Huberman Backs Low-Intensity Static Stretching Over PNF for Flexibility

Huberman推荐低强度静态拉伸而非PNF以提升柔韧性 每个肌群每周仅以30%至40%的强度累计拉伸5分钟，即可比更高强度的拉伸更有效地扩大主动关节活动度，同时在结构上重塑大脑，使疼痛耐受度提高一倍。 本期节目剖析了柔韧性本质上是如何由神经系统主导的：一方面通过肌梭和高尔基腱器官等局部反射回路调控，另一方面通过大脑岛叶皮层进行认知调节。基于全面的科学综述，Andrew Huberman强调低强度静态拉伸——特别是疼痛阈值30%到40%的微拉伸——是增加主动关节活动度最有效的方法。为实现持久的身体组织重塑，该方案建议每个肌群每周累计拉伸至少5分钟，并分散在5天内，每次拉伸保持30至60秒。此外，讨论还将瑜伽等常规练习与大脑结构改变联系起来，展示了耐受身体不适如何使基线疼痛耐受度翻倍，并增加岛叶的灰质体积。 柔韧性依赖于三个相互交织的主要要素：神经系统、肌肉和结缔组织。 (0:00) 神经系统是肌肉的终极控制者，通过运动神经元释放乙酰胆碱来引发肌肉收缩。 (0:22) 肌梭构成了一个感觉反馈回路，作为一种生物安全机制，在肢体过度拉伸时强制肌肉收缩。 (1:28) 高尔基腱器官（GTO）通过感知力量和张力充当应急断路器，在负荷可能损伤组织时抑制运动神经元。 (3:15) 岛叶是大脑中负责内感受以及追踪体内感觉的主要区域。 (4:42)

Andrew Huberman explains that flexibility is primarily governed by the central nervous system rather than muscle tissue alone, with research indicating that frequent, low-intensity static stretching totaling at least five minutes per week per muscle group produces optimal, lasting adaptations. Neuromuscular Mechanics and Conscious Reflex Overrides (0:00) Huberman emphasizes that flexibility depends on the nervous system, muscles, and connective tissue, with motor neurons initiating contraction via acetylcholine release. Within muscle fibers, sensory muscle spindles monitor stretch and reflexively contract the muscle if it elongates excessively, preventing joint or tissue injury. Conversely, Golgi tendon organs (GTOs) located at muscle-tendon junctions sense load and force; if mechanical tension threatens to tear tissue, GTOs completely shut down motor neuron activity as an emergency circuit breaker. Higher cortical structures can consciously override these spinal reflexes. The posterior insula evaluates internal bodily states, housing specialized, enlarged von Economo neurons that integrate pain signals, spatial awareness, and goal-directed focus. By shifting the autonomic nervous system from sympathetic stress toward parasympathetic relaxation, these neural pathways allow individuals to suppress reflexive contractions and relax into end-range positions. Frequency, Duration, and Superiority of Static Holds (14:11) Comparing dynamic, ballistic, static, and proprioceptive neuromuscular facilitation (PNF) modalities, Huberman cites a scientific review showing that static stretching produces significant flexibility improvements (p < 0.05), mathematically outperforming both ballistic and PNF protocols. Static stretching eliminates momentum by holding the joint at its absolute end range. The literature identifies total weekly volume as the critical variable for remodeling connective tissue and expanding range of motion. Huberman notes that muscles require a minimum threshold of five total minutes of stretching per week, ideally divided into two to four sets of 30-second static holds performed across five days. Efficacy of Low-Intensity Micro-Stretching (19:28) Citing the Anderson method, Huberman emphasizes defining end range by where tension is actively felt rather than comparing against arbitrary daily expectations. Addressing exertion, a six-week intervention study on recreational dancers compared low-intensity "micro-stretching" (30% to 40% of pain threshold, held for 60 seconds) against moderate-intensity stretching (80% of pain threshold). Participants in the low-intensity group achieved significantly greater gains in active range of motion than the moderate-intensity cohort. Huberman concludes that pushing near or into pain is counterproductive and that mild, relaxed static holds are safer and more effective for expanding functional mobility. Warm-Up Requirements and Workout Placement (16:20) Static stretching requires an elevated core body temperature to reduce injury risk, achieved either through five to ten minutes of light cardiovascular activity or by scheduling flexibility sessions after physical exercise. Huberman notes that static stretching prior to running or weightlifting can limit speed and force output, making post-workout sessions the optimal timing for most individuals. However, pre-workout static stretching is justified when acute tightness impedes safe movement mechanics or during injury rehabilitation. Dynamic and ballistic stretching remain appropriate before exercise to prime joints and activate neural circuits without sacrificing strength. Insular Cortex Remodeling and Pain Tolerance (26:10) A study published in Cerebral Cortex evaluated practitioners across diverse yoga traditions (including Vinyasa, Ashtanga, Iyengar, and Sivananda) against non-practitioners using thermal pain tests. The yoga practitioners demonstrated double or more the pain tolerance of control subjects. Brain imaging revealed that yoga practitioners had statistically significant increases in gray matter volume within the insular cortex. Huberman notes that repeatedly and intentionally tolerating positional discomfort physically alters brain regions responsible for interoception, training the nervous system to handle internal stress and pain more effectively. While scientific evidence clearly favors frequent, short, low-intensity static stretching for safe tissue remodeling and neurological pain tolerance, Huberman notes that the exact performance trade-offs of pre-exercise static stretching remain an area of ongoing debate among athletic researchers.

