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Jem Arnold Profile picture
@jem_arnold
Oct 29, 2022 • 17 tweets • 12 min read • Read on X
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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
pubmed.ncbi.nlm.nih.gov/35321522/
2/15
Perrey & Ferrari's review on NIRS in the context of sport science gives background and is a great jumping off point for NIRS studies in your particular sport of interest
pubmed.ncbi.nlm.nih.gov/29177977/
3/15
Barstow has a comprehensive overview of technically and biologically important aspects of NIRS, with recommendations for standardised methodology and nomenclature. This is a must read IMO for starting to understand the nuances of NIRS interpretation
pubmed.ncbi.nlm.nih.gov/30844336/
4/15
@JanBoone2906 et al at Ghent University have published definitive experiments describing NIRS response profiles during incremental ramp testing. Start here to visualise how NIRS responds in an intensity-dependent manner
pubmed.ncbi.nlm.nih.gov/27613650/
5/15
@MuriasLab et al at U of Calgary have also exhaustively investigated NIRS responses during exercise, characterising the deoxygenation breakpoint / HHb-plateau along with other threshold demarcations
pubmed.ncbi.nlm.nih.gov/25606817/
6/15
There is a wonderfully productive ongoing debate on the association between NIRS and other physiological breakpoints
pubmed.ncbi.nlm.nih.gov/29975303/

pubmed.ncbi.nlm.nih.gov/30134366/
7/15
This debate has helped reveal operational limitations of how we use and think about 'thresholds'. To me, a critical aspect is the uncertainty inherent to any breakpoint detection method. Elegantly demonstrated by @KevinCaen @JanBoone2906 et al
pubmed.ncbi.nlm.nih.gov/35435465/
8/15
Another exciting application of NIRS is for non-invasive measurement of mitochondrial function, introduced by Ryan, @InfraredRx, @harrybrossiter et al. This method is now widely used across clinical and sport applications
pubmed.ncbi.nlm.nih.gov/28684592/

pubmed.ncbi.nlm.nih.gov/22582211/
9/15
It's important to consider what *isn't* illuminated by NIRS. NIRS is hyper-local. There are critical spatial and (bio)mechanical effects to consider, such as deep vs superficial muscle heterogeneities
pubmed.ncbi.nlm.nih.gov/26404619/

pubmed.ncbi.nlm.nih.gov/28912130/
10/15
Vastus lateralis is the primary locomotor muscle studied in cycling. Rectus femoris in running. There are important modality- and quadricep head-specific recruitment & deoxygenation patterns
pubmed.ncbi.nlm.nih.gov/28970805/

pubmed.ncbi.nlm.nih.gov/29722622/
11/15
Consider NIRS responses of non-locomotor muscles during exercise such as bicep or deltoid, and what this might reveal in terms of systemic metabolic priorities
pubmed.ncbi.nlm.nih.gov/20204819/

pubmed.ncbi.nlm.nih.gov/35431982/
👆my colleague's paper
12/15
Adipose tissue thickness has large effects on NIRS signals. Especially consider differences in male & female subcutaneous fat distribution on quadriceps when interpreting locomotor NIRS signals
pubmed.ncbi.nlm.nih.gov/28151429/

pubmed.ncbi.nlm.nih.gov/28935822/

also
13/15
Consider how NIRS measurements at the microvasculature (capillaries) are *expected* to differ from classical experiments that measure at larger conduit vessels (e.g. femoral or brachial aa. & vv.)
pubmed.ncbi.nlm.nih.gov/32940560/
14/15
We have to consider *mechanical effects* like isometric vs rhythmic (e.g. cadence) contractions, which change recruitment patterns and spatial distribution of tissue & fluid volumes into and out of the illuminated area
pubmed.ncbi.nlm.nih.gov/27126859/

pubmed.ncbi.nlm.nih.gov/15557016/
15/15
There are so many more applications & nuances to NIRS

Start with the reviews at the top of this thread and come back later for the more nuanced experiments toward the bottom

Dig through the citation trains of these papers to discover what else you might be interested in!
16/15
Or listen / watch me try a few times recently to articulate a story about oxygenation response profiles during incremental exercise testing, trying to keep all of these nuances straight 🥴

scientifictriathlon.com/tts358/

Another very recent application from Pilotto, @AdamiAlessandra, @harrybrossiter, @PorcelliSimone et al is the evaluation of O2 diffusion capacity

This is quite exciting to understand muscle O2 delivery & uptake kinetics after higher intensity exercise

pubmed.ncbi.nlm.nih.gov/35930524/

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More from @jem_arnold

Jem Arnold Profile picture
Feb 18
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% change in VO2max was associated with only +0.04% change in TT performance. But why? 1/15🧵 A one-stage linear mixed effects model meta-analysis based on our individual participant dataset (but not peer reviewed) showing individual athlete percentage change scores for both VO2max (maximal oxygen uptake) and time-trial (TT) performance, for 236 trained athletes in 6 studies. The relationship (correlation) between change in VO2max and change in performance was not significant and not meaningful. The overall change in VO2max only explained around 25% of the total variance in the change in endurance performance, across athletes.
This is the third thread about our recent meta on training intensity distribution (TID)

The last thread was about our secondary findings 👇. This one is about some interesting exploratory observations
🔗Links below, more details in the 📊Alt text 2/
Conceptually, endurance performance is an integration of many interrelated physiological components

VO2max is only one piece, and may not be the limiting factor to improving performance 3/
Read 17 tweets
Jem Arnold Profile picture
Feb 10
In our recent meta-analysis we found:
🔴Higher level competitive athletes improved VO2max modestly more with Polarised training
🔷Lower level recreational athletes modestly more with Pyramidal training

