Box Lifting Research Articles

Kinematic cues in perceptual weight judgement and their origins in box lifting

When accepting a parcel from another person, we are able to use information about that person's movement to estimate in advance the weight of the parcel, that is, to judge its weight from observed action. Perceptual weight judgment provides a powerful method to study our interpretation of other people's actions, but it is not known what sources of information are used in judging weight. We have manipulated full form videos to obtain precise control of the perceived kinematics of a box lifting action, and use this technique to explore the kinematic cues that affect weight judgment. We find that observers rely most on the duration of the lifting movement to judge weight, and make less use of the durations of the grasp phase, when the box is first gripped, or the place phase, when the box is put down. These findings can be compared to the kinematics of natural box lifting behaviour, where we find that the duration of the grasp component is the best predictor of true box weight. The lack of accord between the optimal cues predicted by the natural behaviour and the cues actually used in the perceptual task has implications for our understanding of action observation in terms of a motor simulation. The differences between perceptual and motor behaviour are evidence against a strong version of the motor simulation hypothesis.

Where does your own action influence your perception of another person's action in the brain?

Activation of premotor cortex during the observation and imitation of human actions is now increasingly accepted, but it remains unclear how the CNS is able to resolve potential conflicts between the observation of another person's action and the ongoing control of one's own action. Recent data suggest that this overlap leads to a systematic bias, where lifting a box influences participant's perceptual judgments of the weight of a box lifted by another person. We now investigate the neural basis of this bias effect using fMRI. Seventeen participants performed a perceptual weight judgment task or two control conditions while lifting a light box, a heavy box or no box during scanning. Brain regions related to perceptual bias were localized by correlating individual differences in bias with BOLD signal. Five regions were found to show correlations with psychophysical bias: left inferior frontal gyrus, left central sulcus, left extrastriate body area, left lingual gyrus and right intraparietal sulcus. The cluster in primary motor cortex was also activated by box lifting, and the cluster in extrastriate body area by the observation of hand actions and the weight judgment task. We suggest that these brain areas are part of a network where motor processing modulates perceptual judgment of observed human actions, and thus visual and motor processes cannot be thought of as two distinct systems, but instead interact at many levels.

Scaling of lifting forces in relation to object size in whole body lifting

Subjects prepare for a whole body lifting movement by adjusting their posture and scaling their lifting forces to the expected object weight. The expectancy is based on visual and haptic size cues. This study aimed to find out whether lifting force overshoots related to object size cues disappear or persist over a number of repeated lifts. In addition, the influence of the degree of alternation between load sizes, and the influence of knowledge of actual object weights prior to the lifts, were investigated with regard to their effect on force overshoots. Four experiments were performed using a large and a small box, each of 8.4 kg weight, and varying degrees of alternation between boxes. In two of the experiments, subjects were informed about the weight of the objects, while in the other two experiments they were not informed about the weight of the objects. When boxes were lifted 15 times before switching to the other box, rapid diminishing of force scaling errors was observed. However, when boxes were alternated each lift or after three lifts, persisting force scaling overshoots were found in lifting the large box compared to the small one. When participants were given information regarding the actual object weight, force overshoots in the first pair of large and small box lifts were not different from overshoots in experiments where subjects were not informed about the weight of the objects. This shows that, for occupational lifting, risks related to force overshoots in lifting large objects can persist despite experience in lifting the objects and despite the use of labels indicating the weight of the objects.

Estimation of load transfer force to the hands during sagittal plane box lifting

Load transfer force to the hands was investigated to provide an accurate estimate of load transfer during sagittal lifting tasks for application in an industrial setting. The effects of gender, load mass, lift style, load transfer duration and participant strength were examined as possible variables to improve the estimation of load transfer force. Ten healthy men and eleven healthy women completed a total of 25 box lifts using a freestyle technique. Kinematic data were collected using the OPTOTRAK™ and a portable video camera. Measured load transfer force (MLTF) was determined as the total load weight minus measured values from a force plate. Five methods of estimating load transfer to the hands were calculated and compared with MLTF. The enhanced load transfer force method (ELTF) of estimating load transfer to the hands was superior to all other estimation methods.

