et l., 4), reported for ultr-mrthons. Hert rte remined stedy t level of 9 ± 5% of the ge-predicted mximum hert rte (HR MAX ), which ws higher thn tht oserved in longer mountin running distnces (85 ± 3% HR MAX, 95 km) (Lzzer et l., 4) ut similr to the one oserved in shorter mountin distnces (9 ± 4% HR MAX, 5.6 km) (Esthope et l., 4). Mintennce of stedy hert rte ws ccomplished y djusting running speed to the ground slope (incresing in downhill slopes nd decresing in uphill slopes), which my e ssocited to the mechnism of pcing strtegy regultion (Tucker nd

6 8 Verticl jump fter mountin hlf-mrthon Displcement (cm) Fz (times BW) Fx (N) Jump initition % t contct tecc % t CONTACT % t contct Mximum eccentric Tke-off displcement tcon Velocity Velocity Velocity (m/s) (m.s (m s - ) - ) Figure 3. Time curves: Displcement (Right top), Fz (Right center), Fx (Right ottom), Velocity (Left top) nd Power (Left ottom) time curves, in Pre (Blck line), Post (Solid grey line) nd Post (Dotted grey line), respectively. Time is expressed s percentge of totl contct durtion (% t CONTACT ). The time intervls of significnt Pre Post (), Pre Post () nd Post Post (c) differences (p.5) re noted Power (Wtts BW (W/BW) - ) Jump initition - tecc % t contct, Pre Post Post tecc: eccentric contct phse tcon: concentric contct phse Mximum eccentric displcement Tke-off tcon % t contct % t CONTACT Nokes, 9). Along with their stisfction of completing the rce, the lst 8 km downhill t 9.9% slope my explin the runners perception of ftigue s medium ecuse this slope pproches the metoliclly optiml running grde nd requires minimum energy expenditure (Snyder et l., ). The decrese in post-rce jump height ws expected due to the functionl ltertions nd the reduced mximl force-generting cpcity induced y prolonged high-intensity running (Millet et l., ; Sugy et l., 3; Vernillo et l., 5). The jump height reductions in Post (-4.%, non significnt) nd Post (-7.9%, significnt) were smller thn the significnt jump height decrese fter 65 km mountin ultr-mrthon (-5.6%, Millet et l., ), 8.4 km flt circuit (-%, Lepers et l., ), s well s, the significnt (-8.8%, Petersen et l., 7) nd non significnt (-7%, Nicol et l., 99) reduction fter rod mrthon. The lck of significnt jump height decrese in Post my e ssocited with the counterction of ftigue y the phenomenon of post-ctivtion potentition, s result of the prolonged eccentric muscle ctions during the lst downhill prt of the rce (Hodgson et l., 5; Tillin nd Bishop, 9). The existence of concurrent ftigue nd potentition hs een previously reported fter ftiguing endurnce running, where the jump height ws incresed while, t the sme time, the pek force ws decresed (Boullos et l., ). The mechnism is yet to e determined with regrd to distnce runners, however, the post-ctivtion potentition profile fter ftiguing running exercises ppers to e protocol dependent (Bullos nd Tuimil, 9). Thus, in protocols inducing mechnicl rther thn metolic ftigue due to high eccentric force requirements nd reltively low energy demnd, s the lst downhill prt of the present rce, one could possily rgue for potentition countercting ftigue

7 Rousnoglou et l. 83 Mximum eccentric displcement tecc, Pre Post Post Mximum eccentric Jump initition Tke-off displcement tecc tcon.5 Pre Pre Post Post Post Post. Jump initition,5,,5 Tke-off tcon Fz (times BW) , Displcement -. (cm) Velocity (m/s) (m s - ),,5, , , -,5 Displcement -, (cm) Fx (N) Fy (N) Power (Wtts BW (Wtts/BW) - ) 3, Displcement (cm) - Displcement (cm) Displcement (cm) - -3 Displcement (cm) Figure 4. Displcement loops: Fz (Right top), Fx (Right ottom), Velocity (Left top) nd Power (Left ottom) Displcement loops, in Pre (Blck solid line), Post (Solid