Stumbling over obstacles in older adults compared to young adults

Even low alcohol concentrations affect obstacle avoidance reactions in healthy senior individuals

BACKGROUND

Alcohol is a commonly used social drug and driving under influence is a well-established risk factor for traffic accidents1. To improve road safety, legal limits are set for blood alcohol concentration (BAC) and driving, usually at 0.05% (most European countries) or 0.08% (most US states, Canada and UK). In contrast, for walking there are no legal limits, yet there are numerous accounts of people stumbling and falling after drinking. Alcohol, even at these low concentrations, affects brain function and increases fall risk. An increased fall risk has been associated with impaired obstacle avoidance skills. Low level BACs are likely to affect obstacle avoidance reactions during gait, since the brain areas that are presumably involved in these reactions have been shown to be influenced by alcohol. Therefore we investigated the effect of low to moderate alcohol consumption on such reactions.Thirteen healthy senior individuals (mean(SD) age: 61.5(4.4) years, 9 male) were subjected to an obstacle avoidance task on a treadmill after low alcohol consumption. Fast stepping adjustments were required to successfully avoid suddenly appearing obstacles. Response times and amplitudes of the m. biceps femoris, a prime mover, as well as avoidance failure rates were assessed.

FINDINGS

After the first alcoholic drink, 12 of the 13 participants already had slower responses. Without exception, all participants' biceps femoris response times were delayed after the final alcoholic drink (avg ± sd:180 ± 20 ms; p < 0.001) compared to when participants were sober (156 ± 16 ms). Biceps femoris response times were significantly delayed from BACs of 0.035% onwards and were strongly associated with increasing levels of BAC (r = 0.6; p < 0.001). These delays had important behavioural consequences. Chances of hitting the obstacle were doubled with increased BACs.

CONCLUSIONS

The present results clearly show that even with BACs considered to be safe for driving, obstacle avoidance reactions are inadequate, late, and too small. This is likely to contribute to an increased fall risk. Therefore we suggest that many of the alcohol-related falls are the result of the disruptive effects of alcohol on the online corrections of the ongoing gait pattern when walking under challenging conditions.

Modulation of cutaneous reflexes from the foot during gait in Parkinson's disease

Normal gait is characterized by a phase-dependent modulation of cutaneous reflexes. The role of the basal ganglia in regulating these reflexes is largely unknown. Therefore cutaneous reflex responses from the skin of the foot were studied during walking of patients with mild to moderate Parkinson's disease (PD). The reflex responses were elicited by stimulation of the sural nerve of the most affected leg. The responses were studied in the biceps femoris (BF) and tibialis anterior (TA) of both legs. The latencies, durations, and phase-dependent modulation patterns of the responses were mostly comparable with those observed in healthy subjects. However, on average the amplitude of the responses in the ipsilateral and contralateral BF was respectively 1.4- and 5-fold larger for the PD patients than that for the healthy subjects. This increase was mostly seen throughout the whole step cycle. However, in some PD patients the crossed BF responses were very large during the contralateral swing phase. In such cases the increase in crossed reflexes sometimes reflected premotoneuronal gating since it was not always due to increased background activation in that period. Fast activation of contralateral BF reflexes is known to occur in conjunction with ipsilateral perturbations when there is a threat to stability. It is concluded that cutaneous reflexes are facilitated in PD but that some of the increase in reflexes in BF may be indirectly related to unsteady gait and to perceived instability.

Injury to endoscopic personnel from tripping over exposed cords, wires, and tubing in the endoscopy suite: a preventable cause of potentially severe workplace injury