METHODOLOGY AND EXPONENTIAL PROPERTIES OF CR-10 RATINGS

INTRODUCTION Perceived exertion is the subjective intensity of effort experienced during the performance of work. A variety of physiological, psychological and performance factors from both internal and external environments shape this perception. A majority of perceived exertion research uses one of several scales developed by Borg. Borg developed most of these scales based upon an adaptation of Stevens' law; which states that perceived intensities follow the form of a power function. When evaluating the stimulus-response relationship with the Borg CR-10 scale, the relation between perceived intensity and workload should be exponential. Furthermore, the exponent should be greater than one. However, some studies have reported exponents less than one. PURPOSE The purpose of this study was to use a standard occupational lifting task and the Borg CR-10 scale to depict the exponential relation between perceived intensity and work load. A secondary purpose was to provide a methodology that can be used to obtain exponents that are less than one, and to distinguish the difference in applications of these exponents. METHODS A total of 473 undergraduate students participated in this study. The subjects performed a box lifting task that consisted of eight. A dynamic lift profile was developed for each subject using their CR-10 ratings as the dependent variable and the weight of the box as the independent variable. Maximum functional lift capacity was estimated using the results of the dynamic lift profile analyses. Then, for each subject, one randomly selected weight load was used to estimate percent of maximum functional lift capacity. RESULTS An exponent greater than one resulted when the data were expressed in standard estimation format (M=2.28). The exponents were significantly different for males and females (p < 0.001). When expressed as a percentage of maximum functional lift capacity, an exponent less than one resulted (0.298). CONCLUSION When CR-10 ratings are expressed in actual estimation form, the resultant exponent should be greater than one. When CR-10 ratings are expressed as a percentage of maximum capacity, the resultant exponent should be less than one.

Reliability assessment of two militarily relevant occupational physical performance tests.

To determine the number of test sessions needed to stabilize performance on two military occupational physical tests and to assess their reliability, 10 male soldiers (22 +/- 3 yrs, 183 +/- 7 cm, 87 +/- 8 kg) performed both an indoor 6-station obstacle course (OC) and a repetitive box-lifting task (RBLT). The OC consisted of 46 cm-high hurdles, zigzag sprint, low crawl, horizontal pipe shimmy, 1.4 m wall traversal, and straight sprint. The RBLT required subjects to lift 20.5 kg boxes, continuously for 10 minutes, from the ground onto 1.3 m high platforms positioned 2.4 m apart. The OC mean +/- SD times (s), for sessions 1-4 respectively, were 37.4 +/- 2.2, 35.8 +/- 2.5, 34.7 +/- 2.1, and 34.5 +/- 1.7 seconds. The number of boxes lifted was 177 +/- 31, 194 +/- 28, 189 +/- 32, and 186 +/- 37 for the RBLT. Performance stabilized on the 3rd session for the OC (7% improvement over first trial, p < 0.05) and on the 2nd session for the RBLT (9% improvement over first trial, p < 0.05). The intraclass correlation coefficients were 0.92 and 0.94 for the OC and RBLT, respectively. This study demonstrates that both are reliable tests, but they do require administration of 1 single-trial session of RBLT and 2 two-trial sessions of OC before highly reliable performance data are obtained.

Resistance training and the enhancement of the gains in material-handling ability and physical fitness of British Army recruits during basic training

The aim was to evaluate the efficacy of a modified British Army basic training that included resistance training in improving material-handling performance and physical fitness, and to compare the modified training directly with the normal basic training. Forty-three males [19.2 (2.6) years of age, 1764 (72) mm in height, 73.0 (10.6) kg in mass] and nine females [19.1 (2.2) years, 1641 (67) mm, 62.0 (7.2) kg] performed the modified basic training. Testing occurred in the week before and in the final week of the 11-week basic training. Improvements with the modified training were observed for all six material-handling tests, including 8–12% for maximal box lifting, 15–19% for repetitive lifting and carrying and 9–17% for loaded marching (all p <0.01), and other established measures of aerobic fitness, strength and kinanthropometric characteristics. Significantly greater improvements were observed for the modified training compared with the normal training in maximal box lift to 1.45 m (12.4 versus 1.7%, p <0.01), 3.2 km loaded march performance with 15 kg (8.9 versus 3.6%, p <0.05), estimated fat-free mass (4.2 versus 1.5%, p <0.001), predicted [Vdot]O2max (1 min -1) (9.3 versus 4.1%, p <0.01) and dynamic lift to 1.45 m (15.5 versus 0.2%, p <0.001). It was concluded that the improvements in material-handling ability and other aspects of physical fitness brought about in recruits by British Army basic training can be enhanced by the use of a physical training programme that includes a carefully designed resistance training element. Of particular note are the improvements shown in performance on material-handling tasks that require muscular strength, as these represent many of the tasks that soldiers encounter in their military careers.

