Physical activity and nutrition are among the most common lifestyle measures shown to maintain and improve skeletal and joint health over the lifespan. Studies have shown the benefits of exercise on bone health as well as joint pain reduction in those suffering from bone degenerative diseases. Regular intense sporting activity also increases the chances of suffering joint and tissue trauma which can result in skeletal trouble later in life. Consuming a balanced diet containing nutrients such as vitamins and minerals that support the health of joint and skeletal tissue is a critical part of maintaining and repairing these tissues and helps to prevent joint and skeletal pain and damage. This article discusses the science of exercise as it relates to bone and joint health and the roles that specific nutrients such as minerals play in promoting health and preventing damage and pain.
Although bone may seem solid and rigid, it is in fact a metabolically active tissue. In the adult skeleton, most metabolic activity occurs by bone remodeling, which is essential to maintain skeletal structure and calcium homeostasis. Bone remodeling involves the removal of mineralized bone and calcium by osteoclasts, followed by the formation of unmineralized bone matrix by osteoblasts, which eventually becomes mineralized. The remodeling cycle consists of three phases: (1) resporption, at which point the osteoclasts digest old bone; (2) reversal, when mononuclear cells appear on the bone surface; and (3) formation, when osteoblasts form new bone in place of what has been resorbed (Figure 1). Thus the purpose of bone remodeling is to prevent the accumulation of old bone. This process is regulated by systemic regulators such as: parathyroid hormone (PTH), calcitriol, growth hormone, insulin-like growth factors (IGFs), thyroid hormones and sex hormones, as well as local regulators, including cytokines and growth factors.
Fig.1. Bone Remodeling Cycle
(University of Michigan, 2005)
Effect of Exercise on Bone Mineralization and Joint Health
All tissues respond to physical stress either through a decreased tolerance, maintained tolerance or increased stress tolerance. If the stress is too extreme, injury usually occurs as a result. However, in cases where the there is insufficient stress or inactivity, the tissue will degenerate. Engaging in regular, moderate intensity exercise is required in order for the adaptation, growth and maintenance of healthy tissues. This principal is also true for injured tissue such that an appropriate amount of exercise exerts therapeutic effects, whereas inactivity has been shown to delay recovery.
Exercise influences the skeleton by three principal processes: (1) a direct impact on bone with the help of mechanoreceptors; (2) an indirect impact by improving muscle mass and strength that in turn stimulate these mechanoreceptors; and (3) an indirect impact by causing changes in the hormone levels affecting bone mineralization, such as calciotropic hormones and local factors (Figure 2).
Fig.2. Schematic Description of the Effect of Exercise on Skeletal Health
(Bonnet & Ferrari, 2010)
Direct Effects of Exercise on Bone Mineralization
Many studies show that weight-bearing exercise positively influences bone mass and bone mineral density in both healthy and arthritic individuals. Osteocytes, which represent the majority of all bone cells, are able to sense the mechanical strain inflicted by exercise. Osteocytes respond to extracellular fluid waves creating skeletal loading, which in turn activates the osteocyte’s mechanoreceptors to generate small changes in electrical charges, activate calcium channels, or other molecular mediators. Other biological components such as ion channels, cell-surface proteins, cytoskeletal proteins and the cell nucleus also respond to mechanical stimulation and strain. These biochemical signals function to activate and regulate bone remodeling.
Indirect Effects of Muscular Strengthening on Bone Health
There is a strong link between muscle mass and bone density, which reinforce the important interaction between the two for optimal mobility over the lifespan. This relationship is shown in numerous studies which have found that peak rates of muscle mass gain are followed by peak rates of bone mineral acquisition, indicating that exercises aimed to improve muscle mass and strength also benefit bone health. Muscles and ligaments connect the joints. During weight-bearing exercise, the muscles strengthen and grow while pulling on the bones causing strain. This mechanical strain exerted on bone by muscle contraction in turn stimulates the bone remodeling process by activating mechanoreceptors, thereby contributing to bone mineralization. More recently, research has found that muscle can secrete growth factors (GF) such as insulin-like growth factor (IGF-1) and FGF’s, which also influence the activation of bone cells.
Hormonal Effects of Exercise on Bone
A variety of calcium-regulating hormones manage the process of bone formation and resorption including: parathyroid hormone (PTH), vitamin D and its metabolites, estrogens, growth hormone (GH), and insulin-like growth factors (IGF). Many studies have shown that exercise can increase the concentrations of anabolic hormones including estrogen, GH and IGF-1. Estrogen in particular has been identified as playing a key role in the activation of mechanoreceptors. Exercise also lowers serum glucose levels, which in turn causes a rise in the production of GH and IGF-1 by the liver. Similarly, parathyroid hormone levels are also increased after maximal exercise, as intense physical activity causes calcium resorption as well as acidosis, which both affect the secretion of the hormone.