BACKGROUND The endoscopy unit before remediation may be a high-risk area for slip and fall injuries due to a large number of exposed above-the-floor wires in the endoscopy rooms, dimmed lighting during endoscopic procedures, and staff inattention to obstacles due to preoccupation with the endoscopic patient. AIM To describe a novel, previously unappreciated workplace hazard to endoscopic personnel: Exposed wires in the endoscopy unit.METHODS This study is a retrospective review of 110,000 endoscopic procedures performed during the last 5 years at an academic, teaching hospital with a high-volume endoscopy unit. All significant orthopedic injuries to endoscopic personnel from slips, twists, and falls from tripping over exposed cords in the endoscopy unit were reviewed. The severity of injury was documented based on roentgenographic findings, number of days of missed work, number of days with a modified work schedule, and requirement for orthopedic surgery. The number of potentially exposed cords per endoscopy room was determined. RESULTS During the 5-year study period, three endoscopic personnel suffered significant orthopedic injuries from slips, twists, and falls from tripping over cords, wires, or tubing lying exposed over the floor in the endoscopy suite: The resulting injuries consisted of fourth and fifth metacarpal hand fractures due to a fall after tripping on oxygen tubing; a rib fracture due to tripping on electrical wires trailing from an endoscopy cart; and a grade II ankle sprain due to the foot becoming entangled in oxygen tubing. All injuries resulted in lost days of work [mean 9.3 +/- 11.0 (SD) days] and in additional days of restricted work (mean 41.7 +/- 31.8 days). One injury required orthopedic surgery. Hospital review revealed a mean of 35.3 +/- 7.5 cords, wires, or tubing per endoscopy procedure room, the majority of which were exposed above the floor before remediation (n = 10 rooms). Remediation of exposed wires included: bundling related wires together in a cable to reduce the number of independent wires, covering exposed wires on the floor with a nonslip heavy mat, and running wires from ceiling outlets to equipment high above ground (e.g. mounted endoscopy video monitors). CONCLUSIONS Tripping, slipping, and falling over exposed wires can cause significant injury to endoscopic personnel. This previously undescribed hazard should be preventable by simple remediation, and all endoscopic personnel, hospital architects, hospital administrators, and governmental regulators should be alerted to this potential hazard

Fast responses to stepping on an unexpected surface height depend on intact large-diameter nerve fibers: a study on Charcot-Marie-Tooth type 1A disease

The contribution of reflexes from the large myelinated afferents in the control of normal and perturbed gait in humans is a highly debated issue. One way to investigate this topic is by studying normal and perturbed gait in patients lacking large myelinated fibers in the distal limb (Charcot-Marie-Tooth [CMT] type 1A disease). Such patients should have delayed and decreased reflexes if the latter depend on these large myelinated fibers. To elicit the reflexes, both patients and controls had to step on a platform that was either at the same level or lowered by 5 cm. In control subjects, landing on a level surface induced short-latency responses in the biceps femoris and tibialis anterior muscles, whereas such responses were largely absent in the patients. Similarly, stepping down unexpectedly induced a very fast muscle synergy, leading to a brake of the forward propulsion in the controls, which was significantly reduced and delayed (on average 32 ms) in the patients. The observed changes correlated with both sensory and motor deficits. Nevertheless, it is concluded that the results are primarily related to the sensory deficits, since the delayed or absent responses appeared in both upper and lower leg muscles, whereas only the latter showed motor deficits. The data are taken as evidence that large-diameter afferents from the distal leg are essential for fast reflex activations induced by stepping on a level or lowered surface unexpectedly.

Age-related effect of static and cyclic loadings on the strain-force curve of the vastus lateralis tendon and aponeurosis

The objective of the present study was to investigate the age-related effects of submaximal static and cyclic loading on the mechanical properties of the vastus lateralis (VL) tendon and aponeurosis in vivo. Fourteen old and 12 young male subjects performed maximal voluntary isometric knee extensions (MVC) on a dynamometer before and after (a) a sustained isometric contraction at 25% MVC and (b) isokinetic contractions at 50% isokinetic MVC, both until task failure. The elongation of the VL tendon and aponeurosis was examined using ultrasonography. To calculate the resultant knee joint moment, the kinematics of the leg were recorded with eight cameras (120 Hz). The old adults displayed significantly lower maximal moments but higher strain values at any given tendon force from 400 N and up in all tested conditions. Neither of the loading protocols influenced the strain-force relationship of the VL tendon and aponeurosis in either the old or young adults. Consequently, the capacity of the tendon and aponeurosis to resist force remained unaffected in both groups. It can be concluded that in vivo tendons are capable of resisting long-lasting static (~4.6 min) or cyclic (~18.5 min) mechanical loading at the attained strain levels (4-5%) without significantly altering their mechanical properties regardless of age. This implies that as the muscle becomes unable to generate the required force due to fatigue, the loading of the tendon is terminated prior to provoking any significant changes in tendon mechanical properties.

