Load, Stress, Strain: Understanding the difference can make you fitter and faster!

There are so many training scores and metrics these days that it is easy to get confused, especially when the same terms get defined in different ways by different "experts". I think we can cut through the confusion and I have tried to do so here.

[@mrwest6150]

God Bless you Stephen, we cannot thank you enough for you quality free content. I believe your information has sparked the interest of many new budding scientists :) Hope you and you family have a great Christmas!

[@sportscientist]

Thank you very much for the kind feedback!

[@Krilin84]

This is very interesting regarding how a lowered HR can be a strain response. Learning how to run as an adult I've found the LIT approach absolutely key to not break down physically and maintain a regular practice of running 4-5 times a week. But as I'm measuring progress primarily in terms of HR vs. pace at low intensity, I've thus far always considered a lower heart rate for the day a positive - no matter the accompanying RPE. Likewise, I've been confused many times when seemingly going backwards in my fitness after a day or two of rest - now having a higher HR at a lower RPE. The "strain" concept makes perfect sense of it and will be very useful when guiding my training load and interpreting my fitness level going forward. Thank you!

[@XX-is7ps]

Really excellent presentation, very clear - appreciate you taking the time to (re)-record and upload this, thank you. It does really show the shortcomings of some of the basic metrics such as TSS in accurately tracking physiological impact of various training prescriptions

[@sportscientist]

My pleasure, thanks!

[@thomaswebster7438]

Thank you for sharing your expertise Stephen. Very clear and easy to understand presentation. I look forward to your next one.

[@luiscolon921]

Dr. Seiler, really love how you break this down in an easy to digest way for even newbies like me to grasp. I'm new to structured cycling training and have been using a Garmin cycling computer with power/HR strap. What I have found interesting is that Garmin has a metric called "Performance Condition" that appears to detect reasonably well if I'm too stressed or perhaps unrecovered at the start of my workout and/or when I start to decouple later in my workout. It appears to highly correlate with my RPE and workout success as well. I believe it uses power, heart rate and HRv to compare with previous measurements as a baseline to provide real time results. It's been extremely beneficial at least for me in this stage of my fitness and finding that training to recovery balance.

[@eric13hill]

I would love to take a series of classes from you. You have a fantastic skill to explain difficult content in a simple to understand way.

[@TheKryztiandivor]

Thank You again for a very informative video. The trinity of external output, internal cost and RPE was very practically explained and comes in use. Also, durability explains well the need for longer low intensity training. Thank You yet again.

[@hadd5106]

Thank you Dr. Seiler. Once again you make complex training responses accessible to the lay person. The concepts of Load - Stress - Strain are both easy to understand and apply to training. Super presentation!

[@7gibbens]

Thanks Dr Seiler Really appreciate the efforts you have made to outline and then re-outline this topic. As a 58 yo runner/cyclist you have given me new food for thought in the quest for Master's records. Correct me if I'm wrong but strain (muscle fatigue, over training, injury) becomes even more problematic in older demographics due to the increased recovery times required. Keep up the great work

[@stanislaogerman3743]

Your the best Dr. Seiler, thank you for the free content.

[@2ctowens]

Thanks you, I learn a great deal from you presentations.

[@neilhughes3542]

Thanks very much for taking the time to do this again. I've learnt a lot from that.

[@rato_gordo]

Thank you very much! Releasing two videos this month i really felt like a christmas gift.

[@yousefosman9051]

Thanks for re-performing the presentation, was a trip down memory lane with the engineering explanations of load/stress/strain. I recently listened to a podcast with Tom Schwartz, he was questioned about warm up, and the answer was it take about 8-10 mins of aerobic low intensity to switch the blood from going to other areas for it to make sure the work muscles are prioritised, then a small amount of higher intensity before the workout or race (summarising) I would be interested to see if you have any data on the influence of warm up on the eventual performance

[@007michaeldavies]

Many thanks Dr Seiler, love your stuff!

[@willjones7132]

45:37 What an excellent way to word that point. Applies to many topics.

