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# GOLD COAST MARATHON SERIES - TRUTH ABOUT HEART RATE TRAINING WITH POLAR
- URL: https://www.inthebeginningpodcast.com/gold-coast-marathon-series-truth-about-heart-rate-training-with-polar/
- Published: 2025-04-22T06:00:00.000Z
- Updated: 2026-08-19T05:14:27.000Z
- Description: Courtney Atkinson and Liam Flanagan on heart rate training, Gold Coast Marathon, Olympics & 2032 — recorded on the Gold Coast.
- Author: Courtney Atkinson
- Tags: Episodes, Gold Coast Marathon, Sports Science, Olympics, #Import 2026-07-28 20:58

*Courtney Atkinson and Liam Flanagan on heart rate training, Gold Coast Marathon, Olympics & 2032 — recorded on the Gold Coast.*

## Listen

Listen on [Spotify](https://podcasters.spotify.com/pod/show/inthebeginningpodcast/episodes/GOLD-COAST-MARATHON-SERIES---TRUTH-ABOUT-HEART-RATE-TRAINING-WITH-POLAR-e31r065?ref=inthebeginningpodcast.com) or [Apple Podcasts](https://podcasts.apple.com/au/podcast/REPLACE?ref=inthebeginningpodcast.com).

## Full transcript

Auto-generated transcript. Timestamps approximate. Hosts: Courtney Atkinson & Liam Flanagan.

**Read the full transcript** 

\[00:00\] In the beginning runs the Gold Coast Marathon. We're continuing the countdown to this fantastic marathon. The programme keeps running with Benita Willis of Lace Up Running, myself, Bronte following along with the training programme, and Courtney. But we're taking a break from the programme this week because we've got a very exciting guest — plenty of partners are involved in making this amazing race happen, and today we're joined by John Easedown, sport scientist and Polar solutions

\[00:30\] specialist. How are you, John? Welcome. Very good, thank you, thanks for having me. Off the bat, you know what's going to be great, mate — we're going to get some proper science points. John, just some background — I've got in trouble previously on episodes for hypothesising without any proper knowledge, and what normally happens is we say silly things and people smack us down in the comments afterwards. Liam pretty much once compared lungs to toilets, didn't go down too well.

\[01:00\] You don't need to revisit that one if you don't want to — you can go back and check it out if you're curious. But welcome. Let's start with Polar, the brand, and the association with the Gold Coast Marathon — how and why did Polar want to get involved with this race? We first got involved with the Gold Coast Marathon, I think, just before Covid, or maybe just after — this will be our third time as one of the key sponsors.

\[01:31\] It's just an awesome event. We were there for the last one, and the amount of people there is amazing — I was on the start line, so many people, and they just keep going. Such a great atmosphere, a great event, it's what Polar's all about. So we're very excited. Have you run it yourself? I did the 10K, picked up an injury, so no is the answer — I wouldn't dream of trying the full marathon. I picked up a calf injury at about the 4K mark and just struggled my way through

\[02:01\] it. But you're a runner yourself, out there week to week — calf injuries have absolutely played a part, and I do all the things I'm probably going to tell people today they should avoid, like training load errors and so on. I try to get out a couple of times a week. We'll get to your expertise from the sports-science side — we're going to talk about some of the wearable tech Polar's offering. Quick heads-up for everyone: Polar has a sale coming, up to 30% off,

\[02:34\] starting April 28th, running through to May 11th. So polar.com — if you're after a new watch, a chest strap, a heart-rate monitor, some wearable gear, if you're looking to take your running to the next level, mark it in your diaries, save it in your phone, whatever you need to do. It's the gold standard for heart-rate monitors and running watches, so just note that down. Now, before we get more into your role with Polar,

\[03:04\] I want a bit of background on you — people might have already picked up on the accent. Originally from the UK, yes. Did your sports-science background start over there or over here? I did my undergraduate degree in sports science in Luton, graduated in 2004 — long time ago now. I didn't come over here until I was about 30\. Just before moving, I went through my accreditation with the UK Strength and Conditioning Association, then the

\[03:35\] ASCA over here, the Australian equivalent, did my postgraduate master's at ECU in Perth, and have been heavily into it ever since. Got on board with Polar from there. What's the difference between Australia and the UK in terms of qualifications — is it basically the same process? Are Aussies a bit more skilled, or what's the deal? You remember when the UK poached all their coaches for the 2012 London Olympics? Yeah, a mass exodus.

