I Spent My Sabbatical Building a Power Meter for Sledgehammers | Hacker News Reader

I Spent My Sabbatical Building a Power Meter for Sledgehammers

leblancfg.com

89 pointsalin2375 comments

Aye, author here. Pleased it's getting visibility ofc, but ABSOLUTELY not expecting to get traction this early.

Please pardon the AI-generated placeholder images and some of the text at https://intensity.systems, I'm still very actively working on that.

I'm curious about the units -- watts doesn't really seem right.

It seems like joules would make more sense, right?

I agree that total work is probably the more relevant metric.

Both are needed, but for an athlete watts is by far the more useful feedback for training, and following the intended stimulus of workouts.

As a workout, "bike 30 km" is vague and meaningless. "bike 30km in 1h" is better, but not specific to the athlete: some have better cardio than others. Most serious cardio workouts are given in zones: "bike 1h at 60-65% of your functional threshold power" [1] – this particular workout would also be known as "zone 2 training session".

(1) https://www.trainerroad.com/blog/what-ftp-really-means-to-cy...

Thinking back, I should also add: if you're interested in how hard a single hit is, then yes joules!

I'm approaching it as a workout, where you're doing dozens of hit. Good idea to have an individual strike joule view to the display though! "carnival mode"

Lovely idea, always nice to put something together and scratch that itch.

What you need is a small weight or something that rises up a pole depending on how hard you hit it, a great visualisation.

You could even have a bell at the top, so if this small weight hits it with enough voom it could making a resounding ding sound, so life affirming.

Perhaps you could charge a 'apenny a go, and give a prize for those that can do it. Saying Roll up Roll up to passers by in a local fair.

"High Striker": https://en.wikipedia.org/wiki/High_striker

Based on the headline, this is the first thing I thought of.

Is anyone else bothered that this was run through an LLM before publication? The tone is a distraction for me.

yes

All the superficial filler leaves a linkedin flavored taste in my mouth. I’d prefer to hear the author’s own voice and thoughts without noise injected to give the illusion of polish.

I thought it was actually quite funny, but I read it as a sarcastic parody of that writing style. I mean there’s no way:

> This is the founder story: what I built, why I chose it, and what a month of hardware taught me. The engineering writeup will come later, once I've talked to someone who actually understands IP strategy.

is for real, right?

Oh this is very real. As someone who lives in Ottawa, Shopify employees are a unique brand of people who think they are tuned into the SV trends but are just huffing their own farts. They're all acting out a small-scale replica of taking peptides and trying to found Uber for Polycules but in a sleepy capital city full of government employees.

So how does the power meter itself actually work? How do you know the output is accurate? How much power is lost from the measurement due to dampening? How do you know it will hold up to cycling in such an aggressive environment? That's kind of the interesting thing here, but there's no mention of it in the article.

Agreed. I was disappointed at the overall lack of engineering content in this piece. Lots of general talk about how there were issues and that they were overcome. But what? And how? I feel like most of the content could apply to almost any project.

Kind of like how “Stuff Made Here” has devolved into mark rober content.

Well “I badgered claude code for a month and got something that seems to work but I don’t remember how or why” doesn’t make for very compelling reading.

We are seeing the rift between actual hacking and vibe-building opening in real time. People always wanted to do this and get the attention. Now they can do it but it isn’t worth the attention.

Cool idea, just wondering why you wouldn't travel during a sabbatical.

> a paid month off

that's not a sabbatical anyway, is it? i thought this was 6-12 months, not one?

https://intensity.systems/ is currently unstyled.

Post also has some LLM sniffs, so I'm unsure how much of the content is true.

At least in North America (and the author seems to be from Canada), having a company give you any sabbatical at all is pretty rare, and 6+ months is pure fantasy:) And not everyone likes travel, the post actually explains his reasoning pretty well.

> and 6+ months is pure fantasy:)

I've seen this before. Had a vendor become helpless after their only engineer took a 6 month sabbatical. Had to cancel orders and switch vendors because they stated "Until the engineer returns, we can not quote a delivery time." Imagine being that company...

Kinda surprising they weren’t able to plan around that, surely The Engineer didn’t just decide randomly to go on a 6 month sabbatical all of a sudden.

It was a small vendor that was bought up into a larger umbrella parent so I'm sure there was no one at the helm capable of thinking ahead of making this months numbers.

"Just so you know, our bus number is 1. Now, about your order..."

Intel at one time did 6 month sabbatical if you worked 10 years.

I work in the US and every year I take 17 days off over the July period which works out (with another company holiday) to be 4 continuous weeks. The first year I did it I told my manager "I'm going to take three weeks off, but what do you think about four?". I got my three weeks and made myself indispensable enough to get the four the next year.

This stuff can be negotiable if asked for and planned correctly. It won't be offered.

