How does age affect flexibility?

Introduction

Ageing is an inevitable aspect of life that presents an unyielding biological march that is both fascinating and deeply sobering. As the years accrue, our bodies betray a gradual, yet inevitable, decline in physical capabilities. This decline is a central theme that shapes our existence in far-reaching ways.

The ageing process is a mosaic of genetic, environmental, and lifestyle factors, each contributing to the gradual erosion of our physiological resilience. Our muscles, once robust and responsive, lose strength and elasticity, a phenomenon affecting both appearance and function. This loss of muscle mass and function - known as sarcopenia - is more than an inconvenience; it's a fundamental alteration in our ability to interact with the world.

Similarly, the bones that provide the scaffold for our bodies become more brittle and susceptible to fracture. This increased fragility is one of the starkest reminders of the vulnerability of age. It's a vulnerability that presents a risk of injury and disablement and speaks to the broader existential threat of losing our autonomy and independence.

Even the cardiovascular system is not immune to the effects of time. The heart, arteries, and veins, through years of relentless use and exposure to various risk factors, begin to show signs of wear and tear. This degeneration can lead to a host of complications, from hypertension to heart disease, each narrowing the horizon of our physical capabilities.

However, ageing is not a straightforward story of decline. It's also one of adaptation and resilience. Despite the inevitable changes, our bodies possess remarkable capacities for repair and recovery. This truth is perhaps most evident in flexibility, which is the capacity to change to adapt to different circumstances. The mind is a vast landscape riddled with the footprints of every thought, belief, and understanding we've ever had. The body is a physical manifestation of this landscape, a terrain that, over time, becomes less malleable and more rigid, akin to how our beliefs can solidify with age.

In this context, flexibility is both a physical attribute and a symbolic reflection of our capacity to adapt, embrace change, and navigate the complexities of our existence with grace. For seniors, cultivating physical flexibility through deliberate practice - be it yoga, stretching, or other forms of training - reinforces the brain's neuroplasticity. It's a declaration that our ability to adapt and grow does not wane with age but requires more attention and dedication.

Decreased flexibility implies a constrained range of motion, increased risk of injuries, and a diminished capacity to perform everyday activities. These physical limitations, much like the rigidities of our thinking, can lead to a narrower experience of the world, a reduced quality of life, and, perhaps most critically, a diminished sense of autonomy.

Moreover, the act of engaging in flexibility-enhancing practices is itself a form of mindfulness, an acknowledgement of the present moment and an acceptance of one's current state while simultaneously working towards improvement. This mindfulness, a cornerstone of a mentally healthy and active lifestyle, fosters a sense of peace and contentment, reducing stress and anxiety, which are particularly beneficial for seniors navigating the later stages of life.

In this article, I will explain how flexibility training is crucial in maintaining the body's range of motion and preserving the fluidity of our existence, ensuring that as our bodies age, they can do so with a grace that reflects a mind open to change, growth, and adaptation. Furthermore, I will highlight research that underscores the ability of seniors to increase their flexibility with dedicated training regimens, even at rates similar to people decades younger.

Flexibility and ageing

Flexibility is crucial for overall health. It represents the capacity of our muscles and joints to stretch and adapt, as well as the ability of our minds to accommodate the ceaseless ebb and flow of life's demands. Understanding flexibility recognises it as the embodiment of resilience and adaptability, indispensable in navigating the complexities and uncertainties that characterise human existence.

In physical health, flexibility training enhances our range of motion, facilitates efficient movement, and reduces the risk of injuries [1-3]. By maintaining or improving flexibility, we ensure that our bodies can perform various activities with greater ease and less strain. This physical attribute, however, is not just about the ability to touch one's toes or execute a perfect backbend. It's about creating a foundation from which our bodies can engage with the world robustly and dynamically.

However, the significance of flexibility extends far beyond the physical. The concept metaphorically applies to the mind's capacity to remain open, adapt, and pivot in the face of new information or unforeseen circumstances. In a world that is perpetually in flux, constantly challenging our beliefs and understandings, flexibility of thought is paramount. It allows us to navigate complex moral landscapes, empathise with diverse perspectives, and evolve our viewpoints in light of new evidence or arguments.