\[04:06\] Now we're getting some of you back. Still the best, exactly. So what got you interested in sports science and strength and conditioning in the first place? Were you an athlete? Actually it started from just being a gym junkie at about 18 — looked around for what to do, went into sports science because it was something I was interested in, and I got really pulled into it. I still go to the gym and train, but I really got into the science side of things.

\[04:37\] Can I ask, quickly, as a former gym junkie — what do you make of Hyrox? I like Hyrox, I like these new formats coming through, they're good events, and the community they generate — my wife's really involved in that kind of thing, she's an absolute weapon. I think it's cool. It's like CrossFit came along, and now there are new offshoots of that kind of activity. I think it gets people doing more —

\[05:08\] more Olympic weightlifting, strength training, high-intensity running. And it's been a boom for running too, because people who were only ever in the gym, especially through Hyrox, are now actually out there — I've seen people at the Gold Coast Marathon who've come from that world, trying to improve their running so they can get into more events. So everyone's winning, fitness is winning at this stage, everyone's getting into everything. I'll jump straight into the big one, because the buzz term at the moment around heart rate and

\[05:38\] fitness is zone 2\. Let's just get into it — Courtney wants to rip the band-aid off. I grew up in a time when, physically, there were zones and heart-rate monitors and all this around, but we used terms like anaerobic and aerobic threshold — there's so much jargon out there online now. Zone 2 has to be the biggest buzzword in endurance

\[06:09\] sport at the moment. Can you give us an easy explanation — what zone 2 actually is, why it matters, and whether it's worth pursuing? Yeah, definitely the buzz at the moment, in my opinion — the pendulum swings too far towards things, and it'll be something else in a couple of years. Zone 2 is typically up to your lactate threshold, and we should probably define some

\[06:40\] of these terms as well. Please do, there are idiots in the room. There are certain key physiological parameters that we all have individually — things our bodies are capable of. Right, OK — no, sorry, no, no, no — because you and Courtney understand this, and some listeners will too, but then there are people like me where the moment you say "physiological," my brain just translates it to, he's talking about your body. So explain it in

\[07:12\] your language, and I'll ask for the layman's version if I don't get it — I'm here as a filter for the idiots out there, I'll trip myself up so you don't have to. OK, so lactate threshold — there are really two thresholds worth knowing about. LT1 is the first sudden and sustained rise in lactate levels in the bloodstream. Let's put that in context — this is individual to everyone. Say I go out and run at 7 minutes per kilometre, and I

\[07:42\] could hold that for three minutes and reach what you'd call a steady state — lactate levels plateau, heart rate plateaus and stays level. I'd take a finger-prick blood sample and look at lactate — say it's 1.5 millimoles per litre. Then I go and run at 6:30 pace, same thing, still 1.5\. Then I go to 6-minute pace, and now it's jumped up to, say, 2.3.

\[08:12\] So that's the first rise — that number climbing just means lactate is starting to build in your body. That's still a sustainable pace for me, at 6-minute kilometres. If I keep increasing the speed, lactate keeps climbing and climbing, until I hit a point where it starts to rise exponentially — on a graph it's this curvilinear rise, it just shoots up.

\[08:43\] That's LT1 — think of it as a sustainable marathon-type pace. Keep increasing further and you hit a point where the curve just goes vertical — that point is LT2, or the lactate turn point. There are lots of different terms for it, which is really confusing for people — different research groups, academics and coaching schools all use different terminology. I'm trying to wrap my head around it myself, so imagine how the average person feels. But once you go above LT2, that's an

\[09:17\] unsustainable speed. And we've all got our own unique numbers — for me it might be that once I start running over 12 kilometres an hour, or 5-minute-K pace, I've got about 20 minutes before I hit fatigue and I'm done. So if you're training for a marathon, you're not running it at LT2\. We can use heart-rate zones to estimate all this too — Courtney, have you done proper lactate and oxygen-consumption testing in your career? I