[@luiscalico]

Always a pleasure, and always learning with this master of endurance

[@SR77SR]

Loving the hight tech cinder blocks that you use in your paincave

[@OmaKahn]

What an amazing Video - very helpful! Thank you Stephen

[@allenrnewbauer]

This is a great breakdown of the Stress, Strain and Load topic. Thanks Doctor Seiler.

[@farukmouhrat6513]

Thank you very very much Dr. Seiler. I just recently discovered your videos, conferences and interviews, and it's really generous from you to share all this great content with all of us. You have an unique and humble way of sharing knowledge, and it really contributes to grow a passion and enthusiasm for sports science. You're in my 'Holy Trinity' along with Dr. Iñigo San Millán and Sebastian Weber. Merry Christmas from Spain, and thank you again!

[@waynehadley1999]

This is a brilliant presentation, excellent information, thank you!

[@mauriciorosales1259]

Thank you so much for making this information available!

[@johnny_fiv3]

Thank you. I learned a lot, but will need to continue repeating this video as my training progresses.

[@Herzwerk14]

Thanks for your brilliant presentation Stephen, It clarified some issues I had when I was overtrained, like having a low heart rate and the feeling of missing a gear. Greetings from Mexico city

[@rallyboy101]

Brilliant, thank you for sharing your knowledge.

[@alisonlumelaudur]

Thank you for sharing your knowledge!

[@tom_sorrell]

Hi Stephen, really enjoyed this, thank you for making it readily available. The part where you discuss changes in HR in accordance to strain is very interesting. Sometimes very hard to establish if this is due to strain or other factors such as life stress, environment or a training response. Or if my trainer is calibrated correctly 😅

[@philipbrocklehurst3745]

Thanks for uploading, super interesting and informative.

[@tonynolan4498]

Excellent as ever..thank you👍

[@pehu1322]

Thank you!!!

[@wbuchmueller]

Thank you for making this publicly available ! Chapeau

[@galaktikosgidas]

Thank you!

[@bitchoflivingblah]

I think the Norwegian Pro cyclist mentioned at 24:50 is Edvald Bosenhagen.

[@hannuliljemark3119]

Thanks for sharing!

[@user-yn5sk5ru5g]

Thank you

[@ernestb.2377]

Great talk!

[@christopherbrand5360]

My takeaway is that you look at the stress to load relationship to indicate or proxy for the presence of strain. So, if the hr versus W is “normal” across a range of output then strain is low. If it is higher or lower then strain is indicated. Within a workout perhaps some strain is desirable near the end of a quality day. In the warm up signs of strain indicate overreaching.

[@jjw2844]

Thanks for that, being concise is an amazing skill, and that was quite illuminating.

[@lottepineau1413]

Thank you Stephen! I've read a lot about training yet your videos often put things in a much more usable perspective. One question that might be interesting for you and other endurance athletes: I find that I can reverse decoupling with breathing, with slower deeper breaths HR goes down without a change in power output. This only works in long endurance workouts, when closer to maximum effort this trick will become less effective. Would this be a good strategy during those early hours of a bike race while power is still fairly low to moderate?

[@patrickkelly885]

brilliant thank you

[@bnfrl2010]

Thank you sir

[@davidmoreno-manzanaro9836]

So the question that arises in my head after the video is about the use of this increased strain when things get complicated. Should athletes and coaches look after that strain in order to get the adaptations? Are the external stressors that increase strain valuable in our training?

[@waynehadley1999]

Random neural firing happening and very futuristic. Given how far we’ve come in the last decade with digital monitoring wearable devices, I can see a day in the future where we’ll be able to monitor hormonal and other biochemical markers and the impact training has on them.

