Altered core temperature and salivary melatonin in athletes with a cervical spinal cord injury

Sleep disturbances are common in athletes with a cervical spinal cord injury (cSCI) and may be associated with circadian alterations. Therefore, the purpose of this study was to compare physiological circadian outputs between athletes with a cSCI and non-disabled controls (CON). Eight male wheelchair athletes with a cSCI and eight male CON (30 ± 4 and 30 ± 6 yrs, respectively) had their core body temperature (T_core), skin temperature (T_skin), and salivary melatonin measured during a 24-h period. In the cSCI group, daytime T_core was significantly lower (36.5 (0.2) vs 36.9 (0.3)°C; p = 0.02) and time of the T_core sleep minimum was significantly earlier (23:56 ± 00:46 vs 02:39 ± 02:57; p = 0.04). The athletes with a cSCI had significantly lower T_core values during the beginning of the night compared with the CON group, but their Tcore increased at a greater rate, thereafter, indicated by a significant time/group interaction (p = 0.04). Moreover, the cSCI group did not display a salivary melatonin response and exhibited significantly lower concentrations at 22:00 (p = 0.02) and 07:00 (p = 0.02) compared with the CON group. Under natural living conditions, athletes with a cSCI displayed circadian changes in the T_core rhythm and nocturnal melatonin production.