In addition to bone health, by improving strength in the surrounding muscle tissues, exercise helps dissipate the stress on cartilage. Cartilage is an important skeletal component as it acts as a cushion between the joints, preventing them from rubbing together, in addition to reducing friction in the joint with movement. Exercise can also directly stimulate cartilage development and repair, resulting in decreased pain and improved skeletal function. As cartilage does not contain blood, it receives nutrients from the synovial fluid that is normally found in the joints. This fluid is displaced in and out of the tissue with movement of the joint. This movement changes the pressures inside the joint, forcing the nutrients into the cartilage and thereby allowing the tissue to remain strong and healthy.
Nutritional Benefits of SierraSil on Skeletal Health
Bone formation, joint cartilage and muscle function require minerals including calcium, phosphorous, magnesium, potassium, manganese, copper, zinc and selenium, all of which are components of the SierraSil® mineral complex. During intense physical activity, the body relies upon nutrient stores including those in bone in order to perform exercise. Additionally, strenuous exercise increases sweat and urinary losses of minerals. Intense workouts can also increase muscular strain and the chances of injury, which can result in inflammation and tissue degradation. SierraSil® provides a wide variety of essential minerals needed to maintain skeletal and muscular health, reduce inflammation and pain associated with exercise and promote recovery.
Skeletal and Muscular Health
As bone remodeling involves the resorption and deposition of calcium from and to the bones, and exercise tends to draw on these stores to meet the needs of other body tissues, it is important to restore calcium stores through diet and appropriate supplementation in order to stimulate bone mineralization. Calcium is also necessary for muscle contraction, nerve conduction and hormone and enzyme secretion, and magnesium has a vital role in managing bone metabolism, muscle relaxation, nerve transmission and blood pressure.
Strenuous exercise can also lead to changes in zinc metabolism, and severe zinc deficiency can affect muscle function as zinc is an important component of several enzymes involved in energy metabolism in the muscle. Furthermore, zinc also plays a role in connective tissue synthesis and osteoblast activity. Manganese is also a critical cofactor for collagen and cartilage synthesis and metabolism. Strong cartilage tissue is important for athletes as it reduces the incidence of cartilage degradation due to over-exertion and protects against joint conditions such as arthritis later in life. In addition, copper acts as an important co-enzyme for lysyl-oxidase, which is responsible for the conversion of collagen and elastin, and subsequently for joint function. It also has anti-inflammatory properties and may ease pain in arthritic and damaged joints.
Although exercise is known to have numerous beneficial health effects, strenuous physical activity also results in the generation of inflammation-causing free radicals in the body due to increased oxygen utilization. Inflammatory markers have been shown to contribute to cartilage and joint breakdown. Fortunately, the body is naturally equipped with anti-oxidant enzymes such as superoxide dismutatse (SOD) and glutathione peroxidase that help scavenge these reactive oxygen species. These enzymes however, function with the help of mineral cofactors, without which their activation would not be possible. Manganese, copper and zinc are the minerals that allow SOD to function, thereby protecting tissues by converting damaging superoxide free radicals into hydrogen peroxide, which is further metabolized into water and oxygen in the body.
Exercise-induced Pain Relief
Overuse of the muscles by participating in strenuous exercise can result in muscle and tissue damage which leads to inflammation as well as pain or muscle cramps. Dehydration or mineral deficiencies such as calcium and magnesium are also common causes of cause painful muscle cramps, especially in the legs and feet. Furthermore, excessive sweating during exercise results in a loss of sodium and potassium. An imbalance of these electrolytes may lead to hypersensitive nerves and muscle cramping; thus replenishing these mineral stores post-workout with a mineral-containing supplement such as SierraSil® along with adequate nutrition helps to prevent exercise-induced muscle cramps and pain.
Minerals: The Athlete Advantage
Minerals are an essential component in any diet, in particular the diets of athletes due to their central role in maintaining bone and joint health. Eating a balanced diet containing a wide array of minerals enhances the body’s ability to maintain skeletal and muscular health, reduce inflammation and pain and recover after exercising. Supplementation with minerals-rich complexes such as SierraSil® allows you to go that extra mile naturally and pain-free.
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