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PubMed2002

Correlation between condylar lift-off and femoral component alignment.

The current study analyzed subjects having a total knee arthroplasty to determine the incidence of condylar lift-off and correlate lift-off with the alignment of the femoral component with respect to the transepicondylar axis. Twenty-five subjects, implanted with a posterior stabilized total knee prosthesis, were asked to do weightbearing deep knee bends while under fluoroscopic surveillance. The two-dimensional fluoroscopic images were converted into three-dimensional images using a fully automated computer model-fitting technique. Each subject then was assessed for the incidence of condylar lift-off. The five subjects having the maximum amount of lift-off were reanalyzed for comparison using computed tomography. Using digitization, the angle between the posterior femoral condylar line and the transepicondylar axis was measured and correlated with the presence of femoral condylar lift-off. The incidence of condylar lift-off was significantly less for subjects in this study compared with subjects reported in previous fluoroscopic studies. Forty percent (10 of 25) of the subjects experienced condylar lift-off. The maximum amount of lift-off was 2.3 mm and the average for subjects experiencing lift-off was 1.4 mm. There also was a distinct correlation between femoral component alignment and condylar lift-off. Using computed tomography, it was determined that 69.2% of the subjects had a correlation between condylar lift-off and malalignment of the femoral component relative to the epicondylar axis. Placement of the femoral component parallel to the transepicondylar axis seems to lessen the incidence of femoral condylar lift-off and may reduce polyethylene wear by reducing eccentric edge loading.

Arthroplasty, Replacement, Knee↗
PubMed2002

Reliability of EMG time-frequency measures of fatigue during repetitive lifting.

PURPOSE: To test the short-term and long-term reliability of time-frequency electromyographic (EMG) measures of fatigue during repetitive dynamic lifting and compare it with the reliability of median frequency (MF) EMG measures of fatigue during static lifting. METHODS: Fourteen' healthy male subjects (26 +/- 5 years) repetitively (12 lifts/min) lifted and lowered a box (29 x 25 x 23 cm, 13 kg) for 4.5 min during 3 different tests on 2 different days. EMG data and the biomechanics of motion were recorded. Before and after dynamic lifting, static maximum lifting tests were performed. At the end of each of the two sessions, subjects performed a static lift at 80% of their maximum lifting force for 30 s. RESULTS: Significant fatigue-related changes were observed during the lifting exercise via EMG time-frequency analysis at the paravertebral L5, L2, T10, and vastus lateralis (VL) electrode sites. Two parameters for assessing fatigue during dynamic contractions [i.e., the Instantaneous Median Frequency (IMDF) and its time dependent change] were shown to be reproducible both in the short-term (2 h) and long-term (2 wk). The corresponding ICCs reflecting the reproducibility of values between sessions were 96.9% (L5), 98.1% (L2), 90.1% (T10), 96.4% (UT), 98.0% (GM), 89.5% (VL), and 99.0% (BF), respectively. For most EMG recording sites, the reliability of the IMDF measures was not dependent upon the postural strategy that the subject used to accomplish the lifting task or on the subject's strength as measured via the static maximum lifting test. A comparison between the ICC values of the IMDF measures and those of the parameters utilized to assess fatigue during static sustained lifts [i.e., the Median Frequency (MDF) and its change during the test] revealed equally good reproducibility for most EMG recording sites. The respective ICC values that took into account time dependent trends for the IMDF parameter were 87.1% (L5), 62.4% (L2), 90.1% (T10), 0% (UT), 72.7% (GM), 45.4% (VL), and 100% (BF), and for the MDF parameter 94.9% (L5), 73.0% (L2), 80.9% (T10), 100% (UT), 89% (GM), 91.7% (VL), and 90.9% (BF), respectively. CONCLUSIONS: The time-frequency approach allows one to derive EMG spectral parameters that can be used to monitor muscle fatigue during dynamic real-world tasks such as lifting.

