Dr. Keith Baar is a Professor at the University of California, Davis in the Department of Physiology and Membrane Biology. During his Ph.D. studies, his research revealed that mechanical strain on muscle fibers activates the mammalian target of rapamycin (mTOR) signaling pathway, a crucial regulator of muscular hypertrophy. Subsequently, he studied the molecular dynamics of skeletal muscle adaptation to endurance training under the guidance of Dr. John Holloszy, a legend in the field of exercise physiology, considered the father of modern exercise biochemistry. Building on all of this experience, he conducted research into tendon health and the potential for engineering ligaments, which could have implications for treatment and recovery from injuries. Sponsors: Cresset prestigious family office for CEOs, founders, and entrepreneurs: https://cressetcapital.com/tim (book a call today) AG1 all-in-one nutritional supplement: https://DrinkAG1.com/Tim (1-year supply of Vitamin D (and 5 free AG1 travel packs) with your first subscription purchase.) Shopify global commerce platform, providing tools to start, grow, market, and manage a retail business: https://shopify.com/tim (one-dollar-per-month trial period) * Links to everything discussed: https://tim.blog/2025/02/26/dr-keith-baar/ Timestamps: [00:00:00] Start [00:07:12] How I discovered Keith’s work through a tweet about tennis elbow and rock climbing. [00:07:54] Emil Abrahamsson’s hangboard training protocol. [00:09:20] The fundamental principles of strength training and connective tissue adaptation. [00:10:36] mTOR complex 1 and its role in muscle growth. [00:12:06] Engineered ligaments and the discovery of minimal effective doses for tendon adaptation. [00:13:50] The refractory period between optimal tendon loading sessions. [00:16:42] Rapamycin’s effects on muscle hypertrophy. [00:18:49] Protocols for tennis elbow rehabilitation. [00:20:28] Why isometrics work better than eccentrics for tendon healing. [00:22:14] Stress shielding and how load distribution affects tendon healing. [00:29:07] The misconception about eccentric loading for tendon injuries and why velocity matters. [00:29:58] Ideal duration for isometric holds (10-30 seconds) based on injury status. [00:33:50] My elbow issues and current rehab approach. [00:36:02] Overcoming vs. yielding isometrics and optimal loading strategies. [00:47:11] Dr. Barr’s movement prescription for my tennis elbow. [00:52:18] Loading timing post-surgery and RICE protocol criticism. [00:56:58] Achilles tendon rehabilitation after surgery. [01:00:18] Critique of orthopedic suturing techniques and recommendation for resorbable sutures. [01:04:02] Multiple position isometrics for tennis elbow rehabilitation. [01:07:26] Collagen synthesis, supplementation, and vitamin C timing. [01:12:59] Critique of BPC-157 and other injectable peptides for tendon healing. [01:18:19] Evaluation of orthobiologics’ (PRP, prolotherapy, stem cells) effectiveness. [01:21:37] JAK-STAT inhibitor drugs and their effects on tendon growth. [01:25:35] Drugs that increase risk of tendon ruptures (fluoroquinolones, AT-1 receptor drugs). [01:29:33] How estrogen affects tendon stiffness and injury risk in women. [01:32:48] Testosterone’s opposite effects on tendon compared to estrogen. [01:35:31] Protein intake recommendations and timing. [01:40:11] Ketogenic diet effects on mitochondrial biogenesis and longevity. [01:41:57] Comparison of ketogenic diet, low protein diet, and rapamycin for longevity. [01:47:19] Inflammation’s role in adaptation and when to reduce it. [01:51:17] Timing of ice baths relative to training for optimal recovery. [01:52:33] Parting thoughts. * For show notes and past guests on The Tim Ferriss Show, please visit tim.blog/podcast. For deals from sponsors of The Tim Ferriss Show, please visit tim.blog/podcast-sponsors Sign up for Tim’s email newsletter (5-Bullet Friday) at tim.blog/friday. For transcripts of episodes, go to tim.blog/transcripts. Discover Tim’s books: tim.blog/books. 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