FIT FOR GRIDIORN: THE PHYSIOLOGY OF AMERICAN FOOTBALL

In New Zealand, the popularity of American sports has soared exponentially since the ’90s. American Football, in particular, has grown to the point that we have our very own local leagues, our national team, and access to thousands of hours of football content from the NCAA and the NFL. This article will discuss the physical demands of a football game and the physical characteristics of different playing positions, and provide some suggestions for appropriately conditioning football players for the rigours of this sport.

For those who are unfamiliar with American Football, the sport is unique. It has a 60-minute duration made up of four 15-minute quarters. Half time is 20 minutes in length. In the professional ranks (NFL), teams are permitted 53 players on a roster. However, only 11 players take the field at any one time (22 players on the field in total). There are three sub-teams within the 53 players; these are Offence, Defence, and Special Teams. While some players will play both offence and special teams or defence and special teams, unless briefly for particular strategic reasoning, offensive players won’t play on the defence and vice versa. Contributing significantly to this reality is the fact each position requires individuals with a specific skill-set. Subsequently, many players cannot play multiple roles due to their body composition and physiological strengths and weaknesses.

The purpose of the game, much like any other team sport, is to score more points than the opposition. During a match, when a team takes possession of the football, they run a ‘series’ of ‘plays’ to advance down the field and score points by way of a touchdown or field goal. Each series is prolonged if a team successfully gains 10 yards within four consecutive attempts. Achieving this results in a ‘new set of downs’ (another four tries at gaining another 10 yards). Failure to do so results in a turnover of possession to the opposing team. Most teams will run three plays, and if 10 yards hasn’t been achieved, they will punt the ball back to the opposition, essentially playing for field position. During a punt, both teams' special units will contest that play. Typically the team which has more series, and runs more plays, has control of possession - which often results in a win. The number of series and plays a team has in a game can significantly impact the physiological demands experienced by the offence or defence. Specific strategic approaches can also drastically alter the demands on players. The physical needs of the game and the position-specific physiological requirements will be discussed in the following sections of this article.

There are 4.6 – 5.6 plays run per series (Hoffman 2008; Pinicevero and Bompa 1997; Wellman et al. 2006). Each play on average lasts 5.49 seconds in duration (play duration ranges from 1.89 to 12.89 seconds) (Hoffman 2008; Pinicevero and Bompa 1997; Wellman et al. 2006). The rest between plays is based on the ‘play clock’, that is, each team has 25-40 seconds to run their next play before they are penalised for delaying the game. Teams can use all of this time or a percentage of it. The no-huddle offence referenced above speeds the game along as the offence attempt to advance down the field quickly. The outcome? A tired defence, due to 25 – 33 % more plays being run against them (McElroy 1998). If the offence runs a play that is 5 seconds long, then runs another play 15 seconds later without a break, the work and rest ratios associated with energy systems tell us that if sustained, primarily because of the intensity, within about 45 seconds all players will be feeling the effects of the waste product accumulation. Suppose you are responsible for the conditioning of a football team who either runs a no-huddle offence, or consistently competes against a team that does. Wouldn’t it make sense to include some training to help prepare your athletes for those situations? Perhaps. A study on collegiate football by Iosia & Bishop (2008), identified that work and rest times on average sit at a ratio of 1:7. At its most demanding, work and rest times were found to be at a ratio of 1:3, in hurry-up/no-huddle situations (Iosia and Bishop 2008). At its most forgiving, work and rest times were at 1:10 (Iosia and Bishop 2008).  Figure 1 (below) shows work and rest times for interval training, and the associated energy systems.

Unfortunately, until research can quantify the percentage contribution of the glycolytic system in these circumstances at all levels of the game, and after that, determine its significance statistically, on the outcome of a game, it probably holds little relevance. Regardless, I theorise it could increase glycolytic contribution to anywhere from 15-30% based on the suggestion that there are 25-33% more plays in a game on both offence and defence when a team is operating the no-huddle strategically. Of course, the game would remain highly anaerobic and explosive, meaning the training approach wouldn’t be drastically altered; just some drills may require decreased rest times to mimic the demands of match-play.

Training recommendations are plentiful. Due to the rapid, explosive nature of the sport, competitors need to be conditioned accordingly. From an energy system development standpoint, emphasis on developing the ATP-PCr system is required, with some glycolytic conditioning recommended for teams running up-tempo offences, or facing teams that operate that way strategically. How this is achieved in training can be based on movement specificity, e.g. wide receivers can run routes as they would do in a game, but with work and rest times that suit the system being trained. Speed, change of direction and agility training is also paramount to developing well-rounded successful athletes. Position-specific body composition should also be considered, with training to develop the desired body type, or maintain the desired body type.

American football is characterised with high speed collisions. Players must be both robust and powerful enough to handle the physicality. Injury rates are high in this sport. Hamstring, calf and ligament tears occur frequently, as well as concussions. Injury prevention efforts can be implemented. A functional movement assessment to detect asymmetries between limbs should be administered, with results carefully considered when designing suitable programmes. Movements specific to the sport, e.g. jump and land, can be utilised as an injury prevention tool either in isolation or as part of a warm up routine. Additionally, sprinting, changes of direction, jumping and landing are all explosive football actions, and muscular strength and power contribute significantly. Due to recommended rest periods typically being 2-5 minutes, I recommend complex training to train both components of performance together, saving time. Complex training is a methodology involving a maximal strength effort, e.g. heavy bench press, immediately followed by a biomechanically similar movement performed explosively, e.g. plyometric push ups. The idea is to excite the nervous system, and then perform an explosive activity through a full range of motion.

American football is a unique team sport. It involves repetitive high-intensity actions, and immense physical collisions. The sport requires athletes to be highly anaerobic regardless of playing position. Characteristics required to excel at one position over another are well documented, with bigger, more robust body types suiting positions on the offensive or defensive lines. More agile, explosive runners make great defensive backs, wide receivers and running backs. Tight ends are typically a combination of size and power, enabling them to block like a lineman, and run and jump like a receiver. Individual training plans are paramount for developing the individual looking to excel at this sport. Energy system development should focus on the ATP-PCr system and to a certain degree, the glycolytic system. Weight training should focus on muscular strength and power to further develop the athlete’s explosive potential. Injury prevention strategies are also encouraged.