Dr. Keith Baar outlines simple, evidence-based strategies for maintaining strength, extending healthspan, and repairing tendon injuries through targeted exercise and nutrition in this UC Davis talk. He stresses staying in the “strongest third” of the population to avoid disability and boost longevity by 2.5 times.youtube​wellness.ucdavis​

Strength training essentials

Baar simplifies resistance training: lift any challenging weight to failure in one set of 8-12 reps for muscle growth, or a heavy weight (80% max) for 8-10 reps without full failure for strength gains—multiple sets add little benefit. Older adults benefit from more frequent sessions (due to shorter protein synthesis windows) and high-intensity efforts to counter dynapenia (faster strength loss than muscle mass decline). High-intensity interval training (HIIT) elicits a larger genetic response in older people, improving neurocognitive function and lifespan more than moderate endurance.youtube​

Protein and nutrition needs

Older individuals require ~0.4 g protein/kg body weight per meal (e.g., 30 g for a 75 kg person) to maximize muscle protein synthesis, nearly double the young adult dose. He discloses sponsorships from gelatin/collagen makers like GelTor and PepsiCo but frames nutrition as supportive to loading.youtube​

Connective tissue and injury prevention

Tendons, ligaments, and bones adapt maximally in short 10-minute “exercise snacks” spaced 6+ hours apart, yielding twice the collagen synthesis of continuous activity. Full-range heavy strength training reduces musculoskeletal injuries by two-thirds by improving tissue suppleness; static stretching alone does not. His lab engineers human ACLs from surgical remnants to test loading/nutrition effects.youtube​

Tendon injury repair protocol

Injured tendons “stress shield” (load bypasses damage), forming scar tissue without tension; immobilization worsens this, causing rapid muscle atrophy and collagen loss. Start loading day 1-2 post-injury (early rehab returns athletes 25% faster); use 30-second isometric holds (exploiting viscoelastic stress relaxation) to direct ~85% load through damaged areas without tearing. Lab data and rat studies confirm isometrics upregulate tendon-specific genes and collagen vs. dynamic loading.youtube​

Key disclosures and caveats

Baar notes potential bias from sponsors when discussing gelatin/collagen, advising a “grain of salt.” The transcript cuts off mid-collagen discussion (around “collagen one”), but his broader work links vitamin C-enriched gelatin (15 g, 1 hour pre-loading) to doubled collagen synthesis markers.pmc.ncbi.nlm.nih​youtube​

1. https://www.youtube.com/watch?v=anB-UMXIDQA
2. https://wellness.ucdavis.edu/videos/enhancing-health-and-longevity-through-exercise-insights-from-molecular-exercise-physiology/
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC5183725/
4. https://tim.blog/2025/02/27/dr-keith-baar-transcript/
5. https://chirofarm.com/the-farm-cast/keith-baar-tissue
6. https://www.facebook.com/IamPhysiotherapy/photos/did-you-know-cocoa-could-support-your-tendon-health-epicatechin-a-powerful-polyp/1146595560830169/
7. https://www.trustme-ed.com/blog/how-does-nutrition-impact-tendon-healing
8. https://www.gssiweb.org/sports-science-exchange/article/minimizing-injury-and-maximizing-return-to-play-research-lessons-from-engineered-ligaments
9. https://www.withpower.com/trial/phase-dietary-supplementation-10-2023-017e4
10. https://www.youtube.com/watch?v=Ylpf88jDGZA

Prof. Baar’s key points in this segment are: use early, slow, low‑jerk isometric loading after tendon/muscle injury; avoid immobilization; and use short (~10 min) bouts of load separated by 6–8 hours because tendon/ligament cells saturate quickly and then need a long recovery window.youtube​

Summary of main points (around 36 min–45 min of talk)

