Age and sex influences on fall characteristics

Leg Press and Chest Press Power Normative Values by Half Decade in Older Women

ABSTRACT

Parrino, RL, Martinez, KJ, Konlian, JA, Conti, JM, and Signorile, JF. Leg press and chest press power normative values by half decade in older women. J Strength Cond Res 38(5): 991-998, 2024-Neuromuscular power is essential for the performance of most activities of daily living and the maintenance of functional independence throughout the aging process. Power declines rapidly in later life; however, this decline may be reduced or delayed with early detection and intervention. Therefore, this study provides leg press and chest press power normative values for older women. Women's power data for this analysis included 229 participants, 60-90 years of age. Power testing was conducted on Keiser A420 pneumatic leg press and chest press machines following a standardized protocol. Data were stratified into half-decade age groups and analyzed using a 1-way ANOVA. Descriptive statistics and quartile rankings are reported, and significant differences between age groups are outlined. There were significant differences in absolute and relative leg press peak power between the age groups ( p < 0.05). However, there were no significant differences in absolute or relative chest press peak power between the age groups. This research established normative values and quartile rankings for leg press and chest press power in older women 60-90 years of age, allowing comparative evaluations with patients and subjects by clinicians and researchers, respectively. These values should improve exercise interventions designed to improve power production by providing assessments of subjects' current status and allowing comprehensive monitoring of progress.

Mapping sex and gender differences in falls among older adults: A scoping review

BACKGROUND

There is growing recognition of the importance of sex and gender differences within falls literature, but the characterization of such literature is uncertain. The aim of this scoping review was to (1) map the nature and extent of falls literature examining sex or gender differences among older adults, and (2) identify gaps and opportunities for further research and practice.

METHODS

We used a scoping review methodology. Eligible studies included participants with a mean age of ≥ 60 years and study aims specifying falls and either sex or gender concepts. MEDLINE, Embase, CINAHL, Ageline, and Psychinfo databases were searched from inception to March 2, 2022. Records were screened and charted by six independent reviewers. Descriptive and narrative reports were generated.

RESULTS

A total of 15,266 records were screened and 74 studies were included. Most studies reported on sex and gender differences in fall risk factors (n = 52, 70%), incidence/prevalence (n = 26, 35%), fall consequences (n = 22, 30%), and fall characteristics (n = 15, 20%). The majority of studies (n = 70, 95%) found significant sex or gender differences in relation to falls, with 39 (53%) identifying significant sex differences and 31 (42%) identifying significant gender differences. However, only three (4%) studies defined sex or gender concepts and only nine (12%) studies used sex or gender terms appropriately. Fifty-six (76%) studies had more female participants than males. Four (5%) were intervention studies. Studies did not report falls in line with guidelines nor use common fall definitions.

CONCLUSION

Sex and gender differences are commonly reported in falls literature. It is critical for future research to use sex and gender terms appropriately and include similar sample sizes across all genders and sexes. In addition, there is a need to examine more gender-diverse populations and to develop interventions to prevent falls that address sex and gender differences among older adults.

A method for simulating forward falls and controlling impact velocity

Assessment of protective arm reactions associated with forward falls are typically performed by dropping research participants from a height onto a landing surface. The impact velocity is generally modulated by controlling the total height of the fall. This contrasts with an actual fall where the fall velocity is dependent on several factors in addition to fall height and not likely predictable at the onset of the fall. A counterweight and pulley system can be used to modulate the fall velocity in simulated forward falls in a manner that is not predictable to study participants, enhancing experimental validity. However, predicting the fall velocity based on participant height and weight and counterweight mass is not straightforward. In this article, the design of the FALL simulator For Injury prevention Training and assessment (FALL FIT) system is described. A dynamic model of the FALL FIT and counterweight system is developed and model parameters are fit using nonlinear optimization and experimental data. The fitted model enables prediction of fall velocity as a function of participant height and weight and counterweight load. The method can be used to provide controllable perturbations thereby elucidating the control strategy used when protecting the body from injury in a forward fall, how the control strategy changes because of aging or dysfunction or as a method for progressive protective arm reaction training.•Construction of device to simulate forward falls with controllable impact velocity using material that are commercially available is described•A dynamic model of the FALL FIT is developed to estimate the impact velocity of a simulated forward fall using participant height and counterweight load•The dynamic model is validated using data from 3 previous studies.

Validity and Reliability of the Seated Medicine Ball Throw as a Measure of Upper Body Power in Older Women

ABSTRACT

Strand, KL, Ly, AS, Barry, SS, Liscano, JA, Trebotich, TL, Martin-Diala, C, Martin, E, and Signorile, JF. Validity and reliability of the seated medicine ball throw as a measure of upper body power in older women. J Strength Cond Res 37(4): 902-908, 2023-In women, aging is associated with diminishing upper body power, which may increase the risk of falls and fall-related injury; however, the validity and reliability of clinical tests to evaluate upper body power need to be confirmed. The seated medicine ball throw (SMBT) is an upper body performance test used to monitor muscle function among older individuals. The purpose of this study was to evaluate the validity and test-retest reliability of the SMBT in older women. Thirty-five women (age = 75.15 ± 6.39 years) participated in this study. Subjects performed SMBT trials using common ball masses (SMBT 4lb and SMBT 3kg ) over 3 sessions. Familiarization with the SMBT and chest press 1 repetition maximum (CP 1RM ) was provided on the first day. On day 2, subjects repeated the tests, but data were recorded. On day 3, SMBT was retested followed by an evaluation of chest press peak power (CP PP ) values at 30-80% of CP 1RM . Significant correlations ( p ≤ 0.05) were found between the CP PP and SMBT 4lb ( r = 0.775, p < 0.001) and SMBT 3kg ( r = 0.734, p < 0.001), and SMBT distance showed expected declines with age ( r = -0.724 to -0.626, p < 0.001), demonstrating its validity. High reliability between testing days was found, and Bland-Altman plots showed few points that fell outside the limits of agreement. In conclusion, the SMBT is a valid and highly reliable tool that can be used by health professionals to monitor deficits in upper body muscular power to improve treatment protocols in older women.