斯坦福大学神经生物学与眼科学教授安德鲁·休伯曼（Andrew Huberman）指出，柔韧性并非单纯取决于肌肉本身，而是由神经系统、肌肉与结缔组织共同决定的，其中神经系统处于终极调控地位。科学证据支持通过每周每肌群累积至少5分钟的低强度静态拉伸方案，借助神经反射抑制与脑岛皮层的感知调节，安全有效地提升关节活动度。 神经回路对肌肉长度与张力的反射保护 (1:28) 休伯曼解释称，运动神经元通过释放神经递质乙酰胆碱引发肌肉收缩，但肌肉内部同时分布着复杂的本体感觉监测网络。缠绕在肌纤维上的肌梭负责实时监测伸展长度；当肢体伸展过度可能造成危险时，肌梭会向脊髓发送电信号，立刻激活对应的运动神经元促使肌肉强行收缩，通过单突触反射机制避免组织受损。相反，位于肌肉与肌腱过渡区的高尔基腱器官（GTO）则专门测量施加在肌肉上的负荷与力量；当承载张力过大可能扯断肌腱或损伤关节时，GTO会充当紧急断路器，直接关闭运动神经元的放电，强行阻断肌肉收缩。 尽管底层反射机制十分稳固，但大脑的高级认知中枢具备完全抑制这些反射的能力。例如，人体在踩到尖锐物体时会自动产生屈曲回避反射，但高级运动神经元和认知控制可在紧急情境下强行压制疼痛回避。通过有意识地将身体内部状态由交感神经的警觉激活转向副交感神经的深度放松，练习者能够在大脑皮层层面主动调低防卫信号，从而在神经肌肉接头处跨越肌梭与GTO的被动防御，实现真正“放松进入拉伸”的生理状态。 脑岛皮层与内在感知介导的疼痛耐受 (4:42) 大脑处理拉伸疼痛与内部感受的核心中枢是脑岛皮层（insula），它负责协调机体的内感受（interoception），即监测内脏饱腹感、器官舒适度及躯体生理指标。休伯曼介绍，后脑岛主要处理原始躯体体验，负责评估感觉并指导趋向或回避行为。在后脑岛内部，存在一类体积巨大且高度富集于人类大脑的特异神经细胞——冯·埃科诺莫神经元（von Economo neurons）。这类神经元整合了空间定位、身体动作与疼痛信号，赋予个体在明确目标导向下主动忍耐身体不适的神经驱动力，使人能够有意识地抑制焦虑并引导神经系统进入放松状态。 发表在《大脑皮层》（Cerebral Cortex）上的一项研究直接证实了拉伸训练对这一神经回路的物理重塑作用。该研究对包含流瑜伽（Vinyasa）、阿斯汤加（Ashtanga）、艾扬格（Iyengar）和希瓦南达（Sivananda）等流派的瑜伽练习者进行了冷热温度刺激测试，发现瑜伽练习者的基准疼痛耐受度达到无瑜伽经验对照组的两倍以上。脑部成像进一步显示，瑜伽练习者脑岛皮层的灰质体积呈现出统计学上显著的增长。休伯曼指出，长期在拉伸终末范围探索并安全应对躯体不适，能够实质性增大神经元胞体密度，重塑中枢神经对内部压力的评估模式。 拉伸形式对比与低强度微拉伸的优势 (19:28) 拉伸方法主要分为利用控制性动作的动态拉伸、利用剧烈摆动惯性的弹跳拉伸、完全消除动量的静态拉伸，以及结合抗阻与放松的本体感觉神经肌肉促进法（PNF）。休伯曼引用的系统性文献综述表明，尽管各类拉伸均有一定作用，但静态拉伸在增加关节活动度上的效果达到了统计学显著水平（P值小于0.05），在数据表现上不仅优于弹跳拉伸，也优于PNF拉伸。此外，经典的安德森（Anderson）方法强调，每日的拉伸终末范围应由肌肉产生牵拉感的主观位置来界定，该节点会随日常压力、肌张力及环境温度产生波动，练习者不应执着于固定的肢体接触距离。 在拉伸强度的选择上，一项针对业余舞蹈练习者开展的为期六周的对照实验表明，施加过多痛苦不仅没有必要，反而会削弱拉伸效果。该研究对比了以最大疼痛阈值30%至40%进行的低强度“微拉伸”（micro-stretching）与80%强度的中度静态拉伸（单组持续60秒）。结果显示，30%至40%强度的微拉伸在改善下肢主动关节活动度方面显著优于80%强度的对照组。数据证实，维持在轻微、放松的低强度区间能够降低组织损伤风险，更有效地诱发神经系统对肌肉拉长的适应。 科学拉伸协议的时间累积与实施时机 (14:11) 关于改善柔韧性的长期方案，科研综述得出的核心指标是每周在目标肌群上累积的拉伸总时长。为引发结缔组织重塑并稳定扩大活动范围，每个肌群每周至少需要5分钟的静态拉伸总量。休伯曼强调，这一目标不应通过单次剧烈拉伸完成，最有效且具科研支持的节奏是每周安排5天，每天对目标肌群进行2至4组、每组30至60秒的静态拉伸。以腘绳肌训练为例，单次进行3组30秒拉伸（单日累积90秒），只要每周坚持5次以上，便能达到并超越抵御年龄相关柔韧度退化所需的累积门槛。 在拉伸的准备与时机方面，受试者在拉伸前应先提升核心体温，通过5至10分钟的轻松有氧运动或健美操预热，或直接安排在跑步、抗阻力量训练结束之后进行。多项文献指出，力量训练或跑步前进行静态拉伸可能会暂时削弱肌肉的力量与运动表现，因此通常建议将静态拉伸置于训练之后。但休伯曼补充指出，若个体存在严重的慢性肌纤维紧绷从而妨碍动作标准规范，或是处于伤病手术康复阶段，运动前进行静态拉伸以确保结构安全性则是完全合理的；而在高强度运动前采用动态拉伸，亦能有效预热神经回路与结缔组织。 休伯曼总结指出，建立长久柔韧性的关键在于遵循神经生物学规律，利用每周至少5分钟的低强度静态拉伸实现生理与神经重塑，而非强行对抗疼痛反射。尽管运动前进行静态拉伸对后续爆发力的潜在抑制在学界仍存争议且需视康复需求权衡，但在快节奏日常中保持每周5次以上的高频次拉伸依从性，仍是广大练习者将该科学协议落地的主要现实挑战。

[0:00] Andrew Huberman: Your nervous system controls your muscles. It's what gets your muscles to contract. [4:42] Andrew Huberman: Today I'm going to teach you about a set of neurons that I'm guessing 99.9% of you have never heard of, including all you neuroscientists out there... They seem uniquely enriched in humans and probably perform essential roles in our ability to regulate our physiology and our emotional state. [17:01] Andrew Huberman: We should be warm or warm up to stretch, although those warm-ups don't have to be extremely extensive. [19:28] Andrew Huberman: The most interesting aspect of the study was the greater increase in active range of motion compared to passive range of motion by the micro stretching group.

