The genu effect on plantar flexor power.

Triceps surae function can be modified by changes in knee joint angle through altering the effective contribution of the bi-articular gastrocnemeii. However, the impact on plantar flexor power from altering knee angle has not been studied systematically across a range of loads. Here, in 11 young men (25.7 ± 2.2 years), we determine the effect of knee angle on torque, velocity and power at loads ranging from 15 to 75 % maximal voluntary isometric contraction (MVC). Contractile properties were recorded with either the knee extended (170º) or flexed (90º). Despite similar voluntary activation (~97 %), peak twitch and MVC torques were 25 and 16 % lower in the flexed than extended knee (P < 0.05), respectively. Across all loads, subjects were 15-24 % less powerful with the knee flexed than extended (P < 0.05). In the flexed knee at relative loads ≤30 % MVC, impaired power was accompanied by 6-9 % slower shortening velocities than the extended knee. However, for the higher loads, limited torque production in the flexed knee was the key factor contributing to the generation of maximal power than for the extended position. This was supported by no change in velocity at higher loads (>30 % MVC) and a 15-22 % lower maximal rate of torque development across all loads. Hence, in a flexed knee position, which disadvantages the contribution of the gastrocnemeii, results in a left-downward shift in the torque-power relationship impairing maximal power production. Thus, the gastrocnemeii are not only a major contributor to plantar flexion torque, but also critical for modifying loaded shortening velocity and ultimately power production.

Potential benefits of warm-up for neuromuscular performance of older athletes.

Demographic trends project increasing numbers of older people to engage in exercise programs and sports. Sustained participation depends on both perceived health outcomes and avoidance of debilitating injuries. This review explores the potential benefits of physiologically based warm-up strategies to alleviate some key age-related decreases in the biomechanical capacity for skilled sport movements.

Towards a biopsychosocial framework of osteoarthritis of the knee.

Research into the causes of osteoarthritis (OA) of the knee has traditionally followed a biomedical approach whereby the disease development and progression is regarded as an internal physiological process. As a result, treatment has focused on symptom reduction with limited modification of psychosocial variables. In fact, psychosocial factors such as environment and employment play a substantial role in the disease process and are important determinants of the overall level of disability of affected individuals. Thus, by placing greater importance on the biomedical aspects of knee OA, a complete representation of the health condition cannot be achieved thereby limiting treatment effectiveness. The purpose of this clinical commentary is to provide a rationale for the implementation of a biopsychosocial model of knee OA that can aid in more effective research and treatment for the disorder.

Lay versus expert understandings of workplace risk in the food service industry: a multi-dimensional model with implications for participatory ergonomics.

The recent trend towards cooperative management and prevention of workplace injuries has introduced numerous health and safety actors to the workplace with varying amounts and types of expertise. The purpose of this qualitative research project was to explore the understandings of risk as experienced by food service workers (FSW) and how these compare with an 'expert' in risk assessment. In total 13 FSW, selected based on age, work location, and gender, and one experienced Ergonomist participated in the study. In-depth semi-structured telephone interviews were conducted with each participant and transcripts of the interviews were analyzed using thematic analysis by drawing on methods closely related to grounded theory. The findings of this study indicated that the risks for occupational injury as experienced by FSW were multi-dimensional in nature representing not only the physical requirements of the individual's job, but also the social interactions of the FSW with their coworkers, management, and the organization. FSW were also found to be a rich source of knowledge and experience concerning occupational risk and may be under-utilized when designing interventions. The results of this study support a cooperative team approach to reduce the risks of injury in the workplace, with a specific emphasis on inclusion of the worker.

A five year retrospective analysis of occupational injuries and incidence reported at a research intensive Canadian university.

Limited information of occupational injury statistics within academic settings exists. Universities and colleges are an important and insightful work environment due to the varied nature of the work performed by employee groups. The objective of this study was to describe occupational injuries for all work groups in a large research intensive university. A retrospective database analysis was conducted on 2029 employee incident reports over a five year period (2000-2004) to determine general and departmental prevalence of injury types, locations, and mechanisms. Demographic analysis revealed an average age of 42 years and 9 years of work experience. Overall, the most frequent injuries were to the hand (40%), were musculoskeletal in nature (42%), and resulted from being "struck or contacted by" (33%). The greatest number of incidents occurred in food services, followed by physical plant and staff services. Closer examination of incidents reported by food services indicated 53% of injuries occurred to the hand and 72% required first aid. Notable too was that 19% of physical plant injuries occurred to the back, but these reports accounted for 40% of total back injuries and 50% of all lost time claims in the total database. Further epidemiological research in academic institutions is needed to better understand the inherent injury risk in this work sector.