\[09:48\] know what you mean — we got thrown terms like zone one, zone whatever, though we really didn't use "zones," it was LT1 and LT2\. I did a proper lab test again last year in America, the first since roughly my Olympic days, and there'd obviously been some changes, but the same basic process. What surprised me is that essentially nothing's changed since 2012 — the scientists I worked with were doing exactly the same tests. It's just the language used with the general public that's changed, and that's what's

\[10:21\] even got me confused sometimes. What you're explaining, I fully get — so if anyone's listening, zone 2 is basically what you're describing as LT1\. To go back to your original question, which I didn't actually answer — zone 2 training, in heart-rate-zone terms, is: there's a common five-zone model people will be familiar with, and when people say zone 2 heart rate, they mean the zone that sits just below

\[10:53\] lactate threshold. It's the low-intensity, long-distance running zone — something you could hold a conversation through, keep talking to someone while you run, and you're probably in zone 2\. There are certain physiological adaptations — changes that happen in the body when you train in zone 2 versus zone 3, 4 or 5\. You mentioned heart-rate zones, but these zones overlap with things like lactate

\[11:24\] threshold and the lactate turn point — so you're not looking at two completely separate scenarios. An elite athlete will have access to labs and sports scientists who generate a lactate profile for them — they'll look at your lactate levels against your corresponding heart rates and running speeds and say, right, if you run over this speed you're on borrowed time, this session is designed to build this capacity, so you need to run at this exact speed.

\[11:54\] It's a very specific prescription. But not everyone has that kind of access — we can use other tools, like rate of perceived exertion, which is subjective: how do you feel, can you hold a conversation with someone you're running with, can you breathe through your nose — if you can, you're probably in zone 2\. If you've got a coach like Benita, who's absolutely awesome, and she says a session should be low intensity, you might use "can I talk, can I breathe through my nose" as your gauge, or you might look at heart rate — but recreational athletes generally aren't going to have access to lactate

\[12:26\] or oxygen-consumption testing. And we're already getting a version of that through Benita, right — her communication is very verbal cues rather than the hard science side. But what's great, whatever your level as a runner, is that in the end it's all the same underlying information, just communicated differently. Sometimes I get the feeling the more

\[12:57\] scientific-sounding the language, the more impressive the idea sounds — but it can be reduced to something really simple, like an RPE, how do you feel while you're running, and that can land you in exactly the same place as spending thousands of dollars getting tested overseas. The results can be very similar. So, to that point — you've explained what zone 2 is, but why is it important, why is there this buzz right now?

\[13:27\] You mentioned the pendulum, what's cool and what's not — zone 2 running and training has clearly been cool lately. Is it the right place to be spending a lot of your training time, do you think, and why? Definitely, yes. Your aerobic base — which I'm sure you've heard about — is built through lots and lots of low-intensity zone 2 running, or cycling in other sports. So you do need to spend

\[13:58\] time there. It develops the aerobic machinery very effectively, but it's also not such a high intensity that it puts you at higher injury risk, and it's easy to recover from. Just on that — the notion of building your aerobic base in zone 2 over however long — how quickly does it fade? How quickly do you lose it, this de-training

\[14:30\] effect? I don't know if this is one you can answer, and it's specific to the individual, but I go through phases as a recreational jogger with high aspirations — training for a sub-three-hour marathon at the moment, doing trail runs — and there are times, with all the noise around running, where I wonder, what's happening to my aerobic base if I take a week off? What's happening to all this

\[15:02\] if I haven't run for two weeks? I genuinely don't know what it means for my base. If I take extended time off, do I need to go back and rebuild zone 2 specifically? How does that work? Well, zone 2 should always be part of your programme, so it's not like you're deviating from it entirely. But if you take a week off, you're not going to start losing real fitness. And actually — Benita's talked about this — you probably should have deload weeks built into your programme, where you back off and let your body

\[15:33\] recover and get a super-compensation effect, a heightened level of fitness afterwards. I like that "super-compensation" phrase — that effect can only occur with adequate rest, and rest should be built into your programme, with target lighter weeks so you can recover and get that super-compensation

\[16:05\] effect. So, to actually answer your question — it's probably weeks to months before you start losing real fitness from the de-training effect. Good for anyone listening to know, because there's obviously some nuance to what we're discussing here. Polar's worked with Benita — well, obviously Benita coaches Bronte and Liam, but you've worked with her in the past, and you can go to polar.com where she's put together template programmes for different distances — 5K, 10K,