Adult↗
PubMed1997

The effect of fatigue on multijoint kinematics and load sharing during a repetitive lifting test.

STUDY DESIGN: A repetitive lifting test in the sagittal plane was performed with a submaximal load at a maximal lifting rate to understand the effects of fatigue on kinematic and kinetic measures of performance. OBJECTIVES: To quantify the effect of fatigue during a highly repetitive lifting task, in terms of lifting force transmitted to the load, joint motion patterns, and internal joint load sharing. SUMMARY OF BACKGROUND DATA: Industrial surveillance and epidemiologic data suggest that repetitive lifting is a risk factor for low back pain. Previous studies examining the effect of fatigue have either been constrained to isolated trunk movement, or have not explored the internal load distribution and potential alteration in the loading patterns. METHODS: Sixteen healthy male subjects performed repetitive lifting in the sagittal plane with a load equal to 25% of their maximal lifting capacity, at a maximal lifting rate. Changes in lifting performance were determined from the power transferred to the box, joint kinematics, and joint kinetics. Data from three cycles at the start and end of the exercise were tested for the effect of fatigue using repeated-measures analysis of variance. RESULTS: Fatigue was documented by a reduction in average lifting force and hip and spine torque generation, whereas internal joint load sharing was relatively unchanged. The fatigue was associated with decreased knee and hip motion, and increased lumbar flexion. Decreased postural stability also was evident. CONCLUSIONS: The significant decrease in postural stability and force generation capability because of the repetitive lifting task indicated a higher risk of injury in the presence of unexpected perturbation. Multijoint coordinated lifting tasks provide a more realistic protocol to study neuromuscular fatigue.

Adult↗
PubMed2004

A patient lifting intervention for preventing the work-related injuries of nurses.

UNLABELLED: The average age of nurses is projected to be 50 years in 2010 [17]. Because nurses are older, a work injury prevention program should change how nurses lift patients. The purpose of this evidence-based practice improvement project was to examine a new lifting intervention. METHOD: An evidence-based process was used to implement an effective lifting intervention, including a back school, a lift team, and mechanical lifting equipment, on the orthopedic and neurology units in a Minnesota hospital. A two-week pilot determined if enough work would be generated to justify hiring a permanent lift team. Then the entire lifting intervention was studied on the two units. RESULTS: The injuries for the two units decreased from 21 to 9 injuries, while the salary and work replacement costs were $48,220 and $2,560 in 2001 and 2002, respectively. The lift team averaged 80 lifts per day and 95% of the nursing staff attended the back school. CONCLUSION: The lift team and new mechanical lifting equipment were successfully disseminated resulting in significant reductions in costs. Suggested improvements include additional supervision and lift team scheduling changes, regular staff meetings, and ongoing education.

Accidents, Occupational↗
PubMedDate not supplied

Static and dynamic lifting strength at different reach distances in symmetrical and asymmetrical planes.

Postural and therefore biomechanical standardization in strength testing has not been rigorously and consistently applied. To develop a quantitative relationship between strength and posture (body position, symmetry, and reach) 30 normal subjects (18 male and 12 females) were required to stoop and squat lift or exert in the relevant posture against a standardized instrumented handle. The isometric lifting efforts and isokinetic lifts were studied. The isokinetic lifts were done at a linear velocity of 50cm/s of the hand displacement from the floor to the knuckle heights of the respective subjects in stoop and squat postures. The isometric stoop lifting efforts were exerted in two standardized postures: (a) with 60 degrees hip flexion; and (b) with 90 degrees hip flexion. The isometric squat lifting efforts were also exerted in two standardized postures: (a) with 90 degrees knee flexion; and (b) with 135 degrees knee flexion. All isometric lifting efforts and isokinetic lifts were performed at half, three-quarters, and full horizontal reach in sagitally symmetrical, 30 degrees left lateral, and 60 degrees left lateral planes. Isometric stoop and squat lifting efforts were also measured in self-selected optimal postures. These 56 conditions were tested in random order. The analysis of variance revealed that the gender, the mode of lifting, the postural asymmetry and reach of lifting affected the strength significantly (p less than 0.0001). Most two-way and three-way interactions were significant (p less than 0.01). Of 108 prediction regression equations, 103 were significant with up to 90% of the variation explained by anthropometric variables and sagittal plane strength. The reach affected the strength most profoundly followed by postural asymmetry and the mode of lifting.

