GUEST SERIES | Dr. Andy Galpin: Optimal Protocols to Build Strength & Grow Muscles

In the second episode of a six-part guest series, Andrew Huberman, a professor of neurobiology and ophthalmology at Stanford School of Medicine, speaks with Andy Galpin, a professor of kinesiology at Cal State Fullerton, about strength, speed and muscle hypertrophy. The preceding episode introduced nine exercise adaptations and tests for assessing them. Here, the opening question concerns why strength and muscle growth matter beyond athletic performance or a desire for larger muscles.

Galpin challenges the assumption that strength training belongs to athletes and people seeking larger muscles, while cardiovascular exercise belongs to people seeking fat loss, heart health or longevity. Those categories, he argues, create unnecessary barriers: someone may avoid lifting because they fear gaining too much muscle, or choose only one form of exercise because they misunderstand its benefits. He tentatively attributes to Nike cofounder Bill Bowerman the saying, "If you have a body, you're an athlete." His broader aim is to match training to a person's actual goals, including energy, confidence and preparedness for daily life.

Galpin describes exercise benefits extending from mood, focus and cognitive performance to immune function and mortality, including his claim that exercisers experience fewer colds and fight them more effectively. He also distinguishes benefits associated with endurance training from those associated with strength training. His central argument is that resistance exercise, specifically strength training with heavy overload, is the principal tool for combating neuromuscular aging. He states this in exclusive terms, saying other forms of exercise cannot provide the same preservation; this excerpt does not present comparative studies establishing that exclusivity.

The functional explanation begins with three linked events: nerves activate, muscles contract and muscles move bones. Preserving that chain supports independent living. Galpin cites approximate annual losses after about age 40 of 1% in muscle size, 2% to 4% in strength and 8% to 10% in muscle power. These are figures he supplies in conversation, without identifying their underlying populations or studies. His practical distinction is that maintaining muscle size alone does not capture the ability to stand, move confidently or catch oneself during a fall, which he associates particularly with power.

When Huberman asks whether strength and hypertrophy training can help keep the nervous system healthy and young, Galpin agrees and cites a 30% to 40% reduction in total motor units among older individuals. Huberman presses for an age definition, asking whether someone aged 45 would count as older. Galpin says decrements begin around age 40, while emphasizing substantial variation related to genetics, sleep, nutrition and other factors. He does not specify the ages of the population underlying the motor-unit figure.

Galpin rejects the idea that missing an early start makes improvement impossible. He recalls reading a paper that morning involving people over age 90, reporting improvements of 30% to 170% in measures he describes as muscle size and hypertrophy over a short intervention. He thinks the duration was 12 weeks. Because neither the study nor its individual outcomes are specified, the example supports his argument about retained responsiveness without establishing exactly what each percentage measures.

His message applies in both directions: someone aged 50 who has not lifted is not beyond recovery, while people aged 20, 25 or 30 still have reasons to begin. He adds that some other health adaptations benefit from starting in one's 20s, without identifying them here. He also describes recent data suggesting that maintaining activity can largely ameliorate losses in strength and hypertrophy. His explanation places substantial responsibility on reduced training, nutrition, anabolic resistance and other factors, rather than an unavoidable age-driven loss of function. The excerpt supplies no study details that would resolve how much each factor contributes.

Huberman connects the discussion to Nobel laureate Sherrington, whom he calls a neuroscientist and Galpin emphatically calls a physiologist. Huberman recalls, with uncertainty about the wording, "Movement is the final common path." He uses that recollection to emphasize how much of the brain supports movement and argues that continued movement, including resistance exercise, helps sustain brain health. When he further describes the nervous system as controlling the strength and types of muscle contractions, Galpin says the account is close but not completely correct. Huberman welcomes the correction, although its detailed explanation does not appear in this passage.

The speakers agree on the importance of developing and maintaining the neuromuscular system across life, including the capacity to lift objects and move through the world. Huberman then broadens the discussion from function and injury prevention to appearance, asking how effectively strength and hypertrophy training change aesthetics compared with cardiovascular exercise.

Galpin organizes exercise goals around a sports saying: "You want to look good, feel good, play good." Appearance is personal; he does not prescribe a preferred physique. Feeling good includes avoiding injury, having energy throughout the day and being capable of activities such as surfing, racquetball and hiking—even all three in one day. Playing well concerns the capacity to execute whatever activities a person values.