Why, then, is flexibility crucial for overall health? Because it embodies the interplay between the physical and the psychological, between the body and the mind. A flexible body supports a life of physical activity and reduces the encumbrances of age or disability. A flexible mind, conversely, fosters a resilient spirit, capable of withstanding the vicissitudes of life while remaining open to growth and change.

Flexibility is an important consideration at any age, but its significance grows with the increase in the number of years. Research has consistently shown that flexibility decreases with age. Interestingly, this gradual age-related loss of flexibility seems to occur with little difference between the sexes [4]. But why does this age-related decline in flexibility happen?

During our youth, muscles and tendons exhibit a remarkable capacity for stretch and recovery. This property allows for a wide range of motion and the swift, graceful movements often taken for granted. However, as we advance in years, these tissues transform, becoming stiffer and less forgiving.

The reason is twofold: firstly, the natural decrease in physical activity accompanying ageing reduces muscle mass and strength, a phenomenon known as sarcopenia. Secondly, the biochemical composition of our muscles and tendons changes, with a decrease in elastin, the protein responsible for the elasticity of these tissues. This combination of reduced physical activity and biochemical alteration impacts our flexibility by increasing passive stiffness, rendering movements that were once effortless now fraught with difficulty.

The increase in muscle passive stiffness as we age is a subject of considerable debate and inquiry, which cannot be divorced from the complex interactions between the mechanical properties inherent within muscle fibres themselves and the extracellular matrix (ECM) that cradles them.

The ECM IS a dynamic entity, secreted by the cells themselves, consisting mainly of proteoglycans and fibrous proteins, with collagen taking the lead in abundance. But to understand the ECM solely in terms of its components would be to miss the forest for the trees. It's the structural support, yes, but it's also the origin of biochemical and mechanical cues that guide and regulate the behaviours of cells.

The ECM experiences tensional, compressive, and shear forces. These physical stresses are translated into biochemical signals through a process known as mechanotransduction. This allows cells to remodel their surrounding matrix, striving to maintain structural integrity, also known as tensional homeostasis.

In skeletal muscle, the ECM is a complex scaffold composed of the endomysium, perimysium, and epimysium. It provides structural support that delicately balances the forces governing our physical form. The endomysium gently enfolds each muscle fibre, the perimysium groups these fibres into bundles or fascicles, and the epimysium encapsulates the entire muscle belly. These components are pivotal in the overall stiffness of muscle.

In the pursuit of empirical clarity, researchers have conducted ex vivo studies of isolated muscles in rodents. These investigations revealed a steeper incline in the length-tension curves of muscles in older animals compared to their younger counterparts. These findings confirm the age-dependent escalation of stiffness in mammals [5-7].

The role of the ECM assumes crucial importance - its mechanical properties are a tangible facet of our biological reality that directly influences muscle mechanics, both in states of rest and during the dynamic act of contraction. This fact is particularly evident when we consider the lateral transmission of fibre forces to the tendons, a phenomenon that is as fascinating as it is essential [8-10]. The degradation of this ability, a subtle yet significant shift, may illuminate why muscle force wanes more precipitously than muscle mass as we age [11]. It is here that multi-scale finite elements modelling - a computational tool that works by breaking down a large, often complex problem into smaller, more manageable sub-problems - becomes an indispensable tool for biomechanics researchers.

Additionally, the methodology of examining skinned muscle fibres strips away the mechanical influence of extracellular connective tissue, offering a purer glimpse into the muscle's inherent properties [12]. This approach reveals a striking contrast: when researchers liberate muscle fibres from the ECM, the elastic modulus of a single fibre pales in comparison to that of a fibre bundle ensconced in the ECM, with the latter being four times as stiff, assuming the ECM occupies just 5% of the bundle's cross-sectional area.

Research into ageing tibialis anterior fibres found that the passage of time does not alter their passive mechanical attributes. Instead, alterations in the ECM's properties solely caused the increased stiffness [7]. Yet, this narrative finds its counterpoint in comparing single muscle fibres of the vastus lateralis in elderly subjects to those of their younger counterparts [13]. Findings from this research painted a different picture: the elderly fibres not only bore a greater passive force but also unveiled a shift towards more pronounced viscoelastic properties, suggesting that the very mechanics of the muscle fibres themselves transform with age, becoming the primary architects of increased muscle stiffness.

