Manual handling performance: the effects of menstrual cycle phase

Physiological and subjective responses to physical performance have been shown to interrelate with fluctuations in the female hormonal environment throughout the menstrual cycle. The aim of this study was to examine whether these fluctuations affect the strenuous performance required in manual handling. Seventeen eumenorrheic females performed lifting tasks in five phases of their menstrual cycle. These tasks were maximal isometric lifting strength (MILS) and an endurance lift at 45% MILS (t), at both knee and waist height; and the selection of a maximal acceptable load (MAL) to lift six times per min, for 10 min, in both the sagittal and asymmetric planes. Heart rate response (HR) and rating of perceived exertion (RPE) were recorded throughout each of the lifting tasks. MILS, t and the chosen MAL were unaffected by menstrual phase over both heights and planes of lift (p>0.05). HR to the isometric endurance lift was greater following ovulation than prior to ovulation by ? 7 beats.min^?1 (p> 0.05). This was true when the data were analysed at 50, 80 and 100% of the time to volitional fatigue, and by an area under the curve procedure. HR to the dynamic lifting tasks was also elevated by ? 7 beats.min^?1 following ovulation. This difference was non-significant due to the low power of the analysis. Re-analysis of the data by re-sampling 1000 matched comparisons produced significant phase variations (p> 0.05). The RPE for all of the lifting tasks was independent of menstrual phase (p> 0.05). The impact of the eumenorrheic menstrual cycle on lifting capability was negligible in the present study. However, the results of this study indicate that all further investigations utilizing HR data to produce recommendations for health and safety in manual handling tasks must control for menstrual cycle phase in female populations.     

Review of:“Sex Differences in Human PerformanceEdited by M. A. BAKER (Chichester,England: John Wiley, 1987.) [Pp. xvi + 202.] £22·00. ISBN 0-471-91119-4.

An experiment was conducted to examine the role that maximal lifting power has in predicting maximum acceptable weight of lift (MAWL) for a frequency of one lift per 8 h. The secondary aim of the study was to compare the ability of power to predict MAWL to previously used measures of capacity including two measures of isometric strength, five measures of isokinetic strength, and isoinertial capacity on an incremental lifting test. Twenty-five male subjects volunteered to participate in the experiment. The isometric tests involved maximum voluntary contractions for composite lifting strength at vertical heights of 15 and 75 cm. Peak isokinetic strength was measured at velocities of 0.1, 0.2, 0.4, 0.6 and 0.8 m s^?1 using a modified CYBEX® II isokinetic dynamometer. Isoinertial lifting capactity was measured on the X-factor incremental lifting machine and peak power was measured on the incremental lifting machine by having subjects lift a 25 kg load as quickly as possible. The results indicate that peak isoinertial power is significantly correlated with MAWL, and this correlation was higher than any of the correlations between the other predictor variables and MAWL. The relationships between the isokinetic strength measures and MAWL were stronger than the relationships between the isometric measures and MAWL. Overall, the results suggest that tests used to predict MAWL should be dynamic rather than static.     

Human capabilities in repetitive lifting

In emergencies, it may be necessary for men to manually handle very large quantities of materials. Although data are available for loads carried on the back and there are specific civilian and military recommendations concerning safe maximum loads and acceptable workloads for repetitive lifting, data quantifying maximum capabilities for repetitive lifting tasks are not available. We have therefore undertaken a preliminary study to determine the relationship between lifting rate and time to exhaustion using three standard loads.

Eight healthy, fit, well-trained young soldiers bimanually lifted three loads (25, 50 and 75% of their maximal lifting capacity (MLC) for a single lift to waist height) from the floor to a platform at waist height (40% stature) situated directly in front of them at lifting rates of 2, 3 and 4 lifts min ^?1 (75% MLC), 4, 6 and 8 lifts min^?1 (50% MLC) and at 8, 10 and 12 lifts min^?1 (25% MLC) for 1 hour or until they become exhausted or were unwilling or unable to continue or maintain the prescribed lifting rate. The observed lifting duration (LD obs) was noted, or if the subject was not exhausted after 1 hour of lifting, he estimated his lifting duration (LD est). Oxygen consumption (VO₂) and heart rate (HR) were measured for 1 min each 10 min.