[0:00] Welcome to Huberman Lab Essentials, [0:01] >> [music] [0:02] >> where we revisit past episodes for the [0:04] most potent and actionable science-based [0:06] tools for mental health, physical [0:08] health, and performance. [0:11] I'm Andrew Huberman and I'm a professor [0:13] of neurobiology and ophthalmology at [0:15] Stanford School of Medicine. Today we [0:17] are going to discuss the science and [0:19] practice of flexibility and stretching. [0:21] The important thing that I'd like you to [0:23] know is that flexibility and the process [0:25] of stretching and getting more flexible [0:27] involves three major components. Neural, [0:31] meaning of the nervous system, muscular, [0:33] muscles, and connective tissue. [0:35] Connective tissue is the stuff that [0:37] surrounds the neural stuff and the [0:40] muscular stuff, although it's all kind [0:41] of weave together and braided together [0:43] in complicated ways. So, here's a key [0:45] thing that everyone should know, whether [0:47] or not you're talking about flexibility [0:48] or not. [0:50] Your nervous system controls your [0:52] muscles. It's what gets your muscles to [0:54] contract. So, within your spinal cord [0:57] you have a category of neurons, nerve [0:59] cells, that are called motor neurons. [1:02] Those neurons release a chemical. That [1:04] chemical is called acetylcholine. The [1:06] release of acetylcholine from these [1:08] nerve cells, these neurons, onto the [1:10] muscles causes the muscles to contract. [1:13] And when muscles contract, they are able [1:15] to move [1:17] limbs by way of changing the length of [1:21] the muscle, adjusting the function of [1:24] connective tissue like tendons and [1:25] ligaments. Now, within the muscles [1:28] themselves, there are nerve connections. [1:32] And these are nerve connections that [1:34] arise from a different set of neurons in [1:36] the spinal cord that we call sensory [1:38] neurons. These [1:40] spindle [1:42] connections within the muscle that wrap [1:44] around the muscle fibers sense the [1:46] stretch of those muscle fibers. [1:49] So, now we have two parts to the system [1:52] that I've described. You've got motor [1:53] neurons that can cause muscles to [1:55] contract and shorten, and we have these [1:59] spindles within the muscles themselves [2:02] that wrap around the muscle fibers, and [2:04] that information is sent from the muscle [2:07] back to the spinal cord. It's a form of [2:10] sensing what's going on in the muscle. [2:12] Now, why would that be useful? Well, [2:14] what this does is it creates a situation [2:16] where if a muscle is or is stretching [2:19] too much because the range of motion of [2:21] a limb is increased too much, then the [2:24] muscle will contract to bring that limb [2:26] range of motion into a a safe range [2:29] again. Okay, so just to clarify, this [2:31] whole thing looks like a loop, and the [2:33] essential components of the loop are [2:35] motor neurons contract muscles, sensory [2:38] neurons that we call spindles are [2:40] sensing stretch within the muscles, and [2:42] if a given muscle is elongating because [2:46] of the [2:47] increased range of motion of a limb, [2:49] those sensory neurons send an electrical [2:51] signal into the spinal cord such that [2:53] there is an activation of the motor [2:55] neuron, which by now should make perfect [2:57] sense as to why that's useful. It then [2:59] shortens up the muscle. It actually [3:01] doesn't really shorten the muscle, but [3:02] contracts the muscle. It brings the limb [3:04] back into a safe range of motion. So, [3:07] that's one basic mechanism that we want [3:09] to hold in mind. This idea of a spindle [3:12] that senses stretch and can activate [3:14] contraction of the muscles and shorten [3:15] the muscles. The next mechanism I want [3:17] to describe, and once again, there are [3:19] only two that you need to hold in mind [3:20] for this episode, has to do with sensing [3:23] loads. [3:24] So, at the end of each muscles, you have [3:27] tendons typically, and there are neurons [3:32] that are closely associated with those [3:35] tendons [3:36] that are called Golgi tendon organs, [3:38] right? These are neurons that are [3:40] sensory neurons that sense how much load [3:43] is on a given muscle, right? So, if [3:44] you're lifting up something very, very [3:46] heavy, these neurons are going to fire, [3:48] meaning they're going to send electrical [3:49] activity into the spinal cord, [3:52] and then those neurons have the ability [3:54] to shut down, not activate, but shut [3:57] down motor neurons and to prevent the [4:00] contraction of a given muscle. So, for [4:02] instance, if you were to walk over and [4:04] try and pick up [4:05] a weight that is [4:07] much too heavy for you, meaning you [4:08] could not do it without injuring [4:10] yourself. There are a number of reasons [4:11] why you might not be able to lift it, [4:13] but let's say you start to get it a [4:14] little bit off the ground or you start [4:16] to get some [4:18] force generated that would allow it to [4:19] move. [4:20] But, the force that you're generating [4:23] could potentially rip your muscles or [4:25] your tendons off of the bone, right? [4:27] That it could disrupt the joints, that [4:29] could tear ligaments. Well, you have a [4:30] safety mechanism in place. It's these [4:32] Golgi tendon organs, these GTOs as [4:34] they're called, that get activated and [4:36] shut down the motor neurons and make it [4:38] impossible for those muscles to [4:40] contract. There are also mechanisms that [4:43] arrive to the neuromuscular system from [4:47] higher up in the nervous system, from [4:48] the brain. [4:49] And those mechanisms involve a couple of [4:52] different facets that are really [4:53] interesting [4:54] and I think that we should all know [4:56] about. In fact, today I'm going to teach [4:57] you about a set of neurons that I'm [4:59] guessing 99.9% [5:01] of you have never heard of, including [5:03] all you neuroscientists out there, if [5:04] you're out there. [5:06] And I know you're out there. [5:08] That seem uniquely enriched in humans [5:12] and probably perform essential roles in [5:15] our ability to regulate our physiology [5:17] and our emotional state. So, within the [5:19] brain we have the ability to sense [5:21] things in the external world, something [5:23] we called exteroception, and we have the [5:25] ability to sense things in our internal [5:27] world, within our body, called [5:29] interoception. Interoception can be the [5:31] volume of food in your gut, whether or [5:33] not you're experiencing any organ pain [5:35] or discomfort, whether or not you feel [5:36] good in your gut and in your organs. The [5:38] main brain area that's associated with [5:41] interpreting what's going on in our body [5:42] is called the insula, i n s u l a. It's [5:45] a very interesting brain region. It's [5:47] got two major parts. The front of it is [5:49] mainly [5:50] concerned with things like smell and to [5:54] some extent vision. Like if you smell [5:56] something good to approach it or if you [5:58] smell something bad to avoid it. The [5:59] posterior insula, the back of the insula [6:02] that is, [6:03] has a very interesting and distinct set [6:06] of functions. [6:07] The posterior insula is mainly concerned [6:10] with what's going on with your somatic [6:12] experience. How do you feel internally? [6:15] It mainly batches information into yum, [6:17] I want to keep doing this or approach [6:19] this thing, [6:20] or continue down some path of movement [6:24] or eating or staying in a temperature [6:26] environment, etc. Or yuck, I need to get [6:28] out of here. I don't want any more of [6:30] this. I don't want to keep doing this. [6:31] This is painful or aversive or [6:33] stressful. In your posterior insula, [6:37] you have a very interesting population [6:39] of very large neurons. These are [6:41] exceptionally large neurons called von [6:44] Economo neurons. Neurons that are again, [6:47] unbeknownst to most neuroscientists, and [6:49] they seem uniquely enriched in humans. [6:53] Why is that interesting? Well, these von [6:56] Economo neurons have the unique property [6:59] of integrating our [7:01] knowledge about our body movements, [7:04] our sense of pain and discomfort, and [7:07] can drive motivational processes that [7:09] allow us to lean into discomfort and [7:11] indeed to overcome any discomfort if we [7:14] decide that the discomfort that we are [7:16] experiencing is good for us or directed [7:18] toward a specific specific goal. And [7:20] then, there's the other really [7:23] interesting aspect of these von Economo [7:25] neurons, which is that these von Economo [7:27] neurons are connected to a number of [7:29] different brain areas [7:31] that can shift our internal state from [7:33] one of so-called sympathetic activation. [7:35] So, this is a pattern of alertness and [7:39] even stress, sometimes even panic, but [7:41] typically alertness stress, to one of [7:43] so-called parasympathetic activation. [7:47] To one of relaxation. Oftentimes you'll [7:50] hear that stretching should be done by [7:51] relaxing into the stretch. Well, what [7:54] does it actually mean to relax into the [7:55] stretch? Well, these von Economo neurons [7:58] sit at this junction where they're able [8:00] to evaluate what's going on inside our [8:02] body and allow us to access neural [8:05] circuitries by which we can shift our [8:07] relative level of alertness down a bit [8:11] or our relative level of stress down a [8:13] bit and thereby to increase so-called [8:16] parasympathetic activation and to [8:19] literally override some of those spindle [8:22] mechanisms, even the GTO mechanisms, but [8:25] especially the spindle mechanisms at the [8:28] neuromuscular and muscular spinal [8:30] junction. I'll give you a brief example [8:32] of this that you've already done in your [8:34] life and that we all have the capacity [8:36] for. What I'm referring to is the [8:38] monosynaptic stretch reflex. [8:40] This is something that every first-year [8:42] neuroscience graduate student learns, [8:44] which is that if you were to step on a [8:46] sharp object with a bare foot, you would [8:48] not need to make the decision to retract [8:51] your foot. You would automatically do [8:53] that, provided you have a healthy [8:54] nervous system. There are mechanisms in [8:56] place that cause the retraction of that [8:59] limb by way of ensuring that the proper [9:02] muscles contract and other muscles do [9:05] not contract, in fact, that they fully [9:06] relax. Okay? So, in the case of stepping [9:09] on a sharp object like a piece of glass [9:11] or a nail or a tack, you would [9:13] essentially activate the hip flexor to [9:15] lift up your foot as quickly as [9:16] possible. [9:18] In doing so, that same neural circuit [9:21] would activate a contralateral, meaning [9:24] opposite side of the body, circuit to [9:26] ensure that the leg, the foot that's not [9:29] stepping on the sharp object, would do [9:31] exactly the opposite and would extend to [9:33] make sure that you don't fall over. All [9:36] of that happens reflexively. It does not [9:38] require any thought or decision-making. [9:41] However, [9:42] if your life depended on walking across [9:46] some sharp objects, let's say let's make [9:48] it a little less dramatic so it's not [9:49] like the Die Hard movie or something [9:51] where you have to run barefoot across [9:53] the glass, although that's a pretty good [9:55] example of what I'm describing here. But [9:57] let's say you had to walk across some [9:58] very hot stones to get away from [10:01] something that you wanted to avoid, you [10:04] could override that stretch reflex by [10:07] way of a decision made with your upper [10:08] motor neurons, your insula, and your [10:10] cognition, and almost certainly those [10:11] van Economo neurons, which would be [10:13] screaming, "Don't do this. Don't do [10:14] this. Don't do this." could shuttle that [10:16] information to brain areas that would [10:18] allow you to override the reflex and [10:20] essentially push through the pain. And [10:22] maybe even, in fact, even [10:25] not experience the pain to the same [10:27] degree or even at all. [10:29] So, these van Economo neurons sit at a [10:31] very important junction within the [10:33] brain. They pay attention to what's [10:35] going on in your body, pain, pleasure, [10:38] etc. And that includes what's going on [10:40] with your limbs and your limb range of [10:41] motion. They also are paying attention [10:45] and can control the amount of [10:47] activation, kind of alertness or [10:49] calmness that you are able to create [10:52] within your body [10:54] in response to a given sensory [10:55] experience. [10:57] And as I mentioned before, they seem to [10:59] be uniquely enriched in humans. They [11:01] seem to be related to the aspects of our [11:04] evolution that allow us to make [11:06] decisions about what