Martial arts fall techniques reduce hip impact forces in naive subjects after a brief period of training
Introduction
Hip fractures in the elderly are among the most serious consequences of falls. Mortality after a hip fracture is 5–10% within the first month (Roche et al., 2005) and even about 30% within a year (Keene et al., 1993, Roche et al., 2005). Furthermore, hip fractures are a common cause of loss of independence or institutionalization. As a result, hip fractures constitute a major burden on health care systems in developed countries, both clinically and financially. Within the next decades, this burden is expected to become much larger, given the aging of the population and the exponential increase of hip fracture incidence with age (Gallagher et al., 1980).
About 90% of hip fractures are caused by falls (Cumming and Klineberg, 1994) and both sideways fall direction (Greenspan et al., 1994) and an impact site at or near the hip (Nevitt and Cummings, 1993) are major determinants of hip fracture risk. A reduction of the number of hip fractures can be assumed the logical result of a reduction of fall incidents in general. Previous research has convincingly shown that exercise programs can reduce fall incidence rates by up to 50% (Gillespie et al., 2003, Province et al., 1995, Weerdesteyn et al., 2006). However, a considerable number of falls and consequent hip fractures remain even after such an intervention. Hence, it is expected to be beneficial if interventions would not only aim at a reduction of fall incidence, but also of fall severity. In this respect, the use of hip protectors has been suggested to absorb the impact energy or shunt it away from the hip, but compliance is poor and even their efficacy in fracture risk reduction is not unequivocally proven yet (Parker et al., 2005).
Alternatively, the practice of fall techniques, in order to achieve the safest possible landing after loss of balance, may possibly contribute to a further reduction of fall-related hip fractures. Which fall techniques would be both effective and suitable for elderly is still a matter of debate. It has been shown that using the arm to block the impending fall results in a 3-fold reduction of the likelihood of hip fractures (Nevitt and Cummings, 1993). When the elbow is not held straight, but slightly flexed at impact, followed by eccentric triceps activity, this fall arrest strategy could go without sacrificing the wrist (DeGoede and Ashton-Miller, 2002). However, in the elderly an age-related reduction in triceps strength will significantly reduce their ability to use their arms for safe fall arrest (DeGoede and Ashton-Miller, 2003). Secondly, the arm is likely to be too late for hip protection in the elderly. Even in young subjects, experimental fall data show mixed results with respect to the sequence of arm and hip impacts (Hsiao and Robinovitch, 1998, Van den Kroonenberg et al., 1996). In older subjects the probability of a late hand impact further increases, as the time to move their hands into a position for breaking a fall was considerably longer than in the young (Robinovitch et al., 2005). The observation in epidemiological studies that the incidence of wrist fractures in the elderly remains at a relatively constant level with increasing age (Owen et al., 1982), whereas the incidence of hip fractures increases exponentially (Gallagher et al., 1980) also provides support for the ineffectiveness of the use of an outstretched arm in protecting the hip in the elderly.
A more promising landing strategy appears to be the Martial arts (MA) way of falling, as this technique has been shown to significantly reduce hip impact forces in falls to the side in experienced martial artists (Groen et al., 2007, Sabick et al., 1999). The main feature of MA fall techniques is rolling on after impact, as opposed to the rather abrupt landing in the ‘natural’ fall arrest strategy. MA techniques reduced hip impact forces by 27.5–30%, in conjunction with a 12–15% decrease in impact velocity. In addition, larger upper body velocities in MA falls after hip impact, indicative of less energy dissipation at the instant of impact, provided support for the role of rolling in the reduction of hip impact force.
Recently, MA fall techniques have been introduced in a fall prevention exercise program (Weerdesteyn et al., 2006). Elderly could learn these techniques within five 45-min training sessions and some participants reported that they had used the technique in a fall in daily life. However, even though the techniques are easy to learn and seem to be executed correctly after a short training, it is not known yet whether extensive training is required in order to benefit from these techniques in terms of impact force reduction. The present study was conducted to investigate whether a reduction in hip impact forces could be demonstrated in naïve young subjects after a brief training in MA fall techniques. It was hypothesized that a reduction of at least 10% could be achieved in hip impact forces. The anticipated reduction, however, was expected to be less than in very experienced martial artists (judokas; Groen et al., 2007). Furthermore, it was hypothesized that the experienced judokas and the briefly trained subjects would show some basic differences in the execution of the MA fall technique, thereby explaining the anticipated superiority of the technique as applied by the judokas. In order to identify such potential experience-related differences in the execution of the MA technique, an additional study was conducted in which EMG patterns of selected trunk, neck, and shoulder muscles were compared between experienced fallers and young subjects (without prior experience) after a brief training session.