Peripheral impairments cause a progressive age-related loss of strength and velocity-dependent power in the dorsiflexors.

Muscle power is more functionally relevant than static muscle strength, particularly with aging. However, the effect of age on power derived from isotonic contractions has been studied sparingly, and it has not been studied at all in subjects >75 yr of age. Thus the purpose was to investigate the magnitude and causes of age-related losses in isotonic power among 13 young (26 yr), 13 old (65 yr), and 13 very old (84 yr) men. Six different loads were employed to create velocity-torque and power-torque relationships. Dorsiflexor cross-sectional area was assessed via magnetic resonance imaging for the calculation of specific power. Electromyographic signals of the tibialis anterior and soleus muscles were recorded to assess agonist activation and antagonist coactivation, respectively. Despite similar contractile masses and levels of voluntary drive and antagonist co-activation, power was significantly impaired in the old vs. young (approximately 25%), and in the very old relative to both the young (approximately 60%) and old (approximately 40%). The novel results punctuate two important considerations for studies concerned with the effect of age on the neuromuscular system. First, the decreased ability of muscles from old men to produce power in the presence of reasonably well-preserved strength indicates the utility of studying isotonic contractions. Second, the precipitous decline in many measures between the seventh and ninth decades underscores the benefit of testing more than one group of aged subjects to improve our understanding of rates of change in key variables.

Seniors Falls Investigative Methodology (SFIM): a systems approach to the study of falls in seniors.

An in-depth understanding of human factors and human error is lacking in current research on seniors' falls. Additional knowledge is needed to understand why seniors are falling. The purpose of this article is to describe the adapting of the Integrated Safety Investigation Methodology (ISIM) (used for investigating transportation and industrial accidents) to studying seniors' falls. An adapted version-the Seniors Falls Investigative Methodology (SFIM)-uses a systems approach to take an investigation beyond the immediate cause of an incident and reveal unsafe acts and deeply imbedded unsafe conditions that contribute to adverse outcomes. An example case study is used to describe six phases of the investigative process in detail. The SFIM has the potential to identify safety deficiencies; utilize existing knowledge about falls; establish a standardized reporting system; shift focus from the faller to the system; and guide targeted prevention.

Defining a fall and reasons for falling: comparisons among the views of seniors, health care providers, and the research literature.

PURPOSE: The purpose of this study was (a) to obtain information about the perceptions held by seniors and health care providers concerning what constitutes a fall and potential reasons for falling, and (b) to compare these perceptions to the research literature. DESIGN AND METHODS: As part of a larger telephone survey, interviewers asked 477 community-dwelling seniors to define a fall and to provide reasons for falling. In addition, we interviewed 31 health care providers from the community on the same topics. In order to capture patterns in conceptualized thinking, we used content analysis to develop codes and categories for a fall definition and reasons for falling. We reviewed selected articles in order to obtain a comprehensive overview of fall definitions currently used in the research and prevention literature. RESULTS: A fall had different meanings for different groups. Seniors and health care providers focused mainly on antecedents and consequences of falling, whereas researchers described the fall event itself. There were substantial differences between the reasons for falling as reported by seniors and the risk factors as identified in the research literature. IMPLICATIONS: If not provided with an appropriate definition, seniors can interpret the meaning of a fall in many different ways. This has the potential to reduce the validity in studies comparing fallers to nonfallers. Research reports and prevention programs should always provide an operational definition of a fall. In communication between health care providers and seniors, an appropriate definition increases the possibility for early detection of seniors in greater need of care and services.

Reliability of a single-session isokinetic and isometric strength measurement protocol in older men.