A longitudinal study of the development of low back pain in an industrial population.

This is a longitudinal study in which industrial workers without chronic low back pain (LBP) were initially assessed with a comprehensive test battery and surveyed every 6 months thereafter for 2 years. To determine factors that may predispose industrial workers who lift over 5000 kg per shift to LBP. Prospective studies are small in number and often limited in breadth or depth of the test battery, methodologic issues, or investigator expertise. There are no prospective studies that focus on a homogeneous work sample of industrial employees. Production workers (n = 149) who volunteered for the 2-year study were assessed using physical measures (e.g., muscular strength, endurance, and flexibility), lifting kinematics (a sagittal plane box lift), and health, lifestyle, and work environment data (paper questionnaires). Follow-up questionnaires were distributed every 6 months for 2 years. Using self-report of LBP as the main outcome measure, eight variables predicted LBP in this sample with a 75% correct prediction rate. Predictor variables included age, thoracic acceleration during the trunk velocity test, median frequency intercept of electromyography of the right L3 erector spinae, quadriceps strength, quadriceps endurance, self-assessment of fitness, having a confidante, and number of medications currently taken. Results confirmed the multifactorial nature of low back pain and suggest that personal fitness is an important defense against low back pain, even in manual handling lifting tasks.

PERFORMANCE RELIABILITY OF MILITARILY RELEVANT OCCUPATIONAL TASKS

Physical performance tests that simulate “real world” occupational tasks can be valuable for screening and assessing workers. Such tests must be reliable. However test performance improves with practice, especially for unfamiliar or complex tasks. To determine the amount of practice needed to stabilize performance on two military occupational physical tests and to assess reliability, ten male soldiers (22 ± 3 yrs, 183 ± 7 cm, 87 ± 8 kg) completed both an indoor 6-station obstacle course (OC) and a repetitive box-lifting task (RBL) in four separate sessions with at least 48 hours rest between sessions. The OC consisted of 46 cm-high hurdles, zigzag sprint, low crawl, horizontal pipe shimmy, 1.4 m wall traversal, and straight sprint. Two trials were performed on each of the four sessions, and the best time of the session was used for analysis. The RBL required subjects to lift a 20.5 kg box from the ground onto 1.3 m high platforms positioned 2.4 m apart, continuously for 10 minutes. One trial was performed in each session. Mean ± SD (different letters denote significant differences (p < 0.05): Performance stabilized on the 3rd session for the OC (8% overall improvement) and on the 2nd session for the RBL (8% overall improvement). After performance stabilized, the intraclass correlation coefficients were 0.92 and 0.94 for the OC and RBL respectively, demonstrating high test-retest reliability for both tests. The mean subject coefficient of variation was 5.1% on the box lift and 4.1% on the obstacle course. This study has demonstrated that both the OC and RBL are reliable tests, but do require 1 (i.e. RBL) or 2 (i.e. OC) practice sessions before highly reproducible results are obtained.Table

LINKING FITNESS LEVELS AND PROGRAMS TO BFORs IN THE CANADIAN FORCES

The Canadian Forces has developed bona fide occupational requirements (BFORs) for their Land Force Command. These include: a 13 km march with a 24.5 kg pack in 2 hr 26 min 20s; a casualty evacuation carrying a soldier of similar mass and height 100m in under 60s; lifting 48 ammunition boxes weighing 20.9 kg in under 5 min; shoveling. 486 m3 of gravel in under 6 min. This project was undertaken to: determine the levels in the fitness components necessary to achieve each BFOR; to establish benchmarks to monitor progress on route to the desired levels; and to design the programs to acquire the appropriate fitness level. Four levels in each fitness component were established with level 3 being the requisite to meet the BFOR's. The scores at level 3 are: The training programs were designed to progress each soldier from their initial level to level 3 over 12+ weeks with monitoring in weeks 1, 5, and 9. The programs feature prescriptions specific to each soldier's fitness status and progress over the 12 weeks from fitness-specific training to task-specific loading. The aerobic power intervals are at speeds corresponding to 90–100% VO2max and the aerobic capacity runs are at a “just talk” pace. The aerobic training begins to incorporate weight load marches in week 7 with progressions in load, distance, pace, and frequency. Strength loads are at specific RM's with reps at one less than failure. The strength training begins to incorporate ammunition box lifts, partner carries, and shoveling in week 7 with progressions in both load and reps.Table