Exercise training can improve spatial characteristics of time-critical obstacle avoidance in elderly people

Fall prevention programs have rarely been evaluated by quantitative movement analysis methods. Quantitative movement analyses could provide insight into the mechanisms underlying the effects of training. A treadmill obstacle avoidance task under time pressure has recently been used to evaluate a fall prevention exercise program for community-dwelling elderly people and it showed that participants improved their obstacle avoidance success rates. The mechanism, by which the increased success rates were achieved, however, remained to be determined. Participants were elderly who had fallen at least once in the year prior to participation. They were assigned to either the exercise or the control group. The control group did not receive any specific treatment. The exercise group was administered a five week exercise program, which consisted of exercises on a functionally oriented obstacle course, walking exercises, and practice of fall techniques. Pre- and post-intervention laboratory obstacle avoidance tests were conducted. Three possible determinants of success were investigated, namely avoidance reaction times, the distribution of avoidance strategies, and three spatial parameters (toe distance, foot clearance and heel distance). Analysis yielded significant TimexGroup interactions in heel distances. The exercise group increased heel distance, while the control group did not. Increased heel distance may result in reduced risk of heel contact with the obstacle and, consequently, larger success rates. The remaining parameters showed no effect of training. In conclusion, the training program was effective in improving time-critical obstacle avoidance skills. In every day life, these effects of training may contribute to less obstacle-related fall incidents in elderly. In addition, these findings could indicate that the execution of other time-critical events, like an actual fall, could also be improved by training.

Acute facial trauma in falling accidents: MDCT analysis of 500 patients

The aim of this study is to assess multidetector computed tomography (MDCT) findings of facial trauma due to a falling accident. Using picture-archiving and communications system, we retrieved all MDCT requests for suspected facial injury during a 62-month period. Images were interpreted by two researchers. Five hundred patients met the inclusion criteria and 329 (66%) had a total of 515 fractures. Falls on stairs were seen in 109 (22%) patients and slips or trips in 391 (78%). The corresponding number of fractures was 169 (33%) and 346 (67%). Males (N = 241) had more fractures than females (N = 259), 327 vs. 188, respectively. The zygomatic complex was the most common fracture, seen in 40% of patients suffering a fracture. Twenty patients (4%) had fractures involving the sinus walls without paranasal sinus effusions. Facial fractures due to falls are common. The zygomatic complex is the most common fracture. A clear sinus sign may be less reliable than previously thought.

Age-related changes in gait for multi-surface terrain

The main purpose of this study was to determine the effects of aging on the variability of gait over multi-surface terrain. An additional aim was to compare this variability to walking on solid ground. Ten young adults and 10 older adults walked along a walkway which contained a middle portion with multi-surface terrain. This multi-surface terrain consisted of solid, compliant, rocky, irregular, slippery, and uneven surfaces. We examined the effects of the multi-surface terrain and age on measures of variability including step length, step width, trunk pitch and roll, trunk centre of mass (tCOM) acceleration, and head acceleration. Step, trunk, and head variability were increased on the multi-surface terrain as compared to solid ground for both young and older adults (p<0.05). Older adults demonstrated larger medial-lateral tCOM acceleration RMS (p=0.0004) and trunk roll RMS (p=0.0001) when walking on the multi-surface terrain. In addition, older adults also walked more slowly (p=0.002) and took shorter steps (p=0.003). However, there were no age-related differences in step variability. The results suggest that multi-surface terrain poses a greater challenge to balance reflected by the increased variability, particularly in older adults.

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

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.

Identification of elderly fallers by muscle strength measures

For efficient prevention of falls among older adults, individuals at a high risk of falling need to be identified. In this study, we searched for muscle strength measures that best identified those individuals who would fall after a gait perturbation and those who recovered their balance. Seventeen healthy older adults performed a range of muscle strength tests. We measured maximum and rate of development of ankle plantar flexion moment, knee extension moment and whole leg push-off force, as well as maximum jump height and hand grip strength. Subsequently, their capacity to regain balance after tripping over an obstacle was determined experimentally. Seven of the participants were classified as fallers based on the tripping outcome. Maximum isometric push-off force in a leg press apparatus was the best measure to identify the fallers, as cross-validation of a discriminant model with this variable resulted in the best classification (86% sensitivity and 90% specificity). Jump height and hand grip strength were strongly correlated to leg press force (r = 0.82 and 0.59, respectively) and can also be used to identify fallers, although with slightly lower specificity. These results indicate that whole leg extension strength is associated with the ability to prevent a fall after a gait perturbation and might be used to identify the elderly at risk of falling.

Age-Related Deficits in Early Response Characteristics of Obstacle Avoidance Under Time Pressure

BACKGROUND

Obstacles in the travel path are a frequent cause of falls among elderly persons. In obstacle avoidance under time pressure, elderly persons have been reported to be less successful than young persons, but possible age-related deficits at the neuromuscular control level have not been studied yet.