BACKGROUND: The purposes of the current study were (a) to determine the test-retest reliability of a single-session isokinetic and isometric strength testing protocol in older healthy men, and (b) to compare the outcomes of the reliability measures derived from averaged torque scores with those derived from a single peak torque score. METHODS: In 19 men (mean age, 72 +/- 5 years), both lower limbs were assessed independently on 2 separate test days using the Biodex System 3 dynamometer. After completing a 5-minute warm-up, each man performed three submaximal knee extensions followed by five maximal contractions at 90 degrees /s (CON), 0 degrees /s (ISO), and -90 degrees /s (ECC). Average (best 3 of 5) and peak CON, ISO, and ECC torque, and CON work and CON power were determined. Peak CON work and CON power were recorded from the highest peak torque concentric contraction (HPTCC). RESULTS: Intraclass correlation coefficients ranging from 0.84 to 0.94 were found to have good reliability. The typical error as a coefficient of variation ranged from 8% to 10% for averaged measures and from 8% to 17% for peak torque and HPTCC. The ratio limits of agreement for average and peak CON, ISO, and ECC torque ranged from 23% to 33% and from 40% to 54% for average CON and HPTCC work and power. CONCLUSIONS: The test-retest reliability of a single-session isokinetic and isometric strength testing protocol in this group of older healthy men displayed good relative reliability (intraclass correlation coefficient > 0.84); however, because the typical error as a coefficient of variation and ratio limits of agreement (absolute reliability) were large, single-session testing is not recommended.

Effects of maximal isometric and isokinetic resistance training on strength and functional mobility in older adults.

BACKGROUND: The aim of the present study was to compare the changes in voluntary strength (isometric, concentric, and eccentric) and functional mobility in response to maximal isokinetic eccentric-only resistance training to those elicited by maximal isometric-only or maximal isokinetic concentric-only resistance training in older adults. METHODS: Twelve women (73 +/- 7 years) and 18 men (73 +/- 5 years) completed a 12-week training program (three times per week) using a Biodex System 3 dynamometer. Primary outcome measures included peak isometric and isokinetic (concentric and eccentric) knee extensor strength, concentric work, concentric power, stair ascent and descent, and gait speed. Participants were randomly assigned to one of three training groups: isometric-only, isokinetic concentric-only, or isokinetic eccentric-only. RESULTS: All three training groups demonstrated an increase in peak isometric and isokinetic concentric and eccentric strength following 12 weeks of training (p <.01). Step time was positively influenced (p <.03) by all three training modes; however, gait speed was unchanged following 12 weeks of training. All three training groups experienced a significant increase in peak concentric work and concentric power (p <.01) with the concentric training group demonstrating the largest increases in both peak concentric work and concentric power when compared to the isometric and eccentric training groups. CONCLUSIONS: It was clear that all three resistance training programs (isometric, concentric, and eccentric) in older adults were effective in increasing strength, concentric work, and concentric power over the 12-week training period. Furthermore, 12 weeks of resistance training resulted in improved stair ascent and descent performance.

Optimizing the benefits versus risks of golf participation by older people.

Currently a strong emphasis is being placed in North American public health messages on the value of an active lifestyle for all age segments, including older persons. However, seniors do not usually take up physical activities, even though they often have extensive leisure time. Thus the purpose of this paper is to review current knowledge regarding the key health issues for physical therapists to consider when dealing with an older person who wishes to participate fully in an active sport. We have chosen the example of golf because of its popularity among seniors, as well as its usefulness in illustrating both the overall benefits and risks of participation. Although playing golf provides a moderate intensity exercise stimulus for seniors, musculoskeletal injuries can also result from unsafe participation, as can the aggravation of pre-existing musculoskeletal problems. Strategies for targeted management of the senior golfer's typical concerns are summarized into 4 categories consisting of: injury rehabilitation coordinated by therapists, warm up routines; club-fitting/coaching on proper technique, and pre-season conditioning programs. Educational programs for older people regarding the benefits of physical activity should also include information about injury prevention strategies that enhance long-term participation.

Risk factors for falling among community-dwelling veterans and their caregivers.