Mortality Trends due to Falls in the Group of People in Early (65-74 Years) and Late (75+) Old Age in Poland in the Years 2000-2020

The aim of the study was to assess mortality trends due to falls in early (65-74 years) and late (75+) old age groups in Poland in 2000-2020. The study used a database of all deaths due to falls in two age groups. Per 100,000 men in early old age, the crude death rate (CDR) increased from 25.3 in 2000 to 25.9 in 2020. After 2012, a statistically significant decrease was observed (annual percentage change (APC) = -2.3%). Similar trends were noted for standardized death rates (SDR). Among men 75 years and older, the CDR values between the years 2000 and 2005 decreased (APC = -5.9%; p < 0.05), while after 2005, they increased (1.3%; p < 0.05). The SDR value decreased from 160.6 in 2000 to 118.1 in 2020. Among women aged 65-74, the CDRs values between 2000-2020 decreased from 13.9 and 8.2 per 100,000 women. The SDR value decreased from 14.0 to 8.3, respectively (2000-2007: APC = -7.2%; p < 0.05). Among women aged 75+, the CDR value decreased from 151.5 to 111.6 per 100,000 but after 2008, they began to increase (APC = 1.9%; p < 0.05). SDR decreased from 188.9 to 98.0 per 100,000 women. Further research on the mortality in falls is needed in order to implement preventive programs.

The timing and amplitude of the muscular activity of the arms preceding impact in a forward fall is modulated with fall velocity

Protective arm reactions have been shown to be an important injury avoidance mechanism in unavoidable falls. Protective arm reactions have been shown to be modulated with fall height, however it is not clear if they are modulated with impact velocity. The aim of this study was to determine if protective arm reactions are modulated in response to a forward fall with an initially unpredictable impact velocity. Forward falls were evoked via sudden release of a standing pendulum support frame with adjustable counterweight to control fall acceleration and impact velocity. Thirteen younger adults (1 female) participated in this study. Counterweight load explained more than 89% of the variation of impact velocity. Angular velocity at impact decreased (p < 0.001), drop duration increased from 601 ms to 816 ms (p < 0.001), and the maximum vertical ground reaction force decreased from 64%BW to 46%BW (p < 0.001) between the small and large counterweight. Elbow angle at impact (129 degrees extension), triceps (119 ms) and biceps (98 ms) pre-impact time, and co-activation (57%) were not significantly affected by counterweight load (p-values > 0.08). Average triceps and biceps EMG amplitude decreased from 0.26 V/V to 0.19 V/V (p = 0.004) and 0.24 V/V to 0.11 V/V (p = 0.002) with increasing counterweight respectively. Protective arm reactions were modulated with fall velocity by reducing EMG amplitude with decreasing impact velocity. This demonstrates a neuromotor control strategy for managing evolving fall conditions. Future work is needed to further understand how the CNS deals with additional unpredictability (e.g., fall direction, perturbation magnitude, etc.) when deploying protective arm reactions.

Machine-Learning-Based Human Fall Detection Using Contact- and Noncontact-Based Sensors

Automated human fall detection is an essential area of research due to its health implications in day-to-day life. Detecting and timely reporting of human falls may lead to saving human life. In this paper, fall detection has been targeted using machine-learning-based approaches from two perspectives regarding data sources, that is, contact-based and noncontact-based sensors. In both of these cases, various methods based on deep learning and machine learning techniques have been attempted, and their performances were compared. The approaches analyze data in fixed time windows and extract features in the time domain or spatial domain which obtain relative information between consecutive data samples. After experimentation, it was found that the proposed noncontact-based sensor techniques outperformed the contact-based sensor techniques by a margin of 1.82%. After this, it was also found that the noncontact-based sensor techniques outperformed the state of the art of noncontact-based sensor results by a margin of 3.15%. To better suit these techniques for real-world applications, embedded board implementation and privacy preservation of subject by using advanced methods such as compressive sensing and feature encoding need to be attempted.

Influence of loading conditions in finite element analysis assessed by HR-pQCT on ex vivo fracture prediction

Many fractures occur in individuals with normal areal Bone Mineral Density (aBMD) measured by Dual X-ray Absorptiometry (DXA). High Resolution peripheral Quantitative Computed Tomography (HR-pQCT) allows for non-invasive evaluation of bone stiffness and strength through micro finite element (μFE) analysis at the tibia and radius. These μFE outcomes are strongly associated with fragility fractures but do not provide clear enhancement compared with DXA measurements. The objective of this study was to establish whether a change in loading conditions in standard μFE analysis assessed by HR-pQCT enhance the discrimination of low-trauma fractured radii (n = 11) from non-fractured radii (n = 16) obtained experimentally throughout a mechanical test reproducing a forward fall. Micro finite element models were created using HR-pQCT images, and linear analyses were performed using four different types of loading conditions (axial, non-axial with two orientations and torsion). No significant differences were found between the failure load assessed with the axial and non-axial models. The different loading conditions tested presented the same area under the receiver operating characteristic (ROC) curves of 0.79 when classifying radius fractures with an accuracy of 81.5%. In comparison, the area under the curve (AUC) is 0.77 from DXA-derived ultra-distal aBMD of the forearm with an accuracy of 85.2%. These results suggest that the restricted HR-pQCT scanned region seems not sensitive to loading conditions for the prediction of radius fracture risk based on ex vivo experiments (n = 27).

In vivo soft tissue compressive properties of the human hand

Background/Purpose

Falls onto outstretched hands are the second most common sports injury and one of the leading causes of upper extremity injury. Injury risk and severity depends on forces being transmitted through the palmar surface to the upper extremity. Although the magnitude and distribution of forces depend on the soft tissue response of the palm, the in vivo properties of palmar tissue have not been characterized. The purpose of this study was to characterize the large deformation palmar soft tissue properties.

Methods

In vivo dynamic indentations were conducted on 15 young adults (21–29 years) to quantify the soft tissue characteristics of over the trapezium. The effects of loading rate, joint position, tissue thickness and sex on soft tissue responses were assessed.

Results

Energy absorbed by the soft tissue and peak force were affected by loading rate and joint angle. Energy absorbed was 1.7–2.8 times higher and the peak force was 2–2.75 times higher at high rate loading than quasistatic rates. Males had greater energy absorbed than females but not at all wrist positions. Damping characteristics were the highest in the group with the thickest soft tissue while damping characteristics were the lowest in group with the thinnest soft tissues.

Conclusion

Palmar tissue response changes with joint position, loading rate, sex, and tissue thickness. Accurately capturing these tissue responses is important for developing effective simulations of fall and injury biomechanics and assessing the effectiveness of injury prevention strategies.

A study on the impact of the users' characteristics on the performance of wearable fall detection systems

Wearable Fall Detection Systems (FDSs) have gained much research interest during last decade. In this regard, Machine Learning (ML) classifiers have shown great efficiency in discriminating falls and conventional movements or Activities of Daily Living (ADLs) based on the analysis of the signals captured by transportable inertial sensors. Due to the intrinsic difficulties of training and testing this type of detectors in realistic scenarios and with their target audience (older adults), FDSs are normally benchmarked against a predefined set of ADLs and emulated falls executed by volunteers in a controlled environment. In most studies, however, samples from the same experimental subjects are used to both train and evaluate the FDSs. In this work, we investigate the performance of ML-based FDS systems when the test subjects have physical characteristics (weight, height, body mass index, age, gender) different from those of the users considered for the test phase. The results seem to point out that certain divergences (weight, height) of the users of both subsets (training ad test) may hamper the effectiveness of the classifiers (a reduction of up 20% in sensitivity and of up to 5% in specificity is reported). However, it is shown that the typology of the activities included in these subgroups has much greater relevance for the discrimination capability of the classifiers (with specificity losses of up to 95% if the activity types for training and testing strongly diverge).