The mean (S.D.) LD obs and LD est at 25% MLC were 156(57), 99(61) and 65 (34) min for 8, 10 and 12 lifts min^?1, respectively. At 50% MLC they were 111(65), 72(45) and 35(18) min for 4, 6 and 8 lifts min^?11 respectively. At 75% MLC they were 93(69), 61(35) and 30(23)min for 2, 3 and 4 lifts min^?1, respectively. The mean relationships between load and lifting rate at 50, 35 and 23% V˙O₂ max (determined for uphill treadmill running), and for an HR of 110 beat min ^?1 were constructed.

These results provide a preliminary quantification of maximum human capabilities in repetitive lifting and an indication of the upper limits of tolerance for industrial workers undertaking repetitive lifting over an 8 hour workday. Further work is necessary to evaluate interpersonal and ergonomic factors in repetitive lifting tasks.     

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]O_2max (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.     

Jerry can carriage is an effective predictor of stretcher carry performance

Carrying a casualty on a stretcher is a critical task conducted in a range of occupations. To ensure that personnel have the requisite physical capacity to conduct this task, two bilateral jerry can carries were used to predict individual performance in a four-person stretcher carry. Results demonstrated a bilateral 22-kg jerry can carry (R² = 0.59) had superior predictive ability of stretcher carry performance than a bilateral 15-kg jerry can carry (R² = 0.46). Pre- to post-carry changes in grip endurance (p > 0.05), back–leg isometric strength (p > 0.05) and leg power (p > 0.05) were not significantly different between carry tasks. There was no significant difference in heart rate (p > 0.05) and oxygen consumption (p > 0.05) between the stretcher carry and either jerry can carry. Thus, on the basis of performance correlations and physiological measures, the 22-kg jerry can carry is an appropriate predictive assessment of four-person stretcher carriage.

Practitioner Summary: This study investigated the ability of a jerry can carry to predict individual performance on a four-person stretcher carry. Performance correlations were substantiated with physiological measures to demonstrate similar physical requirements between task and test. These results can be used to set physical employment standards to assess stretcher carriage.     

Immune and inflammatory responses of Australian firefighters after repeated exposures to the heat

When firefighters work in hot conditions, altered immune and inflammatory responses may increase the risk of a cardiac event. The present study aimed to establish the time course of such responses. Forty-two urban firefighters completed a repeat work protocol in a heat chamber (100 ± 5°C). Changes to leukocytes, platelets, TNFα, IL-6, IL-10, LPS and CRP were evaluated immediately post-work and also after 1 and 24 h of rest. Increases in core temperatures were associated with significant increases in leukocytes, platelets and TNFα directly following work. Further, platelets continued to increase at 1 h (+31.2 ± 31.3 × 10⁹ l, p < 0.01) and remained elevated at 24 h (+15.9 ± 19.6 × 10⁹ l, p < 0.01). Sustained increases in leukocytes and platelets may increase the risk of cardiac events in firefighters when performing repeat work tasks in the heat. This is particularly relevant during multi-day deployments following natural disasters.

Practitioner Summary: Firefighters regularly re-enter fire affected buildings or are redeployed to further operational tasks. Should work in the heat lead to sustained immune and inflammatory changes following extended rest periods, incident controllers should plan appropriate work/rest cycles to minimise these changes and any subsequent risks of cardiac events.     

A history of low back pain affects pelvis and trunk mechanics during a sustained lift/lower task

This study compared three-dimensional trunk and pelvis range of motion (ROM) during a sustained asymmetric box lift/lower task between a group with a history of low back pain (HBP, n = 9) and a group with no history of low back pain (NBP, n = 9). Participants lifted an 11-kg box for 10 min at 12 cycles/min from ankle height in front to shelves 45 deg off-centre at waist height. Kinematic data were collected at the beginning (min1), middle (min5) and end of the bout (min9). Two-way analyses of variance were performed for all variables. Pelvis and trunk transverse ROM were similar at min1. By min9, HBP group did not change (31.9 ± 9 deg); however, ROM decreased in NBP group (21.6 ± 6 deg, p < 0.05). Therefore, despite no current pain, the HBP group demonstrated protective lifting mechanics compared to controls. Also discussed are implications for studying lifting paradigms at sub-maximal effort over longer periods of time.

