Boston Marathon Analysis: Des Linden and Reed Fischer

Boston, one of the six major marathons. Not only is this one of the most prestigious races in the world, but it also brings out the largest names in all of professional running. What does it take to run in the professional field? How do they pace their efforts? What type of cadence do they maintain? Sit back and relax as we provide a marathon analysis of Des Linden (3rd American Female) and Reed Fischer (5th American Male).

Pre-Race Insights

Many athletes will circle Boston on the calendar as one of their top events. With so much preparation going into this race, how do professionals ensure they are ready? How much training do they accomplish prior? What does the training look like?

Des Linden

Base Fitness

Des had an aggressive build into the marathon. Having started her marathon training in February, that only gave her 12 weeks to ramp up base fitness. Des started her build at 60 Base Fitness and went into Boston at 136. Her peak on April 14th was 140 which equates to roughly 80 Base Fitness points gained in 11 weeks. In other words, Des averaged 7.27 base fitness points per week during her Boston build. This is extremely aggressive and something only an experienced runner could handle. For average runners, we recommend targeting 2-4 points per week during training builds.

Fatigue/Load Impact

When starting her focus in February, Des went into an overreach period to get things started. This is a tactic to spike training fatigue and create larger adaptation responses to your stress and training. Starting off with a low Base Fitness, and needing to ramp things up quickly, this worked out perfectly. Des went from a fatigue score of 16 (minimal) on Feb 8th to 59 (optimized/high) by Feb 17th. This overreach is also shown with the load impact metric (monitoring your last 7-days training load). The largest 7-day jump in her training block was her first week. Between Feb 8th and Feb 15th, Des went from a load impact of 24 to 119. This is roughly a 5x increase on training load over a one-week period. This is an aggressive increase and only something an experienced runner should take on! As for a taper, Des slightly pulled back training for the final 3-4 days before Boston, but did not bring her fatigue down as much as she could have. This was probably a tactical decision and could have been made for multiple reasons.


When looking at pro runners, its always amazing how many miles they are able to put in. Over the last 12 weeks, Des put in 975 miles. With the first two weeks being smaller overall, the bulk of her distance came in the final ten weeks. Over the final ten weeks, Des ran 941 miles. On average, that is 94.1 miles per week. Her largest week was Feb 14th-Feb 20th with 108.37 miles. This was the last week of her overreach period. Following the overreach, Des ran between 80-100 miles each week with her next peak week coming March 28th to April 3rd. She ran 102.51 miles and then began to scale things back ahead of Boston.

Pace Zone Distribution

When running a marathon at the elite level, you will be spending most of your time in the Aerobic Power zone. Athletes at this level can run at Threshold for certain parts, but the sweet spot is between 80-90% effort the entire time. When looking at Des’ data from her build, she spent 66% of her time at Aerobic Endurance and 17.9% at Aerobic Power. Due to her incredible run volume and quick build, she needed to rely more on Aerobic Endurance to reduce overall fatigue. If she were to run any harder, she would ultimately reduce her mileage and not obtain the same overall Base Fitness.

Marathon Level

The Marathon Level within the COROS ecosystem shows how strong a runner is over the marathon distance on a flat road. Given the training that Des put in prior to Boston, along with her past experience, it is no surprise that she is stronger than 99.39% of COROS users!

Reed Fischer

Base Fitness

Similar to Des, Reed started his marathon build roughly 10-12 weeks out from race day. Prior to starting his build, Reed was sitting comfortably near 110 Base Fitness. On Feb 17th, Reed completed a 20 mile workout to launch his Boston build. Over the next six weeks, Reed would take a more gradual approach and eventually top out at 139 on March 25th.

Fatigue/Load Impact

When taking a more gradual approach from an already strong starting point, load impact and fatigue have less of an impact. The impressive data point through Reed’s build is that his fatigue never went above 56 (optimized). This means that Reed was able to execute workouts everyday without requiring large recovery blocks. This again stems from his starting point of 110 Base Fitness. What you can see from Reed is a more defined taper. From March 25th through race day, Reed took his fatigue from 49 down to 32 which is firmly within the performance range. While Reed did give up some fitness for freshness, this is generally what you see during a structured taper.


The distance Reed was able to run in training is incredible! If we start at his first long run during his build (Feb 17th), Reed ran 917.74 miles over a 9 week period. This averages out to 101.9711 miles per week. The largest week of Reed’s build was from March 28th through April 3rd. Just like Des, Reed used this week to max out his training before a taper. During this week, he ran 112.14 miles.

Pace Zone Distribution

There was a slight difference here between Reed and Des. Des focused on increasing mileage during her build and running mostly at Aerobic Endurance. Reed already had a firm Base Fitness (110) in place, and therefore focused more on Aerobic Power. During his last four weeks, Reed ran 54% of his miles at Aerobic Power and 39% at Aerobic Endurance. The remaining percentage came from speed work.

Marathon Level

Reed is exceptionally talented. This is just about as strong as you can be! Reed is one of the fastest COROS athletes on the planet and only falls behind 0.06% of all users. His training was dialed in heading into Boston!

Finishing Times & Splits

Des Linden

Des Linden Data from Boston

Overall Des ran Boston in a time of 2:28:47. This equates to a 5:40/mile average. As noted above, this falls within her Aerobic Power zone and is the ideal range for running a marathon to your potential.