to do with our body [11:09] in ways that other animals just simply [11:11] can't. Now, there are a number of [11:12] different types of stretching or methods [11:14] of stretching. [11:15] Broadly defined, [11:17] we can describe these as dynamic, [11:20] ballistic, static, and what's called PNF [11:24] stretching. PNF stands for [11:26] proprioceptive neuromuscular [11:27] facilitation. The first two that I [11:29] mentioned, dynamic and ballistic [11:31] stretching, both involve some degree of [11:33] momentum and can be distinguished from [11:36] static and PNF type stretching. [11:38] Now, to distinguish dynamic stretching [11:40] from ballistic stretching, [11:42] I'd like to focus on this element of [11:43] momentum. [11:45] Both involve moving a limb through a [11:48] given range of motion. [11:51] In dynamic stretching, however, [11:53] it tends to be more controlled, less use [11:55] of momentum, especially towards the end [11:57] range of motion. Whereas in ballistic [11:59] stretch there tends to be a bit more [12:01] swinging of the limb [12:03] or use of momentum. But again, dynamic [12:06] and ballistic stretching both involve [12:08] movement, so we have to generate some [12:10] force in order to create that movement. [12:13] Ballistic stretching involving a bit [12:15] more momentum or sometimes a lot more [12:16] momentum, especially at the end range of [12:18] of motion. Now, both of those are highly [12:21] distinct from static stretching, which [12:23] involves holding the end range of [12:25] motion, so minimizing the amount of [12:27] momentum that's used. Static stretching [12:29] can be further subdivided into active or [12:31] passive, right? There are different [12:34] names for these kinds of approaches. You [12:36] can hear about the Anderson approach or [12:38] the Janda approach. You can look these [12:39] sorts of things up online. There's also [12:41] passive static stretching, in which it's [12:44] more of a relaxation into a further [12:47] range of motion, and that can be a [12:48] subtle distinction. Nevertheless, static [12:49] stretching involves [12:51] both those types of elements, active and [12:53] passive, but is really about eliminating [12:56] momentum. [12:57] And then there's the PNF, the [12:59] proprioceptive neuromuscular [13:00] facilitation. And proprioception has [13:03] several different meanings in the [13:04] context of neuroscience and physiology. [13:07] To just keep it really simple for today, [13:09] proprioception involves both a knowledge [13:11] and understanding of where our limbs are [13:14] in space and relative to our body, [13:16] typically relative to the midline. So, [13:18] the brain is often trying to figure out [13:20] where are our limbs relative to our [13:22] midline down the center of our body. And [13:24] if your goal is to increase your [13:26] hamstring flexibility and the [13:28] flexibility and range of motion of other [13:31] related muscle systems, you might put a [13:33] strap around your ankle and pull that [13:36] muscle, or I should say, excuse me, that [13:39] limb toward you. You're not going to [13:40] pull the muscle toward you. You're going [13:41] to pull that limb, your ankle, toward [13:42] you to try and get it sort of back over [13:44] your head, and then progressively [13:46] relaxing into that, or maybe even [13:49] putting some additional force to push [13:51] the end range of motion, and then [13:52] relaxing it, and then actually trying to [13:55] stretch that same limb or increase the [13:57] limb range of motion without the strap. [14:00] There's a huge range of PNF protocols. [14:02] Those protocols can be done both by [14:05] oneself, with or without straps, with [14:07] machines, with actual weights, or with [14:10] training partners. So, specific [14:12] exercises to target specific muscle [14:14] groups aside, we've now established that [14:16] there are four major categories of [14:18] stretching, or at least those are the [14:19] four major categories I'm defining [14:21] today. But in terms of increasing limb [14:23] range of motion in the long term, of [14:26] truly becoming more flexible, as opposed [14:29] to transiently more flexible, static [14:31] stretching, which includes PNF, appears [14:34] to be the best route to go. So, whether [14:35] or not you want to maintain, [14:37] reestablish, or gain limb range of [14:40] motion, static stretching of holds of 30 [14:44] seconds appear to be best. Now, the [14:45] question is, how long should you do [14:48] that, and how many sets should you do [14:49] that, and how many times a week should [14:50] you do that? To answer those questions, [14:52] I'm going to turn to what I think is a [14:54] really spectacular review. The title of [14:56] the paper is "The Relation Between [14:58] Stretching Typology and Stretching [14:59] Duration: The Effects on Range of [15:01] Motion." First of all, and I quote, "All [15:04] stretching typologies showed range of [15:06] motion improvements over a long-term [15:08] period. However, the static protocols [15:09] showed significant gains with a P value [15:12] less than 0.05, which means a [15:14] probability that cannot be explained by [15:16] chance alone, [15:18] when compared to ballistic or PNF [15:20] protocols." So, again, what we're [15:21] hearing is that static stretching is the [15:23] preferred mode for increasing limb range [15:25] of motion. Although, here they make the [15:27] additional point [15:28] that static stretching might even be [15:31] superior not just to ballistic [15:33] stretching, but also to PNF protocols. [15:36] The authors go on to say [15:38] time spent stretching per week seems [15:39] fundamental to elicit range of movement [15:41] improvements when stretches are applied [15:43] for at least or more than 5 minutes per [15:46] week. Okay, this is critical. This is [15:48] not 5 minutes per stretch. Remember, 30 [15:51] seconds per static stretch, but at least [15:53] 5 minutes per week. So, what this means [15:56] is that we should probably be doing [15:58] anywhere from two to four sets of [16:01] 30-second static hold stretches 5 days [16:04] per week. So, what would effective [16:06] stretching protocol look like? [16:08] We're all trying to improve limb range [16:10] of motion for different limbs and [16:12] different muscle groups. Let's talk [16:13] about hamstrings [16:15] for the time being. This could, of [16:17] course, be applied to other muscle [16:18] groups. Let's say you want to improve [16:20] hamstring