Practitioner summary: Differences between groups over time demonstrate residual consequences of low back pain (LBP) in a manual materials handling scenario. Individuals with a history of LBP (pain free for 6 months) demonstrated more conservative lifting mechanics towards the end of the bout compared to controls with no history of LBP.     

Measures of localized spinal muscle fatigue

The objective of this study was to determine the best variable, if any, to indicate the level of localized muscle fatigue. Six male and six female subjects were studied while they exerted their maximal voluntary contraction and 40% of maximal voluntary contraction of spinal extensors in an isometric lifting activity. The electromyography (EMG) of erectores spinae at thoracic and lumbar levels was measured bilaterally. Also, the muscle bed blood volume, level of blood oxygenation to erector spinae at L3 level and heart rate were measured. The initial and final values of subjective feelings of fatigue through visual analogue score, rate of perceived exertions and body part discomfort rating were recorded. The mean maximal voluntary contraction forces for males and females were 899 (238) N and 431 (135) N respectively. The mean durations of hold in maximal voluntary fatiguing contraction were 68.1 (39.9) s and 72.3 (37.0) s for men and women respectively. By the end of the hold the force declined to 52% for males and 62% for females. The EMG amplitudes and median frequencies also progressively declined (p < 0.01). ANOVA revealed that the task percentile values of all variables were significantly different (p < 0.01). Gender had a significant main effect (p < 0.01). The correlation coefficients between force and other individual variables were weak to modest, but significant (p < 0.001). None of the single variables predicted fatigue reliably for either gender and levels of contraction. The regression equations developed were highly significant (p < 0.01) and they explained 96 to 98% of variance in both genders and contractions.     

Changes in stature following plyometric drop-jump and pendulum exercises

The aim of this study was to compare the changes in stature following the performance of plyometric exercises using drop-jumps and a pendulum swing. Eight male participants aged 21.7 ± 1.8 years with experience of plyometric training gave their informed consent to act as participants. Participants undertook two exercise regimens and a 15-min standing test in a random order. The exercises entailed the performance of 50 drop-jumps from a height of 0.28 m or 50 pendulum rebounds. Participants were instructed to perform maximal jumps or rebounds using a ‘bounce’ style. Measurements of stature were performed after a 20-min period of standing (pre-exercise), 2-min after exercise (post-exercise) and after a 20-min standing recovery (recovery). Back pain and muscle soreness were assessed using an analogue-visual scale, at each of the above times and also 24 and 36 h after the test. Peak torque during isokinetic knee extension at 1.04 rads^?1 was measured immediately before and after the exercise bouts, to assess the degree of muscular fatigue. Ground/wall reaction force data were recorded using a Kistler force platform mounted in the floor for drop-jumps and vertically on the rebound wall for pendulum exercises. Drop-jumps resulted in the greatest (p<0.05) change in stature (-2.71±0.8 mm), compared to pendulum exercises (-1.77±0.7 mm) and standing (-0.39±0.2 mm). Both exercise regimens resulted in a significant (p<0.01) decrease in stature when compared to the standing condition. Dropjumps resulted in significantly greater peak impact forces (p<0.05) than pendulum exercises (drop-jumps = 3.2±0.5 × body weight, pendulum = 2.6±0.5×body weight). The two exercise conditions both invoked a small degree of muscle soreness but there were no significant differences between conditions. Both exercise regimens resulted in a non-significant decrease in peak torque indicating a similar degree of muscular fatigue. Based on the lower shrinkage resulted and lower peak forces, it can be concluded that pendulum exercises pose a lower injury potential to the lower back than drop-jumps performed from a height of 28 cm.     