His answer about aesthetics focuses on the speed and motivational value of feedback. He says noticeable changes in muscle size can occur within a month and certainly within six weeks, later describing early successes within three to five weeks. He contrasts that experience with fat loss, which he characterizes as a longer, more difficult process with greater dependence on nutrition and other variables. He describes strength training as having relatively minimal nutritional requirements beyond which training itself becomes decisive; he does not specify those requirements or provide a controlled comparison with cardiovascular exercise here.

The underlying argument concerns adherence. Galpin says the exercise literature often identifies adherence as the strongest predictor of whether a program works. Methods can vary enormously, but a small set of concepts must be satisfied, including consistent participation. Visible changes in the mirror and improvements in how a person feels or performs can reinforce that consistency. Early success therefore matters particularly for people who do not already enjoy exercise enough to continue regardless of results. His point is about a reinforcing behavioral cycle, rather than a specific lifting prescription.

Before returning to the science, Huberman states that the podcast is separate from both his Stanford teaching and research and Galpin's teaching and research at Cal State Fullerton. He frames it as an effort to provide science information and related tools to the public at no cost to the consumer. The subsequent supplement, sleep and glucose-monitoring material is presented as sponsorship, with promotional claims and personal experiences rather than evidence developed in the interview.

For Momentous, Huberman emphasizes what he describes as high supplement quality, generally single-ingredient formulations and international shipping. He argues that single-ingredient products make it easier to construct a logical, effective and cost-effective regimen. He directs listeners interested in supplements discussed for hormone health, sleep, focus, exercise recovery and other purposes to livemomentous.com/huberman, spelling the ending of Momentous as O-U-S.

For Eight Sleep, he describes mattress covers offering cooling, heating and sleep tracking. After about eight months of use, he reports similar sleep duration but deeper sleep, improved proportions of REM and slow-wave sleep, and greater mental and physical recovery. He links these experiences to temperature regulation, stating that falling asleep requires a core-temperature decrease of about one to three degrees and waking involves an increase of one to three degrees; he does not specify the temperature scale. He says the cover permits different temperatures at bedtime, during the night and toward morning. The offer is $150 off a Pod 3 cover at eightsleep.com/huberman, with shipping then available in the USA, Canada, United Kingdom, selected EU countries and Australia.

For Levels, Huberman describes continuous glucose monitoring as a way to observe how food, exercise, environmental temperature, meal timing and sleep relate to blood glucose. He presents glucose regulation as relevant to fat loss, muscle gain, cognition and aging. Having begun using Levels about a year earlier, he reports learning how to adjust eating, exercise, work and sleep schedules from the feedback. He directs listeners to levels.link/huberman. These are his reported experiences and sponsor descriptions; this passage does not supply comparative outcome data for the products.

Returning to training, Huberman asks what strength and hypertrophy actually represent as adaptations. Galpin defines strength through function: the ability to produce force across a muscle, muscle group or complete movement. Hypertrophy describes increased size, without itself specifying function. A muscle can therefore become larger without technically becoming stronger, even though the two adaptations have a strong relationship.

That relationship is especially close among beginners and people with intermediate training experience. At more advanced levels, the distinction becomes clearer. Galpin compares powerlifters, whose competition tests one-repetition maximums in the deadlift, bench press and back squat, with bodybuilders. Both groups tend to be strong and muscular, but he says powerlifters are stronger on average while bodybuilders carry more muscle. He explicitly allows individual exceptions. He distinguishes powerlifting's maximal-strength test from World's Strongest Man events involving repetitions or time.

Galpin invokes weight classes to illustrate the relationship between body size and absolute strength, while allowing strength gains with little additional muscle. Later he gives programming examples for that goal: low repetitions, often one to three, more sets with ample rest, and attention to food intake and training frequency. His eight sets of three provide 24 high-quality practice repetitions. These are his examples for emphasizing strength; the stated calorie thresholds and other physiological claims are not independently verified by this discussion.

He divides strength into physiology and mechanics. Physiology includes the neuromuscular system's capabilities and muscle fibers' capacity to contract and produce force. Mechanics includes anatomy, such as femur length relative to tibia length, together with technique, skill, movement smoothness and the sequence in which muscle groups activate. A competitor with greater force-producing capacity can lose because of poorer technique. In jumping and sprinting, the rhythm of the movement is another mechanical contribution. Hypertrophy, by comparison, remains a measure of muscle size.

