Tissue Temperature Transients in Resting Contra-Lateral Leg Muscle Tissue During Isolated Knee Extension

Abstract

This study was designed to evaluate the role of non-active tissue in the retention and dissipation of heat during and following intense isolated muscle activity. Six subjects performed an incremental isotonic test (constant angular velocity, increases in force output) on a KIN-COM isokinetic apparatus to determine their maximal oxygen consumption during single knee extensions (VO2sp). In a subsequent session, a thin wire multi-sensor temperature probe was inserted into the left vastus medialis under ultrasound guidance at a specific internal marker. The deepest temperature sensor (tip, Tmu10) was located approximately 10 mm from the femur and deep femoral artery with 2 additional sensors located at 15 (Tmu25) and 30 (Tmu40) mm from the tip. Implant site was midway between and medial to a line joining the anterior superior iliac spine and base of patella. Esophageal temperature (Tes) temperature was measured as an index of core temperature. Subjects rested in a supine position for 60 min followed by 30 min of seated rest in an ambient condition of 22 degree C. Subjects then performed 15 min of isolated single right knee extensions against a dynamic resistance on a KIN COM corresponding to 60% of VO2sp at 60 degree x sec(-1). Exercise was followed by 60 min of seated rest. Resting Tes was 37 degree C while Tmu10, Tmu25, and Tmu40 were 36.58, 36.55 and 36.45 degree C, respectively. Exercise resulted in a Tes increase of 0.31 C above pre-exercise resting. Tmu of the non-exercising leg increased 0.23, 0.19 and 0.09 degree C for Tmu10, Tmu25, and Tmu40, respectively. While Tes decreased to baseline values within approximately 15 min of end-exercise, Tmu10 reached resting values following approximately 40 min of recovery. These results suggest that during isolated muscle activity, convective heat transfer by the blood to non-active muscle tissue may have a significant role in maintaining resting core temperature.

External muscle heating during warm-up does not provide added performance benefit above external heating in the recovery period alone

“…There are however, some discrepancies in the exact nature of this decline. Some authors report that upon exercise termination, there is still a gradual increase in T m which can continue for up to 10 minutes before T m begins to drop (Aikas et al 1962;Kenny et al 2002), whereas others report an immediate decline in T m (Allsop et al 1991;Kenny et al 2003;Saltin et al 1970). It is possible that the differences reported are due to different protocols used between studies, e.g.…”

“…The data which does exist tends to show a transient decline in T m following exercise termination (Aikas et al 1962;Allsop et al 1991;Faulkner et al 2013;Kenny et al 2002;Kenny et al 2003;Saltin et al 1970;Saltin et al 1972). In rats, T m has previously been shown to follow an exponential decline immediately following moderate exercise cessation, with resting temperatures reached within 60 minutes (Brooks et al 1971).…”

“…It is possible that the differences reported are due to different protocols used between studies, e.g. leg extensions (Kenny et al 2002;Kenny et al 2003) continual cycling (Aikas et al 1962;Allsop et al 1991;Saltin et al 1970) or even variations in environmental conditions. Saltin et al, (Saltin et al 1968) suggest that cooler conditions will have a greater effect on reducing muscle tissue temperature following exercise.…”

“…Where athletes experience a delay in performance onset following the completion of a warm up, or between bouts or rounds of activity it is possible that T m may drop below an optimal level (Faulkner et al 2013;Kenny et al 2002;Kilduff et al 2012). This may have a detrimental effect on performance, particularly during power-based activities such as weight lifting, jumping and sprinting.…”

“…This may have a detrimental effect on performance, particularly during power-based activities such as weight lifting, jumping and sprinting. A detailed time course of post exercise decline in T m has been reported on a number of occasions (Aikas et al 1962; Allsop et al 1991;Kenny et al 2002;Kenny et al 2003;Saltin et al 1970;Saltin et al 1972) however, with none directly assessing any subsequent performance changes following reductions in T m . In general, it appears that T m begins to decline immediately post exercise (Allsop et al 1991;Kenny et al 2003;Saltin et al 1970), with the rate at which T m declines being affected by environmental conditions (Saltin et al 1970;Saltin et al 1972) with colder ambient conditions leading to a faster decline in muscle temperature.…”