METHODS

In the present study, obstacle avoidance reactions were investigated in 15 young and 9 older adults. While the participants walked on a treadmill, an obstacle was dropped in front of the left foot either in late stance, early swing, or mid-swing. Muscle activity in response to the obstacle was measured from the left biceps femoris (BF), rectus femoris (RF), tibialis anterior (TA), and medial head of gastrocnemius (GM). Avoidance success rates, as well as initial response latencies and response amplitudes over the first 50 ms of the response, were determined.

RESULTS

In both young and older adults, a large initial response was consistently observed in BF at very short latencies (104-111 ms in the young group), especially for mid-swing obstacle presentations (yielding the highest time pressure). Onset latencies in the elderly group were delayed by 10 ms on average. Response amplitudes were larger in young than in older adults, most prominently in BF and RF, but with a similar tendency in TA. Both onset latency and response amplitude were significantly associated with avoidance success rates.

CONCLUSIONS

The results of the present study suggest that age-related deficits in the neuromuscular control of obstacle avoidance could play a role in the large numbers of obstacle-related falls in the elderly population.

Proper assessment of the falling risk in the elderly by a physical mobility test with an obstacle

The Timed "Up & Go" (TUG) is a representative mobility test for assessing the falling risk of the elderly. Although several tests have been developed, including the TUG, these do not include a "tripping" element, and tripping is a major cause of falling. This study examined the influence of various obstacle heights on test performance in the TUG test and test-retest reliability. Twenty-two healthy elderly women participated in the TUG test and in the TUG test with an obstacle (TUGO). The obstacle is a box (width 120 cm and depth 20 cm), the height of which varies (0, 5 and 17 cm). In the 0-cm height condition, a thin sheet was laid down instead of the box. In the TUGO, subjects stood up from an armchair, walked 5 m, stepped over the box, turned, stepped over the box again, walked back to the chair and sat down. The reliability of the time required for the motion around the obstacle was high and the total time in the TUGO test increased (intra-class correlation coefficient = 0.74-0.99). These parameters were significantly larger for the height order 17, 5, and 0 cm and exhibited significant correlations with time required for the TUG (r = 0.61 - 0.92) and the height of subjects. An obstacle with 5 cm height prolonged the time during standing on one leg just before the obstacle and the time during turning motion after stepping over it. By adding the obstacle to the TUG, the physical mobility of the elderly is assessed more properly.

EMG modulation in anticipation of a possible trip during walking in young and older adults

This study investigated whether changes in lower limb muscle activity occurred in anticipation of a possible perturbation in 11 young (mean age 27 years) and 11 older (mean age 68 years) adults. Altered muscle activity could affect tripping responses and consequently the ecological validity of experimental results of studies on tripping. It was hypothesized that anticipatory muscle activity would be present immediately after a trip, and decrease after several subsequent unperturbed (forewarned) walking trials. Electromyograms of lower limb muscles were measured in 3 conditions: during normal walking, during forewarned walking immediately after a trip, and during forewarned walking several trials after a trip had occurred. Small but statistically significant differences in averaged muscle activity over a stride were found among conditions. Young adults showed slightly increased activity immediately after tripping (co-contraction) in hamstrings, quadriceps and tibialis anterior muscles. This increased activity diminished after several unperturbed trials, although it did not return to the baseline activity levels during normal walking. In older adults, an increased muscle activity among conditions was only discerned in tibialis anterior and soleus muscles. This suggested that older adults prefer to avoid contact with the obstacle over joint stiffening. Yet, for both age-groups, the increases in muscle activity were very small when compared to tripping responses reported in the literature. Therefore, anticipatory effects are not expected to jeopardize the validity of experiments in which subjects are perturbed more than once.

Biomechanical aspects of dynamic stability

Walking is a fundamental motor skill that significantly affects the level of independence in older adults. The amount of variability present in a walking pattern reflects the quality of neuromuscular control. It is well established that a large proportion of falls in older people occurs when walking. The prevention of falls is vital for minimizing disability, preventing injury, and impeding the development of frailty and subsequent deterioration in quality of life. The present literature review focuses on dynamic stability. In dynamic stability, both the base of support and the center of mass are in motion, and effective balance function is required. In general, older adults are expected to have different movement patterns from younger adults, expressed by differences in limb kinematics and kinetics. A better understanding of the biomechanical variables involved can help anticipate and prevent potential falls.