Does functional performance and upper body strength predict upper extremity reaction and movement time in older women?

BACKGROUND

Reaction time to initiate upper limb movement and movement time to place hands on the landing surface may be important factors in forward fall landing and impact, contributing to injury reduction. The aim was to investigate the relationship of physical function and upper body strength to upper limb reaction and movement time in older female participants.

METHODS

75 female participants (72 ± 8 yrs) performed 5 arm response trials. Reaction time (signal to initiation of movement), and movement time (initial movement to contact), were collected using 3D motion capture. Additional variables were: handgrip; sit-to-stand; shoulder flexion and elbow extension strength measured by hand-held dynamometry; one-legged balance; fall risk; and physical activity scores. Prediction variables for reaction and movement time were determined in separate backward selection multiple regression analyses. Significance was set at P < 0.05.

FINDINGS

Significant regression equations for RT (r² = 0.08, P = 0.013) found a relationship between stronger handgrip (Beta = -0.002) and faster reaction time, accounting for 8% variance. For movement time (r² = 0.06, P = 0.036) greater shoulder flexion strength (Beta = -0.04) was related to faster movement time, explaining 6% variance. Stronger SF strength was related to a decrease in MT by 4%.

DISCUSSION

A relationship between arm strength measures and faster upper body reaction and movement time was shown, with 10-20% higher strength associated with a 5% faster response time. Even though this was a relatively weak relationship, given that strength is a modifiable component this provides a potential avenue for future intervention efforts. This in turn could have an impact on forward fall landing and potential reduction of injury risk.

Feasibility of Using Floor Vibration to Detect Human Falls

With the increasing aging population in modern society, falls as well as fall-induced injuries in elderly people become one of the major public health problems. This study proposes a classification framework that uses floor vibrations to detect fall events as well as distinguish different fall postures. A scaled 3D-printed model with twelve fully adjustable joints that can simulate human body movement was built to generate human fall data. The mass proportion of a human body takes was carefully studied and was reflected in the model. Object drops, human falling tests were carried out and the vibration signature generated in the floor was recorded for analyses. Machine learning algorithms including K-means algorithm and K nearest neighbor algorithm were introduced in the classification process. Three classifiers (human walking versus human fall, human fall versus object drop, human falls from different postures) were developed in this study. Results showed that the three proposed classifiers can achieve the accuracy of 100, 85, and 91%. This paper developed a framework of using floor vibration to build the pattern recognition system in detecting human falls based on a machine learning approach.

Fall inducing movable platform (FIMP) for overground trips and slips

Background

The study of falls and fall prevention/intervention devices requires the recording of true falls incidence. However, true falls are rare, random, and difficult to collect in real world settings. A system capable of producing falls in an ecologically valid manner will be very helpful in collecting the data necessary to advance our understanding of the neuro and musculoskeletal mechanisms underpinning real-world falls events.

Methods

A fall inducing movable platform (FIMP) was designed to arrest or accelerate a subject’s ankle to induce a trip or slip. The ankle was arrested posteriorly with an electromagnetic brake and accelerated anteriorly with a motor. A power spring was connected in series between the ankle and the brake/motor to allow freedom of movement (system transparency) when a fall is not being induced. A gait phase detection algorithm was also created to enable precise activation of the fall inducing mechanisms. Statistical Parametric Mapping (SPM1D) and one-way repeated measure ANOVA were used to evaluate the ability of the FIMP to induce a trip or slip.

Results

During FIMP induced trips, the brake activates at the terminal swing or mid swing gait phase to induce the lowering or skipping strategies, respectively. For the lowering strategy, the characteristic leg lowering and subsequent contralateral leg swing was seen in all subjects. Likewise, for the skipping strategy, all subjects skipped forward on the perturbed leg. Slip was induced by FIMP by using a motor to impart unwanted forward acceleration to the ankle with the help of friction-reducing ground sliding sheets. Joint stiffening was observed during the slips, and subjects universally adopted the surfing strategy after the initial slip.

Conclusion

The results indicate that FIMP can induce ecologically valid falls under controlled laboratory conditions. The use of SPM1D in conjunction with FIMP allows for the time varying statistical quantification of trip and slip reactive kinematics events. With future research, fall recovery anomalies in subjects can now also be systematically evaluated through the assessment of other neuromuscular variables such as joint forces, muscle activation and muscle forces.

Fall-related measures in elderly individuals and Parkinson's disease subjects

Falls pose a serious problem in elderly and clinical populations. Most often, they lead to a loss of mobility and independence. They might also be an indirect cause of death. The aim of this study was to determine an objective predictor of the fear of falling and falls in elderly subjects (ESs) and Parkinson's disease (PD) subjects. Thirty-two ESs were examined in this study, of whom sixteen were diagnosed with PD. The testing procedures comprised force plate measurements (limit of stability test-LOS test) and clinical tests (Berg Balance Scale, Functional Reach Test, Timed Up and Go test, Tinetti test). The Falls Efficacy Scale International (FES-I) was used to evaluate the fear of falling. The range of the maximum forward lean was normalized to the length from the ankle joint to the head of the first metatarsal bone and was named the functional forward stability indicator (FFSI). The FFSI, derived from the LOS test, allowed us to demonstrate the real deficit in functional stability and individual safety margins. Moreover, the FFSI was highly correlated with the FES-I score and almost all clinical test results in elderly subjects (r>0,6; p<0.05). In PD subjects, the FFSI was poorly correlated with the fear of falling, the BBS score and the FR distance; however, a high correlation with the Tinetii test (r>0,6, p<0.05) was noted. The PD subjects presented a different balance strategy when close to their stability limits, which was also reflected in the lower values of sample entropy (t = (-2.40); p<0.05; d = 0.87). The FFSI might be a good predictor of the fear of falling in the group of elderly people. Additionally, the FFSI allows us to show real balance deficits both in PD subjects and in their healthy peers without the need for a reference group and norms. In conclusion, it is postulated that the popular clinical assessments of postural balance in PD subjects should be accompanied by reliable posturography measurements.

Clarifying differences in injury patterns between ground-level falls and falls from heights among the elderly in Japan

OBJECTIVES

With the progress of aging, fall injuries have become a global public health issue. This research was conducted to describe in detail situations of injury occurrence among the elderly by distinguishing between falls from heights and ground-level falls. We assume that different fall mechanisms occur in different situations and result in a wide range of consequences.