flexibility and limb range of [16:22] motion about and around the hamstring. [16:26] And involving the hamstring, you would [16:27] want to do three sets [16:30] of static stretching for the hamstring. [16:32] You would do that by [16:35] holding the stretch for 30 seconds, [16:37] resting some period of time, then doing [16:39] it again, holding for 30 seconds, [16:40] resting some period of time, and then [16:43] holding it for 30 seconds. That would be [16:45] one training session for the hamstrings. [16:47] I have to imagine that you'd probably [16:48] want to stretch other muscle groups as [16:50] well in that same session. So, three [16:53] sets of 30 seconds each, [16:56] get 90 seconds, and you would do that [16:58] ideally five times a week, or maybe even [17:01] more. One thing that did show up in my [17:04] exploration of the peer-reviewed [17:05] research is this notion of warming up [17:08] for all this. We haven't talked about [17:09] that yet. In general, to avoid injury, [17:11] it's a good idea to raise your core body [17:13] temperature a bit before doing these [17:14] kinds of stretches, [17:16] even these static stretches, which can [17:18] sort of ease into and don't involve [17:20] ballistic movement by definition. [17:23] And [17:24] the basic takeaway that I was able to [17:26] find was that if we are already warm [17:29] from running or from weight training or [17:31] from some other activity, that doing the [17:34] static stretching [17:36] practice at the end of that weight [17:38] training or cardiovascular or other [17:39] physical session would allow us to go [17:42] immediately into the stretching session. [17:45] Because we're already warm, so to speak. [17:47] Otherwise, [17:48] raising one's core body temperature by a [17:50] bit by doing [17:52] 5 to 7, maybe even 10 minutes of [17:55] easy cardiovascular exercise or [17:56] calisthenic movements, provided you can [17:58] do those without getting injured, [18:00] seems to be an ideal way to warm up the [18:02] body for stretching. We should be warm [18:04] or warm up to stretch, although those [18:06] warm-ups don't have to be extremely [18:07] extensive. And then just by way of [18:09] logic, doing the static stretching after [18:12] resistance training or cardiovascular [18:13] training seems to be most beneficial. In [18:15] fact, and unfortunately, we don't have [18:17] time to go into this in too much detail [18:19] today. I was able to find a number of [18:20] papers that make the argument that [18:24] static stretching prior to [18:26] cardiovascular training, and maybe even [18:28] prior to [18:29] resistance training, [18:31] can limit our performance in running and [18:34] resistance training. I realize that's a [18:36] controversial area. You have those who [18:38] say, "No, it's immensely beneficial." [18:40] You have those who say, "No, it inhibits [18:42] performance." And the those that say, [18:44] "No, it's a matter of how exactly you [18:46] perform that static stretching and which [18:47] muscle groups and how you're doing this [18:49] and how much time in between static [18:51] stretching and performance." But to [18:52] leave all that aside, doing static [18:54] stretching after some other form of [18:56] exercise, [18:57] and [18:58] if you not after some form of exercise, [19:00] after a brief warm-up to raise your core [19:02] body temperature, definitely seems like [19:04] the right way to go. I'm guessing that [19:05] most people are not doing 5 days a week [19:08] of dedicated static stretch range of [19:10] motion [19:12] directed training. But it does appear [19:14] that that frequency about the week, [19:17] getting those repeated sessions even if [19:18] they are short for an individual muscle [19:20] group, turns out to be important. [19:21] They're going to offset the age-related [19:23] losses in flexibility for sure if one is [19:26] dedicated about these practices. Some of [19:28] you may be familiar with the so-called [19:29] Anderson method. It's been around for a [19:31] long time. Anderson has an interesting [19:33] idea and principle which is thread [19:35] through a lot of his teachings that I [19:37] think are very much in keeping with the [19:39] study that I'm about to describe next [19:41] where [19:42] he emphasizes to yes to stretch to the [19:46] end of the range of motion, but not to [19:49] focus so much on where that range of [19:50] motion happens to be that day. So for [19:53] instance, not thinking, "Oh, I can [19:56] always touch my toes for instance, and [19:58] therefore that's the starting place for [20:00] my flexibility training today." But [20:03] rather take the entirety of your system [20:05] into account each day and understand [20:07] that okay, provided you're warmed up [20:08] appropriately, [20:10] that you're now going to stretch your [20:11] hamstrings for instance, and you're [20:13] going to reach down for your toes, but [20:15] that your range of motion might be [20:17] adjusted that day by way of tension and [20:19] stress or by way of ambient temperature [20:21] in the room. And to basically define the [20:24] end range of motion as the place where [20:26] you can feel the stretch in the relevant [20:28] muscle groups. So what does this mean? [20:30] This means feel the muscles as you [20:31] stretch them. Don't just go through the [20:33] motions. And this means don't get so [20:35] attached to being able to always achieve [20:38] for instance a stretch of a given [20:39] distance on a within a given session. [20:41] You might actually find that by just [20:44] finding the place where you can't get [20:46] much further and holding the static [20:48] stretch there, that on the second and [20:50] third set that you happen to be doing [20:51] that day that your range of motion will [20:52] be increased considerably. Now, [20:56] along these lines, there's this even [20:58] more nebulous variable, this even more [21:00] kind of subjective thing of [21:03] how much effort to put into it. Should [21:05] you push into the stretch? Would you [21:07] even want to bounce a tiny bit? Would [21:09] you want to reach into that end point [21:12] and try and extend it within a given set [21:14] and session? [21:15] And for that reason I was excited to [21:17] find this paper entitled a comparison of [21:20] two stretching modalities on lower limb [21:22] range of motion measurements in [21:23] recreational dancers. It's a six-week [21:25] intervention program that compared [21:27] low-intensity