Jem Arnold @jem_arnold Twitter profile

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Jem Arnold

5 months

Vascular conditions in athletes often require more specialised testing than hospitals & vascular clinics can provide We are introducing a screening protocol in Vancouver to help improve detection and treatment options for these patients. More to come!👀

Sport-related vascular conditions are uncommon but problematic conditions which can affect the arteries of the legs in otherwise healthy, highly trained endurance athletes. In recent years a rising...

www.allanmcgavinphysio.com

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Jem Arnold

@jem_arnold

8 months

🩸Blood lactate [BLa] does NOT increase exponentially during high intensity exercise 🧑‍🔬 Why do we make this common mistake? I think because we have focused too much on the lactate test And forgotten what information that test is trying to give us about real exercise 🧵1/14

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Jem Arnold

@jem_arnold

1 year

Does training above max metabolic steady state MMSS (CP, FTP, MLSS, LT2) improve V̇O₂peak & time-trial in endurance-trained athletes MORE than training only below MMSS? Think the answer is obvious? We kinda did too. So we did a meta-analysis! 📚🔖 🧵/13

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Jem Arnold

@jem_arnold

1 year

Critical Power (CP) is ⬇️ at 100 vs 60 rpm, and costs ⬆️V̇O2 But preferred cadence is typically 80-100 rpm 🤔 Does training at ⬇️or ⬆️cadence improve CP & V̇O2max more? I find the physiology fascinating! Here’s some of what I'm learning🚴‍♀️🚴🚴‍♂️ 1/🧵

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Jem Arnold

@jem_arnold

2 years

An overly-long and still non-comprehensive reading list for understanding #NIRS #muscleoxygenation in sport science! 🧵 1/15 Start with this concise opinion piece from Perrey on the emerging promise and future direction of NIRS research & application

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Jem Arnold

@jem_arnold

2 months

100 'essential' papers in sports and exercise physiology, mapped (nearly completely) by references & citations between them This is a great resource for ‘keystone’ papers to learn about foundational concepts in sports science & exercise physiology Link to this map below👇🧵

Andrew Jones

@AndyBeetroot

2 months

A view on the 100 ‘essential’ articles in sports and exercise physiology.

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Jem Arnold

@jem_arnold

5 months

How does VO2 scale with Height, Weight, & Age? Where do you land vs population norms? I suspect if you're seeing this, you probably skew high on these plots 💪 Predictive modelling from FRIEND registry, healthy USA adults (n=7759, M=4601, F=3158) DOI: 10.1016/j.pcad.2019.11.011

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Jem Arnold

@jem_arnold

2 years

Intensity domains are descriptive Training zones are prescriptive At least, this is how I'm thinking about the two. This discussion has certainly been done, but here's another chance to question & refine language. 1/🧵 Inspired by CriticalO2

Phil Batterson, Ph.D. | Integrative Physiologist (@criticalo2) • Instagram photo

www.instagram.com

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Jem Arnold

@jem_arnold

2 years

Body position can have big effects on cycling comfort & performance. Hip flexion can reduce blood flow at the iliac artery Lets use #NIRS to examine an athlete with LEFT-leg flow limitation #FLIA who shows exaggerated L/R differences Left SmO2 here is higher, so better? 🤔 1/🧵

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Jem Arnold

@jem_arnold

8 months

I was just reminded of this nice test-retest reliability study for intensity @ Fatmax & fat oxidation This week are we the red line or the blue line? How about next week?? 🤷‍♂️ Fatmax can be useful, but it isn't magic 🧙‍♂️ .

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Jem Arnold

@jem_arnold

4 months

Here's a very nice visual of hip & torso angles with crank length changes Small changes can make quite meaningful impact to comfort. Good option to consider when there is a specific issue, but not gonna magically add +50 W

Jem Arnold

@jem_arnold

4 months

3) the big one for me: shorter cranks ⇒ lower pedal-stroke top ⇒ more open hip angle ⇒ more comfort at worst, and improved blood flow & O₂ delivery at best How much power do you lose between hoods and drops? Want to lose half of that? (results may vary😅) 4/6

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Jem Arnold

@jem_arnold

11 months

👀👀 .

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Jem Arnold

@jem_arnold

1 year

Brief summary of our new paper 📚🧑‍🏫🚴 @AssafYogev How does wearable #NIRS reliability compare to lactate, V̇O₂, or HR? When we use NIRS to assess athletes, how much day-to-day variation should we expect in #muscleoxygenation ? 🧵/12 free open access

Frontiers | Comparing the reliability of muscle oxygen saturation with common performance and...

