Bit of a medical question. Is pressure in the chest (certainly heart-related) in keeping with a hiking trip (hilly terrain) in pants during a heat advisory while carrying the party's water supply?

This was about a week ago with no recurrence, so no immediate worries. Though something similar happened previously during a long bike ride under similar weather conditions.
The pressure went away after a pause and passing off the water. I remembered reading once that firefighters face cardiopulmonary difficulties, between the weight of their gear and the heat of their surroundings, and currently hold that it was simply overexertion.