More Than Splits: Sunmaya Shines at COROS 50k

As one of the top female athletes within ultra-running, Sunmaya continues to demonstrate her overall fitness and ability. Over the past two weeks, Sunmaya has set a 40 minute course record at The North Face 50k, along with placing top female (only seconds away from overall win) at the COROS 50k in Hong Kong. At COROS, we love to showcase what the best athletes in the world are doing as they prepare for their seasons and execute on their race plans. Sit back and relax as we do a deep dive into the data behind Sunmaya’s COROS 50k win!

Watch: COROS APEX 2 Pro

Data Analysis: COROS Training Hub

Training With COROS Data

COROS Education: The Training Load Management chart allows athletes to monitor their fitness and fatigue over long periods of time.

What we are looking at above is the 24-week chart of Sunmaya’s fitness/fatigue. We can see that she took her off-season from 11/28 through 12/16. Following this, she started to slowly build training back into her schedule. Since December, Sunmaya has been in a steady build consisting of increases in her weekly Training Load (stress on the body) to allow for more training adaptations. Simply put, Sunmaya is building fitness heading into the summer months.

Increase in Training Load

COROS Education: Every workout generates a Training Load. This number represents the stress your body received from the workout. Intensity x duration = Training Load

As can be seen in Sunmaya’s training, her Training load has built from January through March. Typical of many athletes calendars, fitness should improve during this time. We point this out for all readers of the article to show what a steady increase looks like and that this data can be collected and monitored for all COROS athletes. Simply go to your Training Hub to see how your data compares.

High Training Load Days!

While ultra runners need to log quite a bit of time and volume, Sunmaya does so on a more frequent basis than we have seen before. Between ultra races and long training days has spiked her Fatigue near 100 on 6 different occasions since January 27th! You can see following each spike in Fatigue, a planned recovery, which allows her body to adapt to the workload. This can be an effective training tactic if monitored closely! Her coach Andy DuBois is world-renown for keeping a close eye on data which tells us this is very strategic and an effective approach for Sunmaya!

COROS 50k Performance

Just having set a 40 min course record and taking the victory the week prior, Sunmaya came into this race looking to treat it as more of a training day. Her strategy was to run at an easier pace and obtain more stress on the body for future improvements going forward. While this was the original mindset, her racing instincts kicked in around the halfway point. Feeling surprisingly well and rested, she made a decision to go for it. Knowing how the race unfolds, let’s break it down by the numbers!

Sunmaya’s heart rate data from COROS 50k

1st Section: Top of The Mountain (0-1:22:40)

COROS Education: Athletes can select portions of their activity for a more in-depth analysis within the COROS Training Hub.

During the first 11.44 kilometers of Sunmaya’s COROS 50k race, she started out as intended. Holding an average heart rate of 162 during this hour and 22 minute span, she was firmly in her Aerobic Power zone. From the data above, you can see that for most of the uphill sections, Sunmaya was holding a higher heart rate to push the uphills, and then lightly recovered on the downhills where possible. Overall this resulted in a true average pace of 7:13/km and an Effort Pace of 5:29/km.

While Sunmaya did intend to take things easier initially, she still let her heart rate climb to a peak of 189 during this first section. Regardless of how easy any athlete intends to race, its always difficult to battle the terrain of the course without pushing your body in certain key spots!

2nd Section: Rolling Mountains (1:23:35-3:01:33)

COROS Education: Effort Pace shows athletes their pace as if they were running on flat ground. This allows athletes to better pace their efforts over terrain.

The 2nd section of the COROS 50k shows Sunmaya continuing to properly pace within her Aerobic Power zone. While she did hit a peak of 201 beats per minute on a technical downhill, she was able to keep her overall average in the appropriate spot! This is critical for any athlete looking to run longer distances. While we understand you may need to surge in select area’s, having a well paced effort is what allows for stronger speeds later on!

One interesting note about this section is that Sunmaya’s actual pace slows (7:13/km in 1st section to 7:32/km in 2nd section), but her Effort Pace has sped up! This is important to note as the terrain in this section was far more difficult. Sunmaya sped up relative to the terrain and therefore was able to pass a few of her competitors during this section. Effort Pace is an extremely effective tool when athletes are able to utilize it for pacing in hilly regions.

3rd Section: The Valley (3:01:33-4:26:18)

Going through the halfway point, Sunmaya had a conversation with her team manager Ryan Blair. She noted she was feeling good and wanted to push. Due to the terrain of this section, you can see a faster overall split with roughy the same average heart rate as before. Sunmaya was able to hold an average of 162 while topping out a 196 over the top of some “small” risers.

Further, this was the fastest split yet for Sunmaya as she turned on the gas. Passing the 3rd and 4th place competitor overall in this section, she now had the motivation to chase down those in front. Clocking an average pace of 6:29/km along with an Effort Pace of 4:54/km, Sunmaya was making up ground and still well within her abilities as a runner. Her first two sections of running more conservative would prove extremely useful as she now chased after 1st place!

4th Section: The Finishing Sprint (4:25:59-5:31:05)

Only one competitor to chase down (1st place male) over the final 1 hour and 5 minutes. Due to Sunmaya’s ability to pace the first three sections, she now had the ability to surge and give it everything she had. With 12.5 kilometers remaining, Sunmaya pushed the downhill section and then elevated her heart rate well into her Threshold zone for the remainder of the race. Holding an average of 175 bpm over the final 12.5 km, she was giving it everything she had.

Final Push to the Finish

The final 6.5 kilometers are where we can really see the ability of Sunmaya. This data is incredible and shows the level of these elite athletes when they properly pace and have the motivation to fight for victory! Sunmaya was able to hold an average pace of 4:20/km (Effort Pace 4:21/km) over this span. This required her to operate well above her Threshold heart rate (187 avg) for the remaining 28 minutes. Firmly in the pain cave and fighting to the finish, Sunmaya was able to get within 5 seconds of the top male and overall winner of the COROS 50k! Finishing in 2nd overall and top female placing, this is a true elite performance and a fantastic display of how pacing your body early results in peak performances later.


While the season is only getting started for Sunmaya, we wanted to give a huge congratulations to her, her team, and her staff for making this happen. The time and energy that goes into not only properly training, but executing a race like this is mind-blowing. We are excited to see what’s to come for the rest of 2023 and will be keeping a close eye on how the season unfolds! As Sunmaya and her staff continue to utilize COROS products and training software for performance, we can only imagine where she will be in a few more months! Congrats again to Sunmaya and we look forward to keeping our readers updated on the results to come!

For more articles like this and other training tips relating to COROS, please visit our training blog for all your needs!

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