• Tendon injuries create an injured zone that becomes “stress‑shielded” so normal load bypasses it; the only way to load it is to temporarily weaken the surrounding healthy tendon with sustained isometrics so force is forced through the injured region.youtube​
• Immobilization (e.g., boots, casts) rapidly produces scar‑like tendon: in animal models, 3 days of unloading can cause ~10% muscle mass loss and ~20% tendon collagen loss with disorganized collagen.youtube​
• Inactivity plus normal/high sugar intake increases non‑enzymatic glycation crosslinks, giving a weak but very stiff “brittle” tendon that is prone to rupture when training resumes (e.g., NFL lockout spike in Achilles ruptures).youtube​
• Clinical data (Michael Kjaer’s group) show starting loading 2 days after injury versus 9 days can reduce time to 50% return to training by ~25% (e.g., ~60 vs ~90 days), so delaying a week costs about a month of recovery.youtube​
• Long‑duration isometric holds at long muscle length, done with slow ramp‑up and ramp‑down (low jerk), provide a safe way to load immediately after injury and improve tendon and muscle health.youtube​
• For patellar tendinopathy, isometric loading (same time under tension as dynamic) increases tendon markers and decreases cartilage stress markers, and early isometric‑only phases (4–6 weeks) improve VISA‑P/return‑to‑play compared with eccentric controls.youtube​
• “Jerk” (rate of change of acceleration) is a key mechanical factor in overuse injuries (tennis elbow, golfer’s elbow); minimizing jerk by slow load application and release is central to early rehab programming.youtube​

Cleaned-up transcript with timestamps (start ≈ 33:20–33:30 in your link region)

Note: The text below preserves content and order but removes filler and obvious transcription noise, while keeping the original meaning. Timestamps are approximate and follow the {ts:} markers.youtube​

{ts:2000}
So no matter what we do, we are going to get these. This right here is a tendon injury. You can see this is a rugby player, a big fellow. You all know there is a severity classification. This is a grade 3, and people were curious whether it is a 3B or 3C. It is a 3B–C because it has a myotendinous component, but it also has an in‑tendon component, because you can see the tendon going into the hamstring and you can see that what we have done is basically torn the muscle off the tendon.

{ts:2056}
When we have a tendon injury, what we get is a process based again on the fact that the tendon is viscoelastic. We get this area that has been injured, and it does not matter how small or how big it is; we will have these little bits of tendon that are injured. The injured tendon does not get loaded. What we do is we stress‑shield it, so the stress goes around that injured region. The only way to really get load through the injured part is to make the strong part of the tendon weaker. You already know how to make the strong part weaker: if you pull on it and hold, the strong part of the tendon will get exponentially weaker. Then this little scarred area will be stiffer than the strong part and it will get a uniaxial load. That is the idea – we want to load it.

{ts:2075}
But what do we actually do in reality? We do not load it. When we do not put load through a tendon, that causes a scar. This is work from Hayashi in Japan. All they did was take rabbits, put a wire between the patella and the tibial plateau, and unload the patellar tendon. Within three or six weeks they had a huge number of cells, decreased fibril diameter, decreased collagen orientation – basically all the things we define as scar.

{ts:2114}
What do we do when somebody gets an injury? We put them in a boot. What is a boot? A boot is a mechanical stress‑shielder. If I model this in a rat for three days – I just put a little tube on the foot – within three days they lost 10% of their muscle mass, and within three days they lost 20% of the collagen within the tendon. The tendon went from looking like this on second‑harmonic generated images to looking like this – looking like a scar. So I can create a scar in a perfectly healthy tendon if I immobilize. After an injury, the last thing in the world I want to do is immobilize. What I want is to get movement in there.

{ts:2171}
What happens with inactivity? The best example is the NFL, American football. This graph shows normal Achilles tendon ruptures in a 5‑year period between 1997 and 2002 – about one per month. In the special year 2011, there was a lockout: the owners locked the doors and did not let the players practice. They were locked out from about March until August. Then they signed a contract and all the players suddenly went in and started training immediately. Within the first month, they had 11 or 12 Achilles tendon ruptures. Remember: they had less collagen, but they were still eating, so they had more sugar crosslinks. That is a brittle tissue. Then they went to load that brittle tissue and, bang, they got injured.

{ts:2227}
So if we have a small injury to a tendon or a big one, when should we load? This is work out of Michael Kjaer’s group – the best group in the world for musculoskeletal rehabilitation. Michael is an outstanding sports medicine doctor. He looked at patient recovery when loading started two days after injury – that is the green line – versus nine days after injury – that is the dotted line. There was about a 25% increase in days to recovery. If you look at 50% recovery rate – 50% of people back to training – you go from an average of about 60 days to an average of about 90 days.

{ts:2269}
That means if I just wait a week, I am effectively waiting a month: it will take me a month longer to get back. So that is something to remember – you want to load right away. But how do you load an injury right away?