grey line) nd Post (Dotted grey line), respectively. t ECC : eccentric contct phse, t CON : concentric contct phse. The time intervls of significnt Pre Post () nd Pre Post () piecewise loop re differences, due to multiple crossings in Fz nd Power Displcement loops (p.5) re noted. (Bogdnis, ; Newhm et l., 987). In Post of the present study, jump height ws mintined despite the eccentric mechnics impirment, s those were denoted y the decrese of Fx (-8%) nd Velocity (-%), which might possily e mountin running dependence of potentition profile. For certin, the ssocition etween ftigue, endurnce running nd post-ctivtion potentition cnnot e sustntited in the present study; however, it constitutes n issue tht wrrnts further investigtion. In studies investigting potentil ltertions of verticl jump performnce, the nterio-posterior jump mechnics re not usully exmined. Given the reduced jump height, the oserved post-rce Fx reduction cnnot e explined s more verticl jump ut rther s the product of insufficient horizontl momentum tht could, in turn, e converted into potentil energy. The Fx-time curve denotes this reduction t time intervls tht re criticl for full odyweight dynmic control, with the Fx- Displcement loop denoting lowered worklod throughout the totl contct durtion. A numer of studies (Boert nd Vn Ingen Schenu, 988; Boert et l., ; Fourchet et l., ; Jones nd Cldwell, 3) suggest tht muscle ftigue my ffect the execution of the verticl jump with regrd to the nterior-posterior direction of the movement. For instnce, forwrd movement my e restricted, mening tht the ftigued hip extensors void configurtions requiring strong posterior ccelertion (Boert nd Vn Ingen Schenu, 988; Jones nd Cldwell, 3). Similrly, the ftigued tiilis nterior restricts the forwrd movement of the ody to prevent the requirement for posterior ccelertion nd to lign the ground rection force line of ction with the centre of pressure (Boert nd Vn Ingen Schenu, 988; Jones nd Cldwell, 3). The ftigued plntr flexors my lso restrict foot rottion (Boert et l., ) nd the forwrd movement of the centre of pressure long the se of the foot (Jones nd Cldwell, 3). In mountin distnce running, plntr flexors ecome more ftigued compred to dorsi flexors (Fourchet et l., ). This

8 84 Verticl jump fter mountin hlf-mrthon imlnce my prevent lignment of the ground rection force with the centre of pressure. The vrile terrin of mountin rce my increse muscle ftigue through unpredicted nd continuously chnging posturl control requirements (Degche et l., 4), condition tht my prtilly ccount for the significnt ltertions of the nterior-posterior component of the ground rection force. Fz (times BW), Velocity (m s (m/s) ) - Figure 5. Force-velocity loops, in Pre (Blck solid line), Post (Grey solid line) nd Post (Grey dotted line). No significnt difference in the totl loop re (p.5). The time intervls of significnt Pre-Post () nd Pre-Post () piecewise loop re differences due to multiple crossings re noted. The ltertion in the timing of the jump vriles is of prticulr importnce. The limited studies on CMJ performnce fter mountin running do not provide timing dt. In rod mrthon study, decrese in CMJ height (-8.8%) ws ccompnied with n lmost triple increse of eccentric (+%) over totl (+7.3%) contct phse (Petersen et l., 7). A short eccentric phse is prerequisite for stretch-induced force enhncement, incresed conservtion of elstic energy (Sunders et l., 4) nd greter force potentition (Vn Ingen Schenu et l., 997). Despite the decrese in jump height, the ftigued jumps of the present study were performed with the sme reltive timing of totl contct durtion, which is in greement with previous studies reporting insignificnt chnges of the