2.4 Bone Health
There are a few factors that influence bone health status which include endogenic factors such as ethnicity, heredity, gender and endocrine status, as well as exogenic factors such as physical activity and nutrition (Javaid & Cooper, 2002:
Rizzoli et al., 2010).Furthermore, muscular strength was a factor that influenced bone health, and there was a link between muscular strength and bone health, Ahedi et al.
(2014) investigated the relationship between muscle strength and bone mineral density (BMD) of the hip and and spine in 321 Tasmanian older adults and reported that BMD was positively related to the muscular strength and authors conclude that higher muscular strength is associated with BMD of the hip in elderly women.
Bone mineral density (BMD) peaks during early adulthood and decreases after menopause in women, and is also influenced by genetics. Maternal nutrition and medications can affect the fetal skeleton which is starting in utero where bone health can be affected. Moreover, other factors that can affect the bone health status of an individual include exercise, diet, smoking, alcohol, medications, and calcium intake.
Nearly 90 percent of peak bone mass can be gained by age 18 years for adolescence, thus young adulthood is the most beneficial time for gains a high level of bone density (Whiting et al, 2004). However, eating disorders, poor nutrition, hypoestrogenism and inadequate calcium intake are the factors for negative consequences that can occur.
Physical activity or bone loading activities act as key roles in maintaining bone mass process during childhood and adolescence continues into adulthood. To reduce fracture risk later in life, physical activities are important for maintaining bone mass (Johnston, 1994; Kam, 2000; Kahn, 2000; Kanis, 2001). Knowledge of the bone composition, formation and adaptation is important in understanding the benefits of exercise on bone health.
Weight-bearing athletes have an approximately 10% higher BMD than nonathletes (Marci et al., 2017). Athletes participating in high-impact sports have a higher BMD compared with medium or low-impact sports (Torstveit, 2005). The effects of exercise on the bone are such as increasing bone mass and strength and reducing the risk of falls (Manske et al., 2009). Exercise should be dynamic, not static, achieve adequate strain intensity, consists of discrete and intermittent bouts, involving
variable loading patterns, supported by optimal nutrition such as adequate intake of calcium and vitamin D to achieve maximum benefit. (Borer, 2005). A 5.4% increase in BMD is equal to a 64% increase in ultimate force and a 94% increase in energy (Robling, 2002). High improvement in BMD and bone strength can be caused by exercise.
Fractures caused by low bone mass can lead to morbidity and mortality.
According to Looker (2005), 52% of adults older than 50 years have low bone mass at the femoral neck or lumbar spine in the United States. There are 9% of them met the diagnostics criteria of osteoporosis at one or both sides. Based on a previous study by Howe (2011), there are benefits of a variety of different types of exercises. For example, cardiovascular exercises and resistance training. Resistance strength training is an example of high-force exercise. This type of exercise is focusing on the lower limb that has the most impact on femoral neck BMD. A combination of the exercise is effective in enhancing BMD at the spine.
Adaptive changes can improve bone architecture through increasing bone density caused by sports participation (Tenforde & Fredericson, 2011). Different strain demands on the skeletal bones can be created by different types of physical activity (Heinonen et al., 1995). Martial arts such as taekwondo, judo, tai-chi and karate are examples of physical activities that impose high and unusual strains on bone and subsequently increase bone health (Creigthon et al., 2001). Based on a previous study carried out by Andreoli et al. (2001), sports involvement elicited beneficial effects on bone density and muscle mass in highly trained male athletes.
DXA in the clinical setting can be used for measuring BMD of an individual.
High resolution peripheral quantitative computed tomography (HR-pQCT) can be also used to distinguish healthy microarchitecture of bone from suboptimal bone by
dimensional information to provides estimates of bone geometry (LeBlanc, 2007:
MacNeil, 2007). In addition, a bone sonometer can also be used to measure the bone speed of sound which can reflect the bone mineral density of an individual.
The most significant medical issue that arose with long-distance backpacking such as during hiking was “gynecologic abnormalities”. It has been reported that 22%
of female backpackers have significant experience amenorrhea (Boulware, 2004).
Complications of intense exercise include low estrogen and progesterone with the risk of loss of trabecular bone and early osteoporosis (Prior and Vigna Y., 1985;
Drinkwater et al., 1984). The observed prevalence of amenorrhea in the athlete is 5%
to 66% compared with 1% to 5% in the general population (Bachman and Kemmann, 1982; Singh, 1981). In a study of adult female athletes, 72% of amenorrheic women were either osteopenic or osteoporotic (Renckens et al., 1996). The duration of amenorrhea and body weight are predictors of BMD.
Weight-bearing exercise does not offset the negative effect of decreased estrogen on the skeleton of amenorrheic athletes (Renckens et al., 1996). Although the incidence of long-distance backpacking and amenorrhea may be only temporary, the BMD loss may be irreversible despite a resumption of menses (Otis et al., 1997;
Drinkwater et al., 1986; Jonnavithula et al., 1993). This raises concern over a possible later increased risk for premature osteoporotic fractures. Moreover, amenorrheic athletes using estrogen in doses used for menopausal women have shown maintenance but no gain of BMD (Hergenroeder, 1995).