{ts:2286}
Again, here, when we look at some of these isometrics, what we are doing is trying to improve muscle morphology and tendon health with these long isometrics. The thing that we talked about as causing injury is that sharp plyometric or sharp dynamic movement, which causes a lot of stiffness in the tendon. If we move slowly, we should be able to decrease that. The best way to move slowly is isometric work.

{ts:2304}
If we isometrically load a patellar tendon injury – this is work from Daniela Stephan, a PhD student in my lab – what she found is that when she did exactly the same time under tension, isometric versus dynamic, the tendon markers went up with isometric loading, and the cartilage markers went down. That tells us that when we load isometrically, we are getting a really healthy load for the tendon and a really healthy load for the muscle.

{ts:2325}
When people do this across big groups – this is a group out of Wageningen in Holland – they did a simple thing. They had an intervention group; this is their VISA‑P or return‑to‑play score – the higher, the better. They compared an eccentric‑only group (control) to a group where the first four to six weeks were isometric training only for patellar tendinopathy, or jumper’s knee. They found that by incorporating very early isometric loading of the patellar tendon, they were able to get return to play significantly better and significantly sooner.

{ts:2362}
So how do we load in that injury I showed you, where you tore the muscle right off the tendon? What we are trying to do is minimize that very quick rise in stress in the tendon. We are minimizing jerk.

{ts:2400}
Jerk is not just our new president; it is a physical property. Position is where I am. The rate of change of position is velocity. The rate of change of velocity is acceleration. The rate of change of acceleration is jerk. We know jerk is damaging. Tennis elbow: I am hitting a tennis ball, my arm is swinging one way, the ball is going another way, I get jerk. Golfer’s elbow: I am swinging, hitting a ball, going through, and I get jerk in the inner tendons of my arm. All these things tell us that jerk is a key component in injury.

{ts:2419}
The way we minimize jerk is we put load on slowly. We ramp into the load, we hold the load, and then we ramp off the load. These are called low‑jerk isometrics.

{ts:2437}
We take our individual – this is him here. You can see he had his leg straight out in front, and this guy jumped on his back; that caused the tendon rupture. They surgically repaired it, and then we had a big argument with the surgeon. The surgeon wanted to wait five weeks; we wanted to start loading the next day. We came to an agreement: nine days post‑operatively we started loading.

{ts:2459}
We started loading at a long muscle length. Basically, we did 4 × 30 seconds of isometrics, with two minutes of rest, repeated twice a day. We had him lengthen the leg to the point where he said, “Yeah, that is tight now; that is about as far as I can go.” That is where we started the contraction. We did a low‑jerk isometric: ramp into the force over three seconds, hold for 30 seconds, then let it off over three to five seconds.

{ts:2479}
As he could do that more and more, he could straighten his leg further. Now he could continue to load from that long position. Once he was at full range of motion, we could start isotonic loading and progress him normally through his return‑to‑play routine.

{ts:2496}
The athlete also took leucine‑rich protein, 15 grams of hydrolyzed collagen and vitamin C. That is good for the muscle and good for the connective tissues. Using this program, we got him back to full international rugby in 11 weeks. The previous fastest they had ever done it was 16 weeks.

{ts:2516}
By about six to eight weeks he had returned to full hamstring strength and then back to full rugby. In his first game back he was intended to play about 20 minutes, but the player in his position got injured, so he had to go in for 40 minutes, and he scored a try in that first game.

{ts:2534}
So we are using these slow, low‑jerk isometrics that allow us to develop force without the damaging component of the load – the jerk.

{ts:2552}
For elite athletes, we aim for zero pain, maximum 2 out of 10. For most individuals with lower pain tolerance, we hold for 30 seconds, release, rest two minutes, and continue. We do about four repetitions – that gives about eight minutes of load, which is all we need for a maximal effective dose.

{ts:2612}
We are going to load musculoskeletal injuries as soon as possible. We have many examples now. We had an Olympic athlete with quadriceps tendon surgery; we loaded him the day after surgery and his return to play was extraordinarily quick – he made it back in time for the Olympics and won two gold medals.

{ts:2671}
We can load at long joint angles. Traditionally we try to “protect” early on, but we go through the same pattern: for a pec strain, he would take his arm back until he felt tension across the pec – “that is as far as I can go” – and that is where we start the isometric. When he can go back to full range of motion, we move into isotonic work and progress his return to play.