IntroductionWearable near-infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO2) demonstrated good test–retest reliability at rest. We ...

www.frontiersin.org

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Jem Arnold

@jem_arnold

2 years

Lactate curves in a 5-1 multi-stage cycling test across workload (W/kg). Modelled with VO2peak (range 44-74 ml/min/kg). ↑ Wpeak ∝ ↑ VO2peak along x-axis. Nice to see the expected longer steady-state achieved by higher fitness subjects before inflection point 1/2

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Jem Arnold

@jem_arnold

7 months

Muscle Oximetry in Sports Science: An Updated Systematic Review from @EuroMov @Marconirs52 Current trends in #NIRS #muscleoxygenation use in sport & exercise science🦵🫘🔦 A quick summary of some of the bits I find most interesting 🧵/10

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Jem Arnold

@jem_arnold

11 months

Significant correlation doesnt imply good individual prediction If you have asked "Why cant my apps predict my response when they have so much data on everyone?" Because lots of data improves *confidence intervals* but DOESNT improve *prediction intervals* Lets simulate! 🧵/14

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Jem Arnold

@jem_arnold

4 months

Is V̇O₂peak the best outcome measure for studying training effectiveness? 🤔 (leading question) Typical error for V̇O₂peak measurement tends to be around 1-5% In 17 training studies of 3-16 wks *~70%* of trained participants showed NO meaningful change in V̇O₂peak

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Jem Arnold

@jem_arnold

2 years

Michael Rosenblat recently meta-analysed the effects of HIIT vs SIT for improving ⬆️VO2peak and ⬆️cycling TT performance HIIT & SIT were similarly effective at improving VO2peak BUT via different mechanisms AND with different results to performance 1/🧵

Trent Stellingwerff, PhD / CSEP-CEP / FACSM / ChPC

@TStellingwerff

2 years

Aerobic high‐intensity intervals are superior to improve V̇O2max compared with sprint intervals in well‐trained men

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Jem Arnold

@jem_arnold

8 months

The transition between "zones" has variability day to day If we're training right at the top or bottom of a target zone, we might unintentionally be over or under To be confident we're in the intended zone, aim somewhere in the middle! Zones are big. Play around in them!

Brady Holmer

@B_Holmer

8 months

@jem_arnold Also why I think “zones” — whole incredible valuable — also aren’t magic. My zone 2 today is not my zone 2 tomorrow if external circumstances are at play.

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Jem Arnold

@jem_arnold

23 days

Just published on #NIRS #muscleoxygenation Thanks to co-authors, reviewers, & editors Muscle reoxygenation is slower after higher cycling intensity, and is faster and more reliable in locomotor than in accessory muscle sites What is it all about? 🧵/12

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Jem Arnold

@jem_arnold

8 months

Preferred cadence tends to optimise between perceived muscular effort (torque) and central effort (V̇O₂ or maybe breathing rate) Torque-contraction velocity relationship depends on power output and fibre recruitment (among other things). Preferred RPM increases with ⬆️power

Dan Bigham

@DanBiggles22

8 months

@irishpeloton Your body perceives a change in the torque-cadence relationship because torque goes up for a given contractile velocity (cadence), so you decide to change gear to bring yourself back to your preferred torque-cadence relationship. Power is something determined by the rider.

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Jem Arnold

@jem_arnold

2 months

Very interesting. There is some emerging evidence that females rely more on peripheral O₂ extraction than males. So decays in VO2max with age for females & males may be related to decrements in these different limiting factors?

Alex Hutchinson

@sweatscience

2 months

New data on how VO2max changes with age: Previous studies in men suggested decline was mostly central (heart, lungs, circulation) rather than peripheral (muscle, mitochondria). But the new data, in women, finds both central and peripheral contributions.

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Jem Arnold

@jem_arnold

2 years

*Corrected!* Association btwn LTmin and FatMax power in 20 trained cyclists performing a 5-1 intermittent step test (1.0 W/kg + 0.5 W/kg per 5-min stage) Trendlines across workload relative to individual peak power, with paired points btwn LTmin & FatMax 🧵1/6

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Jem Arnold

@jem_arnold

2 months

Doing science! We have two Parvo TrueOne carts daisy chained and reading within 0.03 L/min VO2 and 1 L/min VE right now 👌 Testing the measurement error between devices and to what extent that error compounds when estimating ventilatory thresholds, substrate oxidation, etc

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Jem Arnold

@jem_arnold

2 years

The 'Incremental RPE Step Test' is a fun and useful experiment to perform with athletes Used to cue athletes to pay attention to sensations across intensity spectrum These are some typical responses I've noticed Have you used something similar?

