Jem Arnold
@jemarnold.bsky.social
PhD candidate & physiotherapist | 🩸Iliac artery endofibrosis / FLIA | Endurance testing & NIRS.
Treat declarative statements as questions?
Treat declarative statements as questions?
Pinned
Jem Arnold
@jemarnold.bsky.social
· Nov 14
Conservative Management and Postoperative Return to Sport in Endurance Athletes with Flow Limitations in the Iliac Arteries: A Scoping Review - Sports Medicine
Background Flow limitations in the iliac arteries (FLIA) is a sport-related vascular condition increasingly recognised as an occupational risk for professional cyclists and other endurance athletes. S...
link.springer.com
Recently published from my (eventual) PhD thesis 📚📑
Review of conservative treatment (CTx) for Flow Limitations in the Iliac Arteries (FLIA, endofibrosis) and proposal of Return to Sport (RTS) guidelines after surgery
Here is what we learned🧵👇/14
(full PDF link at end of thread)
Review of conservative treatment (CTx) for Flow Limitations in the Iliac Arteries (FLIA, endofibrosis) and proposal of Return to Sport (RTS) guidelines after surgery
Here is what we learned🧵👇/14
(full PDF link at end of thread)
The making of this week's #TidyTuesday plot recorded with {camcorder} in #RStats 📊📹
September 19, 2025 at 4:46 PM
Saw a question "what %FTP should my first threshold be at?"
How do we begin to guess? Start with a prediction interval, not a falsely precise point estimate
Data from Sitko et al 2022 helps as a starting estimate (link below 👇)
Any similar datasets? (particularly for female cyclists?)
How do we begin to guess? Start with a prediction interval, not a falsely precise point estimate
Data from Sitko et al 2022 helps as a starting estimate (link below 👇)
Any similar datasets? (particularly for female cyclists?)
September 10, 2025 at 3:12 AM
Saw a question "what %FTP should my first threshold be at?"
How do we begin to guess? Start with a prediction interval, not a falsely precise point estimate
Data from Sitko et al 2022 helps as a starting estimate (link below 👇)
Any similar datasets? (particularly for female cyclists?)
How do we begin to guess? Start with a prediction interval, not a falsely precise point estimate
Data from Sitko et al 2022 helps as a starting estimate (link below 👇)
Any similar datasets? (particularly for female cyclists?)
This is really, really good 👀
August 24, 2025 at 3:08 PM
This is really, really good 👀
Reposted by Jem Arnold
New paper with @drphilipskiba.bsky.social is now out: journals.humankinetics.com/view/journal...
We took a new approach to modeling the power duration curve in cyclists using functional principal component analysis.
We took a new approach to modeling the power duration curve in cyclists using functional principal component analysis.
journals.humankinetics.com
August 19, 2025 at 4:41 PM
New paper with @drphilipskiba.bsky.social is now out: journals.humankinetics.com/view/journal...
We took a new approach to modeling the power duration curve in cyclists using functional principal component analysis.
We took a new approach to modeling the power duration curve in cyclists using functional principal component analysis.
Faith Kipyegon & Dr. Brett Kirby using MoxyMonitor #muscleoxygenation #NIRS during training for her 4-min mile attempt coming up now!
They have published how they might be using this information (see links below 👇)
From their promotional bit a few minutes ago
They have published how they might be using this information (see links below 👇)
From their promotional bit a few minutes ago
June 26, 2025 at 6:01 PM
Faith Kipyegon & Dr. Brett Kirby using MoxyMonitor #muscleoxygenation #NIRS during training for her 4-min mile attempt coming up now!
They have published how they might be using this information (see links below 👇)
From their promotional bit a few minutes ago
They have published how they might be using this information (see links below 👇)
From their promotional bit a few minutes ago
Reposted by Jem Arnold
I had the opportunity to contribute to Matt de Neef's wonderful article on iliac artery endofibrosis/FLIA in cyclists
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
As many as 1 in 5 pro cyclists will experience a pelvic artery issue during their career. Learn all about iliac artery endofibrosis in our deep-dive feature. escapecollective.com/why-are-so-m...
Why are so many pro cyclists getting iliac artery surgery?
We're hearing more about external iliac artery endofibrosis than ever before, but is it actually on the rise? Plus: what even is it? And how is it treated?
escapecollective.com
June 20, 2025 at 12:31 AM
I had the opportunity to contribute to Matt de Neef's wonderful article on iliac artery endofibrosis/FLIA in cyclists
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
I had the opportunity to contribute to Matt de Neef's wonderful article on iliac artery endofibrosis/FLIA in cyclists
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
As many as 1 in 5 pro cyclists will experience a pelvic artery issue during their career. Learn all about iliac artery endofibrosis in our deep-dive feature. escapecollective.com/why-are-so-m...
