The energetic, kinematic and kinetic responses to load carried on the back, on the head and in a doublepack.

The determinants of energy saving phenomena reported for load carried on the head, back and in a doublepack remain unclear. This study compared the energetic, kinematic and kinetic responses to head (H), back (B) and doublepack (DP) loading. Fifteen volunteers walked on an instrumented treadmill at 3 kmh with 0, 3, 12 and 20 kg in each loading method.

Inter-individual variability in load carriage economy and comparisons between different load conditions.

Equivocal findings exist for the economy associated with load carried close to the body's centre of mass. Individual variation could explain some of the equivocal findings. This research aimed to examine the extent of individual variation in loaded walking economy.

Interaction Between Ambient Temperature, Hypoxia, and Load Carriage on Respiratory Muscle Fatigue.

While respiratory muscle fatigue is present following load carriage activity at sea level, the effect of environmental conditions on respiratory strength while undertaking load carriage is unknown. The effect of thoracic load carriage during walks (5.5 km) in four environments [(thermo-neutral sea level (SL), -10°C (C), 4300 m (H) and 4300 m at -10°C (HC)] was evaluated on respiratory muscle fatigue.

A comparison of economy and sagittal plane trunk movements among back-, back/front- and head-loading.

It has been suggested that freedom of movement in the trunk could influence load carriage economy. This study aimed to compare the economy and sagittal plane trunk movements associated with three load carriage methods that constrain posture differently. Eighteen females walked at 3 kmh with loads of 0, 3, 6, 9, 12, 15 and 20 kg carried on the back, back/front and head.

The effect of temperature, gradient, and load carriage on oxygen consumption, posture, and gait characteristics.

Purpose: The purpose of this experiment was to evaluate the effect of load carriage in a range of temperatures to establish the interaction between cold exposure, the magnitude of change from unloaded to loaded walking and gradient.

Methods: Eleven participants (19-27 years) provided written informed consent before performing six randomly ordered walking trials in six temperatures (20, 10, 5, 0, -5, and -10 °C). Trials involved two unloaded walking bouts before and after loaded walking (18.

The reliability of the Extra Load Index as a measure of relative load carriage economy.

The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h, 6 km·h and a self-selected speed. Trial conditions were repeated 7 days later to assess test-retest reliability.

High intensity training improves health and physical function in middle aged adults.

High intensity training (HIT) is effective at improving health; however, it is unknown whether HIT also improves physical function. This study aimed to determine whether HIT improves metabolic health and physical function in untrained middle aged individuals. Fourteen (three male and eleven female) untrained individuals were recruited (control group n = 6: age 42 ± 8 y, weight 64 ± 10 kg, BMI 24 ± 2 kg·m-2 or HIT group n = 8: age 43 ± 8 y, weight 80 ± 8 kg, BMI 29 ± 5 kg·m-2).

Regression models of sprint, vertical jump, and change of direction performance.

It was the aim of the present study to expand on previous correlation analyses that have attempted to identify factors that influence performance of jumping, sprinting, and changing direction. This was achieved by using a regression approach to obtain linear models that combined anthropometric, strength, and other biomechanical variables. Thirty rugby union players participated in the study (age: 24.

A biomechanical comparison of the traditional squat, powerlifting squat, and box squat.

The purpose of this study was to compare the biomechanics of the traditional squat with 2 popular exercise variations commonly referred to as the powerlifting squat and box squat. Twelve male powerlifters performed the exercises with 30, 50, and 70% of their measured 1 repetition maximum (1RM), with instruction to lift the loads as fast as possible. Inverse dynamics and spatial tracking of the external resistance were used to quantify biomechanical variables.

Effect of load positioning on the kinematics and kinetics of weighted vertical jumps.

One of the most popular exercises for developing lower-body muscular power is the weighted vertical jump. The present study sought to examine the effect of altering the position of the external load on the kinematics and kinetics of the movement. Twenty-nine resistance-trained rugby union athletes performed maximal effort jumps with 0, 20, 40, and 60% of their squat 1 repetition maximum (1RM) with the load positioned (a) on the posterior aspect of the shoulder using a straight barbell and (b) at arms' length using a hexagonal barbell.

Kinematic and kinetic analysis of maximal velocity deadlifts performed with and without the inclusion of chain resistance.

The purpose of this study was to investigate whether the deadlift could be effectively incorporated with explosive resistance training (ERT) and to investigate whether the inclusion of chains enhanced the suitability of the deadlift for ERT. Twenty-three resistance trained athletes performed the deadlift with 30, 50, and 70% 1-repetition maximum (1RM) loads at submaximal velocity, maximal velocity (MAX), and MAX with the inclusion of 2 chain loads equal to 20 or 40% of the subjects' 1RM. All trials were performed on force platforms with markers attached to the barbell to calculate velocity and acceleration using a motion capture system.

A biomechanical analysis of straight and hexagonal barbell deadlifts using submaximal loads.

