Relation between running injury and static lower limb alignment in recreational runners.

OBJECTIVES: To determine if measurements of static lower limb alignment are related to lower limb injury in recreational runners. METHODS: Static lower limb alignment was prospectively measured in 87 recreational runners. They were observed for the following six months for any running related musculoskeletal injuries of the lower limb. Injuries were defined according to six types: R1, R2, and R3 injuries caused a reduction in running mileage for one day, two to seven days, or more than seven days respectively; S1, S2, and S3 injuries caused stoppage of running for one day, two to seven days, or more than seven days respectively. RESULTS: At least one lower limb injury was suffered by 79% of the runners during the observation period. When the data for all runners were pooled, 95% confidence intervals calculated for the differences in the measurements of lower limb alignment between the injured and non-injured runners suggested that there were no differences. However, when only runners diagnosed with patellofemoral pain syndrome (n = 6) were compared with non-injured runners, differences were found in right ankle dorsiflexion (0.3 to 6.1), right knee genu varum (-0.9 to -0.3), and left forefoot varus (-0.5 to -0.4). CONCLUSIONS: In recreational runners, there is no evidence that static biomechanical alignment measurements of the lower limbs are related to lower limb injury except patellofemoral pain syndrome. However, the effect of static lower limb alignment may be injury specific.

Shivering thermogenesis during acute hypercapnia.

The effects of acute hypercapnia on human thermoregulation during cold exposure were investigated by immersion of eight male subjects to the neck in a 15 degrees C water bath until their core temperatures dropped to 35 degrees C or until 1 h of immersion had elapsed. Air was inspired throughout each experiment, with the exception of a 15-min period commencing with the attainment of an esophageal temperature (Tes) of 36.5 degrees C, during which subjects inspired a gas mixture containing 4% CO2, 20% O2, and 76% N2. Oxygen uptake (VO2, L.min-1), inspired minute ventilation (Vi, L.min-1), esophageal temperature (Tes, degrees C), rectal temperature (Tre, degrees C), mean unweighted skin temperature (Tsk, degrees C), mean heat flux (Q, W.m-2), and electromyographic activity (EMG, mV) of the trapezius and masseter muscles were recorded continuously. VO2 and integrated EMG activity (IEMG) were used as the primary indicators of shivering thermogenesis. Shivering EMG was attenuated immediately following the switch of the inhaled gas mixture from air to 4% CO2. For both the masseter and trapezius muscles the IEMG was significantly suppressed (p < 0.05) during the hypercapnic period. The IEMG values preceding the switch to the hypercapnic mixture were 15% greater than those during the CO2 period. Similarly, IEMG values in the post-CO2 period were 55% greater than during the CO2 period. It is concluded that acute periods of hypercapnia during cold exposure may result in transient suppression of shivering tremor, but this does not appear to affect thermal balance, as reflected in the absence of any significant effect on Tes.

Effects of prolonged CO2 inhalation on shivering thermogenesis during cold-water immersion.

We investigated the effect of prolonged hypercapnia on human thermoregulation during immersion of seven male subjects in a 15 degrees C water bath until their esophageal temperature dropped to 35 degrees C or until 1 h had elapsed. In the control trial, subjects inspired room air, whereas in the other trial the inhaled gas mixture was a 4% CO2:20% O2:76% N2 gas mixture. Oxygen uptake (VO2, liter.min-1), inspired minute ventilation (VI, liter.min-1), esophageal temperature (Tes, degree C), mean unweighted skin temperature (Tsk, degree C), mean heat flux (Q, W.m-2), and electromyographic (EMG, mV) activity of the trapezius muscle were recorded. VO2 and integrated EMG (IEMG) activity were used as the primary indicators of shivering thermogenesis. There was a tendency for elevated VO2, albeit not significant, in the CO2 trial compared to the air trial. We observed no significant differences in the IEMG between the air and CO2 trials. These results suggest that prolonged inhalation of a gas mixture containing 4% CO2 does not have a significant inhibitory effect on shivering thermogenesis and does not enhance the cooling rate of the body core. The absence of any shivering attenuation is most likely due to the small blood PCO2 increase incurred by inhalation of 4% CO2, compensation of hypercapnic-induced respiratory acidosis, and a strong thermal drive from core and peripheral regions. It is unlikely that elevated PICO2 levels contribute significantly to the etiology of hypothermia in divers.