Huberman next asks whether ligaments and tendons grow or become stronger alongside muscles. Galpin says this is a difficult research area because connective tissue has much less plasticity than skeletal muscle, attributing that difference to its lack of vascularity. He describes skeletal muscle as exceptionally responsive to the body's internal environment, including changes in blood pressure, pH and circulating macronutrients. These are his physiological explanations in the conversation; no direct measurements or studies accompany them here.

The discussion briefly becomes a Jeopardy! joke when Galpin calls muscle the body's largest organ system. Huberman offers skin as the expected answer and jokes that he will cite or call Galpin if answering muscle costs him the question. Galpin suggests Celebrity Jeopardy!; Huberman questions the celebrity designation but says the show would be fun. The exchange illustrates Galpin's effort to make listeners think of muscle as an organ system, although it does not examine the definitions underlying the comparison with skin.

Galpin develops that organ-system argument by describing muscle as both receiving and sending signals. He says it influences immune function and blood-glucose regulation and serves as a central amino-acid depot supporting processes such as immune regulation and production of new red blood cells. He explains his use of the word organ through communication with other organs and the wider system. Connective tissue, he says, does not behave in the same way.

Nevertheless, he says connective tissue does adapt to strength training, though less readily than muscle and in ways that are difficult to measure. He identifies those adaptations as a probable major contributor to reduced injury risk. His concrete example is a person returning to activities after roughly 10 years away, perhaps at 25 or 35, and attempting what they could do at 20. The intended load may exceed the tissues' current tolerance, leading to sprains or tears, including an Achilles tear. He attributes a substantial role in reducing stress, strain and overuse injuries to strength training's effects on connective tissue.

The measurement problem leads to Galpin's account of patellar-tendon biopsies during his doctoral training, including one performed on himself. He estimates that he has performed well over 1,000 biopsies on others and undergone about 35 or 40 himself, with samples taken from sites including his quadriceps, soleus and gastrocnemius. He reports no scar tissue or loss of function in his own experience. He describes removing a tissue sample with a needle resembling a pen, and agrees when Huberman asks whether he can visit the lab for a biopsy. The anecdote conveys his research experience; his personal outcomes do not establish general procedural risks. The interview subsequently continues through muscle physiology and detailed programming examples.

Andy Galpin opens with an anecdote about a mutual friend deeply involved in lifting and strength training whose muscle biopsy revealed exceptionally large muscle fibers. He also acknowledges that the friend had well-documented assistance with muscle growth, without specifying it. The example illustrates striking muscle morphology, but it does not establish what training alone produced.

Huberman asks how large a muscle cell can be, prompting Galpin to distinguish length from diameter. Using the sartorius, which runs from the front of the hip toward the inside of the knee, Galpin says a single fiber could theoretically span the muscle’s length. He describes isolating a fiber with tweezers and seeing the cell with the naked eye. He never supplies a numerical diameter in this excerpt; later, he directs listeners to his YouTube explanations for that measurement and related visuals, which Huberman says they will link.

The larger question is how the whole movement system adapts. Huberman asks about tendons, ligaments, bones, nerves and their relationships with muscle: what changes allow someone to lift 100 pounds one day and 105 pounds a week later? The discussion develops an explanation across neural signaling, muscle contraction and muscle architecture, rather than treating visible muscle growth as the sole explanation for strength.

Huberman initially distinguishes his question about bones growing and becoming stronger from bone mineral density. He connects it to research from Eric Kandel’s laboratory at Columbia, describing several studies in which load-bearing exercise stimulated bone to release osteocalcin. In Huberman’s account, osteocalcin acts more or less as a hormone, travels to the brain and supports memory systems by enhancing neuronal health. He presents this as another reason he became interested in resistance exercise alongside aerobic exercise; the excerpt supplies no study methods or quantitative outcomes.

Galpin says bones can become stronger through training, but his answer centers on bone mineral density rather than separately resolving whether bone dimensions increase. He describes the teens and twenties as the period with the greatest capacity to improve density, with that capacity diminishing with age. He identifies axial loading as particularly relevant, explaining it as vertical compression; Huberman pictures loading the small ends of a cylinder. Galpin explicitly qualifies his expertise: he specializes in muscle, and a bone specialist could provide greater precision.

Asked whether people who missed that earlier period can still improve, Galpin answers yes, while emphasizing smaller adaptations. He reports that women in their twenties and thirties entering his Rapid Health program with significant bone mineral density problems showed positive changes after eight months that exceeded DEXA measurement error. This is a program observation as presented in the conversation, without participant counts, a comparison group or a breakdown of the interventions responsible.

