No abstract

In most types of protective clothing heat strain is an important issue. The wildland firefighter clothing system in the USA has seen no major revision over the last decades. In this project the wildland firefighter clothing system was studied at the material and the systems level. On the sweating guarded hot plate and the sweating thermal manikin effects of different base layers (cotton and modacrylic) and meta-aramid outer layers of different fabric weights were evaluated. Then, a human subject trial was performed on a limited set of clothing systems to validate the results from materials and manikin testing. The clothing systems were composed of relevant materials for wildland firefighters with extra configurations added to explore the effects of the highest and lowest levels of protection. All measurement techniques were reverted to a calculation of the total heat loss (THL), as predicted from the hot plate and the manikin and compared to the calculated heat loss from the human subjects. The prediction of the heat strain, based on the sweating guarded hot plate only, gives a large overestimation of the actual heat loss in humans. The currently used standard in the USA that utilizes THL values has no link to actual human heat loss. The manikin showed much better comparison to the human data in absolute terms, but in general underestimated heat loss and showed worse overall correlation to the human heat loss data than the hot plate values.

The primary purpose of the study was to determine whether atypical knee biomechanics are exhibited during landing on an inverted surface. A seven-camera motion analysis system and two force plates were used to collect lower extremity biomechanics from two groups of female participants: 21 subjects with chronic ankle instability (CAI) and 21 with pair-matched controls. Subjects performed ten landings onto inverted and flat platforms on the CAI/matched and non-test limbs, respectively. Knee and ankle joint angles, joint angular displacements, joint moments and eccentric work were calculated during the landing phase and/or at the initial contact. Paired t-tests were used to compare between-group differences (p<0.05). We observed that CAI group displayed a significantly increased knee flexion angle, knee flexion displacement, peak knee extension moment and internal rotation moment, and eccentric work in the sagittal plane, possibly due to altered ankle biomechanics. Participants with CAI employed some compensatory strategy to improve their ankle and postural stability during landing onto the tilted surface. The increased knee extension and internal rotation moments of CAI participants could potentially result in a greater ACL loading. In future studies, it may be worthwhile to measure or estimate the ACL loading to confirm whether CAI could relate to the mechanism of ACL injury.

No abstract

The purpose of the present study was to examine the effect of chronic ankle instability (CAI) on lower-extremity joint coordination and stiffness during landing. A total of 21 female participants with CAI and 21 pair-matched healthy controls participated in the study. Lower-extremity joint kinematics were collected using a 7-camera motion capture system, and ground reaction forces were collected using 2 force plates during drop landings. Coupling angles were computed based on the vector coding method to assess joint coordination. Coupling angles were compared between the CAI and control groups using circular Watson–Williams tests. Joint stiffness was compared between the groups using independent t tests. Participants with CAI exhibited strategies involving altered joint coordination including a knee flexion dominant pattern during 30% and 70% of their landing phase and a more in-phase motion pattern between the knee and hip joints during 30% and 40% and 90% and 100% of the landing phase. In addition, increased ankle inversion and knee flexion stiffness were observed in the CAI group. These altered joint coordination and stiffness could be considered as a protective strategy utilized to effectively absorb energy, stabilize the body and ankle, and prevent excessive ankle inversion. However, this strategy could result in greater mechanical demands on the knee joint.