\[16:35\] half marathon, marathon, beginner through to intermediate, two different programmes for each. There's a base template there anyone can go and look at — it's not a replacement for a personalised coach by any means, but with everything we're discussing here about heart rate, deloading and so on, having that structure is really important. It's another resource worth checking out if you like what you're hearing from Benita each week. Yeah, they're great programmes, and they've got heart-rate zones built into them, so if you've got a Polar watch or any wearable you can use the zones directly. Great time to

\[17:07\] ask — how do we actually work out these zones with a heart-rate monitor? We're talking Polar today, but for anyone running with any heart-rate monitor — how do I work out my zones, what's the most effective way? They're based off your own individual maximum heart rate, so that's the starting point — you need to find your max heart rate, and we've all got our own, which will be

\[17:40\] different. What's the easiest way to get that? The easiest, though probably not the most accurate, is a prediction equation — the most common is 220 minus your age. So if you're 40, your predicted max heart rate is 180, and the zones are based off that. Zone one runs from 50% to 60% of max heart rate, and zone 2, which we've been discussing, is 60 to 70%. What would that look like in numbers — zone 1 would be 90 to 108 beats per minute, and zone 2 would be 109 to 117\. So if you're running along wearing a device and your heart rate sits in that range, you're in zone 2\. If you're

\[18:12\] following Benita's programme and it tells you a workout should feel a certain way, I'm sure she's got heart-rate markers in there too, and you can check your watch to confirm you're in the right zone. I'll give you a story about my own heart rate in a minute, but before I do — is there a way for the watch to work this out for me automatically, guide me through it, suggest it based on my runs? If I want to go beyond the basic formula and work it out physically, how do I do that? There are other prediction

\[18:43\] equations where you plug in a recent race time, and there are hundreds of them. But probably the best way — you've likely done a ramp test in a lab, an incremental test where they keep increasing the speed until you simply can't sustain it any more, and that gets you there. Polar actually has a great feature built into the watch called the Polar Running Test — a field version of that ramp test, done outdoors instead of in a lab, where it keeps asking you to increase your pace until you reach exhaustion.

\[19:14\] The GPS sensor picks up when you're not able to maintain the speed and terminates the test, and — provided you actually go to volitional exhaustion — that gives you your maximum heart rate. It walks you through the whole thing in real time, prompting you if you start dropping out of the target speed zone. Once the test's complete, it updates your maximum heart rate and recalculates your zones from that new max. That's really cool — I also enjoyed the phrase "volitional exhaustion," that's another one for the

\[19:45\] layman's list, along with "super-compensation effect." The reason I pushed for a more accurate version than 220-minus-age is my heart rate isn't exactly normal. I had a CT scan the other day, and the technicians came in really worried, asking if I'd seen a cardiologist — my heart rate was dropping to 36 while I was lying on the bed. At the time they were also having a look

\[20:19\] at my heart on the CT, with no background on me at all. So — this is a scan of my heart. My heart normally sits about in this area, but it's extending right over into my

\[20:51\] side ribs, which is presumably a result of endurance training — that's probably when you talk about it, a bit of a "healthy" heart falling apart in the best way. She saw this scan and had me lying in the machine at 36 beats per minute and literally wanted to call the doctor. So — that's one case, but at points where you're just using the 220-minus-age formula, it's a great starting guide, though I'd suggest if you've got access to the technology, go get the more accurate version tested. And if you don't, polar.com has that sale from April 28th, worth mentioning again. Quickly, on that — I don't have a horse's heart like this one over here, but I did do the Noosa Triathlon

\[21:21\] last year and came back with data from just the wrist monitor, not a chest strap — it told me my heart rate got up to 208 during the run, which is clearly an inaccurate reading. We should probably demystify the different heart-rate sensors while we're here. Let's do that — can you talk about how they actually work, and how accurate each type is? For sure, I'd love to. So, still pretty much the gold

\[21:52\] standard is the good old chest strap — this is the Polar H10\. When I say gold standard, I mean literally — when researchers want to validate a new heart-rate sensor coming onto the market, they'll compare it against the Polar H10, because it's known to be extremely accurate. We've talked before about

\[22:22\] a range of different GPS watches, had the audience weigh in on different ones — but whenever it comes to chest straps, Polar's always the one I come back to. How old is this particular strap? About seven years old, I think. Doesn't matter which watch I've used since, that's the strap I still use — there's one in my garage right now.

