PHILADELPHIA -- In the absence of pre-existing disease or drugs, heat-related illness is among the most-readily explainable causes in the death of San Francisco 49'ers offensive lineman Thomas Herrion.
It also highlights the burgeoning problem of player weight, which would also contribute to heat-related illness.
The 23-year-old, 6-3, 310-pound offensive lineman collapsed in the locker room following San Francisco's game against the Denver Broncos on Saturday.
An exact cause of death will not be known until toxicology tests are performed, according to an investigator with the Denver coroner's office.
Investigator Howard Daniel said that following an autopsy that there was nothing readily apparent as to Herrion's cause of death. "There's no conclusion, pending further studies, a process that usually takes three to six weeks," Daniel said.
Nolan recounted the events immediately following the game during a press conference on Sunday afternoon in San Francisco.
"We went into the locker room after the game. I usually take about two minutes before I speak to the team," said Nolan. "I gathered the team up, which we always do, everyone comes from their lockers, comes up fairly close. I delivered a message, as you typically do following a game, and then we had the Lord's Prayer."
Nolan added that "right about the time of completion someone in the back had said that Thomas was down. At that time everyone kind of stood up and cleared out. The medical staff immediately came to Thomas, who at that time was lying on the ground."
Resuscitative efforts were immediately begun by team physicians and paramedics before Herrion was transported to St. Anthony's Central Hospital in Denver. He died approximately three hours later according to team reports.
Herrion was on the field for San Francisco's 14-play, 91-yard drive which resulted in a touchdown in the final seconds of the game. Reports indicate that while Herrion was noticeably winded as he walked off the field, he didn't look much different than teammates who played beside him at game's end.
"We didn't see anything happen," San Francisco defensive lineman Marques Douglas said in a previously released statement. "I sat by my locker and prayed for him."
"During and immediately following the game Thomas was responsive," said Nolan. "He came off to the sideline, communicated with Guy McIntyre and asked Guy how he thought he'd done on the drive. He was very pleased that he was on the field for the touchdown."
While temperatures at game time in Denver were in the mid-60s with 50 per cent humidity, ambient temperature is just one factor in heat-related illness.
Heat-related illness traditionally includes the syndromes of heat exhaustion and heatstroke. In athletes, exertional heatstroke has a rapid onset usually within a few hours, compared to a slower onset form that affects individuals of extreme ages (young and the elderly).
From 1960 through 2004, data collected by the National Center for Catastrophic Sport Injury Research found 104 heat stroke cases in football players which resulted in death. Obesity, the intensity and duration of physical activity, and dehydration are well-known contributing factors to heat-related illness.
A 2003 study in The New England Journal of Medicine reported at least 350 active players over 300 pounds -- up from 10 in 1986.
Heat-related illness occurs when the heat load on the body (from internal and ambient sources) exceeds the body's ability to exchange heat with the environment. The body responds to an increased internal or core temperature by shunting blood to the skin surface where heat can be lost through a variety of mechanisms. Evaporation or sweating is the primary means of dissipating heat.
As sweating continues, fluid shifts within the body result in pseudo-volume depletion.
The 2002 Gatorade Sports Science Institute Guidelines on Heat Safety in Football found that even mild dehydration (as little as 2 per cent of body weight or six pounds in a 300-pound player) can contribute to potential heat illness and impair football performance.
Various reports show that core-body temperature can rise an additional 0.15-0.2 degrees Celsius (32 degrees Fahrenheit) for every 1 per cent of bodyweight lost to dehydration during exercise.
The body responds to dehydration by shunting less blood to the skin surface thus allowing core temperature to rise. According to a 2004 article in the journal Sports Medicine, Coris et al. reported that during periods of maximal exercise, the muscles can produce 15 to 20 times more energy than when the body is at rest. The bulk of the energy according to Coris is converted to heat which quickly raises the core body temperature.
Following the training camp death of Minnesota Vikings lineman Korey Stringer, a stronger emphasis was placed on preventing and monitoring players for exertional heat-related illness.
One such method involves the use of technology originally developed for NASA.
In 2003, the Philadelphia Eagles became the first team to use the Cor Temp Temperature capsule (manufactured by HQ Inc. of Palmetto, Fla.) which transmits the core body temperature from the player's intestines to a hand-held computer. The Vikings and the Jacksonville Jaguars are also reported to be using the device.
"It's sad that it has to keep happening," Kelci Stringer, widow of former Vikings lineman Korey Stringer, told the South Florida Sun-Sentinel. Stringer felt that "If it's a business (NFL teams) need to protect their product.
"The NFL has networks for everything you need: real estate, doctors, domestic abuse, and alcohol. They know every move the players make. Why not pay extra to hire a heat specialist? It infuriates me that the players don't realize how much their lives are in jeopardy and that [the NFL] can't play without them," added Stringer.
Herrion was originally signed by the Dallas Cowboys as an undrafted, rookie free-agent. He was among the final cuts prior to the start of the 2004-05 season but was re-signed to the Cowboys' practice squad. Herrion joined the 49'ers practice squad in January and was allocated to the Hamburg Sea Devils of NFL Europe where he started 10 games.
Plans for a team memorial service have yet to be finalized.
David W. Unkle is a freelance sports and healthcare journalist. He is a Fellow of the American College of Critical Care Medicine and an Instructor at the University of Medicine and Dentistry of New Jersey - Stratford Campus.
David can be contacted at firstname.lastname@example.org
--Wire reports and previous reports were used in the preparation of this article.