Adult↗
PubMed1991

Independent digit control: failure to partition perceived heaviness of weights lifted by digits of the human hand.

1. A weight-matching task was used to investigate the ability to estimate heaviness when weight lifting was isolated to the extrinsic flexor muscles (or portions thereof) that act on the digits of the hand. 2. Subjects matched a reference weight (200 g) lifted by a digit on the right with a variable weight lifted by the left thumb; a concurrent weight was simultaneously lifted by a digit on the right (reference) side. The reference and concurrent weights were lifted either by the same muscle (digital portions of flexor digitorum profundus), or anatomically separate but functionally related muscles (flexor digitorum profundus and flexor pollicis longus). Anaesthesia of the radial nerve and/or posturing of the hand was used to eliminate any small forces generated by co-contraction of the extensor muscles of the digits. 3. When the concurrent weight was equal to or greater than the reference weight, the perceived heaviness of the reference weight increased significantly from control trials (in which no concurrent weight was lifted). Although perceived heaviness of the reference weight increased progressively as the concurrent weight increased, reproducibility (expressed as the coefficient of variation) did not deteriorate when a weight was lifted concurrently. These findings were qualitatively similar when the reference and concurrent weights were lifted by two digital portions of flexor digitorum profundus or when the weights were lifted by flexion of the thumb and index finger. Also, anaesthesia of the digits which lifted the reference and concurrent weights did not alter the changes in perceived heaviness. 4. Perceived heaviness of the reference weight lifted by flexor digitorum profundus did not change when subjects lifted the concurrent weight with a remote muscle group (ankle dorsiflexors). 5. This study shows that signals of heaviness are systematically overestimated whenever more than one portion of the extrinsic muscles which flex the different digits are simultaneously active. Given that estimates of heaviness are biased by the central motor command, one explanation is that when the total motor drive increases, the central nervous system is unable to partition precisely the destination of motor commands to functionally related 'muscles'.

Electromyography↗
PubMedDate not supplied

Heel lifts and the stance phase of gait in subjects with limited ankle dorsiflexion.

CONTEXT: Heel lifts are often prescribed as part of the treatment program for patients with overuse injuries associated with limited ankle dorsiflexion. However, little is known about how joint kinematics and temporal variables are affected by heel lifts. OBJECTIVE: To determine the effects of heel lifts on selected lower extremity kinematic and temporal variables during the stance phase of gait in subjects with limited ankle dorsiflexion. DESIGN: Two-way, fully repeated-measures design. The 2 factors were side (right or left) and walking condition (shoes alone, 6-mm heel lifts in shoes, 9-mm heel lifts in shoes). SETTING: University biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-six volunteers (21 females, 5 males) with no more than 5 degrees of ankle joint dorsiflexion. INTERVENTION(S): Subjects were tested in shoes alone and in shoes with 6-mm and 9-mm heel lifts. MAIN OUTCOME MEASURE(S): We used the Qualisys Motion Analysis System to measure ankle dorsiflexion excursion, maximal knee extension, and time to heel off during the stance phase of gait under the 3 walking conditions. RESULTS: On the right side, ankle dorsiflexion excursion increased significantly with the 6-mm and 9-mm heel lifts compared with shoes alone (P < .05). On the left side, ankle dorsiflexion increased significantly with the 9-mm heels lifts over shoes alone and with the 9-mm heel lifts compared with the 6-mm heel lifts (P < .05). Time to heel off increased significantly for walking with the 9-mm heel lifts compared with shoes alone (P < .05). No differences were noted for maximal knee extension (P > .05). CONCLUSIONS: Clinicians may consider prescribing heel lifts for patients with limited dorsiflexion range of motion if increasing ankle dorsiflexion excursion and time to heel off during the stance phase of gait may be beneficial.