Why are so many pro cyclists getting iliac artery surgery?
We're hearing more about external iliac artery endofibrosis than ever before, but is it actually on the rise? Plus: what even is it? And how is it treated?
escapecollective.com
June 20, 2025 at 12:31 AM
I had the opportunity to contribute to Matt de Neef's wonderful article on iliac artery endofibrosis/FLIA in cyclists
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
Mostly by knowing where to find the great published diagnostic images, and adding some knowledge we've gained from my recent PhD work on screening and conservative management👇
Reposted by Jem Arnold
As many as 1 in 5 pro cyclists will experience a pelvic artery issue during their career. Learn all about iliac artery endofibrosis in our deep-dive feature. escapecollective.com/why-are-so-m...
Why are so many pro cyclists getting iliac artery surgery?
We're hearing more about external iliac artery endofibrosis than ever before, but is it actually on the rise? Plus: what even is it? And how is it treated?
escapecollective.com
June 20, 2025 at 12:17 AM
As many as 1 in 5 pro cyclists will experience a pelvic artery issue during their career. Learn all about iliac artery endofibrosis in our deep-dive feature. escapecollective.com/why-are-so-m...
Reposted by Jem Arnold
This is a really elegant design/result.
To find COT, knee extension max reps were compared in 'free flow' and with external cuff occlusion
At loads below COT, reps increased exponentially in free-flow conditions, compared to cuff-occluded
At loads above COT, there were no differences between occluded & free-flow 3/
At loads below COT, reps increased exponentially in free-flow conditions, compared to cuff-occluded
At loads above COT, there were no differences between occluded & free-flow 3/
June 14, 2025 at 8:02 PM
This is a really elegant design/result.
Thoughts about running? Will propulsion phase be above the critical occlusion tension in locomotor muscles? During sprints? Middle-distance? Marathon??
I'd expect it probably is in gastroc at least, based on how mNIRS deoxygenates during incremental running in many athletes 🤔
I'd expect it probably is in gastroc at least, based on how mNIRS deoxygenates during incremental running in many athletes 🤔
June 7, 2025 at 1:43 PM
Thoughts about running? Will propulsion phase be above the critical occlusion tension in locomotor muscles? During sprints? Middle-distance? Marathon??
I'd expect it probably is in gastroc at least, based on how mNIRS deoxygenates during incremental running in many athletes 🤔
I'd expect it probably is in gastroc at least, based on how mNIRS deoxygenates during incremental running in many athletes 🤔
Reposted by Jem Arnold
Is COT prior work dependent, W’bal dependent etc ? It can be manipulated by BFR, so I would think W’bal sensitive
COT represents a phase transition across a range of loads, as occlusive tension increases heterogenously within and between muscles
As likely are all metabolic “thresholds” 👇
COT is muscle & task-specific. How might this apply in sport? 6/
bsky.app/profile/capt...
As likely are all metabolic “thresholds” 👇
COT is muscle & task-specific. How might this apply in sport? 6/
bsky.app/profile/capt...
To elaborate, here’s a visualization from @jemarnold.bsky.social illustrating the number of “thresholds” and how they stack one on top of another. This is what I mean by measuring the width of a mountain peak, at what level do you measure the “width” at what threshold does the peak start ?
June 7, 2025 at 4:28 AM
Is COT prior work dependent, W’bal dependent etc ? It can be manipulated by BFR, so I would think W’bal sensitive
When does #ResistanceExercise become #EnduranceExercise? 🏋️↔️🏃
It might depend on the critical occluding tension in our muscles 💪🩸
🧵/11👇
A Critical Occluding Tension Phase Transition Occurs Between 30-40% 1RM in Dynamic Knee Extension Exercise
onlinelibrary.wiley.com/doi/10.1111/...
It might depend on the critical occluding tension in our muscles 💪🩸
🧵/11👇
A Critical Occluding Tension Phase Transition Occurs Between 30-40% 1RM in Dynamic Knee Extension Exercise
onlinelibrary.wiley.com/doi/10.1111/...
June 6, 2025 at 2:06 PM
When does #ResistanceExercise become #EnduranceExercise? 🏋️↔️🏃
It might depend on the critical occluding tension in our muscles 💪🩸
🧵/11👇
A Critical Occluding Tension Phase Transition Occurs Between 30-40% 1RM in Dynamic Knee Extension Exercise
onlinelibrary.wiley.com/doi/10.1111/...