Using MODIS time series data to estimate aboveground biomass and its spatio-temporal variation in Inner Mongolia’s grassland between 2001 and 2011

It is critical to understanding grassland biomass and its dynamics to study regional carbon cycles and the sustainable use of grassland resources. In this study, we estimated aboveground biomass (AGB) and its spatio-temporal pattern for Inner Mongolia’s grassland between 2001 and 2011 using field samples, Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index (MODIS-NDVI) time series data, and statistical models based on the relationship between NDVI and AGB. We also explored possible relationships between the spatio-temporal pattern of AGB and climatic factors. The following results were obtained: (1) AGB averaged 19.1 Tg C (1 Tg = 10¹² g) over a total area of 66.01 × 10⁴ km² between 2001 and 2011 and experienced a general fluctuation (coefficient of variation = 9.43%), with no significant trend over time (R² = 0.05, p > 0.05). (2) The mean AGB density was 28.9 g C m^?2 over the whole study area during the 11 year period, and it decreased from the northeastern part of the grassland to the southwestern part, exhibiting large spatial heterogeneity. (3) The AGB variation over the 11 year period was closely coupled with the pattern of precipitation from January to July, but we did not find a significant relationship between AGB and the corresponding temperature changes. Precipitation was also an important factor in the spatial pattern of AGB over the study area (R² = 0.41, p < 0.001), while temperature seemed to be a minor factor (R² = 0.14, p < 0.001). A moisture index that combined the effects of precipitation and temperature explained more variation in AGB than did precipitation alone (R² = 0.45, p < 0.001). Our findings suggest that establishing separate statistical models for different vegetation conditions may reduce the uncertainty of AGB estimation on a large spatial scale. This study provides support for grassland administration for livestock production and the assessment of carbon storage in Inner Mongolia.     

Gravitational demand on the neck musculature during tablet computer use

Tablet computer use requires substantial head and neck flexion, which is a risk factor for neck pain. The goal of this study was to evaluate the biomechanics of the head–neck system during seated tablet computer use under a variety of conditions. A physiologically relevant variable, gravitational demand (the ratio of gravitational moment due to the weight of the head to maximal muscle moment capacity), was estimated using a musculoskeletal model incorporating subject-specific size and intervertebral postures from radiographs. Gravitational demand in postures adopted during tablet computer use was 3–5 times that of the neutral posture, with the lowest demand when the tablet was in a high propped position. Moreover, the estimated gravitational demand could be correlated to head and neck postural measures (0.48 < R ² < 0.64, p < 0.001). These findings provide quantitative data about mechanical requirements on the neck musculature during tablet computer use and are important for developing ergonomics guidelines.

Practitioner Summary: Flexed head and neck postures occur during tablet computer use and are implicated in neck pain. The mechanical demand on the neck muscles was estimated to increase 3–5 times during seated tablet computer use versus seated neutral posture, with the lowest demand in a high propped tablet position but few differences in other conditions.     

Metabolic cost and subjective assessment of palletizing and subsequent recovery

Twenty-one male blue collar workers repeatedly lifted (palletized) a box weighing 22 kg six times min^-1 for 5 min to a shelf of fixed height. The experimental conditions included two planes of lifting (symmetries), two shelf clearances, and three headrooms. The metabolic (heart rate, caloric cost and ventilation volume) and psychophysical variables (rate of perceived exertion, RPE; visual analogue score, VAS; and body part discomfort ratings, BPDR) were measured during resting, palletization, and recovery phases. In palletization the heart rate and metabolic cost ranged between 25 to 35% of the maximal aerobic capacity. Of the three factors only headroom had a significant effect on metabolic cost (p < 0.02) and the BPDR for low back (p < 0.05). In the recovery phase only headroom had significantly effect (p < 0.001) on metabolic cost. The metabolic recovery took 10 min; however, recovery measured through psychophysical indices appeared to continue for 20 min.     