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Jem Arnold

@jem_arnold

8 months

We don’t actually care about the deflection point in a lactate curve on its own True exponential curves don't have deflections. it's like finding the corner of a circle There are lots of corners depending on our operational definitions 🫣 3/ DOI: 10.1371/journal.pone.0199794

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Jem Arnold

@jem_arnold

8 months

This one didn't make it into my cadence mega-thread (👇) In cycling,🩸BLa stabilises at higher concentration with cadence, but the same power @ MLSS ⬆️metabolic rate at ⬆️cadence ⇒ ⬆️BLa production & disposal rates ⇒ ⬆️ steady state equilibrium DOI: 10.1123/ijspp.2015-0573

Johan Röjler

@johanrojler

8 months

@feelthebyrn1 @jem_arnold @R_Herradura @justindaerr Would be interesting to see mlss @ low rpm biking. Speedskating on 400m track which i suppose this is has natural intervalls of say 8-9 sec turn(harder) 8-9 sec straight (easier). Rpm in SpeedS is about 42-48 /min (a bit higher in turns, lower on straights)))))))

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Jem Arnold

@jem_arnold

1 year

TLDR: 2-12 weeks training including intensity above MMSS, V̇O₂peak was improved more than training only below MMSS, but TT improvement was not different Future studies must be higher powered to detect small meaningful differences in trained athletes /13

(PDF) The Additional Effect of Training Above the Maximal Metabolic Steady State on VO2peak, Wpeak...

PDF | Background To improve sport performance, athletes use training regimens that include exercise below and above the maxi- mal metabolic steady state... | Find, read and cite all the research you...

www.researchgate.net

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Jem Arnold

@jem_arnold

7 months

Low-intensity eg. "zone 2" volume VS including 0-2 sessions/wk high-intensity intervals for ⬆️VO2max &/or performance? Answer is probably "yes, and". Why do we think they're mutually exclusive? HIIT can, in my opinion, be a regular part of sustainable 'infinite-game' training

Jason Fitzgerald

@JasonFitz1

7 months

All this advice about "workouts to increase your VO2 Max" are missing a key phrase: "in the short term." Because if you want to increase your VO2 Max *in the long term*, you wouldn't do any of those workouts. You'd build a massive aerobic engine with Z1/Z2/Z3 running over years!

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Jem Arnold

@jem_arnold

1 year

Nice review of wearable NIRS breakpoint just published @csendra_perez @Jose_I_Priego Reliability of NIRS-BP compared to gold-standard ventilatory (VT) & lactate thresholds (LT) in endurance sport Quick summary 🧵/10

Reliability of threshold determination using portable muscle oxygenation monitors during exercise...

Scientific Reports - Reliability of threshold determination using portable muscle oxygenation monitors during exercise testing: a systematic review and meta-analysis

www.nature.com

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Jem Arnold

@jem_arnold

4 months

Shorter cranks for performance 👇 More aero, more watts, more comfortable. Less torque, but that's why we have gears Glad to hear it from someone who actually knows what they're talking about

Jeroen Swart

@JeroenSwart

4 months

@ToutpourmaSante @peter__leo @science2sport @WendzH @Pelotrain Short answer is that it’s very complex. Going shorter has a number of gains: reduced inertial change per pedal stroke ; more open hip angle ; better corner clearance ; faster time to peak power during acceleration ; aero gains. But the trade off is loss of torque.

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Jem Arnold

@jem_arnold

1 year

With Train Red #NIRS and Lode ergometer pedal force recording at 100 samples per second we can evaluate #muscleoxygenation responses within a single pedal cycle Nice illustration from my colleague's project, some thoughts below 🧵

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Jem Arnold

@jem_arnold

5 months

Incredible! @kilianj with the mobile-science-kit collecting data on himself sitting on a mountain at 8000m 😮👏👨‍🔬 HR, lactate, NIRS, SpO2 respiration, glucose, ketones... The ultimate n=1 mad science field test!

kilian jornet

@kilianj

5 months

@jem_arnold @willkirousis @EliasLehtonen Yes it was self tested. I took a minimal “testing pack” that allowed some measurements without making the ascents much harder:

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Jem Arnold

@jem_arnold

2 years

More Lactate #dataviz revealing an interesting question 🤔 Dmax LT2 plotted on BLa curve for each subject, ordered by VO2peak 5-min stages cycling Females n = 10, males n = 11 Nice horizontal spread Higher fitness subjects reach LT2 at higher W/kg No surprises yet...👇 1/5

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Jem Arnold

@jem_arnold

1 year

Where are all the studies of the effects of cycling cadence on lactate thresholds? I figured this would be easy to find.. am I missing them? @doctorinigo @SportResearchEx @Alan_Couzens

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Jem Arnold

@jem_arnold

6 months

@PeterAttiaMD and Olav Aleksander Bu recently mentioned that while we're cycling at 200 W, our intra pedal-cycle power might be spiking >1000 W This is what that looks like, with the same data left (downsampled) and right (high sample rate) 1/🧵

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Jem Arnold

@jem_arnold

2 years

Weekend project: simulated data based on observed NIRS recordings during 4x4-min cycling HIIT session in severe (SVR) domain with @MoxyMonitor End-work SmO2 (last 60-sec mean of each bout) may ⬆️or⬇️ across the session related to caliper skinfold thickness (SF) at VL 1/🧵

