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[[High Intensity Interval Training]] has been shown to be is a highly effective form of exercise, but running at very high intensities is problematic. If you run much faster on level ground, your stride becomes a radically different as you are sprinting more than running, and this is an elongation of your stride increases injury risk quite dramatically. It's also very hard to keep your running form under control at such high speed and high intensity. Running uphill alleviates this someone, but it's hard to find a hill long enough and steep enough, and even then, the biomechanics are different enough that you're training somewhat different muscle groups. These differences are one of the reasons for the increase in injury risk. One solution to the injury risk is to train on a stationary bike. If you're out of the saddle, your muscle recruitment is somewhat similar to running, but with much a lower injury risk. This page is a guide to performing HIIT on a stationary bike for runners. Some of this may apply to cyclists, but a cyclist will have somewhat different requirements as they will perform more than just HIIT on the stationary bike.

Unlike running, you'll need rather more equipment. I initially brought the Wahoo Kickr Snap, a "wheel-on smart trainer" which is cycling a talk that means you put a bike with its rear wheel in place on to the trainer. It's a trainer that I liked was quite affordable, but I found the trainer became such a core part of my training regime that I upgraded to the Tacx Neo2. This is a top -end bike trainer, that is more responsive to changes in resistance, as well as much quieter. However, the biggest thing that attracted me to the Neo2 is that you don't have to calibrate it. Most bike trainers, including the Kickr, have to do a "spin down". As the name suggests you ride the bike until you hit the specified speed, and then stop pedaling. The app measures how long it takes for the wheel to stop spinning, and uses that time to estimate the braking forces and inertia. I found this tedious, and it was worth it to me to know that the power was accurate every time.These "smart trainers" are more than just marketing, and it means that the trainer can be controlled wirelessly. There are several wireless control modes, such as simulation where software tells the trainer to mimic going uphill and ERG mode, where the trainer requires you to generate a certain fixed amount of power. ERG mode is a bit weird at first, as it means that the faster you pedal, the less resistance, and the slower you pedal the more resistance. The trainer maintains whatever resistance is required to keep your power output of at the target. The Kickr can be controlled using either Bluetooth or Ant+, and transmits your power and speed over both simultaneously.

I used a mountain bike that's nearly 30 years old, as things like weight don't really matter. I did put on a tire specifically designed for use on an indoor trainer, as the slightly nobly tires that were on the bike made an outrageous noise. It doesn't matter about brakes, or steering, as it's a stationary bike after all. You do want comfortable handlebars, and I much prefer the straight bars of a mountain bike to the drop handlebars of a road bike. You should be spending a lot of your time out of the saddle, so that's not as important for a runner just doing HIIT as it would be for a cyclist. You certainly don't need to spend loads of money on this gorgeous leather saddle, even though its design has been unchanged for over 100 years. When I got the saddle I thought it was a gratuitous waste of money, loosely justified as an "objet d'art", but having used it since early 2018, the comfort has justified the price. While I don't spend as many hours in the saddle as a cyclist would, having a comfortable interface doesn't make a difference.

I did end up refurbishing the group set, mostly because my old mountain bike was five -speed, and my new TACX trainer wasn't compatible, though my bottom bracket bearings were also disintegrating. I ended up going with a Shimano Zee/Deore 1x10 drivetrain, though in practice I don't think I've shifted gear once since I got the bike set up. A single -speed would have been cheaper with hindsight. If I'm honest, I really only have the frame, forks, and handlebars from the original bike, and I've replaced pretty much everything else.

Software that runs on iOS uses Bluetooth, and of course , only one device can receive data from a Bluetooth sensor. This means that if you have a Bluetooth heart rate monitor, it can only be paired with iOS or a sports watch, not both at the same time. The same is true of the Bluetooth communication from the Kickr.

most of the training software available will allow you to create a structured work outworkout. This allows you to define the workout as something like two minutes at 100w, followed by repeats of 30s at 200w with 30s recovery at 100w. As noted above, if you say 100w, the trainer will vary resistance to keep power output constant. The software and trainer can also do a fixed resistance, so the faster you pedal the more power output, typically configured as a percentage slope. The big problem I've found is that you can do power output by time, or slope by distance, but there are few options for doing slope by time. The only software I found that will do slope by time is the Tacx, though I heavily modified Golden Cheetah to support this for my personal use. If you know of other software that does structured workouts using slope by time, please let me know.

You can use Zwift for free, but you're limited to 25 km per calendar month. That's really not very much, and probably not enough to support more than 2, maybe 3 HIIT sessions per month. Zwift works out your based on your power output, so cranking out lots of watts will get you through your free kilometers even faster. The good news is that Zwift has a nice visual workout editor that allows you to put together your HIIT session fairly easily. Zwift provides a virtual riding environment that's gorgeous, and each interval transition is shown by a translucent virtual barrier, so you can see the transitions coming up. I found this was a great for preparing for an upcoming interval, or holding on for an upcoming rest period. Because of Zwift scales your speed to your power output, you get a nice sense of achievement when you're pushing hard. If you do much indoor cycling, then I think it's worth considering a subscription to Zwift. The software is available as an app for an iOS or android Android device, and I found it worked nicely on an iPad. There is a PC version, but I never got that to work properly (I didn't try terribly hard.)