\[22:53\] So that's the gold standard. What makes that particular Polar strap so good, technically, that it's outlasted everything else? I think Polar's got about five decades of scientific research and innovation behind their products, and they've just fine-tuned it so well. Though to be fair, any good brand's chest strap should be near the top of the list, it doesn't have to be Polar specifically. The chest strap is the most accurate because it works via ECG — it's measuring the electrical activity, the electrical impulses of your heart.

\[23:23\] That's your number one option. After that, we've got what are called optical heart-rate sensors — worn on watches.

\[23:54\] This one here is called the Polar Verity Sense, which for me would be a strong second option. Optical sensors use a process called photoplethysmography, PPG for short — basically shining light into your body. This one can go on your forearm or upper arm; it's got a photodiode, a light detector, that reads the reflected light, picking up changes in arterial blood flow, because each time your heart beats and ejects

\[24:25\] blood through your system, that shows up in the reflected light. There are things that can interfere with the light picking that up, though — I've got a really bony wrist myself, so I don't get great readings from watches using this technology. I've got clients with different wrist structures who get brilliant heart-rate readings from the exact same devices. I'm fine with steady-state exercise — a steady 5K run, it's perfect —

\[24:56\] but the moment I do higher-intensity intervals, it just doesn't pick it up properly. My wife does intervals and gets this beautiful, clean heart-rate reading the whole time. The watches have gotten much better — the recent generation is probably the most accurate I've seen on a wrist. But to go back to the ranking: chest strap first, then an optical sensor like the Polar Verity Sense, which mimics the strap's accuracy fairly closely because of where it's placed on the

\[25:26\] body — same underlying technology as a watch, though. Is upper arm or forearm the preference? Either works, but I'd go for wherever there's the most tissue — more capillaries there, versus a bony wrist-to-tissue ratio, which is my problem, not much tissue there for the sensor to work with. How do you find optical sensors on your own wrist? I gave up on wrist optical years ago too. Some people just don't get on with it and say the watch is rubbish, it just doesn't work for them — for others, they get very good readings.

\[25:57\] It's refreshing to hear people do get good readings from them, because I'd normally just write the whole thing off and wonder why you'd bother. But it really is individual. Apart from that 208 reading I got at Noosa last year, the zones my watch puts me in for the most part seem fine — but I've genuinely never used a chest strap, so I don't actually know how inaccurate the numbers I'm

\[26:27\] getting really are. What watch do you use, by the way? I've just never really looked into swapping. Obviously the Gold Coast Marathon can still be pretty humid at that time of year — does humidity affect the optical sensors too? This is me just theorising off the top of my head, but I've had a theory that in Queensland, more sweat has an effect on some heart-rate readings. Am I

\[26:58\] onto something there? You don't want water or fluid getting between the light sensor and the skin, so it could affect it slightly, but I don't think it's a major factor — there's not really solid science behind that specifically. It's more things like tattoos affecting the reading, skin tone, how fleshy your wrist is, and whether it's actually positioned correctly and worn snugly. Some people say a device doesn't work and I look at it and it's just hanging loose on their wrist, not snug enough, not worn correctly. But some people wear it exactly right and still don't get accurate readings —

\[27:28\] there are just more variables that can affect accuracy on a wrist device versus a chest strap, where there's really not much that can go wrong — it's accurate something like 99.9% of the time. With all this wearable tech — chest straps, watches, everything you've talked about — have recreational athletes ever had it this good in terms of monitoring all this information? Or do you think

\[27:58\] it's sometimes too much — that some of us don't need as much data as we're now getting? I think we've never had it this good in terms of the tools and technology available to support the training process. But on the flip side, sometimes there's just so much data that it becomes noise, and people get paralysed by it, not knowing what to actually do with it. Someone might buy a watch and there's just so much on there — it's telling me I'm overreaching and I don't really know what to do with that. It can be