[@heikkisanelma6625]

Stephen, this is very informative and interesting. Thank you. I've a follow up Q for you. Q: For LIT ride, is it important to go to the phase where the decoupling starts to occur for example that high aerobic, under VT/LT1? I.E for me riding at 210w? Or running 2-2,5hr around 4:50/km? Could we use this as mark of our physiology pressing on for adaptations to cope with the similar load next time even better, going longer without decoupling? And in heat training, on can manipulate the physiological adaptations as the internal stress accumulates faster? In Dr. Dan Plews work and podcasts he addresses to go more for hr than output when doing heat training, in heat blocks for a race in hot conditions?

[@bitchoflivingblah]

Great lecture and the relationship between Load, Stress and Strain was simply and beautifully explained. I have one question: in the paper describing Functional Over-reaching the abstract says that the intensely trained experience performance supercompensation after a taper. It does not state that the normally trained athletes had the same effect. Does this then mean that F-OR intensified training has a place in producing supercompensated performance if the taper is applied? With of course the proviso that you will be highly stressed for the duration of the intensified training period.

[@gilleek2]

Excellent

[@jasperlinnartz9995]

Hi Stephen, Interesting to relate training to physics. As a physicist I would say this makes total sense. Maybe you thought already about this, similarly to work=force*distance. Work (or energy) can also be defined as stress*strain. Have you tried moddeling trainingsload as stress (external factors like TSS)*strain (internal load like relative effort)?

[@user-rl3ef4ju9k]

I'd like to know how long into 'decoupling' you want to go in a training session in order to get maximal results extending the low intensity capacity. I.e. how to get maximal adaptive signal with minimal stress? I guess you need to be able to extend the period of 'no decoupling' bit by bit almost every session, extending or keeping the decoupling period the same and backing a bit if it seems to take too much toll.

[@Chuck19990]

@Stephen Seiler the ride you are sharing at 18:55, from a training perspective, would it make sense to just reduce the power to stay on the target heart rate for the whole time, instead of drifting towards threshold?

[@jonaslindholm8523]

Very interesting and easy-to-grasp even for an idiot such as myself. What would you argue is true or applicable for people exercising 1-4 hours per week - in relation to the topic of this presentation? Many of your statistics and examples were taken from ”endurance athletes” and with the help of some imposter syndrome I can never really identify myself as an athlete of any kind. Sure it could be argued that Load -> Stress -> Strain will always occur but is there a lower limit?

[@danielweller6442]

Hi Stephen, I really enjoyed this video. Thanks! Just wondering, would parasympathetic hyperactivity also decrease resting HR? Or only HR during exercise? I looked up the study you mentioned and a number of other studies on this and I'm having trouble interpreting the acronym heavy abstracts!

[@mattBLiTZ]

An easy 13 hours at 230w...I'll just be over here crying

[@bitchoflivingblah]

you're not on your own, make some space !!

[@paulobarrameda7507]

what’s your take on MAF training dr seiler?

[@user-sc3on5ov3e]

Steve, I have started to understand heart rate drift from you and my own endurance riding. My question is how much increase in HR would be typically expected while continuing to maintain: speed, cadence and PE variables?

[@juancarloshernandez2187]

you must have a power meter to be precise on the drift, the other metrics that you mention also have a lot a variability. And it is in the range of 0-5%, more than that might be too much.

[@Saintzel]

I have a question related to training by minutes vs miles. Assume 2 athletes are both running (or any sport) for 100km a week, but one athlete is training significantly slower during their non-workout runs. The faster runner obviously is training at a faster pace but the slower runner is training for a longer duration in minutes. Which training is correct?

[@edsassler]

