Fitness and health are a part of your life. You aim to stay fit and enjoy a few events or races throughout the year. But you only have 5, maybe 6 hours, per week to dedicate to the training process.
You consider yourself a time-crunched athlete.
But can you still get the enjoyment and success out of the sport? Of course! One of the benefits of being time-crunched is that when you do have the chance to train, it can be a fun, focused way to drive fitness and enjoy time doing what you love.
The important question is how do you make the most of that time and how do you incorporate high intensity interval training (HIIT) into the plan? This is a particularly relevant question if you’ve been doing a steady routine of consistent training at lower or moderate intensities, or you’ve done too much high intensity in the past and are unsure how to effectively bring it back into the fold.
Wait, What’s HIIT?
HIIT, HIT, SIT, LSD, MICT: These are terms used in the literature and “thrown around” in the fitness world. So, let’s do a quick review; because understanding exactly what these are will inform your plan and help you develop the right expectations from your training. We’ll start on the low intensity side of the spectrum and work our way up.
FROM: MacInnis, MJ Gibala, MJ. Physiological adaptations to interval training and the role of exercise intensity. J Physiol. 2017;595(9):2915-30
LSD: Long, slow (or steady), distance
This is your bread and butter for developing your “base” aerobic fitness. It’s a very conversational effort that you can hold for a very long time. Rates of energy expenditure are relatively low overall, and heart rate is likewise low and controlled. This is pretty much your “all day” effort.
MICT: Moderate intensity continuous training
As the name suggests, this is a medium effort where energy expenditure and the perception of the effort increase, but it’s still a relatively comfortable intensity that you can maintain for a prolonged period of time (think 60 to 90 minutes versus hours for LSD).
HIT: High intensity training
HIT is often used interchangeably with, and sometimes used incorrectly to define, HIIT. The “single I” HIT is generally not used in endurance sports as much as other sports. The goal here is to achieve complete failure in a muscle group. Think about that person doing drop sets in the gym – complete failure; then you’re done!
HIIT: High intensity interval training
The “double I” HIIT is what endurance athletes have come to know and love over the years. This is done as brief, intermittent burst of high intensity efforts interspersed with rest periods. Intensity is generally quite high, achieving targets of 85-95 percent of maximum heart rate.
SIT: Sprint interval training
Sprint interval training is an extension of HIIT where we do very brief work periods of supra-maximal intensity (e.g., 300 percent of VO2max) with very long rest periods. For example, the work to rest ratio might be 1:15 for SIT and 1:1 for HIIT.
The Cons of HIIT Training for Time-Crunched Athletes
When it comes to training fundamentals, one key principle is overload. We apply enough of a training stimulus to overload the body. Enough to require recovery. That’s when we adapt and improve.
Here’s the tricky part – as a time-crunched athlete your ability to put in volume is limited, so you will quickly hit a point where additional training stress can no longer come from volume alone. The next logical step? Intensity.
Before we get into the types of workouts or any specifics on intensity, it is important to understand the potential pitfalls of a time-crunched training approach. Here are a few of the big ones:
- Too many intensity days per week
- Incorrect intensity for the chosen intervals
- Unstructured intensity (e.g., just racing on Zwift all the time)
- Not enough intensity to create overload
- Too frequent interval sessions leading to low quality HIIT work
The Benefits of HIIT
Depending on where you look, you can find reports that HIIT will improve everything from VO2max to VLamax, enhance endothelial function (5), reduce free radicals (6), decrease fat mass (3), and a host of other health and performance improvements.
Some research claims that all of these improvements are plausible from HIIT work. However, it’s important to look at the results in the context of the study participants. Many of the large improvements in VO2max come from untrained, overweight study participants or subjects that are in poor health. Trained, experienced athletes would likely not see the same improvements, but that’s not to say HIIT doesn’t work for them.
One key takeaway for a trained, athletic individual versus an untrained exerciser is that the interventions appear to have a greater overall benefit for athletes when the HIIT intervention took place over a shorter training period. (8) So rather than 10-12 weeks, athletes may consider a HIIT intervention over as little as 2-3 weeks. Since athletes have a much higher capacity for work and generally put in higher volume than untrained individuals, they are at a greater risk for over-reaching or over-training if they do HIIT work for too long a period of time. Additionally, trained athletes have generally achieved a high percentage of their maximum capabilities, so the law of diminishing returns can kick in sooner for trained athletes and HIIT.