Effects of basic training on material handling ability and physical fitness of British Army recruits

No study has yet evaluated the efficacy of British Army basic training in improving material handling performance. Therefore, the purpose of this study was to evaluate the efficacy of the current British Army basic training in improving material handling performance and physical fitness. Forty-seven males (19.4 (3.2)years of age, 1753 (59)mm in height, 71.0 (9.6)kg in weight) and 10 females (21.5 (3.5)years, 1623 (45)mm, 62.5 (5.2)kg) served as subjects. Testing was carried out in the week prior to, and in the final week of, an 11-week basic training course. Maximal box lifts to two different heights, and repetitive lifting and carrying of a 10 kg load did not improve with training. Static (38 cm upright pull) and dynamic (incremental dynamic lift to 145cm) lifting strength data concurred with the maximal box lift data in that no improvement was observed. Repetitive lifting and carrying of a 22kg load improved (29.5%, p<0.001), as did 3.2km loaded march performance with 25 kg (15.7%, p<0.001), but march performance with a 15kg load did not. Predicted VO2 max improved from 48.4 to 51.4 ml.kg-1.min-1, a change of 6.1% (p<0.05). Fat-free mass increased by 0.9 kg (1.5%, p<0.01), and body fat reduced by 2.7% of body mass (20.1%, p<0.001), resulting in a loss of 1.2 kg of body mass (1.7%, p<0.01). It is concluded that basic training in the British Army produces some favourable adaptations in recruits, especially in terms of aerobic fitness. However, the poor development of strength and material handling ability during training fails to improve the ability of soldiers to perform simulated military tasks, and it does little to reduce future injury risk while performing these tasks.

A LONGITUDINAL STUDY OF THE DEVELOPMENT OF LOW BACK PAIN IN AN INDUSTRIAL POPULATION

Study design This is a longitudinal study in which industrial workers without chronic low back pain (LBP) were initially assessed with a comprehensive test battery and surveyed every 6 months thereafter for 2 years. Objective To determine factors that may predispose industrial workers who lift over 5000 kg per shift to LBP. Summary of background data Prospective studies are small in number and often limited in breadth or depth of the test battery, methodologic issues, or investigator expertise. There are no prospective studies that focus on a homogeneous work sample of industrial employees. Methods Production workers (n = 149) who volunteered for the 2-year study were assessed using physical measures (e.g., muscular strength, endurance, and flexibility), lifting kinematics (a sagittal plane box lift), and health, lifestyle, and work environment data (paper questionnaires). Follow-up questionnaires were distributed every 6 months for 2 years. Results Using self-report of LBP as the main outcome measure, eight variables predicted LBP in this sample with a 75% correct prediction rate. Predictor variables included age, thoracic acceleration during the trunk velocity test, median frequency intercept of electromyography of the right L3 erector spinae, quadriceps strength, quadriceps endurance, self-assessment of fitness, having a confidante, and number of medications currently taken. Conclusion Results confirmed the multifactorial nature of low back pain and suggest that personal fitness is an important defense against low back pain, even in manual handling lifting tasks.

The muscular load on the lower back and shoulders due to lifting at different lifting heights and frequencies

The aim of the study was to investigate the muscular load on the lower back and shoulders and the circulatory load on employees at a post center during repetitive lifting of mail transport boxes. A mock-up was designed in the laboratory, a total of nine combinations of lifting height and frequency were studied. Surface EMG was recorded bisymmetrically from m. erector spinae (L3-level) and m. trapezius. The circulatory load was evaluated by measuring the heart rate. The results show a trade off between the low back and shoulders. The maximum load on the low back occurred at the low lifting height (36.3 and 54.4 cm) whereas the maximum load on the shoulders occurred at the high lifting height (144.9 and 163.0 cm).