Section snippets
Methods
Fall experiments were conducted in a group of healthy young women, with and without experience in martial arts fall techniques. Prior to the experiments, participants without judo experience were administered a 30-min training session in which they practiced sideways martial arts (MA) fall techniques on a safety mat (4 cm polyurethane foam, Agglorex®, Lommel, Belgium). A sideways MA fall technique is characterized by trunk lateral flexion and rotation and shoulder protraction in order to enable
Part 1
Hip impact forces and velocities were compared between fall techniques (MA-a, MA-na, and Block), as learned by previously inexperienced subjects after a 30-min training session. Analysis yielded a significant main effect of technique on hip impact force (F (2,8) = 10.35, p = .006). Post-hoc contrasts revealed that, compared to Block falls, MA-a and MA-na techniques reduced hip impact force by 16.7% (p = .001) and 15.5% (p = .006), respectively (Fig. 3a). In every participant, the average impact force
Discussion
The main result of the present study was that after a 30-min training MA fall techniques could reduce hip impact force in sideways falls in subjects without any prior fall experience. These results support the idea that such short training periods are effective and potentially useful although long-term effects have still to be investigated. The finding that MA fall techniques substantially reduced hip impact forces is in agreement with previous studies on MA fall techniques (Sabick et al., 1999
Acknowledgements
Financial support was provided by a grant from the Organization for Healthcare Research in the Netherlands (ZonMW) (VW and JD), POM Nijmegen (BG) and the G.J. van Ingen Schenau Promising Young Scientists Award (RS).
Vivian Weerdesteyn graduated as a physiotherapist at the Hogeschool Nijmegen in 1996. She received her M.Sc. degree in Biomedical Health Sciences (specialization Kinesiology) in 1999 and her Ph.D. degree in Medical Sciences in 2005, both from the Radboud University Nijmegen, the Netherlands. She currently works as a research fellow at the Department of Rehabilitation of the Radboud University Nijmegen Medical Centre and at Sint Maartenskliniek Research, Development, and Education, Nijmegen. Her
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Vivian Weerdesteyn graduated as a physiotherapist at the Hogeschool Nijmegen in 1996. She received her M.Sc. degree in Biomedical Health Sciences (specialization Kinesiology) in 1999 and her Ph.D. degree in Medical Sciences in 2005, both from the Radboud University Nijmegen, the Netherlands. She currently works as a research fellow at the Department of Rehabilitation of the Radboud University Nijmegen Medical Centre and at Sint Maartenskliniek Research, Development, and Education, Nijmegen. Her main research interests are reactions to balance and gait perturbations and exercise interventions to prevent falls and fall injuries, both in elderly people and in groups of patients.
Brenda Groen received her M.Sc. degree from the Faculty of Human Movement Siences of the Vrije Universiteit Amsterdam (Amsterdam, The Netherlands) in 1999. She has been working at the department of Research, Development and Education at the Sint Maartenskliniek (Nijmegen, The Netherlands) since 2001. Currently, she is a Ph.D. student. Her research interests are in the field of falls in the elderly and clinical gait analysis.
Roos van Swigchem worked as a physiotherapist from 1986 to 2002 in Wormerveer, the Netherlands. She studied Human Movement Sciences at the Vrije Universiteit in Amsterdam, the Netherlands, and got her M.Sc. degree in 2006. Currently, she works as a PhD-student at the Radboud Universiteit in Nijmegen, the Netherlands, and investigates the influence of functional electrical stimulation on gait in stroke patients.
Jacques Duysens received his M.D. from the KUL (Leuven, Belgium) in 1972 and his Ph.D in Physiology from the U. of Alberta (Canada) in 1976. Since 1987 he has been working at the Radboud University and at the Sint Maartenskliniek (Nijmegen, The Netherlands). Currently, he is a professor in Motor Control and Rehabilitation. His main research interests are focused on reflexes, locomotion and on falls in the elderly.