When we delve deeper and examine the passive mechanical properties inherent to single fibres and fibre bundles of both young and elderly subjects at any sarcomere length, the resting passive tension is conspicuously higher in the fibre bundles of older people when compared to younger individuals.

However, when the lens narrows to focus on single fibres in isolation, this age-related disparity in passive tension vanishes. There is no discernible difference, suggesting that the fibres themselves may not be the primary agents of change. This leads us to a fascinating conclusion: the divergence between the young and the elderly in mechanical stiffness can largely be attributed to the ECM that interlaces the fibres within a bundle.

ECM stiffness increases with age due to a number of molecular and biological processes, including enhanced matrix deposition (increased accumulation of ECM components in tissues), cross-linking of the existing matrix, and fibre alignment [14-16] . Another major cause of increased ECM stiffness is dysregulated matrix synthesis and remodeling by activated fibroblasts that have dedifferentiated into myofibroblasts.

A myofibroblast is an essential cell type in the processes of tissue repair and wound healing. These cells possess characteristics that lie between those of smooth muscle cells and fibroblasts, the cells responsible for producing collagen and other fibres). The capacity of myofibroblasts to contract aids in the closure of wounds and the reduction of scar tissue dimensions that ensue throughout the healing process.

The ECM itself is generated and structured by myofibroblasts. They play a critical role in collagen synthesis, which is indispensable for maintaining the integrity and strength of tissues that have been repaired.

Myofibroblasts typically endure apoptosis - programmed cell death - and are eliminated from the tissue once the healing process is complete. Nevertheless, certain age-related pathological states, such as fibrosis, may result in the continued production of extracellular matrix components by myofibroblasts, which can cause an excessive stiffening of the surrounding tissue.

The impact of poor flexibility - and what can we do about it?

It's an undeniable truth that as we journey through the arc of life, our physical flexibility doesn't quite keep pace with the passage of time. One might ponder whether this gradual diminution of our body's pliability is an inevitable harbinger of decline or just a normal hallmark of ageing. The reality, however, is far from benign. The erosion of flexibility is not just a matter of losing the ability to touch one's toes or perform a perfect backbend; it strikes at the very heart of our health, autonomy, and the essence of a life lived fully.

The consequences of this decline are immense. As our flexibility wanes, so does our freedom - freedom of movement, independence, and the overall quality of our existence. The stakes are high, as a diminished range of motion directly correlates with an increased susceptibility to musculoskeletal injuries. The mechanics are straightforward yet unforgiving: our joints and muscles, constrained and less capable of yielding to the demands we place on them, become veritable tinder for the sparks of injury during our daily activities or any physical exertion.

The implications extend into basic functional capabilities; our ability to carry out the motor tasks that constitute daily living becomes compromised, painting a stark picture of the cascade of limitations resulting from lost flexibility. Moreover, the spectre of falls in older adults looms large, a tangible manifestation of vulnerability that research has unequivocally linked to inadequate flexibility [17]. This raises questions of how we preserve our independence and quality of life as we age. The data speaks with clarity: maintaining flexibility is not just a component of physical health but a cornerstone of living well into our later years.

The literature shows that engaging in flexibility training regularly enhances our overall functional capacity and also our agility and dynamic balance. This is a benefit with tangible outcomes, especially when considering individuals grappling with conditions such as Alzheimer's disease. The significance of this cannot be overstated; the ability to perform activities of daily living independently is a cornerstone of maintaining dignity and quality of life for patients facing such debilitating conditions [18].

In one experiment, researchers sought to illuminate the effects of flexibility among the elderly. Sixty-two participants living in a retirement housing complex were the focal point of this study, engaging in a regimen of hamstring stretches of 15, 30, and 60 seconds in duration. This routine was adhered to five times per week over the span of six weeks. Flexibility enhancements were observed across all groups, yet it was the cohort subjected to 60-second stretches that displayed the most progress, achieving the most significant leap in flexibility. Moreover, this group maintaining the greatest increase in range of motion four weeks post-intervention [19].