{ts:2712}
We supplement with leucine‑rich protein, about 30 grams (usually whey), and then add 15 grams of hydrolyzed collagen and vitamin C. You can do that either before or immediately after training because this is a muscle–tendon unit with better blood flow than tendon alone.

{ts:2732}
Take‑home messages:

• In the gym, weight determines movement velocity. Heavy weight means slow movement; light weight means fast movement. If we want slow movement and a positive tendon effect, we use heavy loads. If we want to increase tendon stiffness for performance, we use fast movements.
• Heavy, slow loads decrease muscle‑end tendon stiffness; tendon and ligament cells respond better to isometric loads than dynamic loads.

{ts:2749}
With fast loading, the load goes only through the strongest part of the tendon. With long isometrics, the strong part relaxes and the next strongest part is recruited, and so on, so the whole tendon gets the signal. Combining isometric and dynamic loads is the best way to increase strength and robustness.

{ts:2804}
No matter how well we prepare athletes, there will be injuries. When they occur, we start loading immediately, using low‑jerk isometrics: ramp three seconds, hold 30 seconds, release three seconds. Loading starts at long joint angles, is pain‑free or nearly pain‑free, with short bouts – 30‑second holds, four repetitions, two minutes of rest – at least once per day.

1. https://www.youtube.com/watch?v=HWSquZWDc5E

Leucine consumed after exercise stimulates muscle protein synthesis (MPS), a key process for muscle gain, particularly through doses around 2-3 grams that activate pathways like mTORC1. Studies show leucine dose predicts post-exercise MPS responses, especially in older adults, though plasma leucine peaks or rates may not always correlate strongly. However, isolated high-dose leucine supplements often fail to enhance muscle mass or strength gains beyond adequate dietary protein in trained young adults.pmc.ncbi.nlm.nih+3​

Milk as Leucine Source

Milk products deliver leucine effectively, with an 8 oz (244g) serving of whole milk providing about 0.65-1.5g leucine, contributing to the 2-3g threshold when paired with other proteins. Whey from milk boosts post-exercise MPS more than soy or regular milk due to rapid leucine absorption, supporting recovery and growth. Leucine-enriched dairy matches regular dairy for muscle mass increases over time, making everyday milk viable for post-workout use.pmc.ncbi.nlm.nih+4​

Evidence Summary

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC10400406/
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC8136571/
3. https://pubmed.ncbi.nlm.nih.gov/32079916/
4. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2021.685165/full
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC5697397/
6. https://pubmed.ncbi.nlm.nih.gov/21623468/
7. https://www.milkfacts.info/Nutrition%20Facts/Nutrient%20Content.htm
8. https://www.milkgenomics.org/?splash=milk-nutrients-augment-muscle-growth-and-recovery
9. https://tools.myfooddata.com/protein-calculator/171265-171269/wt9-wt9/1-1
10. https://www.sciencedirect.com/science/article/pii/S0261561423002583
11. https://gonnaneedmilk.com/articles/how-dairy-milk-can-help-you-recover-and-replenish-after-a-workout/
12. https://www.sciencedirect.com/science/article/pii/S1279770723006346
13. https://www.dairymax.org/blog/unlocking-peak-performance-how-milks-essential-amino-acids-fuel-athletic-recovery
14. https://physoc.onlinelibrary.wiley.com/doi/10.14814/phy2.13725
15. https://www.thebullvine.com/news/the-ultimate-sports-recovery-drink-the-benefits-of-milk-and-dairy-for-post-exercise-recovery/
16. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0316603
17. https://nutrabay.com/magazine/leucine-food-sources-health-benefits
18. https://pmc.ncbi.nlm.nih.gov/articles/PMC3909458/
19. https://www.nature.com/articles/s41430-023-01360-1
20. https://www.nal.usda.gov/sites/default/files/page-files/leucine.pdf

Background and career (0:00–3:00)

• Keith Baar explains he was a good but not elite basketball/volleyball player, which pushed him to study why some athletes become great and how to improve performance scientifically.youtube​
• He describes his master’s at UC Berkeley, PhD work identifying molecular mechanisms of muscle hypertrophy with strength training, and a postdoc on endurance adaptations (mitochondria, capillaries, fat burning), then founding a lab in Scotland and later moving to UC Davis.youtube​

