Muscle Blood Flow and Lactate Removal
Adequate muscle blood flow is important for energy supply and maintenance of homeostasis in the muscle and plays a critical role in the
prevention of muscular fatigue (Sjogaard, 1987). During dynamic exercise, muscle blood flow (MBF) increases linearly with increasing exercise intensity and is dependent on mean arterial blood pressure (MABP), venous blood pressure (VBP) and local vascular resistance (LVR) (Sjogaard, 1987). This is described by the Haagen -Poiseuille equation
MBF= (MABP -VBP) x LVR-1
From this equation, we can conclude that MBF decreases when LVR or VBP increases, and increases when MAPB increases and LVR decreases. During dynamic muscle contractions, vascular resistance decreases and this increases the MBF (Laughlin and Armstrong, 1985, Delp and Laughlin 1998).
This has been confirmed during knee extension exercise by using invasive techniques (Bangsbo et al., 1993, 1994). Additionally, the effect of muscular contractions (muscle pump) facilitates increased MBF by changing the arterial-venous blood pressure gradient (Rowel, 1993).
The measurement of muscle blood flow in humans in vivo is very difficult, given that each muscle may have a different blood flow at any given time (Rowel, 1993). Suzuki and Bonde-Peterson (1983) found increased MBF (measured by 133-Xe clearance) after 100 and 400 m running. The MBF was maintained for a longer period after the 400 m run compared to the 100 m run.
In other types of exercise such as swimming, a horizontal body position changes the internal hydrostatic pressure. It has been shown that in the supine position, the hydrostatic pressure is similar in all parts of the body (Wilcock et al., 2006). In addition, the total peripheral resistance decreases during supine compared to seated recovery (Johnson et al., 1990). These differences between exercise modes such as land-based (running, cycling) and water-based activities (swimming) may cause a higher stroke volume and blood pressure during swimming compared to running exercise (Holmer et al., 1974) and possibly affect the muscle blood flow. At this point, it should be considered that during the interval period after a swimming bout, in most of cases, swimmers stand in an upright position in the water. Using this practice, swimmers may eliminate any positive effect of horizontal position on haemodynamics. However, even in the upright position in the water up to the mid-sternum level, swimmers may benefit from the hydrostatic pressure applied on their body (Wilcock et al., 2006). Swimmers, who go out of the pool during the rest interval may experience a decrease in performance during a maximum intensity training set (Buchheit et al., 2010). In summury, active recovery of about 10 to 15 minutes will maintain an increased muscle blood flow and will decrease blood and muscle lactate levels.