\[28:29\] a lot, especially if you're not well informed, which most people aren't. So, with all this wearable tech, the watches and everything else — say I'm not being coached through this marathon like you are, Bronte, say I've just grabbed a training plan online somewhere — how do I best use the information my watch is giving me? What's the important stuff my watch might be telling me that I should be

\[29:01\] paying attention to, in terms of training and recovery? There are a few answers to that — let's start with how it can help your training. In the moment, if you've been assigned a zone 2 session, the watch tells you in real time whether you're actually in zone 2 or not via heart rate. It's accurate, and it acts as a kind of intensity discipline, because people go out too hard — that's one of the most common mistakes we

\[29:31\] make, and how we get injured — we feel good, so we run faster, and everything regresses to the middle: every session becomes kind of hard but not that hard, and not easy either. You lose the clear split between easy days and hard days, it all becomes the same intensity. And that middle zone is oddly the hardest to recover from — you don't get a huge stimulus from it, so it's not that you

\[30:02\] never want sessions there, but it becomes a form of intensity control while you're training. I think I've lived in that middle zone for the last nine years, John, so I know exactly what you mean. Sticking to the right heart-rate zones is the key. My question is about heart-rate creep, or drift — if I'm out there, fairly new to all this, watching my heart rate and trying to keep it steady, can you explain how that

\[30:34\] works, and what I should actually do about it? You're getting quite technical now — there's a newer term for this, "durability." We talked about lactate threshold, running at a speed that's sustainable for you, but after a while at that speed you start fatiguing, so your threshold isn't static, it can shift during a run. One way to think about it is relative

\[31:05\] to your own effort — because you're so experienced, Courtney, and you've been looking at this kind of data for so long. They look at heart rate relative to output — what's your running speed, and what's the heart-rate response to that speed, how is your body responding. They split a run into the first and second half, and if you get heart-rate drift, you can express it as a ratio: in the first half, at a given running speed, you've got a given heart rate.

\[31:37\] You maintain that speed into the second half, and your heart rate starts creeping up — that's heart-rate drift, a sign you're heading towards fatigue. Elite athletes, among other things, have really good durability or resilience — they can tolerate training stress for a long time without experiencing that creep, they stay very consistent. Does that answer the question? It does. I just —

\[32:07\] the reason I wanted to ask is, had you heard of this before, did you understand what was going on? It was all new to me. I think I just want anyone listening, if they're playing around with heart-rate data and getting into the tech, to understand it's not necessarily normal to hold one exact heart rate the whole way through a run — you might go out for a two-hour long run thinking you can sit at one number and

\[32:38\] still be running the same pace by the end. The likelihood is, even if you manage the effort well, there'll be a slight drift upward in heart rate as the run goes on. That's not necessarily detrimental — it's just part of how the body responds to a long effort. The flip side is I've seen people who are so data-driven, brand new to a heart-rate monitor,

\[33:10\] absolutely fixated on staying in their zone, over-focused on keeping the heart rate pinned — and by the end of the run they're running 20 seconds a kilometre slower because they're so locked onto the number. So there's a happy medium — all this technology's a great guide, but it comes back to RPE too, understanding and listening to your body, because the moment you're racing, you want to race, and to a degree these are all

\[33:40\] just guidelines. Pace is a guideline, heart rate's a guideline — great tools to help you hold an even effort, but you've still got to learn to listen to what's going on inside. I was going to add — they're tools to assist the training process, not the be-all and end-all dictating everything you do. You've got to listen to your body — your heart rate might start creeping up a bit, but if you feel great, your perceived effort and fatigue are genuinely fine, you might just continue on

\[34:11\] rather than dropping the pace purely to keep the heart rate in the blue zone — zone 2 shows as blue on these monitors. What about recovery — because we've talked about all this data and how you can get fixated on the numbers while training, how can we use this stuff as a recovery tool? When it flags you as strained or underperforming,

\[34:42\] should we listen to that, or ignore it? How accurate is all that? Should I take a rest day just because the watch told me to? I'd say, not necessarily — like I said, it's just one stream of information to help you make a more informed decision, and your own perception matters just as much. It depends how deep you want to go — it might start with what they call subjective wellness

\[35:12\] questions, no technology involved at all: how do I feel out of five for fatigue, how did I sleep, how sore are my muscles. You might just track that daily, not even write it down, just do it on the fly. Or go a step further — measure your resting heart rate first thing in the morning, still no technology needed,

