## 4 Discussion  
The interim period did not alter the magnitude of performance significantly given that there were only a few participants who saw reduced performance (see results for specific changes). The hypothesis that increased cold exposure (longer rest) would reduce performance was not confirmed either, with only one female in the 12 IP (1% reduction) and two males in the 6 IP condition (1% reduction) asking for a treadmill speed reduction late in the performance trial. These minimal reductions in distance with prolonged cold exposure are consistent with previous research with no interim period (like our CON condition), where no differences in distance travelled were found at an air temperature of \(-15\)\({}^{\circ}\)C compared to warmer air temperatures of 0 \({}^{\circ}\)C, \(-5\)\({}^{\circ}\)C, and \(-10\)\({}^{\circ}\)C [27]. The performance measured as running speed is, however, significantly reduced in \(-18\)\({}^{\circ}\)C conditions compared to 20.2 \({}^{\circ}\)C [38], which illustrates that cold air may have an effect on performance. Given that there were negligible changes in running performance, it is reasonable to assume that fatigue, measured as the change in MVC from pre- to post-trial in the key locomotor muscles of the leg, would also not be significantly different across conditions. However, there were some noticeable differences in MVC between conditions, where on average, the MVC increased from pre- to post-trial in the CON and 6 IP conditions, while it decreased in the 12 IP condition. There were 10 participants (5 females) in the CON condition that increased MVC, on average by 38.9 N, whereas in the 12 IP, there was an average decrease of 22.7 N for 8 participants (4 females). The reduced MVC in the 12 IP condition may be explained by greater cooling affecting the muscle temperature, which can reduce muscle power [11; 22] and peak power by up to 7.2% at \(-14\)\({}^{\circ}\)C [23]. Given that the 12 IP condition did not have a significantly lower core body temperature compared to CON and 6 IP, this points to muscle tissue temperature potentially being the more important factor in muscle power decline. This is in contrast to previous research, which showed that the core temperature and muscle tissue temperature fall in parallel with reduced muscle power immediately after cooling has occurred in the leg muscle [22]. We would hypothesize that the warm-up with the slow walking that occurred in the interim period might have been sufficient to maintain the core temperature but not sufficient to maintain the muscle tissue temperature; however, more research should explore this hypothesis. Given that the time course of muscle temperature cooling has been shown to occur within 10 min [21], it also makes sense that in the 12 IP condition, the cooling time was sufficient to have an effect on the muscle tissue temperature. Thus, given that high-intensity exercise has a significant effect on raising the muscle temperature in warmer conditions, it appears that the 8-min performance trial in this study was not sufficient to overcome the cooling effect of the 12 IP interim period on muscle force production post-trial. Collectively, these results indicate that going directly from your warm-up to the start of your race likely has key benefits to muscle power compared to a longer rest period as shown by the reduced MVC in the 12 IP condition. Further research should look at the time course of muscle tissue temperature changes in cold-air environments to understand how the tissue temperature affects muscular performance both before and after a high-intensity aerobic exercise bout. In addition, longer durations of cold exposure could be applied. It was expected that HR in the first minute of the performance trial would be less in the 12 IP condition due to a combination of the time HR recovery duration [13] and cold-induced HR reduction during the interim period [39].