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Jem Arnold

@jem_arnold

24 days

NIRS + ICG (indocyanine green) to measure direct blood flow during cycling @ 90% VO2max🚴‍♀️🦵🩸🔦 One @Artinis_MS NIRS probe on VL (bottom two plots, ICG on right). What muscle do you think the other probe was on (top plots)?🫁 @UBCKin grad student Eva piloting her MSc experiment

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Jem Arnold

@jem_arnold

7 months

a plot of peak 5min power and weight combinations that produce similar 'compound scores' (C = W · W/kg) @peter__leo @spragg247 @JeroenSwart

Cycling-Research.com

@CyclingResearch

1 year

[JSC] Abstract: The Compound Score in elite road cycling

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Jem Arnold

@jem_arnold

2 months

Preliminary results of doing science. n=1 pilot comparison of two Parvo metabolic carts during an incremental ramp cycling trial Agreement for V̇O₂ is excellent at ±70 ml/min (1.6%) 🥳

Jem Arnold

@jem_arnold

2 months

Doing science! We have two Parvo TrueOne carts daisy chained and reading within 0.03 L/min VO2 and 1 L/min VE right now 👌 Testing the measurement error between devices and to what extent that error compounds when estimating ventilatory thresholds, substrate oxidation, etc

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Jem Arnold

@jem_arnold

2 years

Sneak peak of test-rest reliability analysis we're working on for NIRS & other measures How does SmO2 compare to VO2, HR, BLa? What Δ should we expect for daily variability at low, medium, high intensity in an incremental step test? What Δ constitutes a meaningful change?

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Jem Arnold

@jem_arnold

4 months

"Emphasizing multiple accelerations 🔄 Emphasizing a fast start 🔄 Prioritized sessions for increased time at high V̇O₂" 👀👀 Looking forward to reading this summary of recent advances in endurance interval training

Knut Sindre Mølmen

@MrMoelmen

4 months

The perspective article of Bent Rønnestad and myself, "A narrative review exploring advances in interval training for endurance athletes", is now freely accessible in Applied Physiology, Nutrition, and Metabolism 🏃‍♀️🚴‍♂️⛷️

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Jem Arnold

@jem_arnold

1 year

Critical Oxygenation may estimate critical power with NIRS measured at the quadricep (RF) in a single-session multi-stage protocol I wanted to test the method with our dataset of mixed fitness competitive F & M cyclists It doesn't quite work for us. but why?🤔 🧵/14

APS Publications

@APSPublications

1 year

Identification of Maximal Steady State Metabolic Rate by the Change in Muscle Oxygen Saturation (Matthews et al.) - new in @japplphysiol ! @GonzagaU #MuscleO2Saturation #Fatigue #Exercise #MetabolicRate

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Jem Arnold

@jem_arnold

2 years

If I have repeat measures data like lactate curves and want to know how the 'shape' of the curve (not just LTs, peak) is associated with baseline characteristics, eg. sex, VO2peak, bodyweight (collinearity expected) What approach should I use? How has this been done before? 🤔

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Jem Arnold

@jem_arnold

2 years

Ventilatory profile in a 5-1 cycling assessment (8-breath avgs) Anyone want to give an estimate for VT1 & VT2? And tell me why?

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Jem Arnold

@jem_arnold

2 years

Here you go! Association btwn LTmin and FatMax power in 20 trained cyclists performing a 5-1 intermittent step test (1.0 W/kg + 0.5 W/kg per stage) Trendlines across workload relative to individual peak power, with paired points btwn LTmin & FatMax 🧵1/x

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Jem Arnold

@jem_arnold

25 days

First paper from my (eventual) thesis accepted for publication! Txitter thread summary to come soon for this and a few other recently accepted manuscripts from various summer side-quests

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Jem Arnold

@jem_arnold

4 months

Coach, I did a treadmill step test with NIRS like you told me How should I pace my next half-marathon? Why do you think that pace? Thanks coach!

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Jem Arnold

@jem_arnold

8 months

Turns out hearing that "BLa increases exponentially at high intensity" is a bit of a pet peeve of mine 😅 Hopefully this thread can help how we think about this If you chose 'exponential' were you thinking about a lactate test? Or were you thinking about it some other way?

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Jem Arnold

@jem_arnold

2 years

I recently spoke with @SciTriat about NIRS muscle oxygenation response profiles we have observed in intermittent cycling step testing. These are some of those trends, and how I think they can be interpreted 🧵1/12

Muscle oxygen saturation and iliac artery flow limitation with Jem Arnold | EP#358

Jem Arnold is a physiotherapist, coach and PhD student. Currently, his main research focus is investigating FLIA: blood flow limitation of the iliac artery, a condition that affects certain athletes...

scientifictriathlon.com

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Jem Arnold

@jem_arnold

8 months

Low cadence/high torque training is commonly used in real-world coaching, however research has not (yet?) been able to identify strong benefits commensurate with it's widespread use Why do we think that is? What are we (coaches & researchers) missing?

