1 Improving Bone Density | 1 2 1Article Type: Commentary
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3Article Category: Sports Fitness and Health
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5Title: Training to Improve Bone Density in Adults: A Review and Recommendations
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7Running Head: Improving Bone Density
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9Authors: Ed McNeely
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11Corresponding Author:
12Ed McNeely, MS
13One Academy Drive
14Daphne Al, 36526
16555-555-5555
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18Ed McNeely is the senior physiologist at the Peak Centre for Human Performance and a partner
19in StrengthPro Inc. a Las Vegas based sport and fitness consulting company he is also a National
20Faculty member of the United States Sports Academy
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24 3 Improving Bone Density | 2 4 25Training to Improve Bone Density in Adults: A Review and Recommendations
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47 5 Improving Bone Density | 3 6 48ABSTRACT
49 The loss of bone density is becoming a major health concern in industrialized
50societies. Increasing bone density during puberty and young adulthood is considered the
51best option for preventing the negative health consequences associated with osteoporosis,
52even in middle aged and older adults an exercise program can increase bone density.
53While low volume impact oriented aerobic activities like running have been shown to be
54effective at increasing bone density excessive endurance training has been linked to low
55bone density. Strength training remains the best option for adults wishing to increase
56bone density. A regular program of high load (60-85% 1RM) training three or more times
57per week using a variety of exercises that challenge all major muscles has been shown to
58significantly increase bone density even in elderly adults.
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60Key words: bone density, exercise, osteoporosis, training
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72 7 Improving Bone Density | 4 8 73INTRODUCTION
74 Osteoporosis, which has been defined as bone mineral density (BMD) more than 2.5
75standard deviations below the young adult mean value (14), is a growing health problem for both
76men and women. In developed and developing countries the incidence of osteoporosis is
77increasing at a rate faster than what would be predicted by the aging of the population alone (15).
78In the U.S. It has been estimated that by 2025 the number of hip fractures attributed to
79osteoporosis will double to nearly 2.6 million with a greater percentage increase in men than in
80women (12).
81 Epidemiological evidence suggests that genetic factors are the most important cause of
82osteoporosis (20) and can account for as much as 80% of the variability in bone density in the
83population (6) but a variety of environmental factors have been linked to bone density including:
84negative energy balance, low calcium intake, lack of fruit and vegetable consumption, low body
85mass index, strength, and hormone levels (13,22,9,7,23), all of which may influence the ability to
86develop or maintain bone density.
87 A well designed exercise can have a tremendous impact on bone, increasing density, size
88and mechanical strength (23) and may be one of the keys to preventing complications associated
89with osteoporosis. If bone density and maximum tensile strength are increased before
90osteoporosis sets in, subsequent complications could be minimized (21). Unfortunately many
91adults wait to start an exercise program once they are diagnosed with low bone density.
92 For middle aged and older adults one of the primary health goals of an exercise program
93is to maintain bone density. Without an exercise intervention, after the age of 40 bone mass
94decreases by about 0.5% per year, regardless of sex or ethnicity (15). Whether appreciable
95increases in bone density can occur for this age group is equivocal (15) and dependant on the
96duration of the exercise program, age, dietary factors, and history of physical activity. A variety
97of different types of exercise have been used in bone building programs middle aged or older
98adults. 9 Improving Bone Density | 5 10 99Training Techniques
100Strength training
101 Although not all studies have shown improvement in bone density with strength training
102(15), strength training, if done with a high enough intensity for a prolonged period of time, seems
103to be effective for improving bone density in middle aged and older women who have low bone
104density (16). Programs that have been successful at increasing bone density have several common
105characteristics; training intensity above 70% 1RM, programs that last more than 12 months, and
106training frequency greater than two times per week.
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108Endurance Training
109 Endurance training can be an acceptable form of exercise for maintaining or increasing
110bone density in middle aged or older adults provided there is sufficient impact. Stuart and Hannan
111(22) examined the effects of cycling, running or both on bone density in recreational male
112athletes. They found that runners had greater total and leg BMD than controls, those athletes
113participating in both cycling and running had greater total and arm BMD whereas the cyclists had
114decreased spine BMD compared to controls. The lack of impact involved in cycling may explain
115the lack of change in BMD even though all groups performed equal volumes of work throughout
116the study period. Walking programs, because of their low impact, tend to show only modest or no
117effects on BMD (3,18). Rowing because of the high compressive and shear forces placed on the
118spine, 4.6 times body weight, has been shown to increase lumbar spine BMD but not at other
119areas (17). Moderate training volumes seem to be more effective for increasing bone density.