eccentric nd concentric contct phses in ftigued CMJs (Rodcki et l., ). However, roust templte motor progrm irrespective of ftigue (Rodcki et l., ) cnnot e completely implemented, due to the ltered reltive timing of the vriles within the time limits of the eccentric nd the concentric jump phses. A prolem when individuls execute verticl jumps is the efficient trnsfer of the trunk nd lower ody rottionl energies into the mximum verticl tke-off velocity (Boert nd Vn Ingen Schenu, 988). For the production of the required rottionl energy under ftigued conditions, it is criticl tht the chnges of motor templte still llow for n optiml timing of segmentl displcement. A timing ltertion my influence verticl jump performnce y disrupting the time difference etween the segmentl ccelertion mxim (Hochmuth, 975). Timing ltertion my lso decrese the shrpness in the ctivtion of the muscles, leding to poor use of mechnicl energy nd incresed metolic energy in the completion of the movement (Luhtnen nd Komi, 978). The erlier timing of Fx, Velocity nd Power whithin t ECC, highlights the ltered timing pttern during the eccentric phse of the jump, which most likely reflects n incresed pssive muscle stiffness (Ishikw et l., 6), triggering n erlier decrese in the ody s grvittionl descent. The lter timing of Fz within the concentric phse of the jump my e ttriuted to reduced strength (Cormie et l., 9) or lower eccentric velocity (Hrmn et l., 99). Of prticulr interest is the opposite direction in the ltered timing of Fz during t ECC (erlier in t CONTACT ) nd during t CON (lter in t CONTACT ). The expnsion of the time intervl defined y the Fz peks in t ECC nd t CON is most possily ssocited with the dely etween the eccentric nd the concentric muscle ctions, clrifying ftigued stretch-shortening cycle (Nicol et l., 6). This reltive time expnsion lso shows n ltered force-velocity reltion, s depicted in the Fz-Velocity loop (Fig. 5), which results from the chnge in the timing rther thn the mgnitude of the produced verticl force. An ltered forcelength reltionship is most likely indicted in the modified Fz-Displcement loop, proly due to the downhill sections of the rce tht impose prolonged worklod on the knee extensors over greter muscle length (Mizrhi et l., ). The coexisting ltertions in the Fz-Velocity nd the Fz-Displcent loops denote tht hlf-mrthon mountin running induces fundmentl chnges in the verticl jump muscle mechnics. These chnges led to lower post-rce jump height, while t the sme time, greter worklod (Fz-Displcement loop) nd greter power (Power-Displcement loop) re produced during the lte prt of the concentric phse, where the ody must return to the initil position of zero displcement. Considering tht pek velocity in the eccentric phse of the CMJ lso decreses post-rce, the oserved ltertions in the Fz- Velocity nd Fz-Displcement loops my lso e ssocited with lower ccelertion levels t the eginning of, nd throughout the concentric phse of the jump (Cormie et l., 9). Conclusion The CMJ mechnics were significntly ltered following the hlf-mrthon mountin running rce, with significnt jump height reduction in Post ut not in Post. The post rce ftigued CMJ mechnics were chrcterised y ltered jump timing, restricted nterior-posterior movement nd ltered force-velocity reltions, tht my denote disrupted energy trnsformtion from rottionl to potentil. The specificity of mountin running ftigue to eccentric muscle work, is most likely highlighted in the different time order of the post-rce reductions, where the eccentric phse reductions preceded those of the concentric one. Thus, those who engge in mountin running should prticulrly consider downhill trining to optimise eccentric musculr ction.