Fastest Mile: Mile 6 at 5:19/mile pace. For this mile, Des went into her Threshold pace zone and was also pushing above threshold for a few minutes! This is a risky tactic in the marathon, but was needed as the pace was being lifted from the leader.

Slowest Mile: Mile 21 was the slowest as it is for most Boston runners. This is Heartbreak Hill and you can see where Des slowed down on the chart above. What’s incredible is that even with this hill, she still averaged 6:05/mile for the split and the slowest she ran was 6:50/mile pace for a brief second.

Adjusted Pace: While there were faster and slower miles due to course terrain, adjusted pace is a better way to look at true effort. Des started the marathon at a slower overall adjusted pace through 5 miles of 5:49/mile (9 seconds slower than her overall average time). Starting at mile 6, Des picked up the pace. Throughout the rest of the race, she was able to hold 5:34/mile adjusted pace. Even during the hardest section of the course (Heartbreak Hill), Des ran mile 21 at 5:34 adjusted pace. Talk about perfect pacing!

Final 5k: 5:45/mile average. After 23 miles of running, Des was still able to hold an Aerobic Power effort and a cadence of 195 steps per minute.

Reed Fischer

Reed Fischer Data from Boston

With a finishing time of 2:10:54, Reed averaged 4:58/mile. Just like Des, Reed ran the majority of his race within his Aerobic Power zone. Between his average pace and adjusted pace, Reed ran within his abilities and maximized his race.

Fastest Mile: Mile 6 was also the fastest for Reed. With a split of 4:43, Reed was able to utilize the downhill section of the course to his advantage. A point to make here is that even with the downhill portion, Reed kept things relaxed and never drifted above Threshold. This is a sign of an experienced runner.

Slowest Mile: Mile 21 and Heartbreak Hill took another victim. With such a strong gradient at mile 21, Reed ran a 5:23 Mile. The slowest portion of this mile was ran at 5:54 pace.

Adjusted Pace: Just like Des, Reed started out a bit slower in regards to adjusted pace. Through 5k, Reed was running at 4:59/mile adjusted pace. Every 5k split after this was between 4:52/mile and 4:56/mile. Even through Heartbreak Hill, his actual split was 5:23/mile, but his adjusted pace was 4:54/mile. Another great example of properly pacing your effort!

Final 5k: Following the first 23 miles, Reed was able to hold 5:01/mile pace for the last 5k. His cadence averaged 197 with an average heart rate of 174.

Marathon Analysis

Des Running the Boston Marathon

Des Linden

Having already won Boston, Des put her racing experience to full use during the race. She knows what she is capable of and stuck to the plan. When looking through the data from the race, you can see this in her pacing. The women’s leader made a strong move just before 10km into the race. Des went with the pack for a moment, but backed off once she realized she was in her “Above Threshold” pace zone.

With Aerobic Power being the ideal zone for faster marathon runners (sub 3 hours), Des did a great job of sitting here for most of the race. Out of the 2:28:47, she spent 1:36:33 in her Aerobic Power zone (64%). Having to push the pace at certain times, Des spent 27:50 in her Threshold zone (19%) and 13:01 Above Threshold (9%). Due to the hills and slower nature of the course, 8% of the race was spent in her Aerobic Endurance zone.

Looking over the output from her race, there is no surprise that she finished 3rd overall American Female. Not only is she an amazing runner, but her pacing was fantastic. While she could have stayed with the leaders for longer based on her Threshold, this would have created fatigue over the marathon distance. Des was able to run near even splits for all 26.2 miles and come home with another fantastic Boston result!

Reed Fischer

Reed Fischer on course in Boston

As an exceptionally talented runner, Reed put his abilities on full display at Boston. When looking at Reed’s data, you can quickly see how fit he is by how his heart rate dips during the downhills. For many athletes, a recovery heart rate of 30 beats per minute after resting for 1 minute is considered healthy. Reed’s heart rate dropped by 20 beats multiple times (within 30 seconds) while running downhill sections. This shows the ability for Reed to continually push the pace and have limited heart rate drift.

In regards to pacing, Reed mimicked Des with the proper Aerobic Power strategy. Reed spent 1:22:09 (63%) of his time in this zone. Only 2% of his total time was spent in Threshold and the rest was made up by his Aerobic Endurance zone (33%).

For the entire 26.2 miles, Reed maintained an average cadence of 197! This number is mind boggling as it is what you’ll see many high school track athletes run for 400 meter intervals. Reed’s combination of cadence and a world-class cardiovascular system is what led to a 4:58 average pace over the marathon distance!


When running in the professional fields at Boston, you need to be an exceptional athlete. Des and Reed were able to run fantastic races and finish 3rd American Female and 5th American Male. By running smart and within their proper pace zones, they were able to maximize their times and have fantastic days!

If you are curious on how to look into your workouts further, simply go to the COROS Training Hub and access your workouts via the Workout List. From there you can do your own marathon analysis to see how you stack up against the pro’s!

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4 thoughts on “Boston Marathon Analysis: Des Linden and Reed Fischer

  1. Thanks for the great stuff. With such examples, I understand better how to analyze my workouts. And now I know exactly in which zone I should hold my race.

  2. Thank you for your comment. Great catch. We have identified the issue with our engineering team and will address this. Thank you again!

  3. I must not understand the workout data screen then. Why does it say for both of them that almost all there running is at a hard pace but the pace zone distribution shows most of their running in zone 1 and 2, this makes no sense to me.

  4. Great stuff, thank you.
    Curious … was a chest strap HR monitor used by these two athletes?

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