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Home / Training Science Series #11 - Peaking: When to Enter a High Intensity Training Phase

Training Science Series #11 - Peaking: When to Enter a High Intensity Training Phase

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This is an article series designed to help further educate my Performance Coaching clients. I am releasing it in this article series to help educate more people to create a life of health and adventure. If you are interested in getting fitter -- irrespective of whether you are a novice or regular athlete -- then please read through this series and learn more about the endurance training process. I welcome you onboard as your performance coach to help guide you to the summit of your athletic potential!

Training Science Series: Why We Focus on Capacity Training…to Eventually Go Really Fast

Part One - Introduction

Part Two - The Utilization Problem

Part Three - Overtraining Syndrome (OTS)

Part Four - Advice for Beginner Runners

Part Five - Aerobic vs Anaerobic Fitness

Part Six - The Aerobic Base - Capacity Training 101

Part Seven - The New Science of Fat Adaptation

Part Eight - Introduction to Threshold Training

Part Nine - A Brief Introduction to Heart-Rate Zone Training

Part Ten - How to Choose Which Zones to Train in Regularly

Part Eleven - Peaking: When to Enter a High Intensity Training Phase

Part Twelve - Keeping the Ego in Check and Sticking to a Long-Term Plan



Part Eleven - Peaking: When to Enter a High Intensity Training Phase


High intensity plays a critical role in every endurance athlete’s training for peaking performance. It is an established sports science training principle that application of high-intensity aerobic training (Zone 3 and above) is most effective when an athlete has a strong base level of aerobic capacity. High-intensity training is a layer that goes on top of a solid aerobic base, and should only be used as a supplement to and not a replacement for aerobic base training.

The ultimate question becomes then what level of aerobic capacity is sufficient before adding more intensity? The answer was revealed in the previous section, you can start to add a diet of utilization training when you have successfully raised your Aerobic Threshold to be within 10 percent of your Lactate Threshold.

Fit endurance athletes typically have a very narrow spread of between 5–7 percent, or only 10 bpm in heart-rate in their Zone 3 range. Most zone 2 training needs to be eliminated at this point. Because the top end of Zone 2 is now so fast, too much Zone 2 training imposes a significantly higher neuromuscular load and vastly increases cumulative fatigue. This becomes quickly unsustainable and the athlete risks developing overtraining syndrome if they carry on with too much zone 2 training.

Because the AT is now efficient and high, no longer does the athlete need to focus on raising the AT and can move onto raising the LT. Utilization training is now used with regular interval sessions in the Zone 3-4 ranges with the goal of narrowing the Z4-5 range (raising the LT to as close to max HR as possible).

As a result of these added intensity demands, recovery sessions must be in Zone 1 or lower to offset this and all zone 2 training should be avoided. The narrower the Zone 3 band becomes, the more polarised the training must become. My motto for training as an aerobically efficient athlete: is train very easy on the easy days and train very hard on the hard days.

High intensity training at its core simply means going hard for a while then resting, and repeating this process multiple times in the one workout. The range of possibilities for high-intensity endurance training is almost unlimited, ranging from intervals as low as 10 seconds, all the way up to 60 minutes, and everything in between.

The most important rule is that high intensity training must be as event specific as possible. If you are training for a fast time on a steep vertical race, your high intensity training ideally should be performed on steep hills of similar gradient to what you will be racing on. If you are training for a trail marathon, the intervals should be on terrain profiles similar to your race.

Secondly, the other rule is you should not decrease your low-intensity aerobic base building work, once you add intensity. At first, intensity additions should be small, but can be slowly increased if the athlete is handling the intensity well, while also maintaining the existing volume of capacity training. If capacity training has to be reduced for an athlete to sustain utilization training, then the high-intensity demands are too high and should be reduced, otherwise you risk diminishing the aerobic base you worked hard to develop and the AT heart-rate will start to lower again.

So, ideally the application of intensity training must be done slowly with only one high intensity session a week, at first. If you end up having to lower your aerobic base volume to handle the newly added intensity, then you’ve added too much intensity too soon and should back it off.

Recovery is paramount during utilization training. So, if your easy days for aerobic maintenance are too hard, then the residual fatigue will prevent your body from opening up to its highest capacities on the high intensity days. Therefore, those intervals you do will not be approaching your VO2 max, thus you will not be increasing your LT which is the overall goal of those training sessions. Instead, you are just tiring yourself out without any significant benefit.

Thirdly, high-intensity workouts should always be spaced 48 to 72 hours apart. Preferably the latter. If you feel drained or tired before a high-intensity workout, and still feel the same way after a warm-up, then its best to hold off on the intensity for another day. A recovery Zone 1 session should be chosen in this situation and high intensity left for days when you feeling fresh. All high intensity sessions should not be performed without a 15-20-minute warm-up that progressively increases heart-rate to the heart-rate intensity you plan to use in the intervals. High intensity training should also be followed with a 10-20-minute cool down that lowers the heart-rate down toward zone 1 and below, this aids in more rapid recovery from the demands of the session, helping the body to clear some of the accumulated ROS through the muscles. Skip the cooldown at your peril, you will be faced with more muscle fatigue and longer recovery between sessions.

Finally, utilization training helps to fine tune an athlete for different types of races. In shorter races, utilization training becomes more important, but for longer endurance races, utilization training isn’t as effective as a training stimulus. Understand that you can never really optimise both the aerobic and anaerobic systems at the same time, but you can optimize the anaerobic system higher than you ever could with a strong aerobic capacity.

Ultimately, how to structure your weekly progression and when to add – and how much to add of – utilization training is where the “special sauce” in training comes and requires a very carefully considered application. The best option for athletes is working with a coach who understands the entire paradigm discussed in this article. Here at Couch to the Summit, I offer very affordable Performance Coaching using the same principles discussed through this article, with the uphill athlete in mind. All my coaching is inline with the methods used by the world’s best mountain runner Kilian Jornet for peak performance.

Next Article -> Part Twelve - Keeping the Ego in Check and Sticking to a Long-Term Plan