John Wakefield

@Pelotrain

9 months

Low cadence work is not a modern trend. Been prescribing them since 2007.

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Jem Arnold

@jem_arnold

2 years

Muscle oxygenation @ LVL during 5min cycling stages, 1min rests I was testing something else, but look at the warm-up hyperemia (increased blood flow, volume, and oxygenated [heme]) to the superficial (~5mm depth) vs deep (~20mm) NIRS channels some observations & thoughts🧵/8

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Jem Arnold

@jem_arnold

8 months

Also this. Check those minimum effective dose numbers. Very achievable. Every step counts

Jem Arnold

@jem_arnold

8 months

'walking is good, actually' is a hill I'll defend pretty hard. Great thread with resources to learn more I suspect we overvalue the 6 hrs/week training we might do as non-full-time athletes, and strongly undervalue our baseline activity levels for the other ~100 hrs/wk 🙋‍♂️

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Jem Arnold

@jem_arnold

6 months

"Classification of Male Athletes Based on Critical Power" @javivirbienolay @Olmedo_tas 24 trained athletes performed 9/3-min running CP test with Stryd to classify performance tiers Good work with an interesting preliminary study 1/5🧵

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Jem Arnold

@jem_arnold

1 year

I've done a few DEXA scans over the past 12 years. Age 22 to 35. Big changes from playing Uni rugby, to elite (amateur) cycling, through some injuries & surgeries, now just trying to maintain high functional fitness. Surprisingly consistent body composition. Happy about that 🧵

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Jem Arnold

@jem_arnold

6 months

My thinking is, we're trying to optimise VO2 onset vs task tolerance. VO2 onset ⬆️through SVR domain with diminishing Δ (Korzeniewski 2022 below) So top of SVR (what I call MAP, ~2-3min MMP) might be a good ceiling target? No need to spike higher. Would be individual-specific

Jem Arnold

@jem_arnold

6 months

@MedBonnevie Any thoughts about how hard a start is too hard? I often see that question. I think we'd agree an all-out Wingate is probably too hard? 🥴 so where are the diminishing returns?

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Jem Arnold

@jem_arnold

8 months

'walking is good, actually' is a hill I'll defend pretty hard. Great thread with resources to learn more I suspect we overvalue the 6 hrs/week training we might do as non-full-time athletes, and strongly undervalue our baseline activity levels for the other ~100 hrs/wk 🙋‍♂️

Tom Hughes 💙

@DrTEHughes

8 months

Walking is a fantastic exercise. Here are 10 reasons why doing more walking should be your a New Years resolution you should make and stick to. A 🧵

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Jem Arnold

@jem_arnold

3 months

Reposting this figure beautifully showing the day-to-day variability we need to expect in substrate (lipid & glycogen oxidation)

Sebastian Sitko

@SitkoSebastian

3 months

Are maximal fat oxydation rates (MFO) and FatMax really that relevant as a metric in running, cycling or triathlon? Both once believed as key metrics in endurance sports but current knowledge shows it is not that easy. Let's discuss the science. A brief thread:

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Jem Arnold

@jem_arnold

8 months

Standard schematic representation of constant workload 🩸BLa response below, at, and above the maximal lactate steady state looks like this At higher intensity 🩸BLa response is *logarithmic*, not exponential! 7/ DOI: 10.1007/s00421-017-3795-6

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Jem Arnold

@jem_arnold

1 month

Nice video. Could teach an entire undergrad bioenergetics course around explaining the errors and oversimplifications in this video. But at least the vibe is right! Sports science is cool!

Trung Phan

@TrungTPhan

1 month

Explainer video on science of why the 400m sprint is considered the most painful track & field event. And why “no person on the planet can run the 400m all out from start to finish". The race pushes the way the body creates energy to the limit: ▫️0-50 meters: ATP-CP (energy

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Jem Arnold

@jem_arnold

9 months

@SciTriat and I just chatted about training above or below threshold to improve V̇O₂max and performance, interpreting group-level research to individual-level application, and how much day-to-day variability to expect in common training metrics

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Jem Arnold

@jem_arnold

1 year

The biggest takeaway for sport science in general is that all studies were SEVERELY under-powered to detect small differences expected in trained athletes For V̇O₂peak SMD=0.44 minimum 81 subjects *per group* is required for 80% power. Largest group was n=16 11/

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Jem Arnold

@jem_arnold

2 years

New research published! 🤓📚📢 Diagnosing Sport-Related Flow Limitations in the Iliac Arteries Using #NIRS #muscleoxygenation #FLIA #endofibrosis Published by my colleagues at @MMC @MaastrichtU @TUeindhoven @MDPIOpenAccess 1/🧵