120Running mileage of 20-30 km per week has a positive effect on bone, particularly lower leg and
121distal femur, but training volumes greater than this may cause a chronic increase in cortisol that
122negatively impacts bone (4) and running 92 km per week has been shown to result in bone
123density lower than sedentary controls (2).
124 11 Improving Bone Density | 6 12 125Jump Training
126 Although effective and popular in school based programs for increasing bone density in
127younger people jump training does not appear to be as effective in middle aged and older women.
128In a study comparing the effects of 12 months of vertical jumping on spine and proximal femur
129BMD in a group of pre and post menopausal women, Bassey, Rothwell, Littlewood and Pye
130(1998) found that 50 jumps six days per week increased BMD in the pre-menopausal group but
131not in the post menopausal group compared to group specific controls. Interestingly, the lack of
132change occurred even though the ground reaction forces and rate of force development on landing
133were higher in the post menopausal group resulting in a greater strain overload than in the pre
134menopausal group.
135 While a variety of exercise modalities have proven to be effective at maintaining bone
136density in adults there some basic principals should be considered when designing a long term
137program for people with osteoporosis:
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139Exercise Considerations
140Use a progressive program
141 Increase resistance and intensity progressively. This is necessary because for bone to
142form it requires a minimum amount of strain. Once a bone adapts to a given strain level, the
143stimulus for bone to form is removed and a higher strain level becomes necessary for it to adapt
144further (10).
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146Use dynamic movements
147 Mechanical loading of bone has an osteogenic effect only if the loading is dynamic and
148variable, static loading of bone does not trigger an adaptive response (23). Impact and rapid
149changes of direction can be particularly effective because ground reaction forces tend to be
150highest during these activities. Jumps, running, and more explosive or dynamic strength training 13 Improving Bone Density | 7 14 151activities should make up the majority of exercise in a bone building program. In adults with
152advanced osteoporosis more explosive exercises should be phased in gradually as their
153conditioning and bone strength improves.
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155Vary the exercises
156 Bone adaptations occur primarily at insertion and origin points where muscles attach to
157the bones. Ryan et al. (1994) suggest that increased BMD from strength training and explosive
158activities is related to the load placed on the muscles that act as prime movers. A wide variety of
159exercises, which change every 2-4 weeks, exercising the whole body will help ensure that all
160bones receive stimulus to increase BMC or BMD.
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162Minimum intensity
163 As with most training there is a minimum level of intensity that is needed to stimulate
164increase in BMD. For strength training activities there is a linear relationship between weight
165lifted and improvements in bone density (5) Chilibeck, Sale and Webber (1995) suggest that for
166strength training intensities of at least 60% 1RM are needed to increase BMD, with faster and
167greater increases in bone density coming as intensity climbs (16). For impact activities like
168running and jumping ground reaction forces of greater than two times body weight can increase
169bone density with higher forces having a greater effect.
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171Training frequency
172 Improvements in BMD can occur with relatively short training sessions if high impact
173activities like jumping are the core of the program. However, there is a need to perform these
174sessions frequently. Studies of jump training have found that where three or more sessions per
175week is sufficient to increase bone two session per week has negligible effect on bone density
176(11). 15 Improving Bone Density | 8 16 177
178Program duration
179 Consistency is one of the keys to long term bone health. Like other tissues bone
180undergoes both adaptation to training and detraining during periods of decreased activity. The
181bone remodelling cycle lasts four to six months (8); this is the minimum period of time needed
182for BMD to change significantly. Training programs need to be designed so that they offer the
183variety and adaptability for people to make them a year round part of lifelong fitness regime.
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185CONCLUSIONS
186 Decreased bone density is a growing problem in modern societies. Exercise remains one
187of the most potent alternatives to drug treatments for maintaining or improving bone density. An
188intensive program, three or more times per week featuring a variety of exercises, that considers
189the individual needs of each person and promotes long term compliance, can have a positive
190impact on bone density.
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192APPLICATIONS IN SPORT
193 Over the past years adults have become more and more active in age group sports,
194particularly in the endurance sports like running, cycling and triathlon. The inclusion of an
195intensive strength training program will not only improve their performance but help offset the
196decrease in bone density that often accompanies aging and higher volumes of aerobic
197training.
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199ACKNOWLEDGMENTS
200 None
201 17 Improving Bone Density | 9 18 202REFERENCES
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