THE EFFECTS OF RESISTANCE TRAINING ON A HIGH INTENSITY MANUAL MATERIALS HANDLING TASK IN WOMEN

1806 Manual materials handling tasks in the workplace place high demands on strength and endurance. It is recognized that men possess advantages (i.e. because of greater size and strength) over women during such tasks, but the potential of training interventions for the improvement of women's occupational performance is largely unexplored. We evaluated the effects of two resistance training programs: (1) upper body training (UBT) and (2) total body training (TBT) on a repetitive box lifting task (RBLT) and a 1 repetition maximum (1RM) boxlift (BL). The RBLT consisted of the maximum # of boxes lifted from the floor to a height of 1.32 m within a 10 min period (subjects moved between two boxes 2.4 m apart between lifts). 37 women (24±4 yrs, 166±6 cm, 64±9 kg) underwent either UBT (n=17) or TBT (n=20) and trained 3 x/wk for 6 months (3 sets/exercise, reps were periodized from 8 to 12; rest periods varied between 45-90 secs). A 20-30 min aerobic component concluded each workout. Testing occurred pre (T1), mid-way (T2) and post (T3) training. An ANOVA with repeated measures indicated significant (p≤0.05) training effects for both the RBLT and 1RM BL (T1<T2<T3), but no group or interaction effects. Results (mean±SD) were: 1RM BL (TBG: T1=30±5, T2=35±5, T3=38±4; T1 to T2%Δ=≈17%, T1 to T3%Δ=≈27%; UBG: T1=31±6, T2=35±7, T3=38±6, T1 to T2%Δ=≈13%, T1 to T3%Δ=≈23%); RBLT (TBG: T1=89±24, T2=109±18, T3=118±16, T1 to T2%Δ=≈22%, T1 to T3%Δ=≈33%; UBG: T1=86±24, T2=108±26, T3=118±20, T1 to T2%Δ=≈26%, T1 to T3%Δ=≈37%). These data indicate that(1) adaptations in the upper body appear to account for a greater proportion than the lower body for the performance changes and (2) women can continue to exhibit performance improvements beyond 3 month of training.

Trunk rotation monitor using angular velocity sensors.

To monitor the low back risk imposed by asymmetric postures at workplaces, a method using angular velocity sensors was studied. According to a simple model analysis, trunk rotation could be calculated from the angular velocities measured at both the waist and shoulder and from the inclination of each angular velocity sensor. We thus developed a new detector consisting of an angular velocity sensor (ENC-05D, Murata, Japan) for detecting angular velocity and an acceleration sensor (ADXL05, Analog Devices, USA) for measuring inclination. The precision of the angular velocity sensor was high as the correlation coefficient between the output of the sensor and the true value was 0.9996. When the detectors were affixed to a subject and compared with data measured by a Vicon System 370 (Oxford Metrics, UK), the correlation coefficients between the two methods were 0.949 and 0.815 during model tasks of box transfer and box lifting, respectively. In a model of lifting boxes at different rates, the mean and standard deviation increased according to the task speed. This method was shown to be of practical use for monitoring trunk rotation.

The Effect of Lift Height on Maximal Lifting Capabilities of Men and Women

The purpose of this study was to determine the effect of lift height on the one repetition maximum box lifting strength (1 RM) of men and women. Ten men and eleven women lifted to heights of 1, 2, 3, 4, 5, and 6 ft using a 46.5 cm long x 31 cm wide x 23 cm high aluminum box with handles. All lifts were accomplished using correct lifting technique while facing forward. An ANOVA, focused on six heights and blocked for gender was used for analysis. A Newman-Kuels post-hoc analysis was used to examine the significant differences between means. Results revealed that men lifted more than women overall (F = 128.9, p &lt; 0.01), and at each individual height (p &lt; 0.01). When the genders were combined, the two highest lifts (5 and 6 ft) were not different from each other, nor were the two lowest (1 and 2 ft). All other heights differed from one another (p &lt; 0.01). For both genders, the greatest percentage decrease from one height to the next occurred between 3 and 4 feet, when more upper body strength and torso involvement were required.

EFFECTS OF A PHYSICALLY DEMANDING TRAINING PROGRAM ON WOMEN'S HEAVY WORK TASK PERFORMANCE 760

To determine if women can be trained to perform heavy work tasks typically performed by men, 41 women (27.5±4 yrs, 164±6 cm, 68.3±12 kg) trained 60-90 mins/day, 5 days/week for 14 weeks, with weight-lifting, running, backpacking, and specificity drills. Testing included 1-rep max box lifts, submax box lifts for reps, load carriage for time, and aerobic power. The following (mean±SD) all improved significantly (p<0.05) with training: Table Lifts over 45 kg are considered “very heavy” work tasks in the U.S. Army (lift height not specified). Virtually all of the subjects could lift over 45 kg to 76 cm even before training. While only 26% of the subjects could lift over 45 kg to 132 cm before training, 60% could do so afterwards.Conclusions: A specially designed physical training program can greatly improve the ability of women to perform job tasks categorized as“very heavy”. The subjects will continue training for an additional 10 weeks to determine if their heavy work performance can be further improved.