The Danes do it best, they basically shut down the country for 3 months every summer and have an unspoken agreement that nothing will get done.

>The Danes do it best, they basically shut down the country for 3 months every summer and have an unspoken agreement that nothing will get done.

Is there a skeleton crew to run grocery and fuel?

OP was talking about white-collar jobs, not service industry.

Yes, but something like 90% of the workforce is unionized, and 5 weeks vacation per year is by law, with a "sixth week" being a common perk.

> Cool idea, just wondering why you wouldn't travel during a sabbatical.

That is really none of your business and sounds judgemental. How about we talk about the pollution you contribute when needlessly traveling for ego boosting?

> Cool idea, just wondering why you wouldn't travel during a sabbatical.

Because they didn't want to? A very odd question; people have motivations/interests that aren't yours.

>After five years at Shopify, employees get a paid month off to do whatever the hell they want. I took mine in April 2026.

Bleak.. Only a month after five years.

I think it's a month in addition to whatever they already get. So that could be pretty good.

I've been with my employer for 12 years and get a total of 296hrs PTO per year. That's probably abnormal now that I think about it and one of the reasons I've stuck around so long. I don't think I've ever used up all my PTO in a year, usually cash out a week or 2 in December.

Not sure why that’s bleak? It’s on top of the regular vacation days you get every year. I don’t know of any other company (at least not here in Canada!) that would give you an entire paid month off.

It's "bleak" because some people enjoy making others feel worse about things they have no control over.

Not bleak for most people. I've never worked anywhere that offers an earned chunk of time off like that (besides standard PTO days).

If by "most people" you mean "most Americans." That is pretty standard in Europe

Fair point. I meant, "most people I know working in America".

This is pretty cool! Your note about cycling power meters changing the way you perceive effort matches my experience as well. One other bit from my experience: I'm a runner and a cyclist, and I've always lusted after having cycling style data and prescribed workouts for my running. When Stryd launched I was all in, but... all it gave me was power numbers. It didn't have the tribal knowledge that came with my cycling power meter. Eg - lots of online content about zones, free and paid workouts / plans to target different goals (eg sprinting vs long endurance). It almost seems like any discussion of serious training on a bike comes back to watts.

But with the Stryd, all I got was power numbers, and the option to signup for a monthly paid subscription with some training plans that were pretty bare bones. It seems like running power meters just haven't been adopted widely enough for that critical mass of information to emerge. My realization from this is the data is useless without the tribal knowledge of how to use it. So my Stryd sits in a drawer somewhere, and I'm back to running by heart rate.

The equivalent in running is pace, at least on flat ground. I don't know that power would really be useful in running, the biomechanics of running hills is sufficiently different that I question the ability to make an equivalence comparison the same way you do in cycling.

Author here: funny you should mention that! Same idea has been on my mind for years at this point.

To me, the holy grail of sports training is to have simple but powerful enough models to estimate power data from dozens of movements, and fit various power curves that match real-world training.

So much promise there.

---

As for Stryd: That's so interesting. I'd imagine a lot of the same parallels to cycling to apply? Once you have your running CP/FTP, I'd imagine you could follow the same cycling training plans (relative to your FTP) for the same intended stimulus.

I'm curious though, can you see the Watts/zone/W'bal/etc. values on a watch or something when you're running?

Very much on the same page as far as the holy grail! Would love if I had all that data (and it was actionable).

As for the Stryd... take this all with a grain of salt because I only have a consumer level understanding but: You can establish your FTP, but then the issue is setting zones from there. My understanding is that the big thing with establishing them is having an accurate estimation of LT1 and LT2 lactate thresholds. Most zone calculators are approximating that, but those calculators are based on a large body of data comparing lactate levels to cycling power in a controlled environment (a lab). That large body of data doesn’t exist for running power, and I recall reading that the little bit that does indicates that formulas for cycling power’s impact on L1/L2 thresholds don’t line up with running power. It’s also been maybe 4 or 5 years since I was engaged with this so the science may have improved!

Watch wise, when I used it, I have a Garmin Fenix, and it had options to show watts/zones/etc. You can even plug in zone based workouts just like you can with cycling power. I did find it a bit of a pain to monitor on a watch vs a bike computer, but not too big of a deal.

I could see this being used for fitness tests for cross country skiers. A very common exercise is med-ball slams. These aren’t a perfect analog to double poling but definitely close.

Being able to track your one rep max force you can generate could be an interesting metric especially for sprinters

100% agree. And the issue with med-ball slams is they also can just be dropped in a testing setting, and the only power needed to be generated is on the "up" cycle. I wouldn't even trust my own med-ball slam benchmarks from one month to the next, as I'm not confident I slammed them with the same intensity.

I'm curious though, wouldn't a Concept2 ski-erg be the best machine for that job?