Aging, muscle, bone, and strength (3:00–13:00)

• From about age 40, everyone loses muscle mass and strength; strength declines faster than mass (roughly three times faster), and bone mass drops about 1% per year, with an acute acceleration around menopause in women.youtube​
• Being in the strongest third of the population in midlife (40–50) is associated with about a 2.5‑fold greater chance of reaching age 100, while being in the weakest third gives about a 4‑fold higher risk of dying of cancer between 40 and 60; “only the strong survive” is essentially literally true within sex‑matched groups.youtube​

Women, estrogen, muscle vs strength (8:44–18:15)

• Estrogen inhibits collagen cross‑linking, which reduces vascular stiffness and lowers blood pressure; this protects women from cardiovascular disease during reproductive years but declines after menopause.youtube​
• Comparisons are always within sex: strong women live longer than weak women, and strong men than weak men; the key variable is strength, not bulk muscle size.youtube​
• Women turn over muscle protein faster (synthesis and breakdown) and are usually smaller, but when they lift weights their strength gains match or sometimes exceed men’s; many find it hard to add large muscle mass but easy to get much stronger.youtube​

Strength vs hypertrophy and mitochondria (13:01–22:58)

• Strength and muscle size diverge with age and training: strength loss outpaces size loss, so training should target force production, not just hypertrophy.youtube​
• To get bigger muscles (hypertrophy):
  • Use light or heavy loads but go near failure, often with multiple sets; BFR + light weights can work.youtube​
• To get stronger without much size gain:
  • Use heavy loads for about 3–5 reps, 1 hard set, not to failure, and increase the load as it becomes easy.youtube​
• For mitochondria/endurance, you can build them with:
  • Long, low‑intensity work where you can converse, or
  • Short, very hard 30 s efforts with 2–4 min rest (preferably low‑impact modes like cycling, swimming, elliptical).youtube​
• Most work should be easy, conversational endurance, with some short fast efforts a couple of times per week to add a different mitochondrial stimulus.youtube​

mTORC1, endurance, strength, and longevity (18:15–22:58)

• PGC‑1α is the key transcriptional coactivator for mitochondrial biogenesis and angiogenesis; it is activated by:
  • AMPK during high‑intensity work done faster than energy can be produced, and
  • CaMK during long, easier contractions via repeated calcium pulses.youtube​
• Endurance exercise in working muscle tends to inhibit mTORC1 and increase PGC‑1α, driving mitophagy (removal of dysfunctional mitochondria) and production of new mitochondria.youtube​
• Resistance training taken toward failure increases mTORC1 in muscle, promoting synthesis of contractile proteins and muscle growth.youtube​
• In other tissues during exercise, mTORC1 is generally downregulated (liver, fat, GI, immune system), while brain mTORC1 is increased; overall basal mTORC1 activity outside muscle decreases, similar to rapamycin or dietary mTORC1‑lowering strategies.youtube​
• This systemic mTORC1 down‑regulation with exercise may drive improved insulin sensitivity, lower inflammation, and better aging trajectories, paralleling rapamycin’s longevity mechanisms.youtube​

Diets synergistic with exercise (22:58–29:27)

• There is no single perfect longevity diet, but most promising patterns reduce chronic mTORC1 activation.youtube​
• Examples he cites in animals:
  • Low‑protein diets (Valter Longo) can extend lifespan in mice.youtube​
  • Low‑carbohydrate diets can also extend lifespan.youtube​
  • Ketogenic diet in mice (low carb, high fat, modestly reduced protein) produced ~13% lifespan extension even versus very healthy, calorie‑restricted controls, while preserving muscle mass and improving strength and endurance into old age.youtube​
• For humans, a ketogenic diet can plausibly synergize with exercise for healthspan and longevity, but very low protein is problematic for maintaining muscle mass and strength in people.youtube​

Why keto is usually bad for peak athletes (29:27–35:33)

• Athletes who must sprint or produce high power need carbohydrate, glycogen, and rapid pyruvate entry into mitochondria.youtube​
• High‑fat, very low‑carb diets up‑regulate fat oxidation and inhibit carbohydrate use by increasing phosphorylation/inhibition of pyruvate dehydrogenase (PDH), which limits pyruvate entry into mitochondria.youtube​
• Because oxidizing fat requires more oxygen per unit ATP than carbohydrate, exercise feels harder, ventilation is higher, and maximal speed/power drop; athletes often appear “slower.”youtube​
• He uses LeBron James as an example: LeBron looked lean and sculpted on a low‑carb, high‑fat diet but appeared slower; after reintroducing carbs for a few weeks, his explosiveness returned.youtube​