BODY COMPOSITION AND MILITARY PERFORMANCE 1181

The relationships between body composition and military task performance are not well understood, despite the existence of body fat standards in the US Armed Forces. The aim of this study was to examine the relationship between three military tasks and indices of body composition. 23 males and 41 females performed three maximal tasks comprising a progressive box lift to 1.45 m (L), a fuel can carry (2 × 20 kg) (C), and a 12.8 km march with 15 kg load(M). Height, body mass, and body composition estimated via the Durnin and Womersley skinfold technique were measured on all subjects.Table Significant correlations existed between body mass and L and M in males(p<0.01), and L (p<0.05) and C (p<0.01) in females; between BMI and%fat in both L (p<0.05) and M (p<0.01) in males; between FFM and L(p<0.05) in males and L and C (p<0.01) in females. Stepwise regression revealed a valid common gender prediction model for C, incorporating FFM and BMI (R2=0.72, see=40.5), and for M, incorporating percentage fat only(R2=0.36, see=13.7). However, gender differences in the L model necessitated different equations for males and females. The male L model included body mass (R2=0.29, see=4.93) and female model, FFM(R2=0.29, see=6.61). In conclusion, the relationships between body composition and military performance are complex and inconsistent both between tasks and between genders.

Postural effects on biomechanical and psychophysical weight-lifting limits

Many believe that biomechanical models and data are not sufficiently refined and validated to be used as the basis for setting 'safe' population load lifting limits. Rather, they advocate that such limits should be based on what a sample of the population demonstrate to be 'maximum acceptable weight limits' (MAWL) resulting from psychophysical tests performed with different populations. Yet, biomechanical models are becoming more robust and valid. Computerized versions of these models are readily available, and these models now can provide a more complete understanding of the pathophysiology of a person's spinal column and supporting structures, thereby providing a means to predict the risk of tissue trauma in given lifting situations for large size populations. NIOSH has recognized the validity of both biomechanics and psychophysics for establishing a Recommended Weight Limit (RWL) in the United States. The implications of using both types of methods and data are explored in this paper. Three case studies are presented that involve infrequent lifting of varied size boxes from near floor level to explore how MAWL and biomechanically determined limits differ. The cases include symmetric, sagittal plane lifting using a freestyle posture, a similar lift but with freestyle and squat lift postures, and an asymmetric load lifting task. In all three case comparisons it is shown that a recommended load to be lifted based solely on a spinal disc compression force tolerance of 3400 N would be much lower than published MAWL values representing 75% or even 90% of young males under 40 years old (i.e. MAWL values may not be protective of some young males). It also is shown that MAWL values do not have as much population variance as the spinal motion segment failure values. Hence, many younger males would be expected to have spinal columns that can tolerate the highest published MAWL values. Several mitigating factors, including load lifting trajectories, lifting dynamics, and biomechanical modeling limitations are discussed, as well as differences in compressive force tolerances and MAWLs associated with age and gender.

Isoinertial tests to predict lifting performance.

Previous research has found isoinertial strength testing to be superior to isometric and isokinetic strength testing for prediction of task performance. The purpose of this study was to investigate tests on an isoinertial lifting machine (ILM) and their ability to predict performance on actual lifting tasks. Sixteen male subjects performed two lifting tasks: maximum box lift to truck-bed height of 1.35 m; and 'speed lifts' of 60 concrete blocks (each 22.7 kg) to the same height. These performance tests were compared to three ILM tests: a maximal lift to 1.83 m, a second maximal lift to 1.52 m, and an endurance test that entailed 60 timed ILM lifts of 22.7 kg to 1.83 m. Pearson product-moment correlations between ILM tests and performance tasks varied from r = 0.55 to 0.71. Therefore, the isoinertial test protocols employed in this study were able to account for only 30% to 50% of the variance in the performance of maximal lifting and endurance tasks. In was concluded that prediction of maximal lifting ability or endurance ability using an ILM might be enhanced by closer approximation of specific task variables, or by inclusion of dynamic parameters to measure technique.