File:Zwift (2).png| Post -workout analysis; fairly simple but a nice overview.

Golden Cheetah is free, open -source software that runs on a PC, Mac, or Linux server. As you might expect from something that runs on Linux, it's not terribly user-friendly, but amazingly powerful. The user interface paradigm is different to from any other software I've tried, and really takes some getting used to. Even after using it for a while, it still feels clunky and awkward. That said, the workout editor is by far my favorite, being both powerful and quick to use (once you've climbed the steep and painful learning curve.) It's always a bad sign when you need to watch a video to understand how to use the software, but it's the only way. Check out [https://vimeo.com/192126358 Workout Editor] and [https://vimeo.com/152278941 Workout Editor QWKCODE and Edit/Run] videos. You can edit a workout visually, but you can also enter what they call "QWKCODES", which is a text -based entry system. So "30s@150" is 30 seconds at 150 watts. You can specify a ramp, so "30s@150-180" will ramp up from 150 watts to 180 watts over 30 seconds. You can add recovery periods, so "30s@350r30s@125" will do 350 watts for seconds then 125 watts for 30 seconds. You can add repeats by saying "6x30s@350r30s@125" for six repeats. Times can be in minutes, so "1m" for 1 minute. There may be more, but I found no documentation.

Golden Cheetah doesn't provide any kind of simulated world, but it does provide a wealth of data that they can display in real -time. You'll need an Ant+ USB adapter, but GC supports a wide variety of sensors.[[File:GC realtime.png|center|thumb|300px| The real -time display, with the workout being filled in with actual data from the ride. ]]

The Tacx software is available for Windows, Mac, iOS, and androidAndroid, but only supports Tacx trainers. It has a monthly subscription to get simulated rides that use real video footage rather than 3-D rendering, but a lot of the functionality is available without a subscription. The killer feature of the Tacx software for me is the ability to do slope by time.

I really expected the Wahoo app to provide all the basic functionality you'd need. Sadly, this is not the case. You can do some manual control of resistance, but there's no way of using it to run a predefined HIIT session. You do need to use the Wahoo app to calibrate the trainer (see above), plus there are a couple of options you can set only thought the app. You can configure the trainer to simulate a speed that is proportional to the power you're applying in ERG mode. By default, it will just report the actual speed of the wheel, and in ERG mode you can be moving very slowly with huge resistance. This setting is overridden by Zwift, which uses its own speed calculation based on power and the virtual slope you're virtually riding on.

Hurts Ergo is a free, minimalist iOS app. You have to edit the HIIT workouts using [www.73summits.com/ergdb], which I found quite cumbersome and clunky. One problem for HIIT workouts is that you have to specified specify the duration in minutes, so 20 seconds is 0.333… minutes, which is unintuitive at best. The app itself doesn't work terribly well, and I found that fractional minutes didn't always results result in predictable interval lengths. So sometimes 0.33 minutes was 17 seconds, and sometimes 23 seconds, which is really annoying. On the other hand, it's a simple, fairly easy to use app.

You'll need a fan. In fact, you'll ; probably need several really big fans. Ideally, you want some way of turning the fans on while you're riding a bike. It can be chilly when you first start, but by the time you've warmed up , you'll want some air movement. In fact, overheating Overheating can be a real serious problem doing HIIT on a stationary bike. To The biggest issue is the possibility of a sudden rise in core temperature that could lead to heatstroke. That's not common, but it's something to be aware of if you're new to HIIT. The more common problem is that to prevent overheating, your subconscious will reduce muscle recruitment well ahead of serious problems arising, so you may feel weak before you feel hot. One approach to cooling that I found helpful is to put a remote-control adapter onto my box fans. This is much cheaper than buying a fan with a remote control, and also makes it easier to control up to 5 fans from one remote. I got the [https://www.amazon.com/gp/product/B01N5JSAHM Etekcity Five Pack Remote Control] which has 2 remote controls, and 5 power adapters. This allows me to start working out without any air movement, and gradually increase the number of fans as a warm-up.

Here's are some pictures of my setup, along with the notes.