Journal Article↗
PubMed1990

Patient lifts.

In this issue, we evaluate conventional patient lifts that operate by hand cranking, hand pumping, or battery-powered motors and are intended for use in the home or in institutions. We did not evaluate lifts that are designed to be used solely in bathrooms or vehicles or those that permanently affix to walls, floors or ceilings. Some of the evaluated lifts are intended primarily for use in specific environments (e.g., one can be easily disassembled into small components for automobile transport). We evaluated 15 patient lifts from eight manufacturers, basing our ratings on performance, safety, and human factors design. Because different designs make lifts preferable for different environments, we rated the lifts for both home and institutional use based on their size, ruggedness, ease of storage, maneuverability, and cost. Seven units-the Arjo 218150; the Handi-Move 1200; the Hoyer C-CBL; the Invacare 9901, 9916 and 9917; and the Porto-Lift PL-1 are rated Acceptable for both home and institutional use. The Trans-Aid S1-600 and the Versa Lift are rated Acceptable for institutional use and Acceptable-Not Recommended for home use because of their size and cost. The Arjo B and the Hoyer Travel Lift are rated Acceptable for home use and Acceptable-Not Recommended for institutional use because they will not comfortably accommodate patients of all sizes; the Arjo B has additional limitations. The Hoyer C-HLA, the Invacare 9902, and the Trans-Aid LAT-2 are rated Conditionally Acceptable for home use on the condition that they are not used to transfer patients who weigh more than 200 lb; all three units are rated Conditionally Acceptable-Not Recommended for institutional use since there is no reliable way to ensure that they will not be used on heavier patients. The Century C-3 lift is rated Conditionally Acceptable for institutional use on the condition that it is used with the base fully extended; because the fully extended base makes the unit awkward to maneuver in narrow corridors or passages, we rated the unit Coonditionally Acceptable-Not Recommended for home use. We also assessed the optional electronic scales provided with the lifts and found the Arjo, Century, and Versa Lift scales acceptable; the Hoyer and Trans-Aid scales are also acceptable, but we do not recommend them for use in areas where exposure to fluid spills or moisture is likely to occur. Users should base purchasing decisions on a thorough understanding of our conclusions, which can be gained only by reading this evaluation in its entirety.

Body Weight↗
PubMed1993

Evaluation of a unique mechanical client lift: efficiency and perspectives of nursing staff.

This study evaluated the acceptability of a mechanical client lift based on the design employed for helicopter rescue lifts. Twenty-three nursing personnel completed questionnaires which explored their preferences, intentions to use the lift, perceptions of helpfulness, and exertion. Sixteen clients in a long term care setting consented to participate. One hundred manual lifts and 100 belt lifts were observed for comparative time and staff measures. The findings suggest that: 1) nursing staff will prefer the belt lift device for changing incontinent briefs; 2) nursing staff will prefer the belt lift device for toileting; 3) nursing staff will prefer the belt lift device to the currently used lift (in cases where either lift is appropriate) for bed/chair transfer; and, 5) the time required to utilize the belt lift as compared to manual lifting methods will not increase significantly.

Back Pain↗
PubMed1998

Effect of semi-rigid lumbosacral orthosis use on oxygen consumption during repetitive stoop and squat lifting.