PURPOSE: To assess the prevalence and strength of association of risk factors for falling in Canadian veterans of World War II and Korea and their caregivers. METHODS: Questionnaires were sent to addresses of 3,000 Canadian veterans (response rate(1/4)70%). Risk factors for falls and the frequency of falls and injurious falls in the past 12 months were collected. RESULTS: Veterans had more risk factors than did caregivers, and more had fallen in the past year (39.8% vs. 29.7%). Risk factors in the logistic model for veterans included lower extremity disability (odds ratio 1.98, 95% confidence interval 1.5-2.6); lower extremity weakness (OR 1.75, 95% CI 1.3-2.3); worse memory than peers (OR 1.67, 95% CI 1.1-2.5); one or more visits to the family doctor in the past month (OR 1.53, 95% CI 1.2-2.0); and worse memory than 5 years ago (OR 1.36, 95% CI 1.0-1.8). CONCLUSIONS: Veterans appear more frail and prone to falling than their caregivers.

Velocity dependence of eccentric strength in young and old men: the need for speed!

Older adults better maintain eccentric strength relative to isometric strength, as indicated by a higher ratio of eccentric:isometric torque as compared with younger adults. The effect of increasing angular velocities (>200°/s) on the age-related maintenance of eccentric strength has not been tested and thus it is unknown whether the eccentric:isometric ratio is velocity dependent in old age. The purpose of this study was to investigate eccentric strength of the ankle dorsiflexors over a large range of lengthening angular velocities in young and older men. Isometric neuromuscular properties were assessed on a HUMAC NORM dynamometer. Nine young (∼24 years) and 9 older (∼76 years) healthy men performed maximal voluntary eccentric contractions at angular velocities of 15-360°/s. Despite near full voluntary activation (>95%), the older men were ∼30% weaker than the young men for isometric strength (P < 0.05). Across all lengthening velocities, older men had a greater eccentric:isometric ratio than young men (P < 0.05). Additionally, there was a velocity dependence of strength in both young and older men: eccentric strength increased as velocity increased up to 120°/s (P < 0.05) and plateaued thereafter. In young and older men, eccentric strength at 15°/s was ∼20% and ∼40% greater than isometric strength (P < 0.05), while at 360°/s eccentric strength was ∼50% and ∼90% greater, respectively (P < 0.05). These findings indicate that with increasing angular velocity, both young and older men have considerable increases in the eccentric:isometric ratio of torque production.

Hemiplegic shoulder pain: implications for occupational therapy treatment.

BACKGROUND: Hemiplegic shoulder pain is common after stroke causing hemiplegia. It adversely affects the recovery of arm function and independence in activities of daily living. Subluxation, abnormal tone and limited range of motion or capsular constrictions have been reported as potential causes. Other factors such as rotator cuff tears, brachial plexus injury, shoulder-hand syndrome and other pre-existing pathological conditions may also be associated with hemiplegic shoulder pain. The etiology remains unclear, but hemiplegic shoulder pain may result from a combination of the above factors. SCOPE: This literature review examines the possible causes of hemiplegic shoulder pain and discusses the implications for occupational therapy treatment. Occupational therapy interventions include proper positioning, facilitation of movement through purposeful therapeutic activities, increasing passive range of motion, implementation of external supports and treatment of shoulder-hand syndrome. PRACTICE IMPLICATIONS: Understanding the processes involved will assist with effective assessment, treatment and prevention of hemiplegic shoulder pain. This will facilitate clients' participation in rehabilitation programs and move them towards attainment of optimal function.

Golf-related low back pain: a review of causative factors and prevention strategies.

Golf is a popular sport with both perceived and real health benefits. However, certain injury risks are also prevalent, particularly to the lower back. Epidemiological studies have shown that lower back pain (LBP) from golf account for between 18% and 54% of all documented ailments, leading many researchers to regard the condition as the most common golf injury. The purpose of this review was to examine the scientific literature to ascertain the risk factors associated with the development of LBP from playing golf and suggest methods to modify or limit these factors. Results of the review indicate that the high frequency of LBP appears multi-factorial although the asymmetrical and forceful nature of the swing along with excessive play and practice, particularly amongst elite players, appear to be common factors. Other factors include swing flaws leading to excessive side-bend and over-rotation of the spine, abnormal muscle recruitment, poor trunk endurance, restricted lead hip internal rotation and the use of unnecessarily stressful club transportation methods. Methods to help control or eliminate excessive stress on the lower back would include reducing the amount spent playing or practicing, seeking professional assistance to assess and adjust swing mechanics, improve trunk and hip flexibility, increase the strength and endurance of the trunk musculature, consider different footwear options and avoid carrying the golf bag. Adopting some or all of these recommendations should allow players to continue to enjoy the sport of golf well into their senior years.