\[35:42\] just count for 30 seconds and double it, or count for a full minute. If your resting heart rate is creeping up over the course of your training block, that can be an early sign of fatigue. Polar's got a feature called Nightly Recharge — wear the watch overnight and it tracks sleep quality, sleep duration, and it also measures heart rate and heart-rate variability to tell you how your body's actually doing. You don't have to do anything, it works in the background, and in the

\[36:12\] morning you get the feedback. But to actually answer the question — just because the watch says you need to rest doesn't automatically mean you should skip training entirely, though often it does mean something's off. I like to look at a few different information streams to make that call, not just one number. If

\[36:43\] the watch flags something and, separately, you genuinely do feel tired and sore, that's two data points lining up, and that's worth listening to. And it might not mean full rest — maybe you just change the session, do something lighter instead of your planned hard session, because your body's not ready for it and, more importantly, you won't adapt well from it, you'll just increase your injury risk. So you do a light session, a recovery session, or you don't train at all — go for a walk, spend time with the family. That's really good advice. I imagine a few people's ears just pricked up at

\[37:14\] "heart-rate variability." Yeah, I knew that one was coming — another buzzword right now. I first came across HRV about 25 years ago — there was a sports scientist at the Australian Institute of Sport, and I remember very clearly being at a world junior championship in Montreal, where for five days before the race the sports scientists would come in,

\[37:46\] have you lie on the ground, take a heart-rate reading two minutes later, then have you jump up. They'd be putting all of that into spreadsheets, doing research on heart-rate variability even back then. I didn't hear much more about it after that until fairly recently, when it started popping up all over social media and consumer tech. Is it actually a useful tool? Can you explain to everyone a bit more what it is,

\[38:18\] what it actually measures? I'll start with what it is — it's not variation in your resting heart rate itself, like going from 60 down to 55 when you sit down. It's the variation in the time interval between each individual heartbeat. Say you've got a resting heart rate of 60 beats per minute — there might be exactly one second between every beat, meaning zero variation, an HRV of zero. The more that interval varies from beat to beat,

\[38:48\] the higher the HRV — say 900 milliseconds between one beat and the next, then 950, then 850\. That changing interval isn't the important part in itself — what matters is that it gives you a window into how your autonomic nervous system is sitting. Simplified, the autonomic nervous system has two branches: fight-or-flight, and rest-and-digest.

\[39:19\] This is good, John, I'm actually keeping up. I'm going to get in so much trouble with my colleagues for saying that. No, this is good — for recovery you want to be leaning into rest-and-digest, and measuring heart-rate variability gives you a window into where your body's sitting on that spectrum. If HRV is low,

\[39:49\] that's a sign of stress, you're leaning towards fight-or-flight. It's a spectrum, not a switch. If HRV is high, that's a sign your body's well recovered and ready to tolerate a training stimulus, another hard session. And it's not about comparing your number to someone else's — it's about tracking your own daily and watching how it changes day to day. There will be variation, and there should be — if you do a hard training session,

\[40:20\] there should be a bit of a drop in HRV afterwards if it was a genuinely strong stimulus your body's adapting to. But if it just keeps dropping and dropping, you're stuck in fight-or-flight, high stress hormones, not recovering well. So you can use it as a recovery marker — it's one metric these wearables draw on alongside things like sleep, and they put it all together into a model to give you an overall readiness score. More and more, because — my alarm goes off at

\[40:50\] 3:30 in the morning for my job, and my HRV number is generally pretty poor. Hearing you explain it now, in terms of rest-and-digest versus fight-or-flight, I know exactly why — I'm just not sleeping enough, so I'm sitting more towards the fight-or-flight end of the spectrum, which is what's

\[41:21\] driving that lower HRV number. It's great, because these are all terms that, as runners — whether you're at beginner level running your first marathon, or well beyond that — you're constantly picking up on social media without really knowing what they mean. It's great to have a simple explanation. You don't necessarily have to act on the advice, but it's good to know where it comes from and what it actually means, so you can decide for yourself whether it's something you listen to. That's really cool, another form of information. But like we said with zone two,