Diagnosing Sport-Related Flow Limitations in the Iliac Arteries Using Near-Infrared Spectroscopy

Background: A flow limitation in the iliac arteries (FLIA) in endurance athletes is notoriously difficult to diagnose with the currently available diagnostic tools. At present, a commonly used...

www.mdpi.com

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Jem Arnold

@jem_arnold

2 months

Efficiency vs capacity "Tortoises’ mitochondria consume less O2 per ATP, thereby reflecting lower whole body BMR and lower mito O2 affinity. Strikingly, Hare’s VO2max decreased considerably in hypoxia, while Tortoise was able to maintain VO2max"

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Jem Arnold

@jem_arnold

1 year

2) Time-trial: We expected training >MMSS to improve TT performance more than training only <MMSS There was NO difference Training only below MMSS/CP/FTP produced the same improvements to TT as including training above MMSS Is anyone else surprised by this? 6/

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Jem Arnold

@jem_arnold

11 months

This has long been the assumption. Great to see it empirically tested

Jem Arnold

@jem_arnold

11 months

👀👀 .

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Jem Arnold

@jem_arnold

2 years

My PhD work is with athletes with FLIA: blood flow limitation of the iliac artery ( #endofibrosis ) Fig.1 cycling ramp test Fig.2 Multi-stage (6-min) test Note L/R Power. L Impairment (and symptoms) begin in HVY domain. This is lower intensity than typically described? @jdostal1

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Jem Arnold

@jem_arnold

7 months

Is there a figure out there for VO2max ~ fractional utilisation at threshold? Like this below for VO2max ~ running economy DOI: 10.1371/journal.pone.0123101 ... could we aggregate data to build one? 🤔

Nick Tiller, Ph.D.

@NBTiller

7 months

@UltraRunningMag Does anyone have insights into the highest recorded threshold? I've heard that skier Bjørn Dæhlie has values that approximate max, but I cannot find documentation.

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Jem Arnold

@jem_arnold

2 years

If we want to compare how 'fitness' is correlated to an outcome in a sample group with females & males, the problem is often F get skewed as 'lower' fitness Here is the problem visualised and one approach that seems to work What are some other ways to normalise for this? 🧵/12

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Jem Arnold

@jem_arnold

3 months

NIRS half-formed hypothesis. Challenge my assumptions 👇🤔 1: Postexercise free-flow SmO₂ reoxygenation is proportional to the different recovery kinetics between local muscle O2 delivery (mQ̇O₂) and uptake (mV̇O₂) (real TSI, simulated the rest) 1/4

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Jem Arnold

@jem_arnold

10 months

Would love to see how different athletes, coaches, sport scientists re-draw this diagram and create a "fuzzy plot" of all the differences in interpretations 🤔

David J Bishop (He/Him)

@BlueSpotScience

10 months

Exercise Intensity Terminology is a bit of a mess 😵‍💫 Here is our attempt to try and summarise some of the different approaches.

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Jem Arnold

@jem_arnold

6 months

What is the correlation between improvement in V̇O₂max and improvement in endurance performance? What are your favourite longitudinal data on that question?

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Jem Arnold

@jem_arnold

8 months

If we continued our incremental lactate test and clamped workload above the lactate threshold, would it continue to increase exponentially? Nope! 🩸BLa accumulation *decelerates* over time, even at high intensity Because⬆️V̇O₂ and ⬆️BLa oxidation (science incoming 🧑‍🏫👇) 5/

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Jem Arnold

@jem_arnold

22 days

Nice work showing total work (W') >CP can be extended by decreasing power output compared to constant workload trial So which pacing strategy do we think would maximise total W' >CP? and minimise residual W'? 🤔 Will they all be the same if kJ output is matched?

Alex James Welburn

@Alex_Welburn

23 days

1/12: A little (🧵) on my conference paper that we presented at this year’s cycling science. My PhD aims to understand what W′ is in terms of physiological underpinning and then how we can use this to develop its modelling with depletion and recovery. i.e W′BAL.

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Jem Arnold

@jem_arnold

8 months

A lesson in carbohydrate research And more importantly, a lesson in cutting through the hype and noise of public debate with the humility of a scientist asking a specific research question and reporting the specific answer they found

Aitor Viribay Morales

@MVAitor

8 months

I've been fortunate this week to chat with 2 professionals in sports science & communication for their respective podcasts. One recurring question was about the intake of 120g CHO/h during exercise and our studies. A perfect opportunity to provide a bit of context to the topic.

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Jem Arnold

@jem_arnold

11 months

Reading now. Hitting a lot of check marks on my training study wishlist 👏👏 @ingvillodden et al The plot thickens on interval programming! Very well described methods. Definitely more papers to come from this dataset

Fredrik Mentzoni

@FredrikMentzoni

11 months

@jem_arnold Nice one, Jem! You may be interested in looking at Figs. 8 and 9 of . E.g. 40 min power (W/kg): One participant had an ~11% reduction (!), another an ~18% improvement (!!!). Both did their intervals, on average, at ~85% of max V̇O₂. 👀?

