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R., revue sur l'entraînement par intervalles, 2024",null,{"h1":22,"summary":23,"purpose":34,"execution":78,"feel":100,"mistakes":107,"not_for":144,"faq":152,"evidence":189},"Fast-start VO₂max intervals on the bike (5 × 5 min)",{"type":24,"children":25},"root",[26],{"type":27,"tag":28,"props":29,"children":30},"element","p",{},[31],{"type":32,"value":33},"text","Fast-start VO₂max intervals: five 5-minute efforts, each opening with 2 minutes at 120–130% of FTP and finishing with 3 minutes at 104–110%, with 3 minutes' recovery. A 62-minute session for advanced riders already used to VO₂max work.",{"adaptation":35,"for_whom":47,"when":71},{"type":24,"children":36},[37,42],{"type":27,"tag":28,"props":38,"children":39},{},[40],{"type":32,"value":41},"Your oxygen uptake doesn't jump straight to its peak: at the start of a steady effort, it takes a minute or two to get close. Over a 5-minute interval, a good chunk of the time is spent getting there. The fast start shortens that phase: 2 minutes at 120–130% of FTP drive your breathing and heart rate close to the ceiling, then you drop to 104–110% to finish without blowing up, while staying right next to your VO₂max.",{"type":27,"tag":28,"props":43,"children":44},{},[45],{"type":32,"value":46},"The idea comes from Bent Rønnestad and his group. It has been measured within a single session: a 2-minute fast start increased the time spent near VO₂max, shorter starts didn't. Nobody has yet checked whether that turns into bigger gains over several weeks.",{"type":24,"children":48},[49],{"type":27,"tag":28,"props":50,"children":51},{},[52,54,61,63,69],{"type":32,"value":53},"Advanced riders with several blocks of ",{"type":27,"tag":55,"props":56,"children":58},"a",{"href":57},"\u002Fen-GB\u002Flibrary\u002Fcycling\u002Fvo2max\u002Fcycling-vo2max-5min-intervals",[59],{"type":32,"value":60},"4 × 5 min",{"type":32,"value":62}," or the ",{"type":27,"tag":55,"props":64,"children":66},{"href":65},"\u002Fen-GB\u002Flibrary\u002Fcycling\u002Fvo2max\u002Fcycling-norwegian-4x4",[67],{"type":32,"value":68},"Norwegian 4 × 4",{"type":32,"value":70}," behind them, who want to get a bit more out of each interval. A recent FTP is essential: a start at 120–130% won't forgive an inflated FTP.",{"type":24,"children":72},[73],{"type":27,"tag":28,"props":74,"children":75},{},[76],{"type":32,"value":77},"One or two VO₂max sessions a week at most, and this counts as one: it replaces a classic 4 × 5 rather than joining it. Keep an easy day before and after, and avoid the day before a race. If five efforts feels like a lot, start with four and add the fifth once the end of the last one stays clean.",[79,86,93],{"type":24,"children":80},[81],{"type":27,"tag":28,"props":82,"children":83},{},[84],{"type":32,"value":85},"15 minutes building from 45 to 75% of FTP, in 5-minute steps. For a session this hard, you can add one or two 20-second pick-ups at the end, without tiring yourself.",{"type":24,"children":87},[88],{"type":27,"tag":28,"props":89,"children":90},{},[91],{"type":32,"value":92},"Five 5-minute efforts, each in two parts: 2 minutes at 120–130% of FTP, or 300 to 325 W for an FTP of 250 W, then 3 minutes at 104–110%, or 260 to 275 W. Between efforts, 3 easy minutes at 50–60%. The start is very hard but controlled: a firm wind-up, not a sprint. When you drop the power, keep the same cadence and let your breathing stay high: that's the point. On a turbo in ERG mode, the switch happens by itself.",{"type":24,"children":94},[95],{"type":27,"tag":28,"props":96,"children":97},{},[98],{"type":32,"value":99},"10 very easy minutes at 40–55% of FTP. If the 104–110% part fell apart on the last efforts, bring the start down towards 120% next time rather than cutting the finish.",{"type":24,"children":101},[102],{"type":27,"tag":28,"props":103,"children":104},{},[105],{"type":32,"value":106},"The first 2 minutes are very hard, so much so that the drop feels like relief. It isn't: your breathing stays maxed out to the end of the effort, and the 3 minutes at 104–110% feel longer than they are. Guide: 9 out of 10 on the start, barely less at the end.",[108,117,126,135],{"title":109,"body":110},"Turning the start into a sprint",{"type":24,"children":111},[112],{"type":27,"tag":28,"props":113,"children":114},{},[115],{"type":32,"value":116},"Going flat out, out