Tripping without falling; lower limb strength, a limitation for balance recovery and a target for training in the elderly

doi:10.1016/j.jelekin.2007.06.004

Journal of Electromyography and Kinesiology

Volume 18, Issue 2, April 2008, Pages 188-196

https://doi.org/10.1016/j.jelekin.2007.06.004 Get rights and content

Abstract

To reduce the number of falls in old age, we need to understand the mechanisms underpinning a fall, who are at risk of falling, and what interventions can prevent such individuals from falling. This paper provides an overview of our recent research on tripping and muscle strength in the elderly, addressing these questions. To prevent a fall after tripping over an obstacle, high demands are posed on lower limb muscles. It was shown that the support limb plays an important role in balance recovery by generating the appropriate joint moments during push-off. Older individuals show lower rates of moment generation in all support limb joints and a lower peak ankle moment than young adults. As strength declines with age (due to muscular, tendinous and neural alterations), leg muscle strength might be the limiting factor in preventing a fall. Indeed, high-risk fallers could be identified based on maximum leg press push-off force capacity. Resistance training can reverse the ageing-related loss of strength. Therefore, the effects of 16-weeks resistance training on tripping reactions were studied in a small group of elderly. Maximum push-off force increased significantly by training. Moreover, trainers improved more than controls in moment generation after tripping, especially around the ankle. It can be concluded that transfer of resistance training effects to balance recovery is feasible.

Introduction

Falls and fall-related injuries can have devastating consequences in the growing populating of elderly (for an overview see Lord et al., 2001). Since the incidence of falls is rising, fall prevention is of utmost importance. To conduct targeted interventions, we need to understand the mechanisms underpinning a fall, who are at risk of falling, and what interventions can prevent such individuals from falling?

Most falls in the elderly occur during daily activities. Tripping over an obstacle has been reported to be one of the main causes, accounting for up to 60% of all falls (Berg et al., 1997, Nevitt et al., 1991, Roudsari et al., 2005, Ryynanen et al., 1991). Several studies have been performed to obtain more insight in the (neuro)physiological and mechanical requirements for preventing a fall after tripping in both young and older adults (see below). In our experimental research, we have investigated the mechanical aspects of recovery reactions after tripping in young and older adults. With this approach, we have identified that lower limb strength and rate of moment generation may be limiting factors for balance recovery after tripping. The question remains whether recovery can be improved by targeting these factors through exercise-based intervention. The aim of the present paper is to give an overview of our research on tripping, muscle strength decline and training in the elderly, in order to gain insight to the questions raised above. In this paper, we also present encouraging results from a pilot study where resistance exercise training has been used as an intervention aimed at improving the tripping responses of older adults.

Section snippets

The probability to trip and fall

It can be questioned whether older people fall more often than young people because they trip more often or because they are less able to regain balance after a trip. The probability of tripping depends on the presence of obstacles, on the individual’s walking pattern, and on the individual’s ability to detect and avoid the obstacle. For instance, ageing-related gait changes in the walking pattern (e.g. reduced speed, stride length and toe clearance and increased double support time) might

Who are at risk of falling after a trip?

In our search for effective fall prevention measures, people who have a high risk of falling and who can benefit most from exercise-based interventions need to be identified. As moment generation in the leg was lower in the recovery reactions of older adults (as described above), leg muscle strength capacity might be the limiting factor in preventing a fall. One should bear in mind, however, that physical limitations are correlated with physical activity. Physically inactive people might be

Resistance training in the elderly

Recently, numerous studies have investigated the effect of resistance training in the elderly (see Barry and Carson, 2004, Hunter et al., 2004, Latham et al., 2004, Macaluso and De Vito, 2004, Reeves et al., 2006 for systematic reviews). Resistance training has been shown to be an effective method for attenuating, or even reversing the ageing-related loss of strength (Kirkendall and Garrett, 1998, LaStayo et al., 2003, Porter et al., 1995, Tideiksaar, 1997) and the ageing-induced adaptations

Conclusions

Based on the studies reviewed above and our recent pilot study, we can conclude that high demands are posed on lower limb strength in balance recovery. Leg strength declines with age and is a limiting factor in the elderly in preventing a fall. Maximum whole leg push-off force is a good measure to identify people who have a high risk of falling and who can benefit most from exercise-based interventions. Finally, resistance training has been shown to have a beneficial effect on muscle strength

Acknowledgements

The authors would like to thank the participants of the training studies and gratefully acknowledge the support from Technogym and the financial support from the “Stichting de Drie Lichten”, Leiden, The Netherlands and “Stichting Annafonds”, Leiden, The Netherlands.