Maximum weights of lift acceptable to male and female industrial workers for extended work shifts

Abstract

This paper reports the development of maximum acceptable weight of lift databases for male and female industrial workers for 12-hour work periods. Using a psychophysical methodology, 37 males and 37 females, experienced in manual lifting, performed various lifting tasks involving four frequencies, three box sizes, and three height levels. The maximum acceptable weight of lift was significantly influenced by the frequency of lift, height of lift, and box size. Box size effects were, however, less profound than frequency, and height effects. The maximum weight, acceptable for 12 hours of lifting, elicited an average heart rate of 90 and 101 beats min ^?1 for males and females, respectively. Males selected weights that, on average, resulted in metabolic energy expenditure rates of 23% of their aerobic capacity for 12 hours of lifting. Females required metabolic energy expenditure rates equivalent to 24% of their aerobic capacity for lifting acceptable levels of weight for 12 hours.     

Changes in trunk muscle activation and lumbar-pelvic position associated with abdominal hollowing and reach during a simulated manual material handling task

The purpose of this study was to investigate the effect of abdominal hollowing (AH) on trunk muscle activation and lumbar-pelvic motion during a controlled lift and replace task. Surface electromyograms were recorded from five abdominal and two back muscle sites. Sagittal lumbar-pelvic motion was recorded by video. Subjects lifted a 3.8 kg load in normal, maximum and extreme reaches, first while performing their preferred lifting style (PLS) and then maintaining an AH technique. The external oblique muscle site activities were significantly higher (p < 0.05) for the AH technique (ranging from 7–20% of maximal voluntary activation (MVIC)) than at any of the abdominal sites for the PLS (ranging from 2–10% MVIC). Differences were found among abdominal sites for the AH, but not for the PLS. The back muscle site activities (ranging from 9–30% MVIC) were significantly higher (p < 0.05) than for any of the abdominal muscles for all conditions, except for the anterior external oblique for AH. The pelvic and lumbar angles changed significantly (p < 0.05) between normal and maximal reaches and between techniques. The AH technique altered abdominal muscle activation amplitudes, with minimal differences in trunk extensors compared to the PLS. The AH resulted in more posterior pelvic tilt.     

Analysing the effects of applying agricultural lime to soils by VNIR spectral sensing: a quantitative and quick method

The potential of visible and near-infrared (VNIR) diffuse reflectance spectra to predict the chemical properties of Ferralsols and Arenosols cultivated with maize during four crop cycles were evaluated. The study was carried out in a greenhouse and aimed to (i) evaluate soil chemistry variation induced by plants and the application of lime with different degrees of reactivity using conventional methods and proximal soil-sensing techniques, (ii) identify the wavelength ranges related to soil chemistry changes, and (iii) construct models that predict soil chemistry attributes using soil VNIR spectra. Treatments used were three lime rates applied to raise the base saturation to 40%, 60% and 80% and one control. Partial least squares regression with cross-validation was used to establish relationships between the VNIR spectra and the reference data from chemical analyses. The predicted results were evaluated based on the values of coefficient of determination (R²), the ratio of the standard deviation of the validation set to the root mean square error of cross-validation (RPD), and the root mean square of prediction. The predicted results were excellent (R² > 0.90 and RPD > 3) for potassium and for the lime requirement calculation. Good predictions (0.81 < R² < 0.90 and 2.5 < RPD < 3) were also obtained for pH and sum of bases. The resulting models for exchangeable calcium, cation exchangeable capacity, and base saturation had moderate predictive power (0.66 < R² < 0.80 and 2.0 < RPD < 2.5). Our findings suggest that VNIR reflectance spectroscopy could be used as a rapid, inexpensive, and non-destructive technique to predict some soil chemistry properties for these soil types. As this methodology evolves, it may eventually permit real-time analyses of soil variability and real-time management responses via sensors installed on tractors.     

Obesity does not reduce maximum acceptable weights of lift

The maximum acceptable weights of lift (MAWL) of obese and non-obese participants were empirically investigated. Three obesity levels were considered: non-obese (18.5 kg/m(2)< or= body mass index (BMI)or= 40 kg/m(2)). Ten male and 10 female participants were recruited for each obesity level. The participants determined their MAWL for 18 different lifting task conditions (six lifting frequencies x three lifting heights). An analysis of variance (ANOVA) was conducted to determine the effects of obesity level, gender, lifting height, lifting frequency and their interactions on MAWL. Overall, the ANOVA results indicated that obesity does not reduce MAWL, and thus, suggested that the existing MAWL data can be used to accommodate both general and obese workers. However, further studies based on the biomechanical and physiological approaches are required to provide more complete understanding of obesity effects on lifting tolerance limits.     

