For our sports science experiment we are going to see which is faster off of the line of scrimmage. A lineman or a skilled position player. To determine this were going to explode between five and ten yards. We will also take into account speed, reaction time, acceleration, stride length, and force. Also different stances will be taken into account. An accelerometer, high speed camera, force pad, and some math skills will be needed.

Here we will measure the reaction time between the two athletes from sound to determine which is quicker.
 REACTION TIME (from sound) LINEMAN SKILLED POSITION

It is already a known fact that reaction time by sound is quicker than from sight. In this part of the experiment were going to be recording which of the two players comes more quickly off the ball than the sound.

 REACTION TIME (from sight) LINEMAN SKILLED POSITION

Although the lineman may be heavier and stronger than skilled players that do not necessarily mean that he can produce more force than the smaller player. Here we will measure which of the two athletes produces a greater amount of force, and its correlation with overall quickness. (More than likely the more force put out, the quicker you will be.)

 Force Generated (from initial push-off) LINEMAN SKILLED POSITION

Here overall speed however, is not being measured because generally a skilled position athlete will be faster than a lineman. So we will be finding which of the two types of athletes can explode the quickest over the given distance.

 Velocity (0-5 yards) LINEMAN SKILLED POSITION

The 40-yard dash, need I say more? For this test we will be looking for not only the overall velocity of the two types of players over 40 yards, but if it has a direct correlation with explosiveness and quickness in the 5 yard dash.

 Velocity (0-40 yards) LINEMAN SKILLED POSITION

* Stride Length will be measured, because it may take one athlete fewer or more strides than the other to complete the 5-yard dash and 40 yard dash.

A few things must be taken into account; this is generally speaking, because not everyone is the same. Some people are faster than others, some weigh more, some are stronger, and some can produce more force. There are just too many variables to make this fact for all lineman and skill position players

Using the force plate,  we will measure the force that each athlete pushes off of the ground during his take off. With the help of a high speed camera we will measure the athletes reaction time to the "go" call, and the visual stimulant. Acceleration will be measured with the accelerometer, this is measured because we want to see how much the athletes force effects his acceleration. The velocity will be measured through us timing the athlete's sprint over 5 yards. All of these experiments will be conducted in a 5 yard sprint. The 40 yard sprint will measure the athlete's velocity to see if there is a relationship between 40 yard speed and explosiveness over 5 yards.

The camera will be used to film the athletes reaction time and stride length.

Actual Project Completed:

Lineman vs. Receiver Reaction Time & Progression

Football players have a variety of skills that help them reach to the next level, but there is one essential skill that all players must develop. It a skill that coaches consider critical, reaction time. In football there are two types of players, skilled position players that run, catch, tackle, block, etc, and lineman that only block and tackle. It is unfortunate that the linemen do all of the dirty work, but so little credit is actually awarded to them. It is key for a team to be as responsive as they can to gain an edge on their opponent and obtain a victory.

Our group attempted to test the reaction time of two high school football players, one lineman and one skilled-position player. It is widely understood that reaction by sound is quicker than reaction by sight, and so we decided to test both as lineman typically respond by sound, and skilled-positions through sight. It is also somewhat of a rivalry to see which positions are actually “skilled”, kind of like an I’m stronger or faster type atmosphere. Before the experiment began we hypothesized that lineman will have a slower reaction time than the skilled-position player at both stages (sight and sound).

On average a football play lasts for 4 to 7 seconds, so it is imperative that as much work be done as possible in the shortest amount of time. Reaction time is so important because it could mean the difference between a weaker opponent beating out a stronger opponent, or vice versa.  For example, even-though a lineman may be strong enough to blow back their opponent; if the other is much faster (reaction) then they have already stalled the other player just long enough for something to happen (i.e. a big block, sack, completed pass, etc.). In the same manner a skilled-position player must also have a good reaction time. A short example would be the a receiver trying to get off of the line of scrimmage, if they are jammed (delayed) from the line then that throws off the timing of the play. On the other hand if the receiver is faster than the defender, it opens up the probability of a high impact play.

In order to measure how quickly the two players reacted off of the sight of the ball and sound of the cadence we used a high-speed camera to capture each athlete’s movements frame by frame. This allowed us to time out and compare each athletes’ movements at any given point in time. We also used an accelerometer to determine the vectors of the accelerations being exerted at any given time as well. And lastly, thanks to the video analysis program, “Tracker”, we could easily pull out important information from each position and time in the high-speed video, such as velocities (both x and y), patterns, and momentum.

àUsing the system above, we captured each athlete reacting by the sound of a cadence or the sight of a ball being “snapped” and compared it to each other. We gathered the following data:

Reaction Time:

This is simply the time it took each athlete to begin moving.

 Sound (sec) Sight (sec) Lineman .02 .28 S.P. Player .02 .24

Here it can be clearly seen that reaction to sound is about .25 seconds faster than to reaction by sight. Both the lineman and skilled player reacted at the same time, around .02 seconds. During the sight segment of the experiment both players experienced a .2 second difference in there reaction times.

Time to Foot Contact:

This is the amount of time it took for each athlete to completely react and reach out with their first step to the ground.

 Sound (sec) Sight (sec) Lineman .052 .046 S.P. Player .038 .036

In the “drive phase” is where the athlete takes their first and most explosive step. It is at this point that we measured the time it took each athlete to move their foot from first reaction to forward ground contact. Reaction times for both athletes are relatively the same, with the skilled-player being a little (about .012) “quicker” than the lineman. However, I feel that in real time there is little to no difference in the reaction times between athletes.

