Juniper Publishers: The Effect of Exercise on Balance: Emphasis on Women Diagnosed with Parkinson’s Disease
JUNIPER PUBLISHERS- JOURNAL OF GYNECOLOGY AND WOMEN’S
HEALTH
Journal of Gynecology and Women’s Health-Juniper
Publishers
Authored by Ronald Davis*
Abstract
The motor symptoms associated with Parkinson’s
disease include tremors, dyskinesis, rigidity, and posture and gait
abnormalities. The incidence, prevalence and mortality rates of the
disease are lower in women compared to men, possibly due to the
neuroprotective role of estrogen. Aerobic, resistance and flexibility
exercise protocols may be effective at improving the functional
limitations, including balance, that are a result of the inherent
pathophysiology of Parkinson’s disease. Resistance exercise that targets
lower torso, pelvic and leg muscles elicits strength changes that
allows for better control of posture and balance, thereby potentially
lessening chronic fatigue and preventing falls.
Abbreviations: PD: Parkinson’s Disease; BMD: Bone Mineral Density
Introduction
Parkinson’s disease (PD) is a neurodegenerative
condition caused by a reduction in dopaminergic neurons located in the
substantia nigra of the brain [1]. The disease is characterized by muscle tremors, rigidity, and dyskinesis leading to posture and gait abnormalities [1]. Although the incidence ratio of males to females is approximately 1.46 [2], the prevalence of PD among men is doubled when compared to women [3].
Females typically have a lower mortality rate associated with PD due
to: 1) the overall longer life expectancy when compared to men in the
general population, and; 2) the factors that predict high mortality in
those with PD, including cognitive impairment and posture and gait
abnormalities, are less common in women [4-6].
In males, there is therefore a greater predisposition to develop PD [7].
This bias may be due to the molecular pathology of PD. Gene expression
profiles in normal substantia nigra dopaminergic neurons are sex-
specific and the survivability of these neurons are dependent on
molecular pathways that are very different in men and women [7].
Therefore, women are thought to have greater protection from PD when
compared to men, which may be due to estrogen concentrations [7].
Estrogen plays a significant role in the
pathophysiology and progression of PD in women. Estrogen influences
dopamine synthesis and release while inhibiting dopamine uptake [8]. The higher concentrations of estrogen is a possible reason for the more benign phenotype in women when compared to men [9,10], particularly before a course of medication has begun [11].
Estrogen may have a protective effect, preventing toxins from
negatively affecting and possibly degrading neurons in the substantia
nigra [8].
However, the protective effect of estrogen was not evident in other
studies, which included women participants who reported a more rapid
onset of symptoms, including dyskinesis, upon diagnosis [12-14].
With regard to motor symptoms, women typically present more with tremors [9] and dyskinesis, but not rigidity [15],
when compared to men. Upon the analysis of non-motor symptoms,
constipation, restless legs, pain and emotional characteristics such as
nervousness and sadness were more prevalent in women [15-17]. A reduction in visuospatial cognition also occurs more frequently in women [11]. When compared to women without PD, women with PD typically report a more frequent loss of interest and anxiety [18].
Effect of Aerobic Exercise on Balance
Genders are not analyzed separately in the majority
of studies that include exercise as an intervention to investigate
functional changes, including balance, in adults with PD. Several
studies have included a large number of female participants with PD.
Cakit et al. [19]
reported significant improvements in the scores on the Berg Balance
Scale following 8 weeks of treadmill training in which intensity was
incrementally increased using speed in 31 individuals (15 females) with
PD [19]. In another study, no difference in functional reach scores [20,21]
were reported between a traditional aerobic exercise program, a
flexibility program, and a home-based exercise program after 16 months
in 121 adults (45 females) with early- to mid-stage PD [22]. Other non-conventional forms of aerobic exercise have demonstrated improvements in balance, such as robotic gait training [23], dance therapy [24-26], boxing training [27] and whole-body vibration [28] in both women and men with PD.
Effect of Spinal Flexibility and Resistance Exercise on Balance
Poor spinal flexibility is moderately correlated with functional limitations in those with PD [29]. Using regression analysis, Shenkman et al. [29] founda greater correlation between females with PD and both poor spinal flexibility and balance [29]. Balance in humans is often correlated with postural control [30].
In fact, many of the same tools are used to assess both posture and
balance. When assessing lower limb strength, Pääsuke et al. [31] found differing reaction times and maximum isometric force between the legs in females with PD [31].
This may be due to the postural asymmetry, and thus balance impairment,
that is prevalent with PD.In a group of 20 adults (7 women) with PD,
power in the leg muscles (i.e., leg extensors, knee flexors, hip
extensors, hip abductors) was significantly increased after 12 weeks of
resistance exercise, leading to improvements with stepping reaction
time, maximal balance range and time in single leg stance [32].
Exercise, Balance, and Fatigue
To achieve proper balance, the muscles that control
and regulate balance must be strengthened through force generation
within the skeletal muscles. The generation of necessary force from
motor tasks, coupled with the power loss in muscle due to bradykinesia
and tremors, may lead to fatigue in those with PD [33-35].
However, there is an inverse relationship between the frequency of
regular aerobic exercise and chronic fatigue both women and men with PD [36].
Exercise, Balance, and Bone Mineral Density
Postural instability and poor balance, in addition to
other neuromuscular and visual impairments, are significant and
independent risk factors for hip fracture in elderly mobile women [37].
Falls are the most common causes of emergency hospital admissions in
those with PD due to the inherent pathophysiology of PD and a lower than
normal femoral-neck bone mineral density (BMD), which may lead to
osteoporosis [38].
The onset and progression of osteoporosis in individuals diagnosed with
PD may be due to a limited exposure to sunlight, a deficiency in
vitamin D, having a classification of advanced PD, immobilization,
hormonal imbalances, or poor dietary habits [39].
In postmenopausal women, exercise, with additional treatments (e.g.,
pharmacological supplementation), can maintain and even increase BMD in
this population [40,41].
Exercise programs that incorporate muscle strengthening and balance can
also potentially reduce the number of falls, thereby preventing hip
fractures [42].
In women with PD, hip BMD is independently associated with leg muscle
strength, as this muscle strength accounts for 8.8 to 10.6% of the
variation observed in hip BMD [43].
Conclusion
Women with PD have greater levels of disability and
reduced quality-of-life when compared to men with PD. Both aerobic and
resistance exercise may elicit functional changes, including balance, in
women diagnosed with PD. Exercise may also reduce chronic fatigue and
increase or maintain BMD, thereby improving balance and decreasing the
risk of hip fractures. More studies are needed that include an analysis
of functional changes, using groups separated by gender, following some
exercise intervention.
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