Effects of Increasing Oxygen Availability on Bicycle Ergometer Endurance Performance

In order to test the effects of increasing oxygen availability on bicycle ergometer endurance performance, 26 subjects completed two criterion endurance performance tests of 6'min duration, (designed to elicit 115% of [Vdot]_O2max) while breathing either room air or 100% oxygen. It was hypothesised that if oxygen availability is a limiting factor in endurance performance, one would expect increased work output in the hyperoxic condition, Hyperoxic conditions that do not result in increased work performance would support the cell as limiting. The results of the present study support the oxygen transport theory as the major limiting factor in aerobic endurance performance. Subjects turned substantially more pedal revolutions (17[sdot]3 revs :p < 0[sdot]01) and had significantly higher oxygen uptakes (650 to 780 cm³ greater: p < 0[sdot]01) in the 100% oxygen condition. In addition, there were no differences in estimated cardiac output between the two conditions while there were substantial differences in the estimated a-v O₂ difference (2[sdot]92 cm³ 100 cm^?3 higher in 100% oxygen, p < 0[sdot]01). The increase in work performance was, therefore, ascribed to increased cellular availability of oxygen during hyperoxia.     

The effect of speech and speech intelligibility on task performance

The aim of this study was to find out what are the effects of three different sound environments on performance of cognitive tasks of varying complexity. These three sound environments were ‘speech’, ‘masked speech’ and ‘continuous noise’. They corresponded to poor, acceptable and perfect acoustical privacy in an open-plan office, respectively. The speech transmission indices were 0.00, 0.30 and 0.80, respectively. Sounds environments were presented at 48 dBA. The laboratory experiment on 36 subjects lasted for 4 h for each subject. Proofreading performance deteriorated in the ‘speech’ (p < 0.05) compared to the other two sound environments. Reading comprehension and computer-based tasks (simple and complex reaction time, subtraction, proposition, Stroop and vigilance) remained unaffected. Subjects assessed the ‘speech’ as the most disturbing, most disadvantageous and least pleasant environment (p < 0.01). ‘Continuous noise’ annoyed the least. Subjective arousal was highest in ‘masked speech’ and lowest in ‘continuous noise’ (p < 0.05). Performance in real open-plan offices could be improved by reducing speech intelligibility, e.g. by attenuating speech level and using an appropriate masking environment.     

Lifting in stooped and kneeling postures: Effects on lifting capacity,metabolic costs,and electromyography of eight trunk muscles

Twelve healthy, experienced underground coal miners performed lifting capacity tests in stooped and kneeling postures using a modified psychophysical, procedure. Subjects adjusted weight in a lifting box to the maximum they could handle without undue fatigue in an asymmetric lifting task. Lifting periods were 20 min in duration and the frequency was 10 lifts/min. Tests were performed under a 48-in. roof that restricted the subject's posture. Psychophysical, physiological, and biomechanical dependent measures included the maximum acceptable weight of lift (MAWL), heart rate (HR), rate of oxygen consumption (V̇O₂), ventilation volume rate (V̇_E), respiratory exchange ratio (R), and integrated electromyography (EMG) of eight trunk muscles. Results indicated that the MAWL was significantly lower when kneeling than when stooped (p < 0.05). Furthermore, metabolic demands were greater in terms of HR (p < 0.005) and VO₂ (p < 0.05) when kneeling. Left and right erectores spinae muscles exhibited increased EMG activity in the kneeling posture (p < 0.001). It was concluded that psychophysical lifting capacity is decreased, while the metabolic stress and internal load on the spine are increased, in the kneeling posture. Results of this Bureau of Mines study indicate that it may be advisable to reduce the weight of materials that are handled repetitively in the kneeling posture.     

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 R² 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.