Distance Covered with First Step:

This is just the distance covered by each athlete with their first step.

 Sound (m) Sight (m) Lineman 1 .8 S.P. Player 1.45 1.5

We felt it necessary to include this piece of data because it shows how much ground is actually covered within the “driving” phase and reaction time frame. The skilled position player here covered as much as .7 meters more than the lineman. I think the main reason behind the difference in the distance covered by each athlete deals with the amount of force being exerted on the opposite foot, and stride-length of each athlete. I believe it also has to do with the short step a lineman must use to engage his counterpart, versus a skilled-player in the open field.

àUsing the accelerometer we also measured the direction and magnitude of the accelerations the athletes were undergoing while reacting from start through the drive phase.

These graphs show the relationship between each of the resulting accelerations during the drive phase in each direction and magnitude. They show that the pattern of acceleration in each magnitude was relatively the same for each direction. During the first parts of reaction there is more acceleration in the x and y velocities than z. The extremely crowded graphs of the skilled-player are due to the length the accelerometer was recording. Aside from that, it is evident that throughout the entire movement the accelerations the athletes underwent were for the most part the same in both tests. The tables can be retrieved from the G-Drive if desired.

Acceleration:

This is the fastest point of acceleration exerted by the athletes.

 X (m/s) Y (m/s) Z (m/s) Angular (m/s) Lineman 7.17 6.08 2.27 5.17 S.P. Player 12.35 5.52 1.74 6.53

This table describes the largest point of acceleration during the “driving” phase of the experiment. It shows that the skilled-player experienced the largest forward acceleration (X). The lineman experienced the largest up and down (Y) and diagonal (Z) accelerations. Again this could be because of the rising motion a lineman must perform to engage his opponent. This also explains the greater distance covered by the skilled-player because of the much larger acceleration.

à Using the masses of the two athletes and the accelerations from above we calculated the forces that were being exerted by the athletes.

Forces Exerted

 Weight (kg) X-Direction (N) Y-Direction (N) Z-Direction (N) Lineman 104.35 748.19 635.18 236.87 S.P. Player 65.77 812.23 363.03 114.43

The forces exerted by the skilled-player were larger than then lineman’s. More specifically less force was placed on moving up or down, and more forward by the skilled position player than the lineman. This is evident because the X-force is greater than then lineman’s, whose Y and Z forces are larger than the skilled position players. This means that more force was applied to move forward by the skilled position player, than by the lineman.

à Using “Tracker” video analysis we derived the velocities for each of the athletes.

 Velocity (m/s) Lineman 3.35 S.P. Player 4.57

These velocities demonstrate how much power that can be generated in a short amount of time (from reaction to first step). This displays the continuation of the reaction and speed, as thought ahead; the skilled position player is usually faster than the lineman. Although this has little do with reaction time, it affects to a great extent exactly what occurs after the “driving” phase. It should be considered that although the skilled-player is faster, the lineman still reacted at the same time as the skilled-player.

àMomentum while accelerating.

 P (kg m/s) Lineman 349.57 S.P. Player 300.56

The graph here shows the momentum of each of the athletes and depicts the amount of momentum helping moving them forward. Because the lineman has a greater mass, it allows for greater momentum to generate, which in turn helps to carry the athlete that much farther. We noticed that even though the lineman has a greater momentum, he still doesn’t surpass the skilled-player when it comes down to reaction time. Momentum has a greater affect in the phases after reaction.

àImpulse

Impulse was measured from reaction time to the first step.

 Impulse Lineman 53.86 S.P. Player 47.10

Although the lineman experienced a greater impulse than the skilled-player, because of his mass it did not accelerate him forward enough. We worked out that because the lineman has more mass, it takes a greater impulse to move him, versus the skilled position player. The skilled position player generated a similar impulse but had a smaller mass, and therefore was propelled forward more forcefully, and thus farther than the lineman in the same time frame.

àDoin’ Work

Work was calculated from the distance covered by the first step.

 Work (j) Lineman 748.19 S.P. Player 1177.73

This was rather different because usually larger masses result in greater work. In this case though, even though the lineman was a greater mass, he did not exert as much force as the skilled position player did during the “drive” phase. This also helps to solidify the timing differences between the two athletes in their first step to ground contact. The skilled position player did more work than the lineman, and therefore covered more distance the same amount of time.

Conclusion:

In agreement with our data, linemen and skilled-players have relatively the same reaction time in from both sight and sound stimulation. In sound they both react at around .02s, and by sight around .25s. The ground contact step is also relatively the same, with both athletes touching the ground at about the same time, .058s. However, the skilled-player covered more ground with his first step than the lineman, roughly .7m more. This is because the skilled-player exerted more force and acceleration (especially in the X direction) than the lineman, which also led to an increase in work (which was also greater than the lineman’s, by more than 300 joules). Even though the lineman had a greater momentum than the skilled-position player (50 kg m/s more), the skilled-player maintained a higher velocity (4.57 m/s).

After retrieving all of this data we still can’t find any correlation with reaction time. We have decided that velocity, momentum, work, force, and acceleration are all key in the “driving” phase of the movement, but do not really affect reaction time. Reaction time seems to be related more so to how quickly one can process the stimulus they are receiving (visual or audible). After primary reaction has occurred however, all of the other parts come into play and affect the ground contact time to the end of the play. Reaction time will remain to be an extremely important advantage of the game of football, and here is one spot where all players on the field have an opportunity to be equal despite physical differences (mass, speed, etc.).

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Steve Dickie,
May 18, 2009, 4:53 PM