Let's get into the numbers. First, a few things to go over.
Hardware: I'm using my time trial bike (an Argon 18) on a Tacx Satori trainer (older model, not a smart trainer like the current model). I'm using a Garmin computer and heart rate strap, and a first-generation Stages power meter, left crankarm only.
Software: I really wanted to like Training Peaks, but I've gone back to my old software (with many updates since the old days) at Cycling Analytics (CA). Cleaner more intuitive interface and great about all the metrics I'm interested in right now. I'm sure Training Peaks and especially their WKO4 software are more powerful, but I found it frustrating to use. One reason I tried Training Peaks first is because it automatically calculates aerobic decoupling (see below) on every ride, which CA didn't. But now CA does, so no problem there.
Absolute power measurements: there are problems with a left-side-only crank. It's measuring power from my left leg and doubling it, so anything other than a completely balanced power output from the rider will throw off the measurement. Aside from that, I don't have other power meters to compare mine to, so I don't know how well calibrated it is. That said, the power number itself isn't of great importance to an amateur rider, only the meter's consistency and accuracy relative to itself. I'm not fussed about it, this meter has the latter qualities.
Functional Threshold Power (FTP): this is an important metric. It is a number, in watts, that is your maximum power output for one hour, in ideally rested condition. The most standard FTP measurement protocol centres on doing a 20 minute maximum effort, and taking 95% of that power. It's an important number because it's used for setting training zones and calculating training stress score (TSS). The best FTP measurement I ever achieved in my racing days was 268 watts. Personal goal to beat that number in the coming years.
Aerobic Decoupling: here's a really useful metric for me now. In a steady-state aerobic effort (high zone 2), split that effort in half. Take the ratio of average power to average heart rate in each half, and compare the drift. Usually, less than a 5% drift is considered good aerobic fitness for that duration.
Now, to business. Post surgery, things look very different than they used to. Most importantly, it's impossible to make apples-to-apples comparisons to any data I have from before because I'm on a beta blocker, which affects how fast my heart pumps, and generally makes exercise harder. Hopefully I'll be getting off this medication soon, as it's prescribed for atrial fibrillation prophylaxis, and that hasn't been a problem for me. Test at the end of the month, fingers crossed. When I eventually do get off the drug, I'm just dying to compare numbers.
FTP is out the window. I have no data to set a power benchmark and doing a test would be far outside my doctor-imposed limits right now. The usual power based training load metric, the 'training stress score' (TSS) depends entirely on your FTP, and so is useless to me. Instead, I'm relying on a heart rate based metric that Cycling Analytics calls 'training impulse' (TRIMP), or Training Peaks calls hrTSS.
As FTP is related to power and TSS is calculated from it, TRIMP is calculated based on threshold heart rate, which is an equivalent sort of metric to FTP. Obviously my heart is running differently than it used to, and I'm not in any position to run a threshold test for power or heart rate. What I've done is set my threshold HR to a point where the top of my target HR range, 140 bpm, is the top of zone 2, the aerobic endurance level where I should be training now. My TRIMP scores are based on that. It's not particularly accurate on an absolute scale, but that's not really important. It gives me a way to assess how rides compare to each other, which is the important thing at this point.
Anyhow, my prescribed heart rate zone for exercise is 110-140 bpm, and boy I didn't expect to be able to get to such a high rate of perceived exertion (RPE) at what was previously quite a comfortable heart rate. I'm running two days a week at the cardiac rehab, and cycling three more days a week at home. I'm also going to stick with the periodization schedule from Joe Friel's seminal 'Cyclist's Training Bible' that I used in my racing days, which is three weeks of training followed by a light week to recover.
When I'm on the bike I get data from my power meter, which is really useful and it's another reason why the bike is my favourite way to exercise.
All my workouts have followed this formula: 5 minutes easy warmup, then the work interval at the top of that 110-140 zone, then a five minute cool down. Over the three weeks of exercise, I've increased weekly: 30, then 40, now 50 minute work intervals. Here's an example of the data chart from a typical ride, with heart rate 'zones', as described above, coloured:
My first rides were pretty exploratory, but I soon hit my stride, though the numbers were woefully low, by my old standards. I have to remind myself regularly that those old numbers are not applicable right now.
Here are the key metrics from my first rides. Note that all this data is just for the work interval, not including warmup and cool down.
|Duration||Avg Power (W)||Avg HR||Decoupling (%)||TRIMP|
What I see from that data is, after the first couple of rides, a steady and fast increase in power output at an approximately steady average heart rate, and a fast increase in endurance as measured by decoupling, taking a bit of a hit as I increased from 40 to 50 minutes (probably due to both the increased duration and accumulated fatigue as I finish my first three week block), but still staying within a range indicating good aerobic endurance.
Seeing as I'm still limited in terms of my HR zone, the plan is to continue to increase duration and strive to have good decoupling numbers going into longer and longer durations at the same heart rate. We'll see how far I can get before restrictions come off at some point, which I would assume would be the end of the rehab programme. I should actually inquire about that, as it would be a big let down if that wasn't the case. I know for certain that I'll have no long-term restrictions, but I should solidify that timeline.