STUDY DESIGN

This is a registry-based descriptive study.

METHODS

The analysis included 55,126 patients with fall injuries, aged 65 years and more, having an Injury Severity Score (ISS) ≧9, and registered in a trauma registry in Japan between 2004 and 2015. We described patients' distribution in terms of age, severity, outcome, season, time, and injured body parts by gender and fall mechanisms.

RESULTS

Falls from heights (n = 15,748) were more common among men and those younger than 75 years. Ground-level falls (n = 39,378) were more common among women and those older than 75 years. The ISS was high in men and for those who fell from heights. Falls from heights were common in autumn, whereas ground-level falls were common in winter. Both mechanisms occurred frequently during the daytime. The head and lower extremities were the most commonly injured parts for those who fell from heights and ground-level falls, respectively. Injuries to the head, chest, spine, upper extremities, and pelvis were common among those who fell from heights. Injuries to the lower extremities were common in ground-level fallers. Among those who fell from heights, women had more frequent lower extremity injuries than did men. Among ground-level fallers, men had more frequent head injuries than did women. The highest case-fatality rate was recorded for abdominal injuries among those who fell from heights and head injuries among ground-level fallers. In both mechanisms of injury, the case-fatality rate of limbs was the lowest.

CONCLUSIONS

Our study showed different patterns between falls from heights and ground-level falls, whereas previous studies rarely distinguished between these two fall mechanisms.

Concomitant hip and upper extremity fracture in elderly patients: Prevalence and clinical implications

BACKGROUND

Hip fracture and upper extremity fracture are most important age-related fracture. However, there have been few reports about the analysis of prevalence or risk factors with concomitant hip and upper extremity fractures. This study aimed to describe the prevalence and clinical implications of the concomitant hip and upper extremity fractures in elderly.

METHODS

We evaluate 1018 patients aged >65 years who were surgically treated for femoral neck or intertrochanteric fractures between March 2008 and December 2018. 35 patients (3.4%) with a hip fracture combined upper extremity fracture. All patients were classified into the isolated hip fracture and the concomitant fracture. We analyzed these patients' characteristics such as age, gender, bone mineral density (BMD), body mass index (BMI), Korean version of Mini-Mental State Examination (MMSE-K), injury mechanism, and length of hospital stay.

RESULTS

The most common site of upper extremity fracture was distal radius fracture of 15 patients (42.8%), followed by proximal humeral fracture of 8 (22.8%). Concomitant fractures occurred on the same side in 30 patients (85.7%). The mean age of patients with a concomitant fracture was younger than that of patients with an isolated hip fracture (p < 0.05). Mean preinjury MMSE-K was 22.7 in isolated hip fracture and 25.6 in concomitant fracture patients (p < 0.05). Mean length of hospital stay was statistically significant different between two groups (p < 0.05). According to fracture site of hip, there was no statistically different prevalence of upper extremity fracture in femoral intertrochanteric fracture compared to the neck fracture.

CONCLUSION

We found a 3.4% prevalence of concomitant hip and upper extremity fractures. It was found that the younger the age with preserved cognitive ability in elderly patients with a hip fracture, the higher the prevalence of upper extremity fracture. In addition, it is important to keep in mind that patients with a concomitant fracture have a longer hospital stay and difficulty in rehabilitation.

A vision-based approach for fall detection using multiple cameras and convolutional neural networks: A case study using the UP-Fall detection dataset

The automatic recognition of human falls is currently an important topic of research for the computer vision and artificial intelligence communities. In image analysis, it is common to use a vision-based approach for fall detection and classification systems due to the recent exponential increase in the use of cameras. Moreover, deep learning techniques have revolutionized vision-based approaches. These techniques are considered robust and reliable solutions for detection and classification problems, mostly using convolutional neural networks (CNNs). Recently, our research group released a public multimodal dataset for fall detection called the UP-Fall Detection dataset, and studies on modality approaches for fall detection and classification are required. Focusing only on a vision-based approach, in this paper, we present a fall detection system based on a 2D CNN inference method and multiple cameras. This approach analyzes images in fixed time windows and extracts features using an optical flow method that obtains information on the relative motion between two consecutive images. We tested this approach on our public dataset, and the results showed that our proposed multi-vision-based approach detects human falls and achieves an accuracy of 95.64% compared to state-of-the-art methods with a simple CNN network architecture.

Evaluation of Inertial Sensor-Based Pre-Impact Fall Detection Algorithms Using Public Dataset

In this study, pre-impact fall detection algorithms were developed based on data gathered by a custom-made inertial measurement unit (IMU). Four types of simulated falls were performed by 40 healthy subjects (age: 23.4 ± 4.4 years). The IMU recorded acceleration and angular velocity during all activities. Acceleration, angular velocity, and trunk inclination thresholds were set to 0.9 g, 47.3°/s, and 24.7°, respectively, for a pre-impact fall detection algorithm using vertical angles (VA algorithm); and 0.9 g, 47.3°/s, and 0.19, respectively, for an algorithm using the triangle feature (TF algorithm). The algorithms were validated by the results of a blind test using four types of simulated falls and six types of activities of daily living (ADL). VA and TF algorithms resulted in lead times of 401 ± 46.9 ms and 427 ± 45.9 ms, respectively. Both algorithms were able to detect falls with 100% accuracy. The performance of the algorithms was evaluated using a public dataset. Both algorithms detected every fall in the SisFall dataset with 100% sensitivity). The VA algorithm had a specificity of 78.3%, and TF algorithm had a specificity of 83.9%. The algorithms had higher specificity when interpreting data from elderly subjects. This study showed that algorithms using angles could more accurately detect falls. Public datasets are needed to improve the accuracy of the algorithms.

Biomechanical and physiological age differences in a simulated forward fall on outstretched hands in women

BACKGROUND

Falling on the outstretched hands, a protective mechanism to arrest the body and avoid injury, requires upper limb and trunk motor control for effective body descent. Older women are particularly susceptible to injury from a forward fall, but the biomechanical and physiological (e.g., muscle strength) factors related to this increased risk are poorly understood. Determining age differences in the modifiable neuromuscular factors related to a forward fall landing and descent could help to inform injury prevention strategies. The purpose was to investigate age related differences in upper extremity strength and fall arrest strategy differences during a simulated fall and to evaluate the relationships between muscle strength and biomechanical variables.

METHODS

Nineteen younger (mean age 23.0 yrs., SD 3.8) and 16 older (mean age 68.2 yrs., SD 5.3) women performed five trials of simulated falls. Biomechanical measures and electromyographic muscle activity were recorded during the descents. Concentric, isometric and eccentric strength of the non-dominant upper limb was measured via a dynamometer using a customized protocol.