I’ve been following your work for over 10 years, I often use your charts and data on endurance athletes to explain the polarized system of training to the cyclists I coach. With each individual the question always comes up - what form of training do they respond to? While a number of my athletes respond well to high intensity interval training, my program sticks with a lot of training in the green zone for a very different reason. My involvement in cycling has two parts with about 8 months in a wheelchair between them because of a back injury. In that time I learned how to remap muscles using machines at the gym. Relearning how to ride a bike was an eye opening experience because I figured out that I never really learned in the first place. Pedaling a bike doesn’t have failure states, if you’re clipped in your feet go around in circles. That doesn’t mean you know how to pedal, it means your efficiency > 0. Most people learn to walk first, then the adapt that skill set to pedaling. The problem is they are two very different skill sets. Walking or standing places the person’s weight directly over their feet, so the quad muscles raise the body weight by extending at the knee. That’s not the position a cyclist is in on a bike. Put a cyclist on a bike, lock the pedal at 3:00 and tell them to push down. They will fire the quad and their hip will get pushed up and back - they are using their most practiced skill set, but they are still pushing the pedal forward at 3:00. The assumption that pedaling is natural is wrong (and a little ridiculous considering you spent the first year of your life learning how to walk) There have been a number of studies on how people pedal a bike, all of the studies that I’ve read made the assumption that motor skills can be had just by doing - it worked so well in The Matrix... The truth is all motor skill learning uses a 3 stage process, and there’s a fair amount of low intensity practice between the associative stage and the autonomous stage - see what I’m getting at here? In the past we had tools to look at internal and external stresses, but not the efficiency of the work being done. That has changed with devices like the Pioneer power meter which shows force vectors every 30 degrees. The problem is that few people understand what the force vectors are telling them, even fewer understand that pedaling is a motor skill that can be learned. I look at the scans from the Pioneer power meter and I see arrows pointing straight down at the bottom with the highest magnitude - that’s a well practiced skill set called standing, it’s also a lot of wasted energy. It’s my belief that what you’re seeing with lots of training in the green zone is a learning process which can’t happen at higher intensity. Before Covid I was the coach of the Harvard University cycling team. I put together a pedal stroke class based on the two largest muscle groups, teaching riders to only use muscles where they were effective. What I found was my second year athletes were riding like racers with far more years of racing in them - making the motor learning process active instead of accidental. My e-mail address is [e-mail] - I would love to introduce some active learning into your data collection.

[@peterojala5948]

How about resting heart rate? If I have a somewhat raised resting heart rate in the morning, I suspect that I either has a virus infection or a strain effect from yesterdays training and in either case should avoid any hard training until my morning resting heart rate is back to normal. This is normally associated with a sense of fatigue. Is the change in morning resting heart rate useable as a remaining strain indicator or sickness and a useable guide for the training plan for the day?

[@samoanryan]

Dr Seiler you are a beast. I quit my job to watch this video.

[@sportscientist]

Hmmm, That does not sound smart😂

[@FranciscoSilva-fq9rb]

I thought that strain was a mathematical model derived from monotony and calculated load.... is this concept the same? Or they are interchangeable?

[@davidmoreno-manzanaro9836]

Let´s say: will an athlete improve more doing 2h ride indoor without ventilation than in 2 hours outside?

[@XX-is7ps]

There is some evidence from research that heat training at low intensity can introduce adaptations such as improved blood plasma volume that are beneficial (see www.trainerroad.com/blog/how-to-get-faster-with-heat-training/ ) however at the same time average power output during the workout will be lower and RPE higher so whether this is more beneficial than just performing workouts with proper cooling at a higher intensity depends (as always) on the exact metabolic adaptation you are chasing - the devil is always in the detail and it would be easy to do this wrong, simply by causing you to reduce your power output in the heat such that you were no longer in the power zone you intended to target.

[@piteiracorp]

happy to know Im not be the only one using bricks on my setup xD

[@wesfree]

Thanks for these valuable insights. I have noticed in my own long duration cycling endeavors at low intensity levels, whether through dehydration, fatigue (stress) etc. that my cognitive functions become mildly impaired. I might make errors doing mental calculations (simple distance differentials, or time math) that would not otherwise occur. It would be interesting to benchmark and then correlate some simple cognitive measurements with other metrics (%HRR, nominal HR, RPE etc.) during various duration sessions. Training decisions might be facilitated. @wesfree

[@TheGatewayProductions]

Nobody likes stress but we can always learn to manage it. Nice work!

[@ironman20803]

Hey Stephen Seiler are you training people right now?