The purpose of the investigation was to compare the kinematics and kinetics of the deadlift performed with 2 distinct barbells across a range of submaximal loads. Nineteen male powerlifters performed the deadlift with a conventional straight barbell and a hexagonal barbell that allowed the lifter to stand within its frame. Subjects performed trials at maximum speed with loads of 10, 20, 30, 40, 50, 60, 70, and 80% of their predetermined 1-repetition maximum (1RM).

The Extra Load Index as a method for comparing the relative economy of load carriage systems.

The Extra Load Index (ELI) has been proposed as a suitable method of assessing the relative economy of load carriage systems. The purpose of this study was to determine, based on empirical evidence, that the ELI can accommodate variations in both body composition and added load. In total, 30 women walked carrying loads of up to 70% body mass at self-selected walking speeds whilst expired air was collected.

A pilot investigation of load-carrying on the head and bone mineral density in premenopausal, black African women.

Although the influence of weight-bearing activity on bone mass has been widely investigated in white women, few studies have been conducted in black, African populations. We investigated bone mineral density (BMD) in black South African women, with and without a history of load-carrying on the head. We also investigated whether load carrying may offer protection against low BMD in users of injectable progestin contraception (IPC).

Contemporary training practices in elite British powerlifters: survey results from an international competition.

The primary objective of this study was to investigate current powerlifting training methods in light of anecdotal evidence purporting increased similarity with the explosive training practices of weightlifters. The study also assessed the prevalence of contemporary training practices frequently recommended for powerlifters in the popular literature. A 20-item survey was distributed to 32 elite British powerlifters at an International competition.

Efficacy of orally administered amphipathic polyaminocarboxylic acid chelators for the removal of plutonium and americium: comparison with injected Zn-DTPA in the rat.

Chelators are used to promote excretion of actinides and some other metals, but few are orally effective. The relative efficacies of orally administered triethylenetetraminepentaacetic acids (TT) with varying lipophilic properties on the removal of 241Am and 239Pu and comparison with parenteral Zn-DTPA was determined. The actinides were administered to adult rats 2 weeks prior to initiation of 30 d of chelation treatment.

Does the severity of radionuclide-induced skeletal malignancy depend upon radiation dose?

The severity of effect as a function of skeletal radiation dose for induced skeletal malignancy was investigated among a relatively large group of beagle dogs singly injected as young adults with soluble radionuclide. Bone-seeking radionuclides considered were 239Pu, 226Ra, 228Ra, 224Ra, 228Th, and 90Sr. Variables included skeletal radiation dose, tumor growth rate, maximum tumor volume, sex of the animals, growth period of the tumor, degree of calcification of the tumor, skeletal location of the tumor, year of death, and occurrence of metastases.

Does low dose internal radiation increase lifespan?

No significant differences in lifespan could be established between control dogs and dogs given 241Am, 228Th, 90Sr, 228Ra, 226Ra or monomeric 239Pu at low dosage levels that induced less than 10% skeletal malignancies (low dose animals) in the Utah beagle colony when all dogs surviving at least 1 y were included in the analysis and dogs given individual radionuclides were considered separately or together. Censoring or exclusion of dogs from these groups that were diagnosed with skeletal malignancies or that died in a gran mal epileptic seizure made no important difference to these results. Therefore, an enhanced lifespan of low dose dogs as compared with controls could not be established.

Does malignant hematopoietic disease result from internal exposure to 239Pu?

Neither Fisher's Exact Test nor linear regression analysis (dose-response relationship) using average skeletal dose from 239Pu as a surrogate for marrow dose could establish a statistically significant association between malignant hematopoietic disease (MHD including leukemia and aleukemia) and exposure to 239Pu among dogs in the Utah beagle colony. In addition, when dog-years at risk was the parameter used to estimate the rate of expected malignant hematopoietic tumors in dogs exposed to 239Pu, the estimate was within the range of the 95% confidence limits of the control dogs for six cases (and also within the 95% confidence limits for five cases when the single case of lymphoma was omitted). It was concluded that if there was an effect of 239Pu exposure on the occurrence of MHD in this beagle experiment, it was not very meaningful.

Comparisons of the skeletal locations of putative plutonium-induced osteosarcomas in humans with those in beagle dogs and with naturally occurring tumors in both species.

Osteosarcomas occur from exposures to bone-seeking, alpha-particle-emitting isotopes, particularly plutonium. The skeletal distribution of putative 239Pu-induced osteosarcomas reported in Mayak Metallurgical and Radiochemical Plutonium Plant workers is compared with those observed in canine studies, and these are compared with distributions of naturally occurring osteosarcomas in both species. In the Mayak workers, 29% and 71% of the osteosarcomas were in the peripheral and central skeleton, respectively, with the spine having the most tumors (36%).

Does soft tissue cancer affect the development of radionuclide-induced skeletal malignancy?

Data in the archives of the beagle project at the University of Utah were used to determine whether there might have been an association between the occurrence of soft tissue cancer and bone tumor (skeletal malignancy) among the dogs injected with bone-seeking radionuclides. In addition to comparing the numbers of animals with and without bone tumors and with and without soft tissue cancers, data on bone sarcomas and soft tissue sarcomas were compared. Longevity (postinjection survival) of the dogs was investigated.