Mirjam Pijnappels studied Biomedical Health Sciences at the University of Nijmegen, The Netherlands, and got her M.Sc. degree in 1997. She worked for two years at the University of Maastricht, The Netherlands. In 1999, she started working at the Faculty of Human Movement Sciences at the Vrije Universiteit in Amsterdam, The Netherlands, where she obtained her Ph.D. degree in 2004 on tripping reactions in young and older adults. Currently, she works as a post-doc researcher at the same faculty

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Trips and slips increase fall risk for young and older adults. To examine recovery responses, studies utilized treadmill and/or over-ground methods to simulate real-world perturbations. However, differences in the recovery response between treadmill and over-ground perturbations remain unexamined.
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PubMed, Medline, Web of Science, SCOPUS, and Cochrane databases were searched for publications examining trips and slips in healthy young, healthy older adults, and older adults who fall. Included articles were in English, full-text accessible, and biomechanically quantified the reactive recovery responses for slips and trips during either over-ground or split-belt treadmill protocols. The initial database search yielded 1075 articles and 31 articles were included after title, abstract, and full-text screening.
For slips, 7 articles utilized lubricated surfaces while 5 articles used treadmills. Further, 3 studies examined differences between older and younger adults. For trips, 9 articles utilized obstacles and 7 used treadmills. Further, 4 articles examined differences between older and young adults and 1 article only examined older adults during over-ground trips. For both perturbations, treadmill and over-ground protocols demonstrated similar anteroposterior destabilization on the center of mass. In the mediolateral direction, over-ground slips consistently found a lateral destabilization while treadmill articles did not examine this direction. Foot placement recovery responses varied less for both perturbation directions on a treadmill compared to over-ground.
Although treadmill and over-ground perturbations destabilize the center of mass similarly, the recovery response to these perturbations were different on treadmills. Specifically, recovery responses were more consistent for both slips and trips on treadmills. As older adults have difficulty in perturbation recovery scaling, treadmills may be limited in their ability to investigate the variety of aging impairments on perturbation recovery responses.
Use of ‘wearables’ to assess the up-on-the-toes test
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Age-related decline in muscle strength and function (Jan et al., 2005; Pijnappels et al., 2008b), compromises everyday functional ability (Stathokostas and Vandervoort, 2016).
The mechanical output at the ankle provides key contribution to everyday activities, particularly step/stair ascent and descent. Age-related decline in ankle functioning can lead to an increased risk of falls on steps and stairs. The rising up-on-the-toes (UTT) 30-second test (UTT-30) is used in the clinical assessment of ankle muscle strength/function and endurance; the main outcome being how many repetitive UTT movements are completed. This preliminary study describes how inertial measurement units (IMUs) can be used to assess the UTT-30. Twenty adults (26.2 ± 7.7 years) performed a UTT-30 at a comfortable speed, with IMUs attached to the dorsal aspect of each foot. Use of IMUs’ angular velocity signal to detect the peak plantarflexion angular velocity (p-fAngVel_peak) associated with each repeated UTT movement indicated the number of UTT movements attempted by each participant. Any UTT movements that were performed with a p-fAngVel_peak 2SD below the mean were deemed to have not been completed over a sufficiently ‘full’ range. Findings highlight that use of IMUs can provide valid assessment of the UTT 30-second test. Their use detected the same number of attempted UTT movements as that observed by a researcher (average difference, −0.1 CI, −0.2 – 0.1), and on average 97.6 ± 3.1% of these movements were deemed to have been completed ‘fully’. We discuss the limitations of our approach for identifying the movements not completed fully, and how assessing the consistency in the magnitude of the repeated p-fAngVel_peak could be undertaken and what this would indicate about UTT-30 performance.
Age-related differences in stepping stability following a sudden gait perturbation are associated with lower limb eccentric control of the perturbed limb
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Falls are a leading cause of severe injuries and a major threat to quality of life in older adults. Elderly fallers demonstrate insufficient eccentric quadriceps control during the weight acceptance phase of initial single limb stance. However, the functional role of eccentric control of the perturbed (leading) leg during walking balance recovery and its age-related differences have not yet been studied; thus we investigated age-related differences in eccentric control at the knee of the perturbed leg and its influence on the postural sway and stability of the trailing leg during balance recovery following unexpected surface drop perturbations.
Ten younger and ten older healthy adults were compared during balance recovery following an 8 cm unexpected surface drop perturbation at gait initiation. Outcomes related to perturbed leg included 1) eccentric knee extensor work; 2) electromyography (EMG) peak amplitude, peak latency, and eccentric EMG burst duration of the rectus femoris (RF); and 3) knee flexion angle during the single limb support. Outcomes related to stability of the trailing leg included 4) margin of stability (MoS) at first compensatory step touchdown after the perturbation. 5) Postural sway (standard deviation of center of mass acceleration) was measured in the anterior-posterior (A-P), medio-lateral (M-L), vertical directions during the single limb support.
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Measures of obesity included 6 anthropometry-based measures (BMI; thigh, hip and waist circumferences; ratio of waist-to-hip circumference; index of central obesity) and 4 dual-energy x-ray absorptiometry–based measures (percentage trunk, leg, and total fat; fat mass index). Measures of risk of tripping during overground walking included median and interquartile range of toe clearance and area under the swing phase toe trajectory. Measures of trip recovery after a laboratory-induced trip included trunk angle and angular velocity at ground contact of the first recovery step, anteroposterior distance from stepping foot to center of mass at the same instant, and step time of the first recovery step.
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Jaap van Dieën obtained a Ph.D. in Human Movement Sciences from the Faculty of Human Movement Sciences at the ‘Vrije Universiteit Amsterdam’ The Netherlands in 1993. Since 1996 he has been affiliated to this faculty, since 2002 as professor of biomechanics. He leads a research group focusing on mechanical aspects of musculoskeletal injuries. His main research interest is on the interaction of muscle coordination, fatigue, disorders, joint load and stability. Jaap van Dieën has (co-) authored over 120 papers in international scientific journals and numerous abstracts and book chapters in the international literature and technical reports and publications in Dutch. He is an editor of the European Journal of Applied Physiology, section editor of Human Movement Sciences and serves on the editorial advisory board of the Journal of Electromyography and Kinesiology and the editorial board of Clinical Biomechanics and is currently a member of the boards of ISEK and the Dutch Society for Human Movement Sciences.