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Jem Arnold

@jem_arnold

9 months

SmO₂ minimum values pre- & post-exercise occlusions (physiological range), and maximal cycling exercise (functional range), using either Moxy or TrainRed NIRS Caliper VL skinfold as continuous covariate, divided into tertile means for display. Significant interactions

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Jem Arnold

@jem_arnold

7 months

Winter self-indulgent-self-testing with DEXA, ISAK anthropometrics, and running economy 🧵 DEXA since 2011 has been very consistent. I've put on ~1kg/yr lean mass over the past 3 yrs with re-introducing running & weightlifting after ~8yrs of 'pure' cycling & ++injuries

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Jem Arnold

@jem_arnold

2 years

If ⬆️VO2peak after 6wk training but no change in power output. Where do you look for the extra VO2? 🤔 Systemic? Accessory stabilisation, resp mm/work of breathing, altered locomotor mm recruitment? Cellular? Mito quality, P/O ratio, leak respiratn, contractn O2 cost, RQ?

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Jem Arnold

@jem_arnold

1 year

Maybe the biggest factor is neuromuscular fatigue with ⬆️torque at ⬇️cadence It is thought that perceived effort (RPE) is minimised around the optimal balance between metabolic efficiency and joint torque Freely chosen cadence minimises both 9/

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Jem Arnold

@jem_arnold

2 years

@stevemagness Here's a great review on exercise prescription for your readers showing the variability in intensity domains between individuals when exercising at a fixed % of peak

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Jem Arnold

@jem_arnold

6 months

NIRS pilot treadmill workout raising some interesting questions Narrowing in on my critical speed. Based on sensations I thought it would be between ~4:15 and 4:45. NIRS deoxygenation & reoxygenation rates seem to agree Interesting look at locomotor RF & stabiliser TFL...

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Jem Arnold

@jem_arnold

2 years

@ergonizer @Toptimum_Perfor @JonasZakaitis @thenwerun eg. this lovely figure from Bourdon et al 2018 Δ ~25 W (visual interpretation) at LT1 from 3-min to 10-min in this subject is well within the group SD of ±40+ W, but I would suggest is meaningful for an individual. Thoughts?

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Jem Arnold

@jem_arnold

8 months

Quick treadmill over/under workout tonight with Moxy Where would you put my critical speed based on muscle oxygenation slopes? 🤔 #trainingistesting

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Jem Arnold

@jem_arnold

4 months

Should be obvious: there are far greater differences in physiological measures like V̇O₂peak *between* individuals, than any change we are likely to see with endurance training *within* any one individual Are there any physiological metrics where the opposite is true? 🤔

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Jem Arnold

@jem_arnold

8 months

We care about what our lactate curve predicts about our *constant workload* performance at every intensity What happens to 🩸BLa if we clamped workload during a lactate test and continued exercising at that constant workload? At lower intensities, something like this 👇 4/

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Jem Arnold

@jem_arnold

24 days

Another nice acceptance letter to wake up to! From one of our datasets with multiple muscle NIRS during an incremental cycling protocol. Now I have another summary thread to write

Jem Arnold

@jem_arnold

25 days

First paper from my (eventual) thesis accepted for publication! Txitter thread summary to come soon for this and a few other recently accepted manuscripts from various summer side-quests

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Jem Arnold

@jem_arnold

8 months

I think amateurs have the same tools and access to *data* now as the pros do But not the same access to *information* Asymmetry is in the ability to filter signal from noise, interpret the data, apply the information, and re-test🔄 Agree? Disagree?

zzoric

@ZdravkoZoric

8 months

@jem_arnold It is a matter of time when ordinary athletes will have at their disposal the tools that top athletes now have.

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Jem Arnold

@jem_arnold

10 months

"Exaerobic" is a better term than "Anaerobic" Change my view? Think "extra-aerobic" (beyond aerobic) or "excluding aerobic". More biochemically accurate term than "without oxygen" ? Thanks for the thought provoking typo @JimGalanes 😁

Jim Galanes

@JimGalanes

10 months

Question I get everyday. How much intensity. Tough to answer. It is more than clear that volume alone does not develop exaerobic capacity and performance for all endurance events, yes even mitochondrial function and motor units needed to move faster and efficiently.

