Acute effects of small changes in antero-posterior shoe-cleat position on physiological and biomechanical variables in road cycling.

The aim of this study was to investigate the effect of changes in cycling shoe-cleat position on pedalling biomechanics, physiological variables, and performance in road cycling. Twelve competitive road cyclists performed three pedalling trials with the cleat positioned at the first metatarsal head, 15-mm anterior and 15-mm posterior. Each trial included three sets of 5 min performed at 35%, 50%, and 65% of maximal aerobic power (MAP) followed by a 10-s sprint. Results showed no significant changes in physiological variables, pedalling kinetics, muscular activity of six lower limb muscles, sprint performance and perceived exertion. However, significant differences were found regarding joint kinematics: hip, knee, and ankle angles during both extension and flexion were reduced in the anterior cleat position. Therefore, this study suggests that cleat position does not affect sprint performance, physiological variables, pedalling kinetics, muscle activity, and perceived exertion regardless of the cycling intensity. However, joint kinematics, and particularly knee extension angle which could be related to the risk of overuse injuries, was affected by the shoe-cleat position.

Physical and thermal strain of firefighters according to the firefighting tactics used to suppress wildfires.

The aim of this study was to analyse the physiological strain of firefighters, using heart rate (HR) and core temperature, during real wildfire suppression according to the type of attack performed (direct, indirect or mixed). Three intensity zones were established according to the HR corresponding to the ventilatory threshold (VT) and respiratory compensation threshold (RCT): zone 1, RCT. The exercise workload (training impulse (TRIMP)), the physiological strain index (PSI) and the cumulative heat strain index(CHSI) were calculated using the time spent in each zone, and the HR and core temperature, respectively. Significantly higher mean HR, time spent in Z2 and Z3 and TRIMP h(-1) were found in direct and mixed versus indirect attacks. The highest PSI and CHSI were observed in the direct attack. In conclusion, exercise strain and combined thermal strain, but not core temperature during wildfire suppression, are related to the type of attack performed. STATEMENT OF RELEVANCE: Our findings demonstrated that wildfire firefighting is associated with high physiological demands, which vary significantly depending on the tactics chosen for performing the task. These results should be kept in mind when planning programmes to improve wildland firefighters' physical fitness, which will allow improvement in their performance.