\[41:52\] zone 2 is a buzzword, HRV is another one. Even as a recreational jogger for however many years, I'd genuinely never heard that number mentioned before, and suddenly, I reckon in the last twelve to twenty-four months, everyone's talking about HRV. I'm sitting there thinking, what are you all on about? Between zone 2 and HRV, I'd say — these aren't gimmicky, there's genuinely solid research

\[42:22\] behind both of these parameters. There's a lot of gimmicky stuff coming out in wearables, throwing in all sorts of extra metrics, but HRV and low-intensity, long, slow-distance training for endurance athletes are well proven — that's what I mean about 25 years of research behind it, there's a lot of substance there. So no, we're definitely not saying they're gimmicky, let's be very clear on that. It's sometimes the way they get presented on

\[42:52\] Instagram, and where that expertise is actually coming from, that ends up looking gimmicky, not the science itself. We're a hundred percent with you on the background here — with endurance training, the more miles you can run generally does improve your probability of a better marathon, but there are a lot of other measures you need to get right to arrive there well, safely and uninjured. So is there something around heart-rate monitors and

\[43:22\] wearables specifically that helps with injury prevention that we should be looking at? Definitely — HRV is a really good one, something you can use daily to adjust your training. There's another great feature on Polar watches, and most other wearables have some version of it, though I can't speak to exactly how each one calculates it — one of the big problems with soft-tissue injuries in endurance athletes is spikes in

\[43:53\] training load. To put some context around that — say you're used to running 50 kilometres a week, and you've probably heard the rule of not adding more than 10% volume per week. If you're used to 50 and suddenly do 80 in a week, that's what you'd call a spike in training load, and you're putting yourself at real risk there. It's not so much that high training loads themselves predict injury — it's sudden

\[44:26\] spikes in load. The watch, if you wear it consistently, tracks your mileage and intensity, feeds it into a model and flags this for you. Research over the past decade or so has found a sweet spot of roughly 90% to 120% week-to-week change in training load — go over 120% of an increase compared to your recent weeks, and it doesn't guarantee injury, but the probability starts creeping up.

\[44:59\] For me personally the model works brilliantly — I've had hundreds of calf injuries over the years. If I'm running twice a week and then suddenly have a free week and think, great, I'll add in an interval session, I'll get a calf injury. Whereas if I build it up slowly, a little more each week, I do a lot better. We're all case studies in this, whatever level you're at. Any more nerdy science questions? I don't have a science one, but — well, this is all science.

\[45:29\] I've got one — what do you see as the next iteration? What's coming next in this space? I reckon the big one's going to be real-time lactate monitoring. Was that too on the nose, right into Courtney's sweet spot?

\[46:03\] We should clip that up for social. Explain what you mean by that. Getting lactate levels currently is quite an invasive process — you've got to draw blood, stop the person mid-session. Whereas if it can move to something like a patch, or built into wearables, you don't have to do that — you could see lactate levels in real time. If a session calls for staying at LT1, and you know your LT1 is 2.2 millimoles or whatever it is, you could just

\[46:34\] glance down and confirm you're in the right zone. Do you think that's actually achievable? Do you reckon they'll get there? Wow, that's exciting. I think it will happen — there are already patches doing continuous blood-glucose monitoring, so the technology direction is there. The question is whether they measure it in sweat or something else, but that's probably the path. That's a better answer than I expected, that's very solid — you can tell we've slowed your response down like a kid

\[47:05\] on Christmas there. Well, look — this has been genuinely great. John Easedown, sport scientist and Polar solutions specialist, thrilled to have you in to talk through this. There are people listening preparing for their first marathon, their tenth marathon, chasing a PB, and the great thing about everything you've just told us is there's something useful in there at every

\[47:37\] level of running, no matter your stage. So thank you for coming in — and thanks to the team at Polar too, because the Gold Coast Marathon doesn't happen without partners, and Polar's been a great partner for a few years now. If you're out there without a watch and saving up for one, there's that sale coming very shortly, so polar.com, go check it out — plenty of products, and if you can get yourself the H10 chest strap, that's the gold-standard, lab-quality option, Courtney's

\[48:10\] had one for a long, long time. All right, mate — when the lactate monitoring thing actually comes out, we'll get you a new one. All right, thank you. Hey, John Easedown, thanks so much for your time. Thank you very much, thanks for coming in.