Ignition is usually the easiest of the three to check because on most engines, all you have to do is pull off a plug wire and check for spark when the engine is cranked. On coil-over-plug DIS systems, there are no plug wires so you have to remove a coil and use a plug wire or adapter to check for a spark.
Stress can affect every part of your body. muscle aches, head aches, how your hair grows, the texture of your skin, it can affect your menstrual cycle.
Heart rate is affected by external stresses on the body such as heat, humidity, cold, wind, and altitude and air quality. With each stress, the human heart is affected and different compensatory changes occur, one of those being adjustment in the beat of the heart.