It might depend on the critical occluding tension in our muscles 💪🩸
🧵/11👇
A Critical Occluding Tension Phase Transition Occurs Between 30-40% 1RM in Dynamic Knee Extension Exercise
onlinelibrary.wiley.com/doi/10.1111/...
Ever wonder what intramuscular contraction pressure and mNIRS look like during knee extensions to max task tolerance? 🦵🔦
mNIRS SmO2 on left. IMP on right. Look closely! 👀
@matthewfliss.bsky.social PhD project
#SportScience #NIRS #ExercisePhysiology
mNIRS SmO2 on left. IMP on right. Look closely! 👀
@matthewfliss.bsky.social PhD project
#SportScience #NIRS #ExercisePhysiology
April 24, 2025 at 3:37 AM
Ever wonder what intramuscular contraction pressure and mNIRS look like during knee extensions to max task tolerance? 🦵🔦
mNIRS SmO2 on left. IMP on right. Look closely! 👀
@matthewfliss.bsky.social PhD project
#SportScience #NIRS #ExercisePhysiology
mNIRS SmO2 on left. IMP on right. Look closely! 👀
@matthewfliss.bsky.social PhD project
#SportScience #NIRS #ExercisePhysiology
Reposted by Jem Arnold
wrote about pogačar's roubaix experiment for @escapecollective.bsky.social escapecollective.com/a-tantalizin...
A tantalizing near-win sends Pogačar back to the forge
Undone by an atavistic race that harshly punishes even the smallest mistake, Tadej Pogačar learned that it's not as if he can't win Paris-Roubaix; he simply didn't.
escapecollective.com
April 13, 2025 at 7:46 PM
wrote about pogačar's roubaix experiment for @escapecollective.bsky.social escapecollective.com/a-tantalizin...
Reposted by Jem Arnold
Collaboration is hard and rewarding. Antagonism is easy and unproductive.
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
April 3, 2025 at 3:17 PM
Collaboration is hard and rewarding. Antagonism is easy and unproductive.
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
Collaboration is hard and rewarding. Antagonism is easy and unproductive.
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
April 3, 2025 at 3:17 PM
Collaboration is hard and rewarding. Antagonism is easy and unproductive.
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
Thanks to IJSPP for this editorial on collaboration in sport & exercise science
I hope we will continue to share knowledge with such generous and excellent colleagues in science
journals.humankinetics.com/view/journal...
A number of big name riders in the Women's & Men's peloton who have returned from surgery(ies) for iliac artery endofibrosis in recent years, in light of the news on Fabio Jakobsen (article in Dutch)
Deze renners gingen Fabio Jakobsen voor: wie kwam er sterker uit slagader-operatie en wie niet?
Deze renners gingen Fabio Jakobsen voor: wie kwam er sterker uit slagader-operatie en wie niet?
Fabio Jakobsen moet noodgedwongen tijdelijk stoppen met wielrennen. Onderzoek heeft uitgewezen dat de sprinter van Picnic PostNL kampt met een doorstromingsbeperking van zijn bekkenslagaders. Hij is zeker niet de eerste renner die last heeft van dit euvel, maar wie kwam er sterker uit een operatie e
www.wielerflits.nl
March 31, 2025 at 10:16 PM
A number of big name riders in the Women's & Men's peloton who have returned from surgery(ies) for iliac artery endofibrosis in recent years, in light of the news on Fabio Jakobsen (article in Dutch)
Ah, sorry to hear this but glad he can get treatment
Bilateral flow limitations are thought to be much less common in cyclists (<15%) but we think there may be higher prevalence with the "unaffected" leg still showing some functional limitations
👉https://www.mdpi.com/2077-0383/11/24/7462
Bilateral flow limitations are thought to be much less common in cyclists (<15%) but we think there may be higher prevalence with the "unaffected" leg still showing some functional limitations
👉https://www.mdpi.com/2077-0383/11/24/7462
March 31, 2025 at 2:43 PM
Ah, sorry to hear this but glad he can get treatment
Bilateral flow limitations are thought to be much less common in cyclists (<15%) but we think there may be higher prevalence with the "unaffected" leg still showing some functional limitations
👉https://www.mdpi.com/2077-0383/11/24/7462
Bilateral flow limitations are thought to be much less common in cyclists (<15%) but we think there may be higher prevalence with the "unaffected" leg still showing some functional limitations
👉https://www.mdpi.com/2077-0383/11/24/7462
Smart people discussing how to model power-duration data from first principles 👇
@rchung.bsky.social Have you ever published or presented the use of the convex hull on work duration data? Anything that I could cite?
