A Sweet Spot Protocol for Hong Kong

The members of the Lantau Buffalos Team Time Trial team are in a heated internal competition, as we had a few more riders than slots for the HKCA race.  We are using the TC10 course just outside Discovery Bay, Hong Kong, to chose the team.  Since this is a great basic test of fitness, the results can also be used to come up with a sweet spot for training for steady state events.  I've drafted the below and copied here in case anyone else might benefit from it.

HOW TO FIND YOUR SWEET SPOT FOR TRI AND TT TRAINING

Based on Friel Heart Rate Zones

Go out and do a test on the 16k TC10 course or any flat, 10 mile (16 km) course.

• 20 minutes easy warm up
• 3 x 1-minute wind ups with a minute rest between (100 RPM pedal cadence)
• 5 minutes easy
• 5 minutes all out (hard at first, but not so hard that you can't complete the effort)
• 10 minutes easy
•  25-30 minute time trial effort (like the previous 5-minute all out effort, keep in control, hard but steady, you don't want to over cook it and die at the end - INSERT YOUR 10 MILE COURSE HERE)
• 10 to 15 minute cool down

Then, take the average heart rate over the last 20 minutes of the TC10 course (you can just eyeball the plot in Strava or Garmin Connect, or if more precision is necessary use a program like SportTracks or Training Peaks to insert a lap at the finish time minus 20 minutes). This number is your Lactate Threshold Heart Rate (LTHR).

Heart Rate Zones:

Then, use the factors below (from this link) to determine your HR zones.

Bike Zones

Zone 1 Less than 81% of LTHR 

Zone 2 81% to 89% of LTHR   

Zone 3 90% to 93% of LTHR   

Zone 4 94% to 99% of LTHR 

Zone 5a 100% to 102% of LTHR 

Zone 5b 103% to 106% of LTHR 

Zone 5c More than 106% of LTHR

More on HR training use the Friel zones can be found here, here, and here.

Sweet Spot:

The Sweet Spot for steady state racing (like triathlons and time trials, as opposed to road races, sprinting, etc.) is 95% of LTHR, plus or minus 5%.  So, for example, if my 20min average is 154bpm.  My sweet spot is 154 x 0.95 = 146, or a range of around 138-154bpm. Note that this corresponds to Friel's zones 3 and 4.

If you are training by power, use the average power over the ENTIRE TC10 test (not just the last 20min).  This is your Functional Threshold Power.  Your power "Sweet Spot" is at 90% of the FTP plus/minus 5%

The advantages of doing this test yourself over a set course and distance is that you are more likely to push yourself harder if it's a fixed distance, plus you might get some bragging rights on Strava!  You don't have to pay a lab to get the numbers, and it's easy to repeat and check your progress over time.  Note that your LTHR won't change much, but your power will increase and time decrease with training.

I don't  recommend any method that uses the 220-AGE formula  to determine heart rate training zones.  The 220-AGE formula has been completely discredited, and just from polling my own small network of bike fit customers, friends, and team mates, doesn't account for the very large range of variability of people's heart rates at threshold, which seems to have little correlation to age.