>track your one rep max force [...] especially for sprinters

Yeaaah that's the ticket =) One level of abstraction higher: you can think of that 1RM as the leftmost point on the max power curve, i.e. max force you've historically generated, from 5secs all the way to e.g. 60 mins [1].

(1) https://www.trainingpeaks.com/blog/4-key-uses-for-the-power-...

I believe there are already various, martial arts related, striking meters - to show how hard you are punching/kicking. Isn't this rather similar (but I guess not mounted vertically and calibrated for harder hits)?

I could see this becoming a tiebreaker or ranking device for lumberjack competitions.

I'm 13 years into my career and I haven't taken more than 5 days off in a row. That's usually a family reunion.

I think 4-8 weeks to recharge and reset would be helpful. What's the research say?

Wish I could do that too. But sabbatical is usually reserved for the elite engineers in elite firms.

"After five years at Shopify, employees get a paid month off to do whatever the hell they want. I took mine in April 2026. Thanks Tobi!"

Work culture is so weird. What do you mean, it's reserved for the elites?

In my country you get to build your holiday days, so I could totally take a month off if I don't take any other days off this year. Hell, we even have a website to perfectly time it here so you get the most bang-for-your-days. lmao.

I will never comprehend this Silicon Valley mindset. You can also be a 10x engineer while drinking a martini in the balkans.

Lives don't exist in vacuums. If I could uproot my close friends and family and we all moved to the same place then I would, but that's not possible. I'm sure it's the same for a lot of people

What does uprooting your friends and family have to do with taking a month off once in your life?

This was mostly in response to "You can also be a 10x engineer while drinking a martini in the balkans." and is likely a bit of an overreaction to the amount of "just move if you don't like it!" things I've seen. Mobility is a luxury

Uprooting family and friends has little to do with taking a month off, but if things don't fall right then one runs the risk of spending their month off mostly by themselves which may or may not be attractive. I've known single teachers complain about this that they have June-August off but no one to spend it with because most of their friends are not teachers

You are right. I was mostly thinking about a sabbatical of about 3 months.

Or Europeans (:

I'm almost 17 years in and there's been a few times where I had more than 10 days off in a row, and I recently had a four week sabbatical. Anecdotally, it was great and reminded me that retirement has always been the goal.

A sabbatical is half a year or a year in germany. NO one would ever say this nonsense of 'four week sabbatical'.

To me, “work 40+ years and retire when you’re already physically and mentally slow” is the real nonsense. A sabbatical thrown in here and there doesn’t make up for it. I’m grateful that I live somewhere with high enough paying jobs that I can simply quit after just 20 years.

Sabbaticals, paid or not, seem to only be somewhat common in western Europe. I'm glad that you're able to able to experience this but recognize it's quite a privilege globally. It's not just the USA that has this "nonsense"

I would agree if the person would live in a 3th world country but not in the country with the highest GDP and comments on a it focused community

I take 3 weeks in a row every summer, couldn't live without it.

Wow thats depressing.

I went to japan and took 14 days. I went to Iran and took 14 days. I went to canada and took 4 weeks. I went to Mexico and took 3 weeks.

Don't you want to do things with your life? Experience them properly?

I, I, I, I...

More to L-I-F-E than "I".

MY examples are MINE not YOURs and not LIFE.

And I brought it up to show the stark difference.

Did i heart your feelings? Are you also only working and calling that a living?

Minimum vacation days here in Germany are 20 with many companies offering 30 so the idea that you can't take of at least a couple of weeks for a vacation is just crazy to me.

How do you travel and see the world like that?

> How do you travel and see the world like that?

Wait until we're old enough to retire and then can maybe afford it.

Wow. Are you in the US? If so, is this the norm in the US? Pretty depressing... why do you want a SV wage then?

I'd think that electronic drum heads would provide a good prototype. I really know nothing about it, so I could easily be wrong, but the basics are all there... They are percussive, and the sound varies by how hard they are hit, so there has to be something like a power meter going on.

Maybe someone else knows more?

Have you met shovelglove?

https://shovelglove.com

did you find any correlation between strike power and recovery — like, does the pad already give you enough signal to say "don't swing hard tomorrow"?

I didn't look into or find any myself, but "power meter enabled" sports like cycling, rowing, etc. have a way to measure the strain/fatigue of efforts relative to the athlete's fitness (FTP). Same would apply here.

There are various methods to measure that strain, e.g. Strava, intervals.icu, TrainerPeak all have their slightly tweaked implementations.

> People I look up to include Frank Zappa, Richard Feynman, J.K. Rowling, Peter Norvig, and Geoffrey Hinton.

TFW you want to seem intellectual

Charpy would like a word.

You remind me of a saying: Boring things are actually interesting.

Now I have Peter Gabriel in my head.

Me too, but it's "Shock the Monkey" which doesn't make sense in this context.

You are just In too deep, Dont give up

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