Another randomised controlled trial engaged forty healthy adults who had an average age of 72. These individuals committed themselves to an eight-week regimen focusing on stretching the hips and ankles. The results were illuminating: those who adhered to the stretching protocol witnessed not only a marked improvement in the combined range of motion across their hips and knees but also enjoyed a discernible uptick in their gait speed [20]. This finding resonates with the outcomes of another study, where an eight-week course of active assisted stretching was administered to a cohort of subjects in their 80s. Remarkably, this intervention significantly elevated both the flexibility and functional performance of these senior participants [2]. These studies underscore the impact that even modest, targeted physical activities can have on the physiological well-being of the elderly, offering a beacon of hope for enhancing quality of life through non-invasive means.

The growing body of research suggests a rather encouraging principle: the capacity to enhance one's flexibility is not impeded by the advancing years. This notion challenges the prevailing wisdom that age is a formidable barrier to the acquisition of physical suppleness. The crux of the matter appears to reside in the absence of dedicated flexibility training rather than in the inexorable march of time. It is this omission, rather than age per se, that significantly contributes to the diminution of our range of motion as we age.

As we delve deeper into the relationship between flexibility and ageing, a question invariably arises: "Can older individuals increase flexibility as fast as younger people?" The empirical data, though not extensive, is illuminative. A select few studies that have endeavoured to compare the effects of stretching across different age groups reveal an enlightening conclusion: the progression of flexibility is ostensibly unaffected by age. Such findings underscore a vital insight — the decline in flexibility commonly attributed to ageing may well be a function of neglected training rather than an inexorable decline dictated by the ageing process itself.

Following a 10-week hamstring stretching programme, both younger (average age: 24) and older (average age: 65) subjects experienced increases in range of motion and decreases in passive stiffness, with no significant differences between the groups [21]. Other studies found greater reductions in passive stiffness in older people compared to younger people [22].

Based on the research literature and everyday observation, it becomes evident that the variables which most significantly dictate the trajectory of our physical evolution are not solely anchored in the years we have traversed around the sun. Rather, it is the baseline flexibility we possess, the consistency with which we dedicate ourselves to our training, the specific methodologies we employ - be it static passive or static active stretching - and the intensity of our training that truly shape our progress. This perspective invites us to reconsider previous deterministic narratives of ageing, opening a discourse on the capacity for growth and adaptation at any stage of life.

Research-informed training guidelines for older people

• When enhancing flexibility in older people, static passive stretching should be the foundational element of any flexibility training regime tailored for this demographic. The rationale behind this recommendation lies in the distinctive benefits of constant torque stretches. By methodically increasing the joint angle multiple times within a single set, we ensure that the muscles are subjected to a uniform tension throughout the duration of the stretch. This approach, particularly when each stretch is maintained for a minimum of 60 seconds - though, to be more effective, a longer duration would be advantageous - targets the reduction of passive stiffness. The relevance of mitigating passive stiffness escalates with age, making such stretching essential.
• It's important to maintain a substantial level of intensity in our stretching routines. The scientific literature reveals that stretching exercises that are characterised by higher intensity, exemplified by methods such as constant-torque stretching, have been consistently shown to yield a more pronounced decrement in passive stiffness and increase in joint angle compared to their lower intensity counterparts. The use of visual analogue scales is useful. These scales, which range from 0 (denoting the absence of pain) to 10 (representing an unbearable level of pain), serve as a quantitative measure allowing individuals to calibrate the intensity of their stretching endeavours accurately.
• Given that loss of flexibility often coincides with a decline in strength due to ageing, it's a good idea to include strength-based stretching. Isometric stretching, such as classic proprioceptive neuromuscular facilitation (PNF). PNF stretching has been shown to improve range of motion, isometric strength, and physical function in older adults living in assisted facilities, with significant improvements in tasks such as sit-to-stand and shoulder and ankle flexibility. If combining static passive and isometric stretching in the same workout, do isometrics first followed by passive stretches.

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References

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