In a perfect world you wouldn’t have to worry about having time to train. You’d have two or more uninterrupted hours every day for your workouts. You’d follow your training plan to a ‘T’ and you’d be performing better than ever.

Unfortunately, this isn’t a perfect world and you won’t always have the time you want or the time you need. That’s reality. You’re probably already committing at least 6-10 hours of time to training every week – That’s a lot of time.

When you don’t have time to go on a multi-hour ‘Long Slow Distance (LSD)’ ride, don’t skip the workout – find a solution. Significant amounts of research are starting to illustrate a possible method of training that significantly reduces your training time without sacrificing any of the training effect – ‘High Intensity Interval Training (HIIT)’.

This training method can be adjusted and modified to fit most training needs in an extremely short amount of time.

Are Intervals Created Equal?

Despite your best intentions there will come a time when life will interfere with your training. You won’t have the time that day, week, month, or year to get it done. It happens – but what are you going to do to combat it? While there may not be an ideal solution – there are ways to get around your lack of time without sacrificing the effectiveness of the workout. In recent years some exercise scientists have shifted their research interests toward the effects of high intensity exercise on aerobic and anaerobic capacity.

While it may be too early to draw conclusions on the effectiveness of this training, the results have been interesting to say the least.

In 2017, research out of Ireland used elite rowers to study the differences between LSD training and HIIT. The rowers were asked to complete 10 training sessions per week for 8 weeks. The LSD group performed 10 aerobic sessions per week, while the HIIT group did 8 aerobic and two HIIT sessions each week. The HIIT sessions were only 15-20 minutes long and comprised of 6-8, 2:30 minute intervals. The results showed that the HIIT group experienced significantly greater improvements to their Vo2 max and power output at lactate threshold (1).

Research from Canadian scientists in 2008 found that 4-6, 30 second Wingate cycling bouts 3x per week produced the same results as 40-60 minutes of continuous cycling 5x per week.  Both groups were found to have experienced relatively equal improvements in endurance performance markers despite weekly time commitments of 1.5 hours vs 4.5 hours (2).

With this research being in its infancy, there is not much consistency in methodology from one study to the next. Each has their own interval time, intensity, target HR, recovery period – it’s impossible to tell what the correct interval “dose” may be.

How Do Intervals Improve Endurance?

The exact mechanisms behind how short duration, high intensity training impacts performance are not entirely understood but its been demonstrated to improve key factors involved in endurance performance.

Research from 2008 found that intervals increased the skeletal muscle oxidative capacity, resting glycogen content, reduced glycogen utilization and lactate production, increased capacity for whole-body and skeletal muscle lipid oxidation, enhanced peripheral vascular structure and function, and increased time to exhaustion (2).

Due to their highly variable nature, the way an interval workout is structured will have a significant influence on how it impacts your physiology.

Adjusting Intervals To Fit All Needs

The adaptations to this type of training are infinitely variable and unique to the individual. It’s unlikely that any two people will respond in exactly the same manner to the exact same workout. With a lack of available research on the topic it’s not yet possible, or responsible, to give exact training recommendations for this method of exercise. Not to say that performing HIIT is dangerous – it just puts a greater demand on your body and mind compared to other types of training.

An interval workout can take many forms – from 10 second all out efforts to less intense 5 minute bouts. Rest periods between intervals can last anywhere from twenty seconds to three or four minutes. The combination of interval length and rest length that you pick will ultimately determine the training effect that you will experience.

By adjusting your interval and rest lengths you’ll change the ratio of energy system contributions. Depending on the length of your intervals, a certain energy system will dominate energy supply and will experience the greatest amount of adaptation.

A Word Of Caution

HIIT may seem like the answer to all of your training problems, but too much intensity can lead to overtraining, injury, and often burnout. “Variety is the spice of life”, and that same motto should apply to your training to preserve your longevity in the sport (3).

An example I keep seeing repeated recently is the athlete who discovers Zwift, gets addicted to racing, races all day every day, and winds up hating their bike a few months later. Training at high intensity frequently is tough on the body, but especially the mind. If you enjoy Zwift racing, as most everyone does, keep doing it, BUT please ensure the training you’re doing is balanced. To use HIIT effectively, you need to arrive at each HIIT workout fresh to get the most out of the session, i.e. approach your training from a polarized point of view where the easy days are very easy, and the hard days are very hard – Doing each session ‘moderately hard’ will lead to stagnation rather quickly.

There is also no replacement for training volume. Increasing intensity will help continue to push your fitness further, but if you are truly at a plateau and can’t stomach another intense day, you need to find a way to increase training volume and/or frequency to continue progressing.