The use of back belts in industry has increased despite the lack of scientific evidence supporting their efficacy. The purpose of this study was to investigate the effect of a semi-rigid lumbosacral orthosis (SRLSO) on oxygen consumption during 6-min submaximal repetitive lifting bouts of 10 kg at a lifting frequency of 20 repetitions min-1. Fifteen healthy subjects (13 men, two women) participated in this study. Each subject performed squat and stoop lifting with and without an SRLSO for a total of four lifting bouts. Lifting bouts were performed in random order. Oxygen consumption during the final minute of each lifting bout was used for analysis. A two-way analysis of variance with repeated measures was used to analyse the effects of lift and belt conditions. The stoop and squat methods were significantly different, with the squat lift requiring 23% more oxygen on average than the stoop lift for equal bouts of work. No significant difference was found between the belt and no belt condition within the same lifting technique and no interaction was present. These data suggest that an SRLSO does not passively assist the paravertebral muscles (PVM) in stabilizing the spine during submaximal lifting bouts.

Adult↗
PubMed1993

Joint moments and muscle activity in the lower extremities and lower back in lifting and lowering tasks.

The mechanical loading on the body during the act of lifting has been estimated frequently. The opposite act of lowering has received much less attention. The aim of the present study was to compare the mechanical loading of the musculoskeletal system in lifting and lowering. Eight subjects repetitively lifted and lowered a load, using two different techniques (a leg and a back technique). The ankle, knee, hip and lumbosacral joint moments were estimated and the myoelectrical (EMG) activity of seven (leg and back) muscles was recorded. The differences between the lifting and lowering phase for the leg technique were similar to those observed when the back technique was applied. The joint moment curves in lifting showed a high level of agreement with the (time-reversed) moment curves in lowering. Peak moments in lowering were only slightly lower than in lifting (peak lumbar moments were 5.4% lower). These small differences were related to different acceleration profiles at the centre of gravity of the body/load complex. The EMG activity was considerably lower in lowering than in lifting. The mean EMG in lowering (average for seven muscles) was only about 69% of the EMG in lifting. This was attributed to the different types of muscle actions involved in lifting (mainly concentric) and lowering (mainly eccentric). Furthermore, the EMG results suggest that similar inter-muscular coordination is involved in lowering and lifting. The results give rise to the assumption that in lifting and lowering similar muscle forces are produced to meet the (nearly) equal joint moments, but in lowering these forces are distributed over a smaller cross-sectional area of active muscle, which might imply a higher risk of injury.

Acceleration↗
PubMed2002

Spinal loads during individual and team lifting.

The aim of this experiment was to compare lumbar spinal loads during individual and team lifting tasks. Ten healthy male subjects performed individual lifts with a box mass of 15, 20 and 25 kg and two-person team lifts with a box mass of 30, 40 and 50 kg from the floor to standing knuckle height. Boxes instrumented with force transducers were used to measure vertical and horizontal hand forces, whilst sagittal plane segmental kinematics were determined using a video based motion measurement system. Dynamic L4/L5 torques were calculated and used in a single equivalent extensor force model of the lumbar spine to estimate L4/L5 compression and shear forces. A significant reduction in L4/L5 torque and compression force of approximately 20% was found during team lifts compared to individual lifts. Two main reasons for the reduced spinal loads in team lifting compared to individual lifting were identified: (1) the horizontal hand force (i.e. pulling force) was greater in team lifting, and (2) the horizontal position of the hands was closer to the lumbar spine during team lifts. The horizontal hand force and position of the hands had approximately equal contributions in reducing the spinal load during team lifting compared to individual lifting.

Adult↗
PubMed2004

The effects of a sloped ground surface on trunk kinematics and L5/S1 moment during lifting.