FINDINGS

Older women demonstrated lower concentric elbow extension strength compared to younger women (p = 0.002). Landing strategies differed where younger women had significantly greater elbow joint angle (p = 0.006) and velocity (p = 0.02) at impact. Older women demonstrated diminished capacity to absorb energy and control descent on outstretched hands compared to younger women (p = 0.001).

INTERPRETATION

The landing strategy used by older women along with decreased energy absorption may increase risk of fall-related injury and increase the likelihood of trunk or head impact with the ground.

Does Fall Arrest Strategy Training Added to a Fall Prevention Programme Improve Balance, Strength, and Agility in Older Women? A Pilot Study

Purpose: The purpose of this study was to determine the effect of a unique exercise programme (Fall Arrest Strategy Training, or FAST) on upper body strength, range of motion (ROM), and fall risk in older women. FAST was designed to improve upper body capacity to prevent injury when a fall cannot be avoided. Method: A quasi-randomized site design included 71 older women (aged 67-95 y, mean age 83 years), who participated either in a standard fall prevention programme (Staying on Your Feet, or SOYF; n=29) or in SOYF combined with FAST (n=42). The women were measured three times-at baseline, after the 12-week intervention, and again 12 weeks later-for upper body strength, ROM, and fall risk factors (fall risk questionnaire, balance, mobility, and leg strength). Results: No significant differences were found in age, physical activity, or cognitive or functional status between the SOYF-standard and the SOYF-FAST groups. Both groups improved their fall risk status after the intervention, with no significant differences between them; however, the SOYF-FAST group showed greater improvements in upper extremity strength and ROM (p=0.007). Conclusion: FAST can feasibly be integrated into fall prevention programming, with additional gains in upper body strength and ROM in older women.

Sideways fall-induced impact force and its effect on hip fracture risk: a review

Osteoporotic hip fracture, mostly induced in falls among the elderly, is a major health burden over the world. The impact force applied to the hip is an important factor in determining the risk of hip fracture. However, biomechanical researches have yielded conflicting conclusions about whether the fall-induced impact force can be accurately predicted by the available models. It also has been debated whether or not the effect of impact force has been considered appropriately in hip fracture risk assessment tools. This study aimed to provide a state-of-the-art review of the available methods for predicting the impact force, investigate their strengths/limitations, and suggest further improvements in modeling of human body falling.

METHODS

We divided the effective parameters on impact force to two categories: (1) the parameters that can be determined subject-specifically and (2) the parameters that may significantly vary from fall to fall for an individual and cannot be considered subject-specifically.

RESULTS

The parameters in the first category can be investigated in human body fall experiments. Video capture of real-life falls was reported as a valuable method to investigate the parameters in the second category that significantly affect the impact force and cannot be determined in human body fall experiments.

CONCLUSIONS

The analysis of the gathered data revealed that there is a need to develop modified biomechanical models for more accurate prediction of the impact force and appropriately adopt them in hip fracture risk assessment tools in order to achieve a better precision in identifying high-risk patients. Graphical abstract Impact force to the hip induced in sideways falls is affected by many parameters and may remarkably vary from subject to subject.

Female Age-Related Differences in Biomechanics and Muscle Activity During Descents on the Outstretched Arms

The purposes of this study were to examine female age differences in: (1) upper extremity (UE) and trunk muscle activity, elbow joint moment, loading force, and UE energy absorption during a controlled forward body descent; and (2) UE muscle strength. Twenty young (mean 24.8 ± 3.4 years) and 20 older (68.4 ± 5.7 years) women were assessed via dynamometry for isometric, concentric, and eccentric UE strength and performed forward descents on force plates at three body lean angles (60°, 45°, and 30° from horizontal). Significant differences (p < .05) were found for muscle strength, biomechanics, and muscle activity. Concentric UE strength averaged 15% lower in older women. At 30° body lean, older women absorbed less energy. Older women had greater biceps brachii activation and less external oblique activation at all body lean angles. Age differences in muscle strength, activation, and energy absorption may contribute to fall-related injury risk.

Arm reactions in response to an unexpected slip-Impact of aging

Slips and falls represent a serious public safety concern in older adults, with the segment of the United States population over the age of 65 accounting for about three quarters of all fall related deaths. The majority of falls in older adults are due to trips and slips. The objective of this study was to investigate how age affects arm reactions generated in response to unexpected slips. Thirty-three participants divided into two age groups (16 young, 17 old) participated in this study. Participants were exposed to two conditions: known dry walking (baseline) and an unexpected slip initiated when stepping onto a glycerol-contaminated floor. The upper extremity parameters of interest included the timing and amplitude of the shoulder flexion moment generated in response to the slip as well as the resulting angular kinematics (trajectories). The analysis of the kinetic data revealed a delayed shoulder flexion reaction to slips in older adults compared to their young counterparts, as well as a greater flexion moment magnitude. Knowledge of such upper body reaction mechanisms to unexpected slips may help to improve balance recovery training in older adults, as well as aid in the implementation of environmental modifications, e.g. handrails, to reduce falls-related injuries.

Single and multiple step balance recovery responses can be different at first step lift-off following lateral waist-pull perturbations in older adults

An inability to recover lateral balance with a single step is predictive of future falls in older adults. This study investigated if balance stability at first step lift-off (FSLO) would be different between multiple and single stepping responses to lateral perturbations. 54 healthy older adults received left and right waist-pulls at 5 different intensities (levels 1-5). Crossover stepping responses at and above intensity level 3 that induced both single and multiple steps were analyzed. Whole-body center of mass (COM) and center of pressure (COP) positions in the medio-lateral direction with respect to the base of support were calculated. An inverted pendulum model was used to define the lateral stability boundary, which was also adjusted using the COP position at FSLO (functional boundary). No significant differences were detected in the COP positions between the responses at FSLO (p≥0.075), indicating no difference in the functional boundaries between the responses. Significantly smaller stability margins were observed at first step landing for multiple steps at all levels (p≤0.024), while stability margins were also significantly smaller at FSLO for level 3 and 4 (p≤0.048). These findings indicate that although reduced stability at first foot contact would be associated with taking additional steps, stepping responses could also be attributable to the COM motion state as early as first step lift-off, preceding foot contact. Perturbation-based training interventions aimed at improving the reactive control of stability would reduce initial balance instability at first step lift-off and possibly the consequent need for multiple steps in response to balance perturbations.