9 Rousnoglou et l. 85 Acknowledgements The uthors hve no conflict of interest to declre. The experiments comply with the current lws of the country in which they were performed. References Boert, M.F. nd vn Ingen Schenu, G.J. (988) Coordintion in verticl jumping. Journl of Biomechnics, Boert, M.F., Houdijk, H., de Koning, J.J. nd de Groot, G. () From one-legged verticl jump to the speed-skting push-off, A simultion study. Journl of Applied Biomechnics 8, Bogdnis, G.C. () Effects of physicl ctivity nd inctivity on muscle ftigue. Frontiers in Physiology 3, 4. Boullos, D.A., Tuimil, J.L., Alegre, L.M., Iglesis, E. nd Lusquiños, F. () Concurrent ftigue nd potentition in endurnce thletes. Interntionl Journl of Sports Physiology nd Performnce 6, Boullos, D.A. nd Tuimil, J.L. (9) Postctivtion potentition in distnce runners fter two different field running protocols. Journl of Strength nd Conditioning Reserch 3, Cormie, P., McBride, J.M. nd McCulley, G.O. 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10 86 Verticl jump fter mountin hlf-mrthon Vernillo, G., Svoldelli, A., Zignoli, A., Skfids, S., Fornsiero, A., L Torre, A., Bortoln, L., Pellegrini, B. nd Schen, F. (5) Energy cost nd kinemtics of level uphill nd downhill running, ftigue-induced chnges fter mountin ultrmrthon. Journl of Sports Science 339, Vernillo, G., Svoldelli, A., Zignoli, A., Trucchi, P., Pellegrini, B., Millet, G.P. nd Schen, F. (4) Influence of the world s most chllenging mountin ultr-mrthon on energy cost nd running mechnics. Europen Journl of Applied Physiology 4, Key points The 4.% reduction of jump height immeditely fter the rce is not sttisticlly significnt The eccentric phse ltertions of jump mechnics precede those of the concentric ones. Force-velocity ltertions present timing shift rther thn chnge in force or velocity mgnitude. AUTHOR BIOGRAPHY Elissvet N. ROUSANOGLOU Assistnt Professor in Sport Biomechnics, School of Physicl Eduction nd Sport Sciences, Ntionl nd Kpodistrin University of Athens, Greece Degree Msc, PhD Muscle mechnics, EMG, motor control E-mil: erousn@phed.uo.gr Kostntinos NOUTSOS Assistnt Professor in Hndll Specilized Trining, School of Physicl Eduction nd Sport Sciences, Ntionl nd Kpodistrin University of Athens, Greece Degree PhD Expertise differences in hndll performnce, Sport-specific nthropometric differences E-mil: knutsos@phed.uo.gr Achilles PAPPAS Post-Grdute student in Biology of Exercise, Sport Biomechnics L, School of Physicl Eduction nd Sports Science, Ntionl nd Kpodistrin University of Athens, Greece Degree Msc in progress Neuromusculr ftigue E-mil: ppps@phed.uo.gr Gregory C. BOGDANIS Deprtment of Physicl Eduction nd Sports Science, University of Athens, Greece Degrees MSc, PhD Muscle metolism, neroic exercise, muscle dmge, muscle power, jumping E-mil: gogdnis@phed.uo.gr Georgios VAGENAS Professor of Sports Sttistics, Deprtment of Theoreticl Studies, School of Physicl Eduction nd Sport Sciences, Ntionl nd Kpodistrin University of Athens, Greece Degrees MA, PhD Quntittive nlysis of sports performnce, socio-economic fctors nd Olympic success; pplied kinesiology, lterlity nd functionl symmetries nd injuries in thletes, methodologicl nd sttisticl qulity in sports science reserch. E-mil: gvgens@phed.uo.gr Ionnis A. BAYIOS Professor in Hndll Specilized Trining, School of Physicl Eduction nd Sport Sciences, Ntionl nd Kpodistrin University of Athens, Greece Degree PhD Expertise differences in hndll performnce, Sport-specific nthropometric differences E-mil: iyios@phed.uo.gr Konstntinos D. BOUDOLOS Professor in Sport Biomechnics, School of Physicl Eduction nd Sport Sciences, Ntionl nd Kpodistrin University of Athens, Greece Degree PhD Humn performnce, Kinesiology of thletic nd dily movement, Enhncement of thletic technique, Sport-specific ge differences, Ergonomics for dily living. E-mil: countol@phed.uo.gr Elissvet Rousnoglou Ntionl & Kpodistrin University of Athens, School of Physicl Eduction & Sport Science, Ethnikis Antistsis 4, Dphne, 737, Athens, Greece