There are many work environments that require workers to perform manual materials handling tasks on ground surfaces that are not perfectly flat (e.g. in agriculture, construction, and maritime workplaces). These sloped ground surfaces may have an impact on the lifting strategy/technique employed by the lifter, which may, in turn, alter the biomechanical loading of the spine. Describing the changes in kinematics and kinetics of the torso is the first step in assessing the impact of these changes and is the focus of the current research. Subjects' whole-body motions were recorded as they lifted a 10 kg box while standing on two inclined surfaces (facing an upward slope: 10 degrees and 20 degrees), two declined surfaces (facing a downward slope: -10 degrees and -20 degrees), and a flat surface (0 degrees) using three lifting techniques (leg lift, back lift and freestyle lift). These data were then used in a two-dimensional, five-segment dynamic biomechanical model (top-down) to evaluate the effect of these slopes on the net moment about the L5/S1 joint. The results of this study showed an interesting interaction effect wherein the net L5/S1 moment was relatively insensitive to changes in slope angle under the back lift condition, but showed a significant effect during the leg lift and freestyle lifting conditions. The results show that under the freestyle lifting condition the peak L5/S1 moment was significantly higher for the inclined surfaces as compared to the flat surfaces (6.8% greater) or declined surfaces (10.0% greater). Subsequent component analysis revealed that both trunk flexion angle and angular trunk acceleration were driving this response. Collectively, the results of this study indicate that ground slope angle does influence the lifting kinematics and kinetics and therefore needs to be considered when evaluating risk of low back injury in these working conditions.

Adult↗
PubMed2006

Can simple anthropometric and physical performance tests track training-induced changes in maximal box-lifting ability?

The objective of this research was to determine if tests of lifting strength and anthropometry could be used to assess training-induced changes in box-lift performance. Ninety-two British Army recruits completed a 10-week training programme. Isometric and dynamic lifting strength, body composition and maximal box-lift to 1.45 m and 1.70 m were assessed before and after training. Training significantly increased box-lift performance, dynamic lifting strength and fat-free mass, and reduced body fat. Statistically significant regression models (adjusted R(2) of 0.299 and 0.152) were produced that predicted the changes in box-lift performance from changes in body composition and lifting strength. However, the 95% limits of agreement between the observed and predicted change in box-lift performance showed wide margins of error (11-13 kg; 26-29%). Training-induced changes in box-lift performance appear to be highly specific, which suggests that both training and testing procedures should also be specific to box-lift performance.

Adult↗
PubMed1994

Dynamic biomechanical modelling of symmetric and asymmetric lifting tasks in restricted postures.

This article describes investigations of dynamic biomechanical stresses associated with lifting in stooping and kneeling postures. Twelve subjects volunteered to participate in two lifting experiments each having two levels of posture (stooped or kneeling), two levels of lifting height (350 or 700 mm), and three levels of weight (15, 20, or 25 kg). One study examined sagitally symmetric lifting, the other examined an asymmetric task. In each study, subjects lifted and lowered a box every 10 s for a period of 2 min in each treatment combination. Electromyography (EMG) of eight trunk muscles was collected during a specified lift. The EMG data, normalized to maximum extension and flexion exertions in each posture, was used to predict compression and shear forces at the L3 level of the lumbar spine. A comparison of symmetric and asymmetric lifting indicated that the average lumbar compression was greater in sagittal plane tasks; however, both anterior-posterior and lateral shear forces acting on the lumbar spine were increased with asymmetric lifts. Analysis of muscle recruitment indicated that the demands of lifting asymmetrically are shifted to ancillary muscles possessing smaller cross-sectional areas, which may be at greater risk of injury during manual materials handling (MMH) tasks. Model estimates indicated increased compression when kneeling, but increased shear forces when stooping. Increasing box weight and lifting height both significantly increased compressive and shear loading on the lumbar spine. A multivariate analysis of variance (MANOVA) indicated complex muscle recruitment schemes--each treatment combination elicited a unique pattern of muscle recruitment. The results of this investigation will help to evaluate safe loads for lifting in these restricted postures.

Adult↗
PubMed1996

Trunk kinematics of one-handed lifting, and the effects of asymmetry and load weight.

