Military load carriage : the effect of increased load, gender and load carriage duration on gait and posture
thesisposted on 18.03.2014 by Renee L. Attwells
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The work presented in this thesis is concerned with the measurement of gait and posture parameters and their variation due to load weight, gender and load carriage duration when carrying military loads. In particular it examines the load carriage system as a whole rather than the backpack alone, which has been the concentration of previous biomechanicalload carriage research. The aims of the thesis work were to (1) develop a protocol for examining the effect of the military LCS on gait and posture; (2) investigate the changes in gait and posture parameters in response to load weight, load position, gender and duration of load carriage; and (3) to gain a better understanding of the contributors to good load carriage system design through assessment with end users. Using Coda™ motion analysis a protocol was developed to investigate gait and posture of a participant by examining changes to lower limb and upper body movement. In order to address aims 2 and 3, the thesis consists of 2 parts. The fIrst part concentrates on short term load carriage. The fIrst trial examined the effect of military boots, indicating restricted ankle movement when wearing such footwear. Three other experimental trials examining the effect of load, gender and load carriage design were also conducted. In the lower limb increased load resulted in increased range of motion of all joints measured. The increase in ankle and femur movement, and decrease in knee movement was greatest for females. However, anthropometric data show that the gender effect could be due to body size alone. The factors studies all altered the range of motion of the lower limb, with increases in range of motion associated with an increased energy cost when carrying loads. Change in the forward lean of the participants was also noted, with greater forward lean as load was increased. Gender differences were seen, with females experiencing a greater range of motion of the trunk than their male counterparts; regardless of body size.Whilst these issues are important to consider, short term load carriage rarely occurs within Defence tasks. Therefore, the second half of the thesis concentrates on longer duration load carriage. Two experimental trials, one in the laboratory and one in the field, were completed. Longer duration carriage resulted in increased range of motion of the lower limb, greater forward lean, a more forward head position and increased discomfort over time. This increased discomfort was particularly evident in the shoulders and the feet. The work highlights the importance of collecting subjective data as discomfort is often the limiting factor when considering the ability to complete a load carriage task. Two different load carriage system designs (webbing + backpack) were considered as part of this work. Experimental work examining the effect on short term and lo"ng term load carriage is discussed. Two systems were examined, the Standard Issue system (currently in service in the British Army) and a prototype system (Airmesh). The Airmesh design presents a system that includes a hip belt and redistributes some of the load onto the front of the body via vest webbing as opposed to the standard design were the predominant amount of the load is on the back and supported by the shoulders. During short term load carriage minimal change was seen between systems, with the exception of less forward lean when carrying the Airmesh design and less trunk range of motion. When longer duration carriage was examined again a more upright walking posture was noted when carrying the Airmesh system, however greater trunk movement was seen. This may have serious implications for the physiological strain that an individual is placed under during longer term carriage. However, the more upright posture may present a safer option in terms of lower back stress and injury. This thesis concludes that a methodology is now in place to examine the changes in gait and posture whilst carrying military loads. The response due to increased load weight, gender, design and increased load carriage duration has also been studied with significant outcomes observed. Concentration in future research should be on including the entire load carriage system and examining the SUbjective response of individuals as well as important· biomechanical and physiological data. This will allow a more complete assessment of the effect military load has on the human body.