Final answer:
During isometric exercise, intense muscle contractions without muscle length change lead to increased peripheral resistance. Muscles demand more oxygen and ATP, and with constant muscle tension, blood vessels are compressed, necessitating an increase in vascular resistance to maintain blood flow.
Step-by-step explanation:
Total peripheral resistance increases during isometric exercise because the intense muscle activity requires a high level of energy production within the muscles, which is achieved through ATP hydrolysis. Resistance exercises engage fast glycolytic (FG) fibers that result in powerful muscle contractions without a change in muscle length. The increased demand for ATP and subsequent ATP regeneration leads to a heightened need for oxygen, thus increasing the overall peripheral resistance to maintain blood pressure and adequate blood flow to the muscles at work.
During isometric exercises, muscles generate tension while remaining at a consistent length. This type of exertion creates a high demand for blood flow within the stationary muscles. However, the blood vessels within these muscles may be compressed due to the intense contractions, effectively increasing the peripheral resistance. Additionally, because there is usually no significant rise in capillary density with resistance training, the existing vessels must handle the increased blood flow demand.