This study investigated trunk kinematic differences between lifts performed using either one hand (unsupported) or two hands. These effects were studied while beginning the lifts from different asymmetric starting positions and while lifting different load weights. Each subject lifted a box from a lower to an upper platform under one- and two-handed lifting conditions. Subjects wore a lumbar spine electrogoniometer, from which relative motion components were calculated in the trunk's three cardinal planes. Results of this study showed that one-handed lifting resulted in significantly higher ranges of motion in the lateral and transverse planes and greater flexion in the sagittal plane. Back motion characteristics previously found to be associated with low back disorders were all significantly higher for one-handed lifts. The two-handed lift technique, on the other hand, produced overall faster trunk motions in the sagittal plane and equal or larger acceleration and deceleration magnitudes in all planes of motion. Increases in load asymmetry affected trunk kinematics, in that magnitude values for range of motion, velocity and acceleration became much greater with increasingly asymmetric load positions. Increasing the load weight appeared to have less of an effect on trunk kinematics, with increases in position mostly occurring during sagittal and lateral bending. These results suggest that unsupported one-handed lifting loads the spine more than two-handed lifts, due to the added coupling. Applying these results to a previously developed model, one-handed lifting was also found to increase one's risk of suffering a low back disorder.

Adult↗
PubMed1997

Estimates of weight that subjects can lift frequently in functional capacity evaluations.

BACKGROUND AND PURPOSE: This study was designed to determine whether the maximum weight that can be lifted during 33% to 67% of a workday (weight lifted frequently) can be accurately predicted from other data gathered during a functional capacity evaluation (FCE). The best equations for estimating weight lifted frequently were also identified, and the interrater reliability for measurements obtained during a 6-day FCE was calculated. SUBJECTS: A retrospective chart audit was conducted of clients (36 female, 93 male) who completed 22-hour FCEs during a 6-day period. Ninety subjects had spinal problems, and 39 subjects had injuries not involving the spine. Subjects were randomly assigned to a model estimation group (n = 109) or a cross-validation group (n = 20). METHOD: A stepwise multiple regression analysis identified the best predictors of weight lifted frequently, with subjects lifting from four different heights. The resulting equations were used to predict the weight for the cross-validation group, and predicted weights were compared with observed weights using t tests and correlation coefficients. RESULTS: Regression equations explained between 27.3% and 93.0% of the variance in weight, with standard errors of estimation between 1.09 and 5.72. No differences between the mean observed and predicted scores were found when estimates were based on weight only occasionally lifted (maximum weight that could be lifted up to 33% of a workday). CONCLUSION AND DISCUSSION: Estimates of weight lifted frequently based on weight lifted occasionally can be made, but the usefulness of these estimates is questionable. Clinicians should use caution when using estimations of weight lifted for return-to-work recommendations. [Saunders RL, Beissner KL, McManis BG. Estimates of weight that subjects can lift frequently in functional capacity evaluations.

Adult↗
PubMed2002

The contribution of aerobic fitness and back strength to lift capacity.

STUDY DESIGN: This study used a concurrent validation design with 45 healthy female participants. OBJECTIVE: To measure the relative contributions of aerobic capacity and back strength to lift capacity. SUMMARY OF BACKGROUND DATA: This was the first concurrent study of the relations among spine strength, aerobic capacity, and lift capacity. Previous research had demonstrated moderate to strong relations between spine strength and lift capacity and between aerobic capacity and lift capacity. METHODS: Multiple regression techniques were used on reliable and valid measures of each construct to study the individual and joint contributions of spine strength and aerobic capacity to lift capacity. RESULTS: Both spine strength and aerobic capacity make significant independent contributions to lift capacity, accounting for 11% and 27% of the variance, respectively. Taken together, the predictive power of these variables on lift capacity accounts for 43% of the variance. CONCLUSIONS: Lift capacity is dependent on both back strength and aerobic capacity. It may be inappropriate to use lift capacity as an indicator for the severity of spine impairment in a disability determination system without taking into account the individual's aerobic capacity. Treatment intended to improve the lift capacity of persons with spine impairment should anticipate that improvement in both back strength and aerobic capacity will improve lift capacity.

Adult↗