Galpin stresses that strength training alone probably will not resolve these cases, particularly among women, because the underlying cause matters. He describes nutrition, blood chemistry, menstrual function and contraceptive use—especially hormonal contraception—as relevant considerations, and says affected individuals should work with a qualified physician or specialist. His account allows for nutritional supplementation and potentially other interventions, rather than presenting resistance exercise as a complete treatment.

For hormonal assessment, Galpin describes using Rhythm Plus, a 30-day salivary test with sampling about every other day, producing 15 or 16 samples across a menstrual cycle. He argues that a single saliva, urine or blood measurement can differ by an order of magnitude for some metrics depending on cycle phase. He also distinguishes outcomes: some measures vary across the cycle, others do not. In his reading of the evidence, strength and one-repetition maximum testing do not require testing at a particular phase, whereas hormone-related measurements require accounting for cycle timing.

Galpin’s central argument is that strength training can improve much of the chain that produces movement. He begins with motor units and the many individual fibers composing a muscle, comparing the whole muscle to a ponytail made of individual hairs. Fibers within a motor unit are generally of the same type, he says, but are distributed throughout the muscle rather than grouped together. He links that distribution to smoother contractions.

On the neural side, Galpin identifies improvements in firing rate, synchronization and acetylcholine release and recycling. His explanation follows transmission across the nerve–muscle gap: acetylcholine binds a receptor that permits sodium entry, after which the signaling machinery must reset. He presents more effective signaling and recycling as ways training can improve performance before any increase in muscle size enters the explanation.

Within the fiber, he distinguishes contractility from size. A fiber can produce greater force or velocity through changes in its contraction machinery. He highlights the sarcoplasmic reticulum, which stores and releases calcium, describing improved sensitivity, calcium release and reuptake. He also describes stronger actin–myosin cross-bridge interactions and increased calcium affinity. In this account, more force can emerge from more effective operation of existing structures, without adding contractile units.

Galpin also identifies changes in fiber type as a possible route to greater force independent of size, including a shift from slow-twitch to fast-twitch characteristics. He cautions against assuming that fast fibers are always larger: in people doing substantial, consistent endurance training, slow-twitch fibers can be as large as, or often larger than, fast-twitch fibers. He characterizes those large slow fibers as metabolically effective and highly fatigue-resistant, making clear that slow is not a judgment of poor muscle quality.

The explanation then moves to muscle architecture. Galpin introduces pennation angle through a simplified description of fiber orientation relative to bone, ranging from almost 90 degrees to about 45 degrees and nearly parallel. His broader point is that geometry changes mechanical performance: arrangements that favor force and those that favor shortening velocity involve trade-offs. He also mentions increased phosphocreatine storage as another adaptation, identifying it as an energy supply for muscle contraction at the fastest rates.

These mechanisms support the distinction he wants listeners to retain: strength and hypertrophy overlap substantially, but they are not identical. Galpin introduces lattice spacing to explain why increasing size need not optimize force production. In his description, a myosin molecule sits among six surrounding actin molecules, and effective contraction requires suitable spacing for the myosin heads to make strong connections.

He illustrates spacing with outstretched arms: an attachment reached only with the fingertips would be weak, while a position that is already too close leaves little room to pull. His wording initially suggests that increasing size can reduce strength, but he subsequently qualifies the point: getting bigger does not inherently make someone weaker. The practical distinction within his explanation is between optimizing size and optimizing strength, with disrupted spacing offered as one possible reason growth and performance may diverge.

A sponsor break separates the strength discussion from the explanation of hypertrophy. Huberman describes Athletic Greens as a vitamin, mineral, probiotic and adaptogen drink intended to cover foundational nutritional needs. He says he has taken it daily since 2012 and currently uses it once or twice a day, emphasizing probiotics and attributing stress-recovery benefits to its adaptogens. These are sponsor-segment claims and personal use statements, rather than evidence developed in the interview. The advertised offer at athleticgreens.com/huberman includes five free travel packs and a year’s supply of vitamin D3K2.

Returning to hypertrophy, Huberman asks about protein synthesis, blood flow, neural innervation and fascia, acknowledging that he does not know specific fascial adaptations. Galpin says strength-oriented and hypertrophy-oriented training share many adaptations because their training demands overlap; five repetitions and eight repetitions are his example. His detailed answer then concentrates on muscle microstructure and protein synthesis, leaving the proposed blood-flow and fascia questions undeveloped in this excerpt.