Collagen, tendons, and connective tissue nutrition (29:27–35:33)

• Modern diets often remove collagen‑rich tissues (skin, gristle, tendons), so many people under‑consume the amino acids needed for connective tissue maintenance.youtube​
• Eating “dietary collagen” (from skin, tendons, bone broth, gelatin, or hydrolyzed collagen) at about 15–20 g with vitamin C prior to loading the tissue can increase collagen synthesis rates.youtube​
• Traditional preparations like long‑boiled bone/skin broths that gel when cooled are essentially collagen sources and can support tendons, ligaments, cartilage, and other connective tissues.youtube​
• Vegan/vegetarian recombinant collagen derived from engineered bacteria is under active study in his lab; it may or may not stimulate collagen synthesis sufficiently, and strict plant‑based athletes may struggle to make enough collagen if training hard, especially with aging‑related declines in collagen turnover.youtube​

Aging, collagen turnover, and stiffness (35:33–40:40)

• With age, collagen synthesis rates decline, so existing collagen is broken down more slowly and remains in tissues longer, becoming stiffer over time.youtube​
• People notice this as:
  • Less plump skin and more wrinkles.
  • Stiffness, “old person” grunting when sitting/standing, loss of joint mobility.youtube​
• Supporting collagen synthesis (nutrition) and applying appropriate mechanical loading are key to maintaining tendon, ligament, and fascia health with age.youtube​

Endurance vs strength for anti‑aging (35:33–40:40)

• Which is “better” depends on personal risk profile:
  • Strong family history of cardiovascular disease: strength training is crucial plus endurance; heavy lifting acutely raises blood pressure and forces the heart to contract more forcefully, hypertrophying it beneficially, while endurance helps general cardiac health.youtube​
  • Family history of dementia/Alzheimer’s: endurance training is especially important because more muscle mitochondria mean more enzymes that clear neurotoxic metabolites from circulation, which supports brain health; large Swedish cohorts show a linear relation between cardiorespiratory fitness and cognitive test scores.
  • Strong cancer family history: higher strength is particularly protective; the strongest third have about one‑quarter the cancer mortality risk of the weakest third, and ~30% of cancer deaths result from cachexia (muscle wasting and weakness), not the tumor itself.
• Diabetes and metabolic disease are more endurance‑sensitive, while heart and cancer risk are strongly affected by strength; an anti‑aging program should therefore combine both, with an emphasis tuned to personal family history.

Avoiding injuries and tendon/ligament health (40:40–43:10)

• Heavy, controlled strength training is one of the best tools for tendon and ligament health: slow lifting with substantial load increases collagen synthesis in the tendon and can reduce excessive tendon stiffness while increasing muscle strength.
• A large meta‑analysis showed:
  • Stretching did not reduce musculoskeletal injury risk.
  • Strength training reduced injury risk by roughly 60–70%, making it highly protective for muscles, bones, and tendons.​

Training frequency, fatigue, and progression (43:10–50:22)

• Recovery requirements differ by individual and by modality, because there are three main fatigue domains:
  • Neuromuscular (central drive; more critical in elites).
  • Mechanical (impact forces, e.g., from running).
  • Metabolic (energy depletion, e.g., from cycling at high output).
• For the same calories burned, running produces more mechanical fatigue than cycling, so running requires more recovery days even at matched energy cost.
• Practical starting points he suggests:
  • For running beginners: 3 sessions/week of intervals like 30 s jog / 90 s walk, progressing weekly toward longer run intervals and less walking while maintaining session count.
  • When continuous running is comfortable, either lengthen some sessions or eventually add an extra session per week, then monitor how performance responds.
• For strength:
  • Start with about 2 sessions/week; log load and reps for key lifts.
  • If reps or load improve over ~2 weeks, you are recovering well; if performance worsens after adding volume or frequency (e.g., a 3rd session), the program is too heavy or too frequent.
• Around 80% of total training time should be at an easy, conversational intensity; only 10–20% should be hard enough that speaking in full sentences is not possible.youtube​