So, what does the literature say about the benefits for trained athletes? At best, HIIT seems to improve VO2 and work rate at threshold, along with increased sprint capability. (3) At worst, there may be no effect or even a slight decline in these parameters.
Something that really stands out in the HIIT research is the variability in participants, experience level, control groups (or lack thereof), interval and rest prescriptions, and other methodological factors. In other words it’s very hard to draw definitely conclusions from the research – especially when you try to apply it to yourself. This is why I always go back to the recommendation of understanding the literature but allowing recommendations to flex to accommodate your needs and goals as an athlete. Don’t get tied down to one specific workout because it worked for the group in that one paper.
Some HIIT Training Options
Getting into specifics, what are some of the HIIT workouts that are known to have benefits, and how can you add those into your training routine on a time-crunched schedule? Let’s start with the workouts themselves. Below are three sessions that show up frequently in the literature and are reasonable options for HIIT work:
15×30-second intervals with 30-second rest
This workout consists of 15 individual 30-second efforts at just below VO2max intensity. The effort should feel like a power or pace you can hold for around 5-6 minutes.
4×4-minute intervals with 4-minute rest
The efforts in this routine are quite long in comparison to the 30-second intervals. 4-minute work bouts with equal recovery, done at 85-95 percent of maximum heart rate.
4×8-minute intervals with 4-minute rest
This longer interval set is done roughly just above threshold, with the same HR target of 85-95 percent of maximum.
How Often to Do HIIT Workouts
Now, how do we go about selecting what we will do on our time-crunched schedule?
First, ask yourself where in your annual plan you are now. Does it make sense to add HIIT currently? Also consider your willingness to commit to this sort of work. Undertaking HIIT work requires:
- Dedicated training time
- Non-HIIT sessions at an appropriately low intensity
- Motivation to put high quality efforts out
In the literature, typical HIIT interventions for trained athletes run between 2-3 days per week for roughly 3-5 weeks. (3) There is research showing that athletes don’t get any additional benefits doing more than three HIIT sessions per week. Some HIIT works achieve gains in as little as 6 total sessions.
Consider what you can do. If you’ve never done this before, I would not jump into three days per week of 20 minutes or longer HIIT sessions. HIIT training provides benefits without a large time commitment and without a large total volume of work time. But you always need to balance your recovery to ensure the overload is not becoming too much for the body to handle.
Finally, be sure to consider psychological factors within your routine. (4) No one wants to go into a HIIT workout lacking the motivation to produce a good, quality effort.
Adding HIIT to Your Weekly Training Plan
Plan for Easy Days and Reduced Volume
To support the benefits of HIIT, you need to plan easy days and reduce volume. This means if you’re simply adding HIIT to an already hard 7–8-hour week, that’s a recipe for a lot of fatigue. Similarly, if you are riding too hard on your easy days and not recovering between your key HIIT sessions, it will leave you feeling flat in the long run, compromising performance.
Here’s an example week from my TrainingPeaks calendar highlighting the layout of sessions that are similar to the 4×4 workout above. These sessions were actually 6×4 on paper, and due to the terrain, the interval lengths were closer to 3:15-3:30, but work to rest ratios were generally maintained at 1:1. Adding additional intervals based on my progress and the sensations I felt in my legs along with perceived effort during the ride allowed for the necessary flexibility.
Surrounding those sessions on Tuesday and Thursday were two full days off, one recovery spin, another light endurance ride (all in that very easy base endurance intensity), and a weekend endurance ride. In this block, the goal was to achieve six quality sessions before taking a break, which took three weeks at two sessions per week.
If you are more experienced, you may be able to do more, but I generally start with two HIIT sessions per week. Going beyond that could require more advanced periodization to avoid staleness.
Consider Your Workout Terrain
When you are considering how to add HIIT, make sure you also consider your terrain. Let’s use the bike commuter example: you have a 40-minute commute to and from work. What’s your terrain like? Is it hilly and punchy or relatively steady? If it’s punchy, you might be able to use shorter intervals to accommodate the terrain. Or consider longer efforts of four-plus minutes where the focus is on making power on the uphills and downhills along the way.
