We found that both high-intensity resistance training and agility training were effective in reducing fall risk compared with a stretching program in older community-dwelling women with low bone mass. After 25 weeks of intervention, Resistance Training and Agility Training significantly reduced the fall risk score by 57% and 48%, respectively, compared with only a 20% reduction in the Stretching group. Based on normative data from the Randwick Falls and Fractures Study 20
, these changes represent a reduction in the risk of falling over 12 months from over 80% to 50–55%.
Of the five components that contribute to the calculation of the fall risk score, we hypothesized that postural sway, quadriceps strength, and hand reaction time would be amenable to change by the intervention programs. We found that both Resistance Training and Agility Training significantly improved postural stability compared with the Stretching group, but that the groups did not differ significantly in the tests of strength and reaction time at the end of the trial. This indicates that for both groups the reduction in fall risk scores was primarily mediated via improved postural stability.
The finding that Agility Training improved postural stability is consistent with previous investigations in other populations of older people 4,28,29
. However, the finding that Resistance Training improved postural stability contrasts with some previous studies 30,31
. The inconsistencies in the findings here may relate to differences in the intensity of the resistance training programs used across studies. For example, the current study and the study by Nelson et al. 32
used high-intensity resistance training programs - 75% to 85% of 1RM, two sets of six to eight repetitions; and 85% of 1RM, three sets of eight repetitions respectively. In contrast, studies with lower intensity interventions such as 70% to 75% of 1RM, 13 repetition maximum 30
, or home-based lower extremity resistance training program using therabands or body weight 31
have not been found to be effective in improving balance.
Although not reflected by the seated isometric knee extension test, the Resistance Training group significantly increased the squat load used in the exercise program. The lack of significant improvement in the strength outcome measure may reflect the specificity of training (standing squats) that differed from the conditions for testing (seated knee extension). The lack of generalization across strength measures has also been reported by Murphy and Wilson 33
, who found that in athletes who trained with standing squats, significant strength gains were demonstrated in a 1 RM standing squat test but not in a seated knee extension test. Increases in squat load were significantly associated with reductions in sway scores on the compliant foam rubber mat, and this interesting association may indicate how resistance training is related to improved balance and reduced falls risk.
It has been postulated that regular exercise may maintain the reactive capacity of older people by delaying the deterioration of the dopamine systems, enhancing cerebral circulation integrity, and having trophic influence on the neurons that supply the muscle fibers 34
. There were strong trends that indicated that the agility and resistance training groups had faster reaction times at the end of the trial for both a finger and foot-press response, but these differences did not reach statistical significance. Significant improvements may have been evident with a longer duration of the intervention period or with increased power with a slightly larger sample 4
At the study mid-point (13 weeks), there were few differences among the groups. However, for both the Resistance and Agility groups further improvements occurred in the second period of the trial, so that significant differences were apparent for the fall risk and postural sway measures. This would indicate that trials of six-month duration or more are necessary to obtain maximal beneficial intervention effects. Improvement in general balance and mobility (CB&M scores) was apparent in the Agility Training group at 13 weeks, but the relative improvement over the other groups was not maintained at the study endpoint. This may be due to the lack of established protocols and appropriate safe environment for progressing an agility training program, compared with a resistance training program. Further, all three groups showed improvements in this measure at the end of the trial, which may reflect direct participation in the programs, indirect activity associated with attending the classes and increased activity outside the program as indicated by the changes in PASE scores.
Both the Resistance and Agility exercise programs were feasible for older adults with low bone mass. However, the Agility Training program carried a higher risk of falls compared with the Resistance Training. Our Agility Training program required considerable planning and many safety precautions. Furthermore, the progression of an agility training program, unlike a resistance training program, is not well defined in both the clinical and research setting. Although adverse effects also occurred in the Resistance Training group, we contend that short-term musculoskeletal complaints are less disabling than sustaining a hip fracture from a fall. Thus, we consider that a community-based agility program is more complex to deliver outside of the research setting than is a resistance training program. On the other hand, it was clear that the Agility Training participants found the program particularly enjoyable, and this may enhance long-term compliance.
We acknowledge that the study has certain limitations. First, the interventions were staff intensive and their availability in the health system may be limited by cost. Second, the primary study outcome was fall risk, as opposed to falls. Thus, future research using falls as the primary outcome measure is needed to confirm the role of resistance training and agility training in falls prevention in those with low bone mass. It would be also be useful to contrast the interventions against proven fall prevention interventions.
In conclusion, we found that both high-intensity resistance training and agility training significantly reduced fall risk in older women with low bone mass compared with a stretching program. Furthermore, this study demonstrated that this group have the capacity to participate in demanding exercise programs with acceptable risk. These exercise programs may have particular public health benefits as it has been shown that older women with low bone mass are at increased risk of falling as well as sustaining fall-related fractures.