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Jem Arnold

@jem_arnold

2 years

Great discussion from @timpodlogar @peter__leo @Spragg_Perform and commentators I wanted to add a hopefully complementary perspective that neither VO2max nor CP alone is sufficient to categorise athletes. To me 3 components are important to consider 🧵/7

Tim Podlogar

@timpodlogar

2 years

Viewpoint: Using V̇o2max as a marker of training status in athletes—can we do better? Our position: Yes: @spragg247 @peter__leo

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Jem Arnold

@jem_arnold

7 months

If high-intensity intervals only work to improve ⬆️VO2max for shorter periods (≤12wks), over what minimum period would we expect EXCLUSIVE low-intensity training (eg. "zone 2") to begin to exceed LOW + regular 0-2 sessions/wk HIIT? Genuine interest. Please challenge my strawmen

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Some HIIT always better

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Jem Arnold

@jem_arnold

8 months

So why do we care about lactate testing? Two reasons: ☝️to monitor change over time The major thing that matters for monitoring is consistency of the test LTs are reliable within around 5-10% (10-15 W) 12/ DOI: 10.1371/journal.pone.0199794

Sean Seale

@SeanSeale

1 year

Here's a comparison chart of a CrossFit athlete I tested a year ago and again today. Very nice progression! 4' work (watts at the bottom), 1' rest. 3 stages more than a year ago, lower HR (last minute average), much-improved lactate trend.

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Jem Arnold

@jem_arnold

9 months

Indeed beautiful! Priming from 1st interval setting up subsequent intervals with faster deoxy (and systemic VO2) kinetics, greater primary amplitude, less O2 debt (less non-oxidative energetic contribution), and less deoxy/VO2 slow component drift (hypothesis, 75% confidence)

Elias Lehtonen

@EliasLehtonen

9 months

Finally, I don’t have any particular insight, but I just find the deoxygenation graph for the 4*8min/2min beautiful. Perhaps observing the slightly lower kinetics on the 1st interval compared to the latter intervals.

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Jem Arnold

@jem_arnold

8 months

Wasserman et al (and others before them) observed this waaaay back in the mid-1900’s MOD & HVY intensity are characterised by transiently⬆️🩸BLa, before settling back to a low baseline over 5-10 minutes SVR intensity sees a rapid increase toward an upper ceiling 6/

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Jem Arnold

@jem_arnold

10 months

Pilot comparison of NIRS oxygen saturation at VL from @TrainRedSensors (SRS-TSI & 40mm 'deep' CW-TSI) vs @MoxyMonitor (monte carlo simulated SmO₂) Pre & post occlusions and 5-1 cycling Different abs values, similar kinetics Also, that's not noise, that's cadence

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Jem Arnold

@jem_arnold

10 months

Good discussion Counterpoint: LTs in an incremental test aren't intended to describe a 'threshold' in incremental metabolism They're intended to approximate differences in metabolic response eg. [BLa] above vs below that intensity if duration were continued at constant workload

Anastasios Makris

@AnastasiosMakr4

10 months

Took this from a book that I was given to my supervisor as a gift from the mighty Bengt Saltin. The authors of the book are trying to explain why there is no “threshold” (break point) in metabolism.

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Jem Arnold

@jem_arnold

1 year

From my dataset with 20 trained cyclists (9F, 11M), 2 trials each, 5-1 @ 1.0 + 0.5 W/kg/stage Highest correlation was between power at FatMax & LT[baseline+0.5] But poor agreement, LT systematically higher power than FatMax by ~1.0 W/kg (2 stages) (F & M pooled) 🧵1/2

Sean Seale

@SeanSeale

1 year

@Alan_Couzens hey Alan, what kind of relationship have you observed in your collected data/experience between FatMax and the absolute (or relative?) power at LT1? Thanks!

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Jem Arnold

@jem_arnold

1 year

A change in already trained athletes of 2.5 mL/kg/min might represent 3-6% improved aerobic capacity That's huge! But measurement error for V̇O₂ can be 100-400 mL/min (2-8 mL/kg/min at 50kg; 1.3-5.0 at 80kg) So how confident can we be in these findings? 🤔 5/

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Jem Arnold

@jem_arnold

2 years

SmO2 work slopes as Critical Oxygenation? SmO2 indicates the balance of muscle O2 delivery (mDO2) & O2 uptake (mVO2) ↑ slope ⇒ mDO2 > mVO2 ↓ slope ⇒ mDO2 < mVO2 ≈ slope ⇒ mDO2 ≈ mVO2 ⇒ critical oxygenation? Fig: slopes through work stage SmO2 omitting onset kinetics🧵1/8

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Jem Arnold

@jem_arnold

1 year

Why is there such an energetically costly 'excess' OxCap? Because it helps maintain catalytic efficiency at high O₂ flux A large mito content working 'submaximally' is more efficient than less mito content working maximally

Elias Lehtonen

@EliasLehtonen

1 year

@johngetstrong @Alan_Couzens To my understanding, muscle oxidative capacity is manifold relative to O2 delivery so likely not a limitation to VO2max in even the most highly trained. In untrained individuals muscle O2 capacity can limit VO2max.

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