The effect of knee joint angle on plantar flexor power in young and old men.

Human adult aging is associated with a loss of strength, contractile velocity and hence, power. The principal plantar flexors, consisting of the bi-articular gastrocnemeii and the mono-articular soleus, appear to be affected differently by the aging process. However, the age-related effect of knee joint angle on the torque-angular velocity relationship and power production of this functionally important muscle group is unknown. The purpose was to determine whether flexing the knee, thereby reducing the gastrocnemius contribution to plantar flexion, would exacerbate the age-related decrements in plantar flexion power, or shift the torque-angular velocity relationship differently in older compared with young men. Neuromuscular properties were recorded from 10 young (~25 y) and 10 old (~78 y) men with the knee extended (170°) and flexed (90°), in a randomized order. Participants performed maximal voluntary isometric contractions (MVCs), followed by maximal velocity-dependent shortening contractions at pre-set loads, ranging from 15 to 75% MVC. The young men were ~20-25% stronger, ~12% faster and ~30% more powerful than the old for both knee angles (P<0.05). In both age groups, isometric MVC torque was ~17% greater in the extended than flexed knee position, with no differences in voluntary activation (>95%). The young men produced 7-12% faster angular velocities in the extended knee position for loads ≤30% MVC, but no differences at higher loads; whereas there were no detectable differences in angular velocity between knee positions in the old across all relative loads. For both knee angles, young men produced peak power at 43.3±9.0% MVC, whereas the old men produced peak power at 54.8±7.9% MVC. These data indicate that the young, who have faster contracting muscles compared with the old, can rely more on velocity than torque for generating maximal power.

Shortening-induced torque depression in old men: implications for age-related power loss.

Following active muscle shortening, the steady-state isometric torque at the final muscle length is lower than the steady-state torque obtained for a purely isometric contraction at that same final muscle length. This well-documented property of skeletal muscle is termed shortening-induced torque depression (TD). Despite many investigations into the mechanisms of weakness and power loss in old age, the influence of muscle shortening on the history dependence of isometric torque production remains to be elucidated. Thus, it is unclear whether older adults are disadvantaged for torque and power production following a dynamic shortening contraction. The purpose of this study was to evaluate shortening-induced TD in older adults, and to determine whether shortening-induced TD is related to power loss. Maximal voluntary isometric dorsiflexion contractions (MVC; 10s) in 8 young (25.5±3.7years) and 9 old (76.1±5.4years) men were performed on a HUMAC NORM dynamometer as a reference, and then again following an active shortening of 40° joint excursion (40°PF-0°PF) at angular velocities of 15°/s and 120°/s. Work and instantaneous power were derived during shortening. Shortening-induced TD was calculated and expressed as a percentage by determining the mean torque value over 1s during the isometric steady state of the MVC following shortening, divided by the mean torque value for the same 1s time period during the isometric reference MVC. To assess muscle activation, electromyography (root mean square; EMGRMS) of the tibialis anterior (TA) and soleus (SOL) was calculated at identical time points used in assessing shortening-induced TD, and voluntary activation (VA) was assessed using the interpolated twitch technique. Old were 18% weaker than young for MVC, and ~40% less powerful for 15°/s and 120°/s of shortening. Old produced 37% and 21% less work for 15°/s and 120°/s than young, respectively. Furthermore, old experienced 60% and 70% greater shortening-induced TD than young for 15°/s and 120°/s, respectively with similar EMGRMS and VA across all conditions. A significant relationship between shortening-induced TD and instantaneous power was found only at the fast angular velocity for both the old (R(2)=0.32) and young (R(2)=0.45) men. The older men experienced greater shortening-induced TD than young while maintaining similar levels of voluntary activation. This previously unaccounted for history-dependent property of muscle may provide insight into power loss in old age.

A literature synthesis indicates very low quality, but consistent evidence of improvements in function after surgical interventions for primary osteoarthritis of the elbow.