stretching, which they [21:29] call micro stretching, but to be very [21:32] clear, micro stretching in the case of [21:34] this manuscript is low-intensity [21:36] stretching and they compared that with [21:38] moderate-intensity static stretching on [21:40] an active and passive ranges of motion. [21:42] Basically, what they found was that a [21:44] six-week training program using very [21:46] low-intensity stretching had a greater [21:49] positive effect on lower limb range of [21:50] motion than did moderate-intensity [21:53] static stretching. Here I'm quoting [21:55] them. [21:56] The most interesting aspect of the study [21:57] was the greater increase in active range [21:59] of motion compared to passive range of [22:01] motion by the micro stretching group. [22:03] So, this relates to what we were just [22:04] talking about a few moments ago as it [22:06] relates to the Anderson method, which is [22:08] that [22:09] very low-intensity stretching [22:12] meaning effort that [22:14] feels not painful [22:16] and in fact might even [22:17] feel easy or at least not straining to [22:22] exceed a given range of motion turns out [22:25] to not just be as effective but more [22:27] effective than moderate intensity [22:29] stretching. So, what is low-intensity [22:31] static stretching? Well, they define [22:33] this as the stretches were completed at [22:35] an intensity of 30 to 40% [22:39] where 100% equals the point of pain, [22:41] right? So, [22:43] 30 to 40% in these individuals, and [22:46] again I'm paraphrasing, induced a [22:47] relaxed state within the individual and [22:50] the specific muscle. And here they were [22:52] holding these static stretches, I should [22:53] mention, for 1 minute, not 30 seconds. [22:57] Now, the control group was doing the [22:59] exact same overall protocol, so daily [23:01] stretching for 6 weeks, [23:04] the same exercises, holding each set for [23:07] 60 seconds, but we're using an intensity [23:11] of stretch of 80% where again 100 [23:14] represents the point of pain, the point [23:16] where the person would want to stop [23:18] stretching. I find these data incredibly [23:20] interesting for I think what ought to be [23:22] obvious reasons. If you're going to [23:24] embark on a flexibility and stretching [23:27] training program, you don't need to push [23:30] to the point of pain. In fact, it seems [23:32] that even just approaching the point of [23:34] pain is going to be less effective than [23:36] operating at this 30 to 40% of [23:40] intensity prior to reaching that pain [23:42] threshold, the pain threshold being [23:43] 100%. Now, of course, this is pretty [23:45] subjective, but I think all of us should [23:47] be able to register within ourselves as [23:50] to whether a given range of motion or [23:52] extending a given range of motion brings [23:54] us to that threshold of pain or near [23:56] pain. And according to this study at [23:57] least, operating or performing [24:00] stretching at an intensity that's quite [24:02] low, that's very relaxing, turns out to [24:05] be more beneficial in increasing range [24:07] of motion than is doing [24:10] exercises aimed at increasing range of [24:12] motion at a higher intensity. Okay, so [24:14] lower intensity stretching, I should say [24:16] lower intensity static stretching, [24:18] appears to be the most beneficial way to [24:21] approach stretching, and I think that's [24:22] a relief um probably to many of us [24:25] because it also suggests that the injury [24:27] risk is going to be lower than if one [24:29] were pushing into the pain zone, so to [24:31] speak. I want to just briefly return to [24:33] this idea of whether or not to do [24:34] ballistic or static stretching before [24:37] some sort of skill training or weight [24:39] training, any kind of sport or even [24:42] cardiovascular exercise like running. [24:44] There are instances [24:46] for example, where an individual might [24:48] want to do some static stretching to [24:50] increase limb range of motion prior to [24:52] doing weight training, even if it's [24:54] going to to [24:56] that person's ability to lift as much [24:58] weight. Why would you want to do that? [24:59] Well, for instance, if somebody has a [25:02] tightness or a limitation in their [25:04] neuromuscular connective tissue system [25:05] someplace in their body and system that [25:09] prevents them from using proper form [25:11] that they can overcome by doing some [25:14] static stretching, [25:15] well, that would be a great idea. There [25:17] are instances where people are trying to [25:19] overcome injuries, where they're trying [25:20] to [25:21] come back from a reparative surgery or [25:23] something of that sort, coming back from [25:25] a layoff where some additional static [25:28] stretching prior to cardiovascular [25:30] weight training or skill training or [25:32] sport of some kind is going to be useful [25:34] because it's going to put us in a [25:36] position of greater safety and [25:37] confidence and performance overall, even [25:40] if it's adjusting down our speed or the [25:43] total amount of loads that we use. And [25:45] similarly, [25:47] there are a lot of data points in the [25:48] fact that doing some dynamic or even [25:50] ballistic stretching prior to skill [25:53] training or cardiovascular weight [25:54] training can be beneficial in part to [25:56] warm up the relevant neural circuits, [25:58] joints, and connective tissue, and [26:00] muscles, and as well to perhaps improve [26:03] range of motion or ability to perform [26:06] those movements more accurately, [26:08] with more stability, and therefore with [26:10] more confidence. Thus far, we've been [26:11] talking about stretching for sake of [26:13] increasing limb flexibility and range of [26:15] motion, but there are other reasons, [26:18] perhaps, to embark on a stretching [26:20] protocol that include both our ability [26:24] to relax and access deep relaxation [26:26] quickly. I'd like to return this to this [26:28] idea and this place, this real estate [26:31] within our brain that we call the [26:32] insular cortex, the insula. [26:34] As you recall, way back at the [26:37] beginning of this episode, we were [26:38] talking about the von Economo neurons [26:39] that Constantin von Economo, the [26:42] Austrian [26:43] uh scientist discovered. And the fact [26:45] that we are able to make [26:48] and perform interpretations of our [26:50] internal landscape, pain, our [26:53] dedication to a practice. For