SisFall: A Fall and Movement Dataset

Research on fall and movement detection with wearable devices has witnessed promising growth. However, there are few publicly available datasets, all recorded with smartphones, which are insufficient for testing new proposals due to their absence of objective population, lack of performed activities, and limited information. Here, we present a dataset of falls and activities of daily living (ADLs) acquired with a self-developed device composed of two types of accelerometer and one gyroscope. It consists of 19 ADLs and 15 fall types performed by 23 young adults, 15 ADL types performed by 14 healthy and independent participants over 62 years old, and data from one participant of 60 years old that performed all ADLs and falls. These activities were selected based on a survey and a literature analysis. We test the dataset with widely used feature extraction and a simple to implement threshold based classification, achieving up to 96% of accuracy in fall detection. An individual activity analysis demonstrates that most errors coincide in a few number of activities where new approaches could be focused. Finally, validation tests with elderly people significantly reduced the fall detection performance of the tested features. This validates findings of other authors and encourages developing new strategies with this new dataset as the benchmark.

Falls and Wrist Fracture: Relationship to Women's Functional Status after Age 50

Women experience a rapid rise in the incidence of wrist fracture after age 50. Accordingly, this study aimed to (1) determine the internal and environmental fall-related circumstances resulting in a wrist fracture, and (2) examine the relationship of functional status to these circumstances. Women aged 50 to 94 years reported on the nature of the injury (n = 99) and underwent testing for physical activity status, balance, strength, and mobility (n = 72). The majority of falls causing wrist fracture occurred outdoors, during winter months, as a result of a slip or trip while walking. Half of these falls resulted in other injuries including head, neck, and spine injuries. Faster walking speed, lower grip strength, and higher balance confidence were significantly associated with outdoor versus indoor falls and slips and trips versus other causes. This study provides insights into potential screening and preventive measures for fall-related wrist fractures in women.

Association between male sex and increased mortality after falls

OBJECTIVES

Whether sex affects the mortality of trauma patients remains unknown. The hypothesis of this study was that sex was associated with altered mortality rates in trauma.

METHODS

A retrospective review of trauma patients' records in the Japan Trauma Data Bank was conducted (n = 80,813) from 185 major emergency hospitals across Japan. The primary outcome variable was in-hospital mortality within 28 days. Secondary outcome variables included serious injuries to different body regions with an Abbreviated Injury Scale of ≥3.

RESULTS

In the analysis of 80,813 trauma patients, males had significantly greater 28-day mortality compared to females (adjusted p = 0.0072, odds ratio [OR] = 1.14, 95% confidence interval [CI] = 1.06 to 1.23) via logistic regression analysis adjusted for age, mechanism, Injury Severity Score, Revised Trauma Score, and potential preexisting risk factors. Of 10 injury categories examined, sex significantly affected in-hospital 28-day mortality rate in falls (adjusted p < 0.0001, OR = 1.34, 95% CI = 1.19 to 1.52). Further analysis of three fall subcategories by falling distance revealed that male patients who fell from ground level had significantly higher 28-day mortality (adjusted p < 0.0001, OR = 1.75, 95% CI = 1.43 to 2.14) and a significantly greater frequency of serious injury to the head, thorax, abdomen, and spine, but a lower frequency of serious injury to the extremities, compared to female patients.

CONCLUSIONS

Compared to female trauma patients, male trauma patients had greater 28-day mortality. In particular, ground-level falls had a significant sex difference in mortality, with serious injury to different body regions. Sex differences appeared to be important for fatalities from ground-level falls.

Older adults who have previously fallen due to a trip walk differently than those who have fallen due to a slip

Studying the relationships between centre of mass (COM) and centre of pressure (COP) during walking has been shown to be useful in determining movement stability. The aim of the current study was to compare COM-COP separation measures during walking between groups of older adults with no history of falling, and a history of falling due to tripping or slipping. Any differences between individuals who have fallen due to a slip and those who have fallen due to a trip in measures of dynamic balance could potentially indicate differences in the mechanisms responsible for falls. Forty older adults were allocated into groups based on their self-reported fall history during walking. The non-faller group had not experienced a fall in at least the previous year. Participants who had experienced a fall were split into two groups based on whether a trip or slip resulted in the fall(s). A Vicon system was used to collect full body kinematic trajectories. Two force platforms were used to measure ground reaction forces. The COM was significantly further ahead of the COP at heel strike for the trip (14.3 ± 2.7 cm) and slip (15.3 ± 1.1 cm) groups compared to the non-fallers (12.0 ± 2.7 cm). COM was significantly further behind the COP at foot flat for the slip group (-14.9 ± 3.6 cm) compared to the non-fallers (-10.3 ± 3.9 cm). At mid-swing, the COM of the trip group was ahead of the COP (0.9 ± 1.6 cm), whereas for the slip group the COM was behind the COP (-1.2 ± 2.2 cm). These results show identifiable differences in dynamic balance control of walking between older adults with a history of tripping or slipping and non-fallers.

Functional limitations as potential mediators of the effects of self-reported vision status on fall risk of older adults

OBJECTIVE

To test whether limitations in mobility and large-muscle functioning mediate self-reported vision status to increase fall risk among respondents age 65 and above.

METHOD

This study used two waves from the Health and Retirement Study. We conducted binary logistic and negative binomial regression analyses to test indirect paths leading from self-reported vision status to falls, via indices of mobility and large-muscle functioning.

RESULTS

Limited evidence was found for a mediating effect among women; however, large-muscle groups were implicated as partially mediating risk factors for falls among men with fair self-reported vision status.

DISCUSSION

Implications of these findings are discussed including the need for prioritizing improved muscle strength of older men and women with poor vision as a preventive measure against falls.

Use of local intelligence to reduce energy consumption of wireless sensor nodes in elderly health monitoring systems

The percentage of elderly people in European countries is increasing. Such conjuncture affects socio-economic structures and creates demands for resourceful solutions, such as Ambient Assisted Living (AAL), which is a possible methodology to foster health care for elderly people. In this context, sensor-based devices play a leading role in surveying, e.g., health conditions of elderly people, to alert care personnel in case of an incident. However, the adoption of such devices strongly depends on the comfort of wearing the devices. In most cases, the bottleneck is the battery lifetime, which impacts the effectiveness of the system. In this paper we propose an approach to reduce the energy consumption of sensors' by use of local sensors' intelligence. By increasing the intelligence of the sensor node, a substantial decrease in the necessary communication payload can be achieved. The results show a significant potential to preserve energy and decrease the actual size of the sensor device units.