March 25, 2025 at 2:24 PM
Smart people discussing how to model power-duration data from first principles 👇
Reposted by Jem Arnold
I have managed to do this with an asymmetric cost function. This is the OmPD model but it works similar for other models.
The challenge is how "asymmetric" the cost function should be so it allows for "gaps" (i.e. sharp declines) in the mean-max data but still stays close to the data.
The challenge is how "asymmetric" the cost function should be so it allows for "gaps" (i.e. sharp declines) in the mean-max data but still stays close to the data.
March 25, 2025 at 9:48 AM
I have managed to do this with an asymmetric cost function. This is the OmPD model but it works similar for other models.
The challenge is how "asymmetric" the cost function should be so it allows for "gaps" (i.e. sharp declines) in the mean-max data but still stays close to the data.
The challenge is how "asymmetric" the cost function should be so it allows for "gaps" (i.e. sharp declines) in the mean-max data but still stays close to the data.
New longitudinal study in female rowers @drake-eserhaut.bsky.social comparing mNIRS oxygenation breakpoints & resaturation with lactate thresholds
As expected, LTs != mNIRS-BPs for individual athletes.
We need more longitudinal mNIRS research like this! But where are the performance outcomes? 👀
As expected, LTs != mNIRS-BPs for individual athletes.
We need more longitudinal mNIRS research like this! But where are the performance outcomes? 👀
March 22, 2025 at 5:45 PM
New longitudinal study in female rowers @drake-eserhaut.bsky.social comparing mNIRS oxygenation breakpoints & resaturation with lactate thresholds
As expected, LTs != mNIRS-BPs for individual athletes.
We need more longitudinal mNIRS research like this! But where are the performance outcomes? 👀
As expected, LTs != mNIRS-BPs for individual athletes.
We need more longitudinal mNIRS research like this! But where are the performance outcomes? 👀
Validation of Xert? www.xertonline.com? 👀👀
I've really liked the Xert model better than classic CP & W'. Another one to look forward to for my weekend reading list!
I've really liked the Xert model better than classic CP & W'. Another one to look forward to for my weekend reading list!
Accumulating work at different intensities relative to CP, Pmax, and remaining W' results in somewhat distinct adaptive responses, which should be taken into account when trying to model training and predict performance gains.
March 20, 2025 at 10:57 PM
Validation of Xert? www.xertonline.com? 👀👀
I've really liked the Xert model better than classic CP & W'. Another one to look forward to for my weekend reading list!
I've really liked the Xert model better than classic CP & W'. Another one to look forward to for my weekend reading list!
Reposted by Jem Arnold
Our new preprint proposes a new way to quantify training loads based on power output. We describe how a 3-parameter CP model may be used to estimate contributions of each energy system, resulting in a "strain score" which overcomes some limitations of other TL metrics. doi.org/10.48550/arX...
March 20, 2025 at 11:47 AM
Our new preprint proposes a new way to quantify training loads based on power output. We describe how a 3-parameter CP model may be used to estimate contributions of each energy system, resulting in a "strain score" which overcomes some limitations of other TL metrics. doi.org/10.48550/arX...
In our recent meta-analysis with trained athletes, did the athletes who improved their VO2max more also improve their endurance performance more?🤔
No! 😮
In this dataset, +1% improvement in VO2max was associated with a negligible +0.04% change in TT performance. But why? 1/15🧵
No! 😮
In this dataset, +1% improvement in VO2max was associated with a negligible +0.04% change in TT performance. But why? 1/15🧵
March 20, 2025 at 2:43 PM
In our recent meta-analysis with trained athletes, did the athletes who improved their VO2max more also improve their endurance performance more?🤔
No! 😮
In this dataset, +1% improvement in VO2max was associated with a negligible +0.04% change in TT performance. But why? 1/15🧵
No! 😮
In this dataset, +1% improvement in VO2max was associated with a negligible +0.04% change in TT performance. But why? 1/15🧵
Reposted by Jem Arnold
This week Dr Steve Ingham is joined by Michael Rosenblat as they discuss how training modal impacts VO2 max and time trial performance. He explores training intensity, distribution and oxygen uptake and how heart rate lag can impact interval training.
• Listen and watch on your usual platforms
• Listen and watch on your usual platforms
March 19, 2025 at 9:00 AM
This week Dr Steve Ingham is joined by Michael Rosenblat as they discuss how training modal impacts VO2 max and time trial performance. He explores training intensity, distribution and oxygen uptake and how heart rate lag can impact interval training.
• Listen and watch on your usual platforms
• Listen and watch on your usual platforms