instance, [26:55] whether or not we are in pain because [26:58] it's a practice that we are doing [26:59] intentionally and want to improve [27:01] ourselves, or whether or not it's pain [27:03] that's arriving through some externally [27:04] imposed demands or situations. The [27:07] insula is handling all that. And [27:09] fortunately, there's a wonderful paper [27:12] that was published is a few years ago [27:13] now in the journal Cerebral Cortex [27:16] entitled Insular Cortex Mediates [27:17] Increased Pain Tolerance in Yoga [27:19] Practitioners. This study explored [27:22] the effects on brain structure volume in [27:27] yoga practitioners. And for those of you [27:30] out there that are aficionados in yoga, [27:31] they they pulled subjects from having [27:35] backgrounds in the Here I'm probably [27:37] going to mispronounce these different [27:38] things and for forgive me, the Vinyasa [27:40] yogas, the Ashtanga yogas, the younger [27:42] yogas, the Sivananda yogas. Okay, so [27:45] some people were new to these practices, [27:46] some were experienced. The The important [27:49] takeaways [27:50] were that they took these yoga [27:52] practitioners and they didn't explore [27:54] their brain structure in the context of [27:55] yoga itself. They looked at things like [27:58] pain tolerance. So they used thermal [28:00] stimulation. Basically, they put people [28:02] into conditions where they gave them [28:03] very hot or very cold stimuli and [28:05] compared those yoga practitioners of [28:08] varying levels of yoga experience to [28:10] those that had no experience with yoga, [28:12] so-called controls. And they found some [28:14] really interesting things. [28:16] There are a lot of data in this paper, [28:17] but [28:19] here's something I'd like to highlight. [28:20] The pain tolerance of yoga practitioners [28:24] was double or more to that of non-yoga [28:27] practitioners. They also found [28:30] significant increases in insular, again, [28:33] the insula, this brain region, gray [28:35] matter volume. Typically, when we talk [28:36] about gray matter, we're talking about [28:38] the so-called cell bodies, the [28:40] the location in neurons where the genome [28:43] is housed and where the kind of all the [28:45] housekeeping stuff is there, and then [28:48] white matter volume tends to be the [28:49] axons, the wires, because they're in [28:51] sheets with this stuff that appears [28:53] white in MRIs, and indeed is white under [28:55] the microscope, and indeed is white. [28:57] It's actually lipid, which is myelin. [28:59] So, increased gray matter volume of the [29:01] insula is a significant finding [29:04] because what it suggests is that people [29:06] that are doing yoga have an increased [29:08] volume of these areas of the brain that [29:10] are associated with interoceptive [29:12] awareness and for being able to make [29:14] judgments about pain and why one is [29:17] experiencing pain. Not just to lean away [29:18] from pain, but to utilize or leverage or [29:20] even overcome pain. And I find this [29:23] interesting because there are a lot of [29:24] activities out there that don't create [29:27] these kind of changes in brain volume, [29:29] especially within the insula. So, it [29:31] appears that it's not just the [29:32] performance of the yogic movements, but [29:35] the overcoming or the kind of pushing [29:37] into the end ranges of motion and to [29:40] push through discomfort to some extent. [29:42] Of course, we want people doing that in [29:44] a in a healthy, safe way, but that [29:46] allows yoga practitioners to build up [29:49] the structure and function of these [29:52] brain areas that allow them to cope with [29:54] pain better than other individuals and [29:56] to cope with other kinds of [29:58] interoceptive challenges, if you will. [30:00] Not just pain, but cold. [30:03] Not just pain, but discomfort of being [30:04] in a particular position to do that. And [30:07] again, we wouldn't want people placing [30:09] themselves into a compromised position, [30:11] literally, that would harm them, [30:13] especially given that earlier we heard [30:15] that micro-stretching of the kind of [30:17] non-painful sort, low-intensity sort, is [30:19] actually going to be more effective for [30:20] increasing end range of motion. But this [30:22] study really emphasized the extent to [30:24] which practitioners of yoga don't just [30:27] learn movements, they learn how to [30:29] control their nervous system in ways [30:31] that really reshapes their relationship [30:33] to pain, to flexibility, and to the [30:37] kinds of things that the neuromuscular [30:39] system was designed to do. So, if ever [30:41] there was a practice that one could [30:43] embark on that would not only increase [30:45] flexibility and limb range of motion, [30:47] but would also allow one to cultivate [30:49] some improved mental functioning as it [30:52] relates to pain tolerance and other [30:54] features of stress management that no [30:56] doubt wick out into other areas of life, [30:58] appears that yoga is a quite useful [31:01] practice. But, of course, yoga isn't the [31:04] only way to increase limb range of [31:05] motion and flexibility. Up until now, [31:08] we've described a number of different [31:09] ways to do that and we've arrived at [31:11] some general themes and protocols. [31:12] Again, we can revisit a couple of them [31:14] now just in summary and synthesis. [31:17] Static stretching appears to be at least [31:19] among the more useful forms of [31:20] stretching. It really does appear that [31:22] getting [31:24] at least 5 minutes per week total of [31:26] stretching for a given muscle group is [31:28] important for creating meaningful [31:30] lasting changes in limb range of motion [31:33] and that is best achieved by 5-day week [31:36] or 6-day week or even 7-day week [31:38] protocols, but those can be very short [31:39] protocols limited to, say, three sets of [31:42] 30, maybe even 45 or 60 seconds of [31:46] static hold, although 30 seconds seems [31:48] to be [31:49] a key threshold there [31:51] um that can get you maximum benefit. [31:53] And, of course, to always warm up or to [31:56] arrive at the stretching session warm. [31:57] Thank you once again for joining me [31:59] today for a discussion about the neural [32:01] and neuromuscular and connective tissue [32:04] and skeletal aspects of flexibility and [32:07] stretching. And as always, thank [music] [32:09] you for your interest in science.