Energy Saving in Forward Fall Detection using Mobile Accelerometer

Fall injury is one of the biggest risks to health and well-being of the elderly especially in independent living because falling accidents may cause instant death. There are many research interests aimed to detect fall incidents. Fall detection is envisioned critical on ICT-assisted healthcare future. In addition, mobile battery is currently another serious problem in which performance feasibility is considered as a standard to verify an effective method. In this paper, the authors study forward fall detection method from mobile phone perspective using accelerometer only without sacrificing accuracy to save energy. Using peak threshold algorithm in axes of mobile accelerometer, transition from activity of daily living (ADL) to forward fall event is recognized. In collected templates, Dynamic Time Warping (DTW) was applied to compute difference among them with new unlabeled samples. Results implemented on mobile phone easily show the feasibility of the method hence contribute significantly to fall detection in healthcare.

Design and evaluation of a new mechatronic platform for assessment and prevention of fall risks

Background

Studying the responses in human behaviour to external perturbations during daily motor tasks is of key importance for understanding mechanisms of balance control and for investigating the functional response of targeted subjects. Experimental platforms as far developed entail a low number of perturbations and, only in few cases, have been designed to measure variables used at run time to trigger events during a certain motor task.

Methods

This work introduces a new mechatronic device, named SENLY, that provides balance perturbations while subjects carry out daily motor tasks (e.g., walking, upright stance). SENLY mainly consists of two independently-controlled treadmills that destabilize balance by suddenly perturbing belts movements in the horizontal plane. It is also provided with force sensors, which can be used at run time to estimate the ground reaction forces and identify events along the gait cycle in order to trigger the platform perturbation. The paper also describes the customized procedures adopted to calibrate the platform and the first testing trials aimed at evaluating its performance.

Results

SENLY allows to measure both vertical ground reaction forces and their related location more precisely and more accurately than other platforms of the same size. Moreover, the platform kinematic and kinetic performance meets all required specifications, with a negligible influence of the instrumental noise.

Conclusion

A new perturbing platform able to reproduce different slipping paradigms while measuring GRFs at run time in order to enable the asynchronous triggering during the gait cycle was designed and developed. Calibration procedures and pilot tests show that SENLY allows to suitably estimate dynamical features of the load and to standardize experimental sessions, improving the efficacy of functional analysis.

Orthopaedic injuries associated with hip fractures in those aged over 60 years: a study of patterns of injury and outcomes for 1971 patients

INTRODUCTION

There has been little research into the consequence of suffering a hip fracture and associated orthopaedic injures. The aim of this research paper is to describe the patient characteristics, patterns of injury and to define the effect on outcomes of orthopaedic injuries occurring simultaneously with hip fractures.

PATIENTS AND METHODS

Hip fracture data was collected prospectively. Patients under 60 years of age were excluded from the study. Between 2004 and 2010 we treated 1971 consecutive patients aged 60 years or older with a hip fracture.

RESULTS

81 (4.1%) patients sustained a simultaneous fracture or dislocation. 90% (73/81) of these injuries were in the upper limb and 88% (71/81) were ipsilateral, with the wrist (34 cases) and the proximal humerus (21 cases) being the commonest site of injury. Median hospital stay was significantly longer for those with additional injures. Pubic rami fractures were not seen in association with a hip fracture. Those patients who sustained a concomitant wrist fracture tended to be slightly fitter than those without associated injuries whist those with an associated humeral fracture were slightly frailer. Mortality was increased for those with an associated proximal humeral fracture but was lower with an associated wrist fracture.

DISCUSSION AND CONCLUSION

Simultaneous injuries occurring with hip fractures are mainly seen in the ipsilateral upper limb. They present a greater challenge to the multidisciplinary team than a solitary hip fracture, experiencing a longer hospital stay and inevitably a higher financial cost. Those patients with wrist fractures have the best prognosis in terms of mortality, whereas a proximal humerus fracture may indicate a higher risk of mortality.

ENERGY ANALYSIS OF DIFFERENT TRUNK TILTING ANGLES ON JOINT LOADING DURING FALL ON AN OUTSTRETCHED HAND

From previous researches, studies on the forward fall had focused on the relationship between the joint loading and position of the forearm and elbow. Previous studies also stressed the importance of energy absorption by the shoulder and elbow during the forward fall. However, the effects of different tilting angles on joint loading of the upper extremity had not been presented. This study investigated the effects of different tilting angles on joint loading of the upper extremity during fall on an outstretched hand. The absorbed energy at Ts, T1, T2 and Te were analyzed. Ten healthy young males were selected in this study. Subjects were adjusted to different trunk tilting angles of 0°, 10°, 20° and 30°with a custom-made suspension system with an outstretched hand of 5 cm height above the ground. The expert vision motion system with 6 CCD cameras and one force plate were used to collect kinetics and kinematics data. The results showed that shoulder would absorb the most impact energy and followed by wrist and elbow. The time period at T2 to Te absorbed more energy in every joint.

Two types of slip-induced falls among community dwelling older adults

Little is known about the landing behavior of the trailing (recovery) foot and ensuing types of falls following a forward slip in walking. The purposes of this study were to (1) determine if community-dwelling older adults experienced bilateral slips at the same rate as had been previously observed for young adults during over-ground walking; (2) determine if fall rate in older adults was dependent on slip type (unilateral vs. bilateral); and (3) identify differences in spatiotemporal variables of the trailing leg step between unilateral and bilateral slips. One-hundred-seventy-four participants experienced an unannounced, unrehearsed slip while walking on a 7-m walkway. Each trial was monitored with a motion capture system and bilateral ground reaction force plates. Although the experimental design, developed with original data from a young adult population, favored bilateral slips, more older adults (35%) than anticipated (10% previously observed in young, p<0.001) displayed a unilateral slip. The probability of fall was equal in the two types of slips. Eighty-two people recovered from the slip, while the remaining 92 (53%) fell. These 92 were classified into two exclusive categories based on the heel distance at the time of fall arrest using cluster analysis: those which resembled a fall into a "splits" position (n=47) or a feet-forward fall (n=45). All (100%) unilateral slips led to splits falls, as expected. Yet, not all bilateral slips (only 83%) resulted in feet-forward falls. A longer forward recovery step with a prolonged step time led to both feet slipping, nearly together, hence a feet-forward fall.

Detection of falls using accelerometers and mobile phone technology

OBJECTIVES

to study the sensitivity and specificity of fall detection using mobile phone technology.

DESIGN

an experimental investigation using motion signals detected by the mobile phone.

SETTING AND PARTICIPANTS

the research was conducted in a laboratory setting, and 18 healthy adults (12 males and 6 females; age = 29 ± 8.7 years) were recruited.

MEASUREMENT

each participant was requested to perform three trials of four different types of simulated falls (forwards, backwards, lateral left and lateral right) and eight other everyday activities (sit-to-stand, stand-to-sit, level walking, walking up- and downstairs, answering the phone, picking up an object and getting up from supine). Acceleration was measured using two devices, a mobile phone and an independent accelerometer attached to the waist of the participants.

