Anaerobic Intervals for XC MTB

Anaerobic intervals for XC MTB are short, high powered efforts that do not use oxygen. A one minute effort performed at 120-150% of the athlete's Functional Threshold Power (FTP) is a great example. These intervals are essential to training  cross country mountain biking to power thru technical terrain and up steep trails. In this training tip I'll explain why anaerobic intervals are important for XC MTB and how you can do anaerobic interval workouts. 

Why are Anaerobic Intervals Important?

Cross country mountain biking requires power to accelerate, overcome an obstacle or carry momentum over a short climb.  That type of power is often times applied for one minute or less at much greater wattages than the athlete's threshold power. These power demands are described as anaerobic power. In mountain biking when there is a root or rock section that can be cleared with speed, that is anaerobic power. The start of a cross country mountain bike race is 'anaerobic' as well.  There are so many instances of anaerobic power it behooves athletes to include anaerobic intervals in their overall training.

Example Anaerobic Interval Workouts:
Anaerobic intervals are prescribed at a maximal effort. We described this intensity as 'hard as you can' or 'full gas'. Common anaerobic interval workouts are prescribed with 30 second, 45 second and 1 minute intervals. Here are 3 introductory anaerobic intervals workouts of each duration:

Zone 6: 4 x 30 seconds ON, 30 seconds OFF Zone 6: 3 x 45 seconds OM, 45 seconds OFF

Zone 6: 3 x 1 minute ON, 1 minute OFF

Once an athlete has successfully completed the above anaerobic interval workouts, they may move on to more intermediate and advanced levels by increasing the number of repetitions such as:

Zone 6: 6 x 30 seconds ON, 30 second OFF

Zone 6: 2 sets of 4 x 1 minute ON 1 minute Off with 5 minutes in-between sets for 8 total intervals (and minutes)

Advanced level would be:

Zone 6: 3 sets of 5 x 30 seconds ON, 30 seconds OFF

Zone 6: 3 sets of 5 x 1 minute ON, 1 minute OFF with 5 minutes in-between sets for a total of 15 minutes in zone 6

Anaerobic Interval Execution:
Instructions for an anaerobic interval workout are as follows:

  • Identify your FTP [Functional Threshold Power]
  • If no powermeter, these are completely Full Gas efforts, as hard as you can go efforts, Heart Rate will lag behind and not represent your effort.
  • Identify what value is 120-150% of FTP*
  • Be well rested, fueled, motivated and hydrated for your workout
  • Find a quiet stretch of road that is free of stop signs / stop lights / or cross traffic. Hills are terrific
  • Go as hard as you can for these efforts! Use your powermeter as a reference but do not stare at it.
  • Alternate in the saddle and out of the saddle for a maximum effort

**you could probably make more watts but the idea is to do 3-10 quality repetitions rather than a few really good ones and be 'blown'.

Use your powermeter to stay above 120% of your FTP from the beginning until the end of each interval. Similarly use your powermeter to pace yourself thru all your anaerobic intervals by not exceeding 150% of your FTP. Still go as hard as you can, but spread that effort evenly for all the intervals, not just the first few. If you are able to exceed 150% for every anaerobic interval in your workout do more repetitions in the next workout. Also double check your FTP but in reality you are probably just good 'anaerobically.

Anaerobic Interval Power Output Analysis:
We like to take the average wattage for each anaerobic interval, add it up and divided by the number of intervals in order to calculate the average interval power. Average interval power gives the athlete a target to beat for the next 1 minute interval workout and a point of reference to compare to for future improvement. Summary:

Anaerobic intervals are specific to cross country mountain biking.  Anaerobic intervals are performed maximally but when executed properly will be between 120 - 150% of the athlete's FTP. These intervals should find their way into one's training program after they have built up sufficient aerobic endurance and/or in the six weeks prior to the event that demands anaerobic power. You will find several anaerobic interval workouts in our xc mountain biking training plan. These efforts are extremely difficult yet produce massive performance gains in as little as 3-4 weeks of training.

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About Frank Overton

Frank founded FasCat Coaching in 2002 and has been a full time cycling coach since 2004. His educational background includes a Masters degree in Physiology from North Carolina State University, pre-med from Hampden-Sydney College. Frank raced at a professional level on the road and mountain bike and currently competes as a "masters" level gravel and cyclocrosser. Professionally Frank comes from medical school spinal cord research and molecular biotechnology. However, to this day it is a dream come true for Frank to be able to help cyclists as a coach.

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