Finally, I construct training blocks in a periodized fashion for the athletes I work with (even though it is partially disputed above), whether traditional or reversed, for many reasons, but in the vein of this conversation, because it will naturally limit the amount of HIIT work you undertake – which is generally 8 weeks. After 8 weeks of HIIT I find the athlete is ready for a break from it, both mentally and physically.

In Conclusion

If you’re looking to get in some extra work during a time crunched period, try adding in some additional HIIT sessions and see if that rights the ship.

With this level of intensity it’s difficult to say how many repetitions are realistic for you to complete, or how intense you can make them. You may be exhausted after one or it may take five. The point is to take your time and figure out what you can tolerate.  

And remember, HIIT is effective and efficient for nearly any cyclist, but can pose a risk if not performed properly – always listen to that voice in your head (no, not the screaming one) and respect how your body and mind are feeling.

References:

1. Niamh J. Ní Chéilleachair, Andrew J. Harrison & Giles D. Warrington (2017) HIIT enhances endurance performance and aerobic characteristics more than high-volume training in trained rowers, Journal of Sports Sciences, 35:11, 1052-1058, DOI: 10.1080/02640414.2016.1209539
2. Burgomaster KA, Howarth KR, Phillips SM, Rakobowchuk M, Macdonald MJ, McGee SL & Gibala MJ (2008). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol 586, 151–160.
3. Foster, Carl, et al. “The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity.” Journal of Sports Science & Medicine, Uludag University, 24 Nov. 2015, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657417/.

TSS^® stands for Training Stress Score and is a way to objectively quantify how hard or easy a workout is via a points-based system.

Dr. Andy Coggan and Hunter Allen pioneered TSS with the original seed concept being developed by Dr. Eric Bannister’s heart rate-based training impulse (TRIMPS).

TrainingPeaks

TSS Points Breakdown

TSS points are accumulated by a workout’s relative duration, intensity, and frequency. Super simple example:

• 1 hour at 100% FTP would equal 100 TSS.
• 1 hour at 50% FTP would equal 25 TSS.

You get the idea! The actual TSS formula =

TSS = (sec x NP^® x IF^®)/(FTP x 3600) x 100

Joe Friel

Where NP = Normalized Power, IF = Intensity Factor, and FTP = Functional Threshold Power.

Now that we understand what TSS is and how it’s calculated, how can we apply it to training?

Enter The PMC

The Performance Management Chart® (PMC) is something most of us have seen before in one form or another and is based on Bannister’s TRIMPS method as well, with it being able to use power data in addition to heart rate data. The PMC is fed TSS data which results in all the pretty lines we see below:

Crash Course For The PMC

If you have no idea what the above is, it’s fairly simple to understand:

• The blue line = CTL (Chronic Training Load) = Fitness
  • “An exponentially weighted average of the last 42 days of training”. If you see the blue line trending upward, that’s a good sign the athlete is doing enough training to create a positive fitness response and vice versa.
• The pink line = ATL (Acute Training Load) = Fatigue
  • An “exponentially weighted average of training stress from the past 7 days”. Fatigue must happen to create an overload and subsequent response, so imagine the pink line “pulling” the blue line upwards. More training fatigue = higher fitness response.
• The yellow line = TSB (Training Stress Balance) = Form
  • Simply CTL minus ATL. A positive TSB is a good indicator the athlete will be fresh and have a good performance, and vice versa.
• You can also see the natural ebb and flow of a season, when the athlete had a taper period, “peak” period, illness/injury, etc.

So, What’s My Problem?

If we remember, 100% FTP for 1 hour = 100 TSS. This statement makes a rather large assumption that everyone can hold their FTP for 1 hour, which isn’t true. This means the TSS accumulated will be skewed for each and every athlete that doesn’t have an exact time to exhaustion (TTE) at FTP of 1 hour. For example:

In looking at the 2 athlete examples above, we’re just concerned with MFTP (modeled FTP from WKO) and TTE, with TTE differing by almost 20 minutes. This should mean that Athlete A will accumulate 100 TSS if they maintained 336w for 32:14, versus Athlete B would if they maintained 299w for 51:54, which isn’t substantiated by the TSS equation.

In understanding that, another can of worms is the relative inaccuracy of the PMC chart, which is based purely on TSS data…

In Conclusion

TSS and the PMC are still useful to track trends in training, but using the data as an absolute can be misleading due to individual differences in an athlete’s FTP and TTE. I recommend looking at the PMC chart loosely to plan your training, but always listen to your body when push comes to shove in providing it with a training load as well as rest – e.g. if your “Form” is a +15, but you don’t feel ready to hammer it on the day, don’t!