RESULTS

Bland-Altman analysis shows a higher degree of agreement between the data recorded by the two devices. Using individual upper and lower detection thresholds, the specificity and sensitivity for mobile phone were 0.81 and 0.77, respectively, and for external accelerometer they were 0.82 and 0.96, respectively.

CONCLUSION

fall detection using a mobile phone is a feasible and highly attractive technology for older adults, especially those living alone. It may be best achieved with an accelerometer attached to the waist, which transmits signals wirelessly to a phone.

Age differences in energy absorption in the upper extremity during a descent movement: implications for arresting a fall

BACKGROUND

Falls are the number one cause of unintentional injury in older adults. The protective response of "breaking the fall" with the outstretched hand is often essential for avoiding injury to the hip and head. In this study, we compared the ability of young and older women to absorb the impact energy of a fall in the outstretched arms.

METHODS

Twenty young (mean age = 21 years) and 20 older (M = 78 years) women were instructed to slowly lower their body weight, similar to the descent phase of a push-up, from body lean angles ranging from 15 degrees to 90 degrees . Measures were acquired of peak upper extremity energy absorption, arm deflection, and hand contact force.

RESULTS

On average, older women were able to absorb 45% less energy in the dominant arm than young women (1.7 +/- 0.5% vs 3.1 +/- 0.4% of their body weight x body height; p < .001). These results suggest that, even when both arms participate equally, the average energy content of a forward fall exceeds by 5-fold the average energy that our older participants could absorb and exceeds by 2.7-fold the average energy that young participants could absorb.

CONCLUSIONS

During a descent movement that simulates fall arrest, the energy-absorbing capacity of the upper extremities in older women is nearly half that of young women. Absorbing the full energy of a fall in the upper extremities is a challenging task even for healthy young women. Strengthening of upper extremity muscles should enhance this ability and presumably reduce the risk for injury to the hip and head during a fall.

A method for automatic fall detection of elderly people using floor vibrations and sound--proof of concept on human mimicking doll falls

Falls are a major risk for the elderly people living independently. Rapid detection of fall events can reduce the rate of mortality and raise the chances to survive the event and return to independent living. In the last two decades, several technological solutions for detection of falls were published, but most of them suffer from critical limitations. In this paper, we present a proof of concept to an automatic fall detection system for elderly people. The system is based on floor vibration and sound sensing, and uses signal processing and pattern recognition algorithm to discriminate between fall events and other events. The classification is based on special features like shock response spectrum and mel frequency ceptral coefficients. For the simulation of human falls, we have used a human mimicking doll: "Rescue Randy." The proposed solution is unique, reliable, and does not require the person to wear anything. It is designed to detect fall events in critical cases in which the person is unconscious or in a stress condition. From the preliminary research, the proposed system can detect human mimicking dolls falls with a sensitivity of 97.5% and specificity of 98.6%.

Fall risk in older adults: roles of self-rated vision, home modifications, and limb function

Objective. To assess direct effects of self-rated vision, home modifications, and limb functioning, and moderating effects of self-rated vision on change in functioning of upper and lower limbs on fall risk in older adults. Method. Logistic regression was used to analyze 2004 and 2006 waves of the Health and Retirement Study. Results. Effects of self-rated vision and home modifications in predicting falls decreased after controlling functioning in upper and lower extremities. Declines/gains in functioning across short periods of time superseded self-rated vision in predicting falls. No evidence was found for a moderating effect of vision status on limb functioning. Discussion. Poor self-rated vision may not be a good indicator of fall risk in older adults. Thus, for older adults with visual impairments, preserving residual limb functioning through exercise and activity has the important potential to reduce fall risk in addition to improving muscle and bone strength as well as improving balance and gait.

Segmental dynamics of forward fall arrests: a system identification approach

BACKGROUND

Fall-related injuries are multifaceted problems. One approach to identify the critical biomechanical factors is biodynamic simulation.

METHODS

A 2-degree-of-freedom discrete impact model was constructed through system identification and validated using experimental data in order to understand the dynamic interactions of various biomechanical parameters in bimanual forward fall arrests.

FINDINGS

The bimodal reaction force responses from the identified models had very small identification errors (<3.5%) and high coherence (R(2)=0.95) between the measured and identified model responses. Model validation with separate experimental data also demonstrated excellent validation accuracy and coherence, less than 7% errors and R(2)=0.87, respectively. The first force peak was usually greater than the second force peak and strongly correlated with the impact velocity of the upper extremity, while the second force peak was associated with the impact velocity of the body. The impact velocity of the upper extremity relative to the body could be a major risk factor to fall-related injuries as observed from model simulations that a 75% faster arm movement relative to the falling speed of the body alone could double the first force peak from that of a soft landing, thereby readily exceeding the fracture strength of the distal radius.

INTERPRETATION

Despite the time-critical nature of falling often calling for a rapid arm movements, the safe use of the upper extremity in forward fall arrests requires adequate reaction times and coordinated protective motions of the upper extremity.

Effect of Upper and Lower Extremity Control Strategies on Predicted Injury Risk During Simulated Forward Falls: A Study in Healthy Young Adults

Fall-related wrist fractures are common at any age. We used a seven-link, sagittally symmetric, biomechanical model to test the hypothesis that systematically alterations in the configuration of the body during a forward fall from standing height can significantly influence the impact force on the wrists. Movement of each joint was accomplished by a pair of agonist and antagonist joint muscle torque actuators with assigned torque-angle, torque-velocity, and neuromuscular latency properties. Proportional-derivative joint controllers were used to achieve desired target body segment configurations in the pre- and∕or postground contact phases of the fall. Outcome measures included wrist impact forces and whole-body kinetic energy at impact in the best, and worst, case impact injury risk scenarios. The results showed that peak wrist impact force ranged from less than 1kN to more than 2.5kN, reflecting a fourfold difference in whole-body kinetic energy at impact (from less than 40J to more than 160J) over the range of precontact hip and knee joint angles used at impact. A reduction in the whole-body kinetic energy at impact was primarily associated with increasing negative work associated with hip flexion. Altering upper extremity configuration prior to impact significantly reduced the peak wrist impact force by up to 58% (from 919Nto2212N). Increased peak wrist impact forces associated greater shoulder flexion and less elbow flexion. Increasing postcontact arm retraction can reduce the peak wrist impact force by 28% (from 1491Nto1078N), but postcontact hip and knee rotations had a relatively small effect on the peak wrist impact force (8% reduction; from 1411Nto1303N). In summary, the choice of the joint control strategy during a forward fall can significantly affect the risk of wrist injury. The most effective strategy was to increase the negative work during hip flexion in order to dissipate kinetic energy thereby reducing the loss in potential energy prior to first impact. Extended hip or elbow configurations should be avoided in order to reduce forearm impact forces.