The Importance of Time at Intensity
In the end, the goal of an HIIT session is to accumulate time at intensity. Look at how much time you can accumulate around 85 to 95% of your maximum heart rate. If you’re getting 10-12 minutes, that’s great. Maybe you can generate 10 minutes per session, 3 times per week. Now you have 30 minutes of high-quality work each week.
This graph shows the heart rate distribution for one of the three-minute HIIT workouts detailed above. You can see that the athlete generated about 14 minutes of work time above 85 percent of maximum heart rate using that series of three-minute maximal intervals:
Increasing your time at or above 85 percent of your maximum heart rate is one way you can set targets for yourself to progressively overload or ensure that your intervals are working as you expect.
For comparison, you can see in the graph below that this athlete spent about 18 minutes above 85 percent of their maximum heart rate in this workout. Also notice the slope of the line and the time above 160 beats per minute (e.g., time at a higher percent of maximum) have both increased. This athlete performed four-minute intervals compared to the three-minute intervals in the graph above. For this athlete, perhaps four-minute intervals are more appropriate, or the longer intervals were executed better than the shorter version.
When designing your structure to accommodate HIIT within your time-crunched routine, consider your long-term goals to determine which intervals you respond to best. I like to ask athletes what types of intervals they really enjoy doing because motivation is such a critical piece of HIIT. This is especially true with Juniors. If you can enjoy what you are doing, you will look forward to it and probably put out your best efforts.
Try not to get too caught up in the details. Realize that you can track time spent at various heart rate levels and use that to inform your upcoming training plans. Ultimately, find an interval routine that speaks to you, that you are motivated to do consistently, and then commit to it for at least six sessions.
Be sure to test and re-test to gauge your improvements. Just as importantly, pay attention to what these sessions are meant to train (e.g., sprinting, threshold power, etc.) so you can realize the benefits and, more importantly, know when the benefits are plateauing. A plateau in performance is your cue to dial it back and take some rest so you can allow your body to repair and adapt.
Have fun and go fast!
- Bailey, S. J., Wilkerson, D. P., DiMenna, F. J., & Jones, A. M. (2009). Influence of repeated sprint training on pulmonary O2 uptake and muscle deoxygenation kinetics in humans. Journal of Applied Physiology, 106(6), 1875–1887. https://doi.org/10.1152/japplphysiol.00144.2009
- Engel, F. A., Ackermann, A., Chtourou, H., & Sperlich, B. (2018). High-intensity interval training performed by Young Athletes: A systematic review and meta-analysis. Frontiers in Physiology, 9. https://doi.org/10.3389/fphys.2018.01012
- García-Pinillos, F., Cámara-Pérez, J. C., Soto-Hermoso, V. M., & Latorre-Román, P. Á. (2017). A high intensity interval training (hiit)-based running plan improves athletic performance by improving muscle power. Journal of Strength and Conditioning Research, 31(1), 146–153. https://doi.org/10.1519/jsc.0000000000001473
- Kilian, Y., Engel, F., Wahl, P., Achtzehn, S., Sperlich, B., & Mester, J. (2016). Markers of biological stress in response to a single session of high-intensity interval training and high-volume training in Young Athletes. European Journal of Applied Physiology, 116(11-12), 2177–2186. https://doi.org/10.1007/s00421-016-3467-y
- Ramos, J. S., Dalleck, L. C., Tjonna, A. E., Beetham, K. S., & Coombes, J. S. (2015). The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: A systematic review and meta-analysis. Sports Medicine, 45(5), 679–692. https://doi.org/10.1007/s40279-015-0321-z
- Shigenori, I. (2019). High-intensity interval training for health benefits and care of cardiac diseases – The key to an efficient exercise protocol. World Journal of Cardiology, 11(7), 171–188. https://doi.org/https://dx.doi.org/10.4330%2Fwjc.v11.i7.171
- Viana, R. B., Naves, J. P., Coswig, V. S., de Lira, C. A., Steele, J., Fisher, J. P., & Gentil, P. (2019). Is interval training The magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT). British Journal of Sports Medicine, 53(10), 655–664. https://doi.org/10.1136/bjsports-2018-099928
- Wen, D., Utesch, T., Wu, J., Robertson, S., Liu, J., Hu, G., & Chen, H. (2019). Effects of different protocols of high intensity interval training for vo2max improvements in adults: A meta-analysis of randomised controlled trials. Journal of Science and Medicine in Sport, 22(8), 941–947. https://doi.org/10.1016/j.jsams.2019.01.013