File:My Tacx Setup (1).jpg| this overview shows the layout, with a big TV and monitor in front of me, and two laptops to the side. I have some old, cheap gym flooring to catch the sweat. You will notice that the TV monitor are is angled upwards, which makes them at right angles to my vision in my natural cycling position. This prevents neck strain while training. Getting sweat on the lower monitor is an issue, but it's a very old monitor, so I'm happy just to wipe it dry after the workout.File:My Tacx Setup (2).jpg| I have one laptop for entertainment, even though the TV has built -in Netflix and Amazon primePrime. That's mostly so I can watch coursera.org lectures and YouTube videos while I'm training. The other laptop runs my training software, currently a heavily customized version of Golden Cheetah. One note is that I originally had a low powered laptop for the entertainment and a more powerful one for the training software, but I found video playback needed more GPU power and I had to swap them over.File:My Tacx Setup (3).jpg| Having two displays is really valuable, as it separates entertainment from data visualization.File:My Tacx Setup (4).jpg| I have a cheap humidifier that blows the moist air onto my face, as I find during intense interval training my throat will dry out and I will end up with a hacking cough. I mounted this in an old water bottle with the top cut open. The one I ordered is https://amzn.to/2J9dG94 though there are a number of several similar personal humidifiers.File:My Tacx Setup (5).jpg| Bike trainers typically come with a small mount for platform to raise your front wheel, which works well enough, but I had two problems with that approach. The first is that it didn't feel quite stable enough when I was at really high intensities. For instance, during a [[3AOT]] workout the low oxygen saturation can make me a little dizzy. The second problem is that having the front wheel on the bike means of that my lower monitor was too far forward for comfort. I solved this problem by getting a wheel -on trainer and using simply to mount the front wheel. I removed the resistance mechanism, which obviously I didn't need. One problem I hit was that the front hub is narrower than the rear hub, but this particular trainer went narrow enough. The train I got is no longer available, but it's still listed on Amazon at [https://amzn.to/3djuNmg https://amzn.to/3djuNmg](I paid about $50, and there are other similar trainers for roughly similar prices.)File:My Tacx Setup (6).jpg| Normally when I get on the bike, I tend to tilted tilt over slightly to get my leg over more easily, but you can't do that on an indoor trainer. I found that having a small step to the side of the trainer makes it a lot easier to get on and off.

Cyclists have been using the power meters of the years, and have a number of several terms that are likely to be unfamiliar to runners.

* '''Power at V̇O₂max'''. This is one that cyclists may not refer to commonly, usually but it is a very common intensity for HIIT workouts used in scientific research. For instance, the well-known [[Tabata]] workout is performed at 170% of the power at [[VO2max|V̇O₂max]]. * '''W′'''. Pronounced "double-u prime", can be thought of as a measure of anaerobic capacity<ref name="MoritaniNagata2007"/>. It's the work that can be performed above CP, in Joules. W' is actually the shape of the power-duration curve. W' can be used to estimate the point of failure for anaerobic exercise, something that Golden Cheetah will visualize for you. So exercise above CP will result in a depletion of W', and when W' hits zero, you should be unable to continue (or at least, only continue at failureyour critical power. )

If you're a runner, there's a good chance you'll have no idea where to start in setting up a power -based workout. I did a little research on the topic, and based on nine studies I found that you can get a rough estimate of power at V̇O₂max from [[VO2max|V̇O2max]] which in turn you can estimate from your running performance. I refined that formula based on a study of 1,715 subjects that I found later<ref name="SilvaAraújo2015"/>.

This gives a starting point for HIIT. While it's tempting to aim for interval intensities above your power at [[VO2max|V̇O₂max]], I'd strongly suggest you start somewhat lower and build up. You can build up the intensity either over several sessions, or have increasing intensity intervals during a single workout. You'll also find that as you get use used to the cycling, the power you can output will increase quite a bit.

If you know your [Maximum Heart Rate]] from a running test, you can perform a submaximal incremental test on the bike to estimate your Power at V̇O₂max. Knowing your maximum heart rate requires a stress test, as it '''cannot be calculated'''! But, if you do happen to know your maximum heart rate, perhaps from a running [[VO2max|V̇O2max]] test, or perhaps from a finishing kick during a short race, this is another approach to consider. Simply warm -up, and then perform an incremental test, recording your heart rate. Make sure you don't get hot, as this will skew the results. I use to five steps going from 150w to 350w in 50w increments. The steps need to be long enough for your heart rate to stabilize, and you take the average heart rate from the last section of each step. For instance, my results were 150w/137, 200w/144, 250w/155, 300w/166, 350/169. Plotting that in Excel gives an R² value of 0.98. This predicts my power at [[VO2max|V̇O₂max]] to be about 455w, which is close to the calculation above.

The best solution is obviously to perform a [[VO2max|V̇O₂max]] test. If you're going to go through the pain and suffering of the maximal incremental stress test, then I'd recommend doing it at a lamp where they can measure your oxygen consumption. You could do a similar test at home with a cycling trainer, but obviously you won't know your oxygen consumption unless you have the budget for lab great gear. Getting the incremental steps right seems to be a bit of a dark art. Typically the steps are 60 seconds long and aim to produce exhaustion in 3-6 minutes. The increments need to be coarse enough to produce voluntary exhaustion, while fine enough to give a reasonable precision. I've seen steps increments of 25w used in research papers. You'll know when you've hit [[VO2max|V̇O₂max]] when the power increases, but your heart rate does not. This deflection is considered the definition of [[VO2max|V̇O₂max]], where work increases but oxygen consumption does not. Note that it's estimated that half of all subjects never demonstrate the heart rate/oxygen consumption deflection that's part of the definition of [[VO2max|V̇O₂max]].