Constantinos N. Maganaris received a B.Sc. in Sports and Exercise Science (1995), from the College of Sports Science in Athens, Greece, a M.Sc. in Sports Nutrition (1996) from the University of Aberdeen in the UK, and a Ph.D. in Musculoskeletal Biomechanics (1999) from the Manchester Metropolitan University (MMU) in the UK. Currently, he holds a Professorship in Musculoskeletal Sciences at the Institute for Biophysical and Clinical Research into Human Movement (IRM) at MMU. His main research interest focuses on the relation between musculoskeletal structure and function in the intact human body.

Neil D. Reeves received a B.Sc. degree in Exercise and Health Science from Staffordshire University in 1999, a M.Sc. degree in Exercise Physiology from the Manchester Metropolitan University (MMU) in 2000 and a Ph.D. in Muscle-Tendon Mechanics from MMU in 2004. He is currently a Post-Doctoral Research Fellow working within the Institute for Biophysical and Clinical Research into Human Movement (IRM) at MMU in the UK. His research interests include musculoskeletal adaptations to ageing, disuse and increased use.

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Tripping without falling; lower limb strength, a limitation for balance recovery and a target for training in the elderly

Abstract

Introduction

Section snippets

The probability to trip and fall

Who are at risk of falling after a trip?

Resistance training in the elderly

Conclusions

Acknowledgements

Gait Posture

J Biomech

J Neurol Sci

Clin Biomech

J Biomech

Gait Posture

J Biomech

Injury

Am J Prev Med

Safety Science

Exercise and physical activity for older adults

Med Sci Sports Exerc

The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults

Med Sci Sports Exerc

Transfer of resistance training to enhance rapid coordinated force production by older adults

Exp Brain Res

Circumstances and consequences of falls in independent community-dwelling older adults

Age Ageing

Falls by elderly people at home: prevalence and associated factors

Age Ageing

Stepping over obstacles: gait patterns of healthy young and old adults

J Gerontol A Biol Sci Med Sci

Effects of age and available response time on ability to step over an obstacle

J Gerontol A Biol Sci Med Sci

Randomised factorial trial of falls prevention among older people living in their own homes

BMJ

Strategies for recovery from a trip in early and late swing during human walking

Exp Brain Res

Exercise training guidelines for the elderly

Med Sci Sports Exerc

Strength and power changes of the human plantar flexors and knee extensors in response to resistance training in old age

Acta Physiol Scand

Kinematics of recovery from a stumble

J Gerontol A Biol Sci Med Sci

Knee extensor strength, activation, and size in very elderly people following strength training

Muscle Nerve

Effects of resistance training on older adults (review)

Sports Med

The effects of aging and training on skeletal muscle

Am J Sports Med

Normalized force, activation, and coactivation in the arm muscles of young and old men

J Appl Physiol

Muscle architectural characteristics in young and elderly men and women

Int J Sports Med

Effects of aging on shortening velocity and myosin isoform composition in single human skeletal muscle cells

Am J Physiol

The positive effects of negative work: increased muscle strength and decreased fall risk in a frail elderly population

J Gerontol A Biol Sci Med Sci

Systematic review of progressive resistance strength training in older adults

J Gerontol A Biol Sci Med Sci

Human aging, muscle mass, and fiber type composition

J Gerontol A Biol Sci Med Sci

Falls in older people: risk factors and strategies for prevention