29.08.2009 » Toptriatleten als proefkonijn

Door marketingjongens wordt te pas en te onpas wel eens met ?wetenschappelijk bewijsmateriaal? geschermd, denk vb. maar aan die sportdrank of het materiaal waarmee je rondfietst. Ten eerste is dan wel de vraag in hoeverre men systematisch te werk gegaan is bij het verzamelen en analyseren van gegevens. Ten tweede stelt zich de vraag naar de representativiteit van de proefgroep. Topatleten laten zich zelden strikken als proefkonijn. Alles wat hun tot in de puntjes uitgekiende trainingsregime kan verstoren is uit den boze. Per slot van rekening hebben ze jarenlang zo weinig mogelijk aan het toeval overgelaten en niet zelden enorme opofferingen gedaan om zich geen strobreed in de weg te laten leggen als het op presteren aankomt ? prestaties waaraan vaak evenveel geld verbonden is als emotionele waarde en roem. Toch slagen wetenschappers er af en toe in om elite-atleten voor hun kar te spannen met een vernuftig experiment.

Het eerstvolgende onderzoek vond plaats tijdens de ITU-wedstrijd in Lausanne, in het jaar 2002.

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J Sci Med Sport. 2008 Jul;11(4):424-32.

Pacing during an elite Olympic distance triathlon: comparison between male and female competitors.

Vleck VE, Bentley DJ, Millet GP, Bürgi A. University of Westminster, Department of Human and Health Sciences, UK.

This study investigated whether pacing differed between 68 male and 35 female triathletes competing over the same ITU World Cup course.

Swimming, cycling and running velocities (m/s and km/h) were measured using a global positioning system (Garmin, UK), video analysis (Panasonic NV-MX300EG), and timing system (Datasport, Switzerland). The relationship between performance in each discipline and finishing position was determined.

Speed over the first 222 m of the swim was associated with position (r=-0.88 in males, r=-0.97 in females, both p<0.01) and offset from the leader, at the swim finish (r=-0.42 in males, r=-0.49 in females, both p<0.01). The latter affected which pack number was attained in bike lap 1 (r=0.81 in males, r=0.93 in females, both p<0.01), bike finishing position (both r=0.41, p<0.01) and overall finishing position (r=0.39 in males, r=0.47 in females, both p<0.01). Average biking speed, and both speed and pack attained in bike laps 1 and 2, influenced finishing position less in the males (r=-0.42, -0.2 and -0.42, respectively, versus r=-0.74, -0.75, and -0.72, respectively, in the females, all p<0.01). Average run speed correlated better with finishing position in males (r=-0.94, p<0.01) than females (r=-0.71, p<0.001). Both sexes ran faster over the first 993 m than most other run sections but no clear benefit of this strategy was apparent.

The extent to which the results reflect sex differences in field size and relative ability in each discipline remains unclear.



Voor het volgende onderzoek fungeerden 5 mannen en 5 dames van het Franse Nationale Triathlon team. Op de wereldranglijst bekleedden ze een plaats tussen nr. 7 en 52, dus absolute top (ter vergelijking: Peter Croes staat op de 33ste plaats, Stijn Goris 117de). De gegevens waarop de studie gebaseerd is werden verzameld tijdens de ITU World Cup in Beijing (test event voor de O.S.), op 24 september 2006 (waar ook Peter Croes en Axel Zeebroek deelnamen).

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Med Sci Sports Exerc. 2009 Jun;41(6):1296-302.

Distribution of power output during the cycling stage of a Triathlon World Cup.

Bernard T, Hausswirth C, Le Meur Y, Bignet F, Dorel S, Brisswalter J. Handibio Laboratory, University of Sud Toulon-Var, La Garde, Cedex, France.

PURPOSE: The aim of this study was to evaluate the power output (PO) during the cycle phase of the Beijing World Cup test event of the Olympic triathlon in China 2008.

METHODS: Ten elite triathletes (5 females, 5 males) performed two laboratory tests: an incremental cycling test during which PO, HR at ventilatory thresholds (VT1 and VT2), and maximal aerobic power (MAP) were assessed, and a brief all-out test to determine maximal anaerobic power output (MAnP). During the cycle part of competition, PO and HR were measured directly with portable device. The amount of time spent below PO at VT1 (zone 1), between PO at VT1 and VT2 (zone 2), between PO at VT2 and MAP (zone 3) and above MAP (zone 4) was analyzed.

RESULTS: A significant decrease in PO, speed, and HR values was observed during the race. The distribution of time was 51 +/- 9% for zone 1, 17 +/- 6% for zone 2, 15 +/- 3% for zone 3, and 17 +/- 6% was performed at workloads higher than MAP (zone 4). From HR values, the triathletes spent 27 +/- 12% in zone 1, 26 +/- 8% in zone 2, and 48 +/- 14% above VT2.

CONCLUSIONS: This study indicates a progressive reduction in speed, PO, and HR, coupled with an increase in variability during the event. The Olympic distance triathlon requires a higher aerobic and anaerobic involvement than constant-workload cycling exercises classically analyzed in laboratory settings (i.e., time trial) or Ironman triathlons. Furthermore, monitoring direct PO could be more suitable to quantify the intensity of a race with pacing strategies than classic HR measurements.




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En voor wie zich ooit al afgevraagd heeft wat het voordeel is van het dragen van een wetsuit tijdens het zwemmen, nog de volgende uitsmijter:



J Sci Med Sport. 2008 Jul;11(4):417-23.

Factors related to the advantageous effects of wearing a wetsuit during swimming at different submaximal velocity in triathletes.

Tomikawa M, Shimoyama Y, Nomura T. KEN'S Co., Ltd, Tokyo, Japan.

This study was designed to compare the effects of wetsuit (WS) to swimsuit (SS) at identical relative velocities in a swimming flume.

Thirteen triathletes performed a continuous progressive swimming test and submaximal steady state swimming tests with a WS and with a SS. Maximal oxygen uptake (VO2max) and the associated velocity at which the VO2max was achieved (VVO2max) were determined during the continuous progressive tests. Two 5 min swims (at 60% VVO2max (V(60%)) and 80% VVO2max (V(80%))) were then conducted to measure VO2max, blood lactate concentration (LA), rating of perceived exertion (RPE), the energy cost of swimming (Cs), stroke rate (SR) and stroke length (SL).

No difference was found in VO2max, but VVO2max with a WS was 5.4% higher than with a SS. VO2 with a WS was lower than with a SS alone at V(60%), but not at V(80%). Cs with a WS was lower by 14.4% at V(60%) and 7.5% at V(80%) than with a SS. No differences were found in LA and RPE between suit conditions during both submaximal swims. Wearing a WS did not affect SL, but SR tended to be higher in a WS for both submaximal velocities.

These results suggest that the benefits of wearing a WS are not only improvement in swimming performance and propulsion efficiency, but reduction in gross energy consumption in the swimming portion of triathlon races. Furthermore, when wearing a WS, incremental changes in SR rather than SL are associated with improved swimming performance.




PS: eventuele verdere vragen aangaande deze onderzoeken zijn steeds welkom via het contactformulier op deze website.

 

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