Quantifying “enough” muscle and tracking progress (50:22–end)

• There is no single “optimal” muscle mass target; function and performance matter more than kilograms of lean mass.
• The key is to:
  • Track what you do: weight used and reps for key lifts each session; distance/time or pace for a standard cardiovascular route/test.
  • Re‑test regularly (e.g., every couple of weeks) on standardized tasks to see if you are getting stronger or faster, maintaining, or regressing.
• If test performance is improving or stable, the loading and frequency are appropriate; if it declines, either overall volume, intensity, or frequency is too high or recovery (sleep, nutrition, stress) is insufficient.youtube​
• For older or sarcopenic individuals, he favors:
  • Prioritizing strength training (to reduce falls, preserve function, and protect against cancer and cardiovascular events).
  • Including endurance work at easy intensities to support heart and brain, adjusted to tolerance.​

Rapamycin and timing of use (around 57:00)

• Rapamycin (mTORC1 inhibitor) is the best‑known longevity drug in animal models, but exercise already provides rapamycin‑like mTORC1 lowering in many tissues without drug side effects.
• Fitness enthusiasts wondering “when to start” rapamycin should recognize that regular exercise plus appropriate diet may produce many of the same signaling changes; any decision on pharmacologic mTORC1 inhibition should be medically supervised and individualized.

Favorite sports and diet (end of lecture)

• Baar mentions his own preferences: he lifts twice per week (because his personal recovery capacity does not support more) and incorporates endurance work, illustrating his own application of mixed strength/endurance principles.
• Diet‑wise, he leans toward patterns that control carbohydrate and overall mTORC1 activation while keeping enough protein to maintain strength, but he does not claim a single universal diet for everyone.

https://www.youtube.com/watch?v=j49FSGTfsRk

https://www.youtube.com/watch?v=j49FSGTfsRk

Keith Baar: Tendon Development and Repair – Main Points & Recommendations

Core Scientific Findings

Tendon Prevalence & Impact

• 75% of athlete performance loss stems from tendon-related injuries
• 75% of elite basketball players show degenerative knee tendon changes on MRI
• Tendon health directly enables cardiovascular health through movement capability
• Problem extends beyond athletes to general population (e.g., mobility in aging)

Tendon is Dynamic Tissue (Not Inert)

• Patellar tendon protein turnover exceeds skeletal muscle turnover rates
• Contradicts textbook claims of 102-year collagen half-life
• Central core injuries compress under load, creating scar tissue through unloading
• Spatial transcriptomics shows genetic changes persist even in histologically normal tissue

Mechanical Basis of Injury

• Tension → tendon-like cells and aligned collagen
• Compression → cartilage-like cells and disorganized structure
• Central “holes” (jumper’s knee) result from outer collagen stress-shielding the core
• Unloading is the injury mechanism, not just the initial damage

Immobilization is Harmful

• 3 days in boot: 10% muscle loss + 20% tendon collagen loss in rats
• Creates tendinopathy without actual tissue injury
• Human data: 5% muscle loss in 5 days with knee brace; 8-12 weeks to regenerate

Key Recommendations (Last Slide Synthesis)

Stress Relaxation Loading Protocol

1. 30-second isometric contraction at ~90° joint angle (e.g., wall sit position)
2. Reduces healthy tendon tension via stress relaxation
3. Transfers load to injured/central core → stimulates repair
4. Proven results: NBA player patellar hole resolved in 12-18 months; elite athlete in 50 days

Avoid Immobilization

• No boots, braces, or extended rest
• Movement and tension sensing are essential for tendon, bone, cartilage, and muscle function
• Dynamic rehabilitation is non-negotiable

Address Mechanics First

• Orthobiologics (stem cells, PRP) won’t work effectively without proper mechanical loading
• Tissue must “feel” tension to heal properly
• Load transfers through mechanical manipulation before cellular interventions

Monitor Tissue Dynamics

• Tendons are highly responsive (50-day recovery demonstrated)
• Imaging (MRI, ultrasound, spatial transcriptomics) reveals changes beyond histology
• Early detection and loading-based intervention = faster outcomes

Bottom Line

Tensional mechanical loading through stress relaxation protocols is the cornerstone of tendon repair. Immobilization accelerates degeneration. Rehabilitation must prioritize dynamic tissue loading over protective rest.