tl;dr - my cycling HR is 27bpm lower than my running HR at an “all out” 20 min effort. Any tips to bring my cycling effort level up to my running level?
Long form - this week I did a 20 min FTP test and a 20 min running test to gauge my current fitness level. I am hugely disappointed to see that I can maintain a cycling effort anywhere near my running effort, based on heart rate. Below are notes and Training Peaks screenshots of both efforts (screenshots might not show up if you reject cookies). I am currently uncoached and figuring things out on my own.
FTP Test (20 min)
Indoors Zwift test (50 min easy with some harder efforts sprinkled in, followed by a 20 min all out effort)Tri bike, 100% in TT positionAvg HR = 150 bpmStarted out at 265w @ 160 bpm, dropped as low as 175w @ 145 bpmMy perceived constraint felt musculoskeletal; it got harder and harder to turn the pedals, could feel it in my quads and hamstrings.
Run test (20 min)
Outdoors (15 min easy, 20 min all out, 55 min easy)Paved trail, out and back with very slight inclineAvg HR = 177 HR5:41/mile pace, 5k @ 17:47My perceived constraint felt cardiovascular; I wanted a faster turnover and push off, but my lungs/heart couldn’t keep up.
Me
35-39 age group147lbs2 years triathlon and running, ran competitively in college 17 years ago (no serious training for 15 years until started tri/running again).
FTP Test (20 min)
Run Test (20 min)
I was a competitive runner for 30 years when I took up Triathlon. My running threshold HR was 161 BPM and my Cycling threshold HR was around 133. I could do a 15K run in under an hour (6:11 LTHR) and my 40K on the bike was about 1:18:30 (19.0 MPH). I was 37 years old when I took up Triathlon (yes, I started USATF Jr Track and Field when I was 7 years old).
So…your HR should be lower on the bike than it is running. You are sitting down after all. There is no way you are going to be engaging as many muscles on the bike as you do running. When you have been standing up all day and get to sit down how do you feel? It is a huge load off of you. Same thing when you are cycling. You are working your quads really hard but it is not the same as when you are running and are using every muscle from your pinky toe to the muscles in your neck when you push off and when you land on every stride. Running is an impact sport that is really hard on the body. Cycling is not an impact sports and is much less stress. So, fewer muscles are working so your HR will not be as high. I guess work on your pedal efficiency so that you are engaging more muscles as your feet travel around the circle. That is supposed to keep your quads from burning out as fast but it might help get your HR up too. I know that increasing your bike cadence increases your HR so that is another area you could focus, but I personally like to focus on a specific Watt/Power and see how low I can get my HR while I hold it steady. The higher my HR is the less efficient/economical I am. I want to keep my HR down, not increase it. 
I has zero competitive cycling experience when I starting cycling. My running coach in college was a pretty smart guy and he told me on more than one occasion that he saw it take an average of about three years for people to peak in endurance sports. He would get college runners, work with them and as soon as they started to peak their eligibility would be done. He said he/they all wished they had another year of two to compete. So…when I started cycling I wasn’t worried about the results (or lack thereof) that I saw in the first three years. I was consistent in my training. I was doing 70.3 races and had a goal to get under 3 hrs on the bike leg in every race (18.67 MPH). I trained 8 months for my first 70.3 and was in the best shape of my life (much better than at any point in my running career) but was not able to break 3 hrs on the bike leg. I trained 10 months for my 2nd 70.3 with a bike focus and still couldn’t break 3 hours. I wasn’t discouraged though. I was building my base and that was what I knew I needed to develop as an endurance athlete in the first few years. In my 3rd year in the sport, like clockwork, I started to peak. I got down to 2hr 38min for my bike split and have progressed ever since. First the goal was to break 22 MPH in a race (sprint because I haven’t done a 70.3 is a few years), then the goal was to break 23 MPH, then 24 MPH. I hit 24.3 MPH average in my last race so the next race I will try to go faster. It didn’t come in the first year. It didn’t come in the 2nd year. When it finally hit I saw a big jump and have continue to PR in almost every year in the 5 year since then. So runners can be good cyclists but they can’t expect for their running fitness to transfer to cycling fitness over night. They have to develop it over years of training just like the cyclists did and just like the swimmer have to do.
Note: I went Bike focused for the first 2 years. I neglected my running but I was crushing everyone on the run so I justified that I didn’t need as much time on the run training. At one point I just wanted to get back into my run training. I went run focused and when I cut back on cycling and increased my running is when my bike times started dropping. I don’t know if I was just set to peak on the bike or if the increased run volume is what made the difference but I was doing about a 75%:25% time split from cycling to running. When I went run focused it was more like 55% running 45% cycling. I have stuck with about a 50/50 time split. I know that doesn’t follow the schools of thought but that is what I do and both my cycling and running have taken off. I have taken 17 minutes off my Open Marathon PR in the past 5 years, 5 minutes off my open half marathon PR. And while not a PR I have done my fastest 5K since high school by about 45 seconds in that time too (and am working towards breaking that High school PR now). Not bad for a M45-49 Ager Grouper. So put the training in. Be consistent and it will come.
Note 2: I did redshirt for a Div I Cross Country and Track team my freshman year of college but was never a top tier runner. I dropped out of track/cross country because I didn’t earn a scholarship. So you probably have more potential than I did/do. I am 180 lbs. I would die to get down to 147. That was my wrestling weight my junior year of high school.