of the saddle, ruins the next 3 minutes. Hold the start at 120–130%, seated, like a very hard 2-minute effort. If you're well above the range after 15 seconds, you've gone too hard.",{"title":118,"body":119},"Easing off after the start",{"type":24,"children":120},[121],{"type":27,"tag":28,"props":122,"children":123},{},[124],{"type":32,"value":125},"Dropping to 104–110% is about holding on, not recovering. Slide back down towards FTP and you lose exactly the time near VO₂max the start was meant to buy.",{"title":127,"body":128},"Fixing the finish instead of the start",{"type":24,"children":129},[130],{"type":27,"tag":28,"props":131,"children":132},{},[133],{"type":32,"value":134},"If the final minutes become impossible, don't cut the end of the effort: bring the start down to 120%, or a touch lower. The settled part is the heart of the session.",{"title":136,"body":137},"Stacking it on another VO₂max session",{"type":24,"children":138},[139],{"type":27,"tag":28,"props":140,"children":141},{},[142],{"type":32,"value":143},"This format is harder than a steady 4 × 5. It takes that session's place in your week, never an extra slot.",{"prerequisites":145,"avoid_if":148},[146,147],"A recently measured FTP.","Several weeks of steady-power VO₂max intervals.",[149,150,151],"You're tired, or a race or long ride is planned for the next day.","You're coming back from a break: go back to steady intervals first.","You have doubts about your health: get medical advice before near-maximal efforts.",[153,162,171,180],{"question":154,"answer":155},"What power should I ride fast-start VO2max intervals at?",{"type":24,"children":156},[157],{"type":27,"tag":28,"props":158,"children":159},{},[160],{"type":32,"value":161},"Start at 120–130% of FTP for 2 minutes, then 104–110% for 3 minutes. For an FTP of 200 W: 240 to 260 W, then 208 to 220 W. For 250 W: 300 to 325 W, then 260 to 275 W. For 300 W: 360 to 390 W, then 312 to 330 W. These are approximate conversions of the intensities described in the studies.",{"question":163,"answer":164},"Why a 2-minute fast start and not a shorter one?",{"type":24,"children":165},[166],{"type":27,"tag":28,"props":167,"children":168},{},[169],{"type":32,"value":170},"Because it's the only length that showed an effect. In measurements by Rønnestad's group, a 2-minute fast start increased the time spent near VO₂max, whereas starts of 90 seconds or 1 minute made no difference. The likely reason: oxygen uptake needs enough time to reach its ceiling before you back off.",{"question":172,"answer":173},"Fast start or variable intensity: which should I choose?",{"type":24,"children":174},[175],{"type":27,"tag":28,"props":176,"children":177},{},[178],{"type":32,"value":179},"Both aim for the same thing, more time near your VO₂max. The fast start front-loads the effort, then lets you hold a steady power: easier to pace. Variable intensity spreads three surges through the effort: more engaging, and more demanding on your concentration. Swap between them from one block to the next if you like variety.",{"question":181,"answer":182},"Can I do fast-start intervals outdoors?",{"type":24,"children":183},[184],{"type":27,"tag":28,"props":185,"children":186},{},[187],{"type":32,"value":188},"Yes, with a power meter and a clear 5-minute stretch of road, ideally a gentle drag. The tricky part is holding 120–130% without overshooting at the start, then dropping at the right moment. On a turbo in ERG mode, both happen for you, which makes the session more precise.",{"level":190,"text":191},"limited",{"type":24,"children":192},[193],{"type":27,"tag":28,"props":194,"children":195},{},[196],{"type":32,"value":197},"Work by Bent Rønnestad and colleagues, partly in cross-country skiers, summarised in a review by Mølmen and Rønnestad (2024). The studies describe a start at about 100% of maximal aerobic power (or speed), then about 85%. The results are mixed: a 2-minute fast start increased the time spent above 90% of VO₂max, whereas 1 min 30 or 1 min starts made no difference. Over 8 × 60 s, decreasing, increasing or constant power gave the same result (2021 study). No multi-week study was found. Converting this to 120–130% then 104–110% of FTP is a Wattson approximation, as are the warm-up and cool-down. Bottom line: good evidence on single-session measures, weak on long-term 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