This is what those differences looks like 👇
But is this meaningful? 🤔1/🧵 A density plot using {ggdist} showing distribution of individual observations for the change in VO2peak pre to post training intervention. For the full meta-analysis sample (bottom grey figure) the mean difference of 0.11 ml/kg/min was not significant between polarised vs pyramidal training intensity distribution (TID) models. For recreationally trained vs competitive athletes, the contrast was significant such that competitive athletes improved more following polarised training (top), and recreational athletes improved more following pyramidal training (middle). But the mean differences wi...
This is the second thread about our recent meta on training intensity distribution (TID)

Start with the first thread 👇for main findings. Keep reading here for more of the story!
🔗Links below, and more detail on figures in the 📊Alt text 2/

~350 trained athletes improved both VO2max and TT performance each by ~ +2% average during their study interventions

But individual variation was very wide, as we see here

Only 60% participants improved VO2max, and 80% improved TT performance at all, over 3-18 weeks training 3/ Box plot of simple mean differences (%Δ) for peak oxygen uptake (VO2peak) and endurance time-trial (TT) for 348 participants in 13 studies captured by the current individual participant data meta-analysis. The simple mean difference is around +2% for each VO2peak and TT performance, however, it is unclear (from this figure) how well associated is improvement in VO2peak with improvement in TT performance. Paired lines for individuals at the outliers of increase (or decrease) in either VO2peak or TT tend to regress toward the mean for change in the other variable.
Read 13 tweets
Jem Arnold Profile picture
Jan 31
Polarised🆚Pyramidal🆚Threshold

Which training model is best?🏆
It might matter how trained you are🤔

Our new meta-analysis tries to answer which training intervention produces the greatest improvements in endurance performance in trained athletes

Thread🧵 & 🔗links below👇
Article link:


Keep reading for a summary of our main findings and questions 📚🧵2/18

Alt text in images have additional details & links. Full access link at the bottom🔗👇 link.springer.com/article/10.100…Image of article title, authors, abstract, and key points. Key points reads: 1. When training load was quantified by time in heart rate zone, our results indicate that the adaptations to maximal oxygen uptake following different training intensity distribution (TID) interventions is dependent on performance level. Athletes at a more competitive level may benefit from a polarized (POL) TID intervention and recreational athletes from a pyramidal (PYR) TID intervention. 2. A pooled analysis using different methods to estimate borders between training zones among the included studies did not a...
This was a huge collaborative effort led by Dr. Michael Rosenblat with 20+ institutions 🏫across 10 countries 🌎🌍🌏 and 20 years worth of published data 🧑‍🔬🧑‍🏫

This project is a model of multi-centre cooperation strongly needed in #SportScience 👏Thanks to all co-authors 3/ A collage of profile pictures from co-authors involved in this study: Michael A. Rosenblat, PT, PhD. Jennifer A. Watt, MD, PhD. Jem I. Arnold, PT, PhD(c). Gunnar Treff, PhD. Øyvind B. Sandbakk, PhD. Jonathan Esteve-Lanao, PhD. Luca Festa, PhD. Luca Filipas, PhD. Stuart D. Galloway, PhD. Iker Muñoz, PhD. Domingo J. Ramos-Campo, PhD. Patrick Schneeweiss, PhD. Sergio Sellés-Pérez, PhD. Thomas Stöggl, PhD. Rune K. Talsnes, PhD. Christoph Zinner, PhD. Stephen Seiler, PhD.
Read 21 tweets
Jem Arnold Profile picture
Oct 21, 2024
Here's a strange new study discussing doping and cyclist's iliac syndrome (FLIA/endofibrosis). I don't think I can take it literally, but I will take it seriously

Can doping increase risks in endofibrosis? Likely yes
Is FLIA/endofibrosis caused by doping? No
Let's discuss💭🧵👇 Image
Although not entirely clear, and entirely un-cited, this sentence speculates on the mechanisms relating PEDs to exacerbated pathological remodelling of the iliac artery. This more or less conforms to my understanding of the risks of PEDs on peripheral vascular health 2/ Image
Here is my wall-of-text summary of mechanisms from my thesis

More simply: endofibrosis develops in response to pathological shear stress from large blood flows during exercise through an artery being repeatedly compressed/kinked/bent/twisted with hip flexions (pedalling) 3/ Image
Read 12 tweets
Jem Arnold Profile picture
Sep 19, 2024
Just 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 Image
Briefly, FLIA is an uncommon vascular condition where the iliac artery is compressed/kinked during exercise and performance is impaired by ischaemia & claudication. Often seen in cyclists in an aero racing position

Good background thread here 2/
Not enough is known about non-operative management for sport-related vascular conditions like FLIA

62 articles mention CTx modalities in FLIA. We categorised them by perspective on effectiveness (colour) and either theoretical discussion or results of direct case application 3/ Image
Read 17 tweets
Jem Arnold Profile picture
Aug 15, 2024
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
frontiersin.org/journals/physi…
Image
We know quite well how quadriceps (VL) responds with cycling intensity, but there are fewer data in other muscles

We want to know how multiple muscles respond simultaneously, to gain insight into how local responses are aggregated into systemic responses 2/ Image
We looked at reoxygenation after incremental cycling stages. Faster reoxy indicates faster recovery and better matching of muscle O2 delivery (mQO2) to O2 uptake (mVO2)

Analogous to post-exercise VO2 or HR recovery kinetics, for skeletal muscle 3/ Image
Read 16 tweets

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