Background. Primary osteoarthritis of the elbow is a debilitating disease with an overall incidence of about 2%. Pain and reduced motion (ROM) lead to disability and loss of functional independence. Purpose. To critically review the literature on patient-related important functional outcomes (pain, ROMs and functional recovery) after surgery for primary OA of the elbow, utilizing the 2011 OCEBM levels of evidence. Design. A literature synthesis. Results. Twenty-six articles satisfied the inclusion and exclusion criteria; 25 of the studies were at level IV evidence, and 1 at level III. All three surgical techniques led to improvement in pain, ROM, and functional recovery in the short- and medium-term follow-up. Long-term follow-up results, available only for open joint debridement, showed recurrence of osteoarthritic signs on X-ray with minimal loss of motion. Recently, there seems to be an increased focus on arthroscopic debridement. Conclusion. The quality of research addressing surgical interventions is very low, including total elbow arthroplasty (TEA). However, the evidence concurs that open and arthroscopic joint debridement can improve function in patients with moderate-to-severe OA of the elbow. TEA is reserved for treating severe joint destruction, mostly for elderly individuals with low physical demands when other intervention options have failed.

Peak power is reduced following lengthening contractions despite a maintenance of shortening velocity.

Following repetitive lengthening contractions, power (the product of torque and velocity) is impaired during shortening contractions. However, the relative contribution of each component to power loss and the underlying factors are unclear. We investigated neuromuscular properties of the dorsiflexors in 8 males (27 ± 3 years) and 8 females (26 ± 4 years) for a potential sex-related difference before, during, and after 150 unaccustomed maximal lengthening actions. Velocity-dependent power was determined from shortening contractions at 8 levels (1 N · m to 70% of maximum voluntary isometric contraction (MVC)) before, after, and throughout recovery assessed at 0-30 min, 24 h, and 48 h. Immediately following task termination, both sexes displayed similar impairments of 30%, 4%, and 10% in MVC torque, shortening velocity, and overall peak power, respectively (P < 0.05). Peak rate of isometric torque development (RTD) was reduced by 10% in males, but females exhibited a 35% reduction (P < 0.05). Rate of torque development for the MVC remained depressed in both sexes throughout the 30 min recovery period; however, the RTD returned to normal by 24 h in males but did not recover by 48 h in females. Power was reduced preferentially at higher loads (i.e., 60% MVC), with a greater loss in females (65%) than males (45%). For lower loads (<20% MVC), power was impaired minimally (4%-8%; P < 0.05) and recovered within 30 min in both groups. The reduction in maximal angular velocity persisted until 30 min of recovery, and peak power did not recover until 24 h for both sexes. Unaccustomed lengthening contractions decreased power preferentially at higher loads, whereas peak power was reduced minimally owing to maintenance of maximal shortening velocity.

Enhanced force production in old age is not a far stretch: an investigation of residual force enhancement and muscle architecture.

In older adults, isometric force production is enhanced following a voluntary lengthening contraction when compared with isometric force produced at the same muscle length without a prior lengthening contraction. This phenomenon is termed residual force enhancement (RFE), and appears to be related to the age-related maintenance of eccentric (ECC) strength. However, it is unknown whether age-related changes in muscle architecture contribute to greater RFE at short and long muscle lengths in old age. Neuromuscular properties of the knee extensors were assessed on a HUMAC NORM dynamometer. Torque was examined in young (26 ± 3 year, n = 11) and old men (77 ± 6 year, n = 11) during brief maximal voluntary isometric contractions (MVC) at 80° and 120° (180° representing full knee extension) and then compared with torque during a steady-state phase at the same joint angle following a maximal voluntary lengthening contraction at 30°/sec over a 60° joint excursion; either from 140 to 80° (long), or from 180 to 120° (short). Ultrasound images were obtained from the vastus lateralis during the isometric phase for each condition. When comparing the ECC torque with the MVC isometric torque, old men had 17% greater ECC:MVC ratios than young men, confirming an age-related maintenance of ECC strength. The extent of RFE was greater at long versus short but independent of age. At rest, old had shorter (∼18%) and less pennated (∼22%) fascicles. However, changes in fascicle length and pennation during contraction did not contribute to RFE in either group. Thus, age-related changes in muscle architecture may not contribute to RFE.