The style of tackling used in rugby may be associated with a lower force of impact than the style used in football, according to a preliminary study of college athletes released today that will be presented at the American Academy of Neurology Sports Concussion Conference in Indianapolis July 26-28, 2019.
“For athletes who participate in a sport that involves a tackle or direct contact, adapting a rugby-style tackle where the players lead with their shoulders, not their heads, could make college sports safer,” said study author Zach Garrett, DHS, of Marshall University in Huntington, W.Va.
“A small number of NFL teams have incorporated the rugby-style tackle in an effort to reduce risk of concussion.”
The study measured impact data from 30 male university athletes during their spring practice season.
Twenty of the participants were football players who had impact sensors placed in their helmets.
Ten of the participants were rugby players who had mouthguards with sensors inserted into them.
At the end of the practice season, the football participants totaled 3,921 impacts over the course of 12 practices, compared to 1,868 impacts over nine practices received by rugby participants.
After researchers adjusted for other factors such as false impacts, different sample sizes, and practices, they found that the frequency of impacts was lower for the rugby players than for the football players.
The research team also found that the sensors recorded lower impact forces to the head in rugby in comparison to football.
Impact was measured in g-force, which is the measurement of gravity described in units of acceleration.
Overall the rugby players had impacts with an average of 21 g-force.
Football players had impacts with an average of 63 g-force.
“Further studies with larger numbers of participants are needed to confirm these results and also to determine whether using a rugby-style tackle could effectively reduce the force of impact and potentially reduce the number or severity of concussions in college football,” said Garrett.
Concussions in high school football occur at a rate of 6.71 injuries per 10,000 athlete exposures, this number jumps to 30.07 injuries per 10,000 athlete exposures in competition.1
Head contact during blocking and tackling are the most prevalent mechanism of injury or activity associated with concussion in American football.1
Despite continued efforts to reduce the occurrence of concussion the incidence continues to increase.2
Recent research has indicated the effectiveness of Heads Up Football (HUF) framework in reducing head accelerations and injury rates in youth football athletes.3
However, previous research does not separate the effectiveness of the coaches’ education program, practice restrictions and the vertical, head up tackling technique instructed in these programs.
Concussion rates for youth football athletes per the Youth Football Surveillance Network accounted for 9.6% of all injuries in youth football.4
The injury rate at this level during game play was 2.38 to 6.16 per 1000 athlete exposures and 0.24 to 0.59 per 1000 exposures in practice.4,5
The median and 95th percentile linear acceleration and rotational acceleration for 9-12 year old athletes was significantly different between games and practices, with game accelerations being higher.6
This trend does not carry forward into 12-14 year olds, who show no difference in accelerations experienced between practice and games.7
Recent research may indicate the effectiveness of the HUF program in reducing head accelerations and injury rates in youth football athletes.
The HUF program provides league coaches receive hands on training regarding proper equipment fitting, didactic and participant demonstration of proper tackling technique and instruction in drills that reduce head contact, as well as general player safety.3
The HUF tackling framework provides coaches with a progression of drills designed to implement a head up, vertical tackling style.
Participants in HUF leagues experienced fewer head impacts during practice registering both 10 and 20 g when compared to non-HUF leagues.3
A 10 g head impact cut off value is often utilized in the literature for counting of number of head contacts.
However, a count of number of impacts rather than measurement of impact values has also been utilized due to concern over the accuracy of the measurements provided by current technology.3
In Pop Warner football leagues that also utilized the HUF program also saw a decrease in practice concussion rates (0.14/1000 athlete exposures) when compared to non-HUF leagues (0.79/1000 athlete exposures) though it is unclear whether these changes are due to contact restrictions or tackling style.8
The Qualitative Youth Tackling Scale (QYTS) is a visually observed, objective based scale created to instruct a vertical, head up tackling form that mimics the form recommended by USA Football (Figure 1).
This scale is designed to provide feedback on the components of the technique believed to be most related to safety while maintaining performance.
This system applies quantifiable, objective actions during the tackle to a subjective feedback mechanism that aligns with the overall form requirements of the HUF tackle.
To determine an overall score participants are subjectively assigned a point for successful completion of the movement measure.
Item 1, short steps, is a measureable variable to represent the “Breakdown” and “Buzz” phases in which the tackler comes under control after pursuit but remains able to adapt to the opponents movements.
Item 2, posterior to anterior movement of the arms, aligns with the “Rip” phase of movement which encourages wrapping up as well as using the arms to encourage an upright posture.
Item 3, low center of mass, is the first phase of the “Shoot” parameter. Starting low allows the player to extend the hips on contact and initiate a rising blow on contact.
Item 4, head across the front, establishes the head outside of the contact zone and encourages tacklers not to lead with the head.
Item 5, contact with the front of the shoulder, was again an encouragement to remove the head from contact by encouraging an alternate first point of contact.
Item 6, maintain and extended neck position, is part of standard safe practices as contact with the crown of the head increases the risk of cervical spine injury.
Items 4, 5 and 6 do not align directly with stated HUF goals but are implied within the tackling methodology and are well known safe tackling procedures.
The six portions of the Head Up Football tackle form given as instruction and feedback to the participants.
Utilization of HUF practice recommendations has been indicated to have the potential to decrease injury risk in youth athletes, though the effect of the tackling technique may not be the primary driver or may not translate to game performance.
The purpose of this study was to examine the effects of training in a vertical, head up tackling style on the number of head accelerations experienced while tackling in a controlled laboratory situation.
A reduction in the head accelerations experienced by the tacklers may indicate a decreased risk for sports related concussion. The authors hypothesized that achieving the proper body position would reduce the number head accelerations over 10g experienced by participants when tackling.
DISCUSSION
The results of this study indicate that training in a head up, vertical style tackle reduces the number of head accelerations over 10 g and 1885 deg/s2 experienced by the tackler. Previous research has indicated the effectiveness of the USA Football Heads Up program overall to decrease the number of head accelerations experienced by tacklers.8
The USA Football Heads Up program provides coaches with a prescribed tackling form along with instructions to reduce the number of high contact drills which may be responsible for the decrease in head accelerations experienced in this previous study.
Concurrently with the decrease in head accelerations, the participants’ form scores on the QYTS improved from baseline to post training.
Results indicated those who took shorter steps toward the target had decreased odds ratios of receiving an impact greater than 10, 15 and 20g in one day of training.
Participants decreased the head accelerations experienced both immediately during a one day training session and in a 48 hour retention with three sessions of training.
Analysis of changes in form indicates the training program was successful in improving the QYTS scores of the athletes over a one day period.
Of these changes in form, a significant increase in the odds ratio of suffering an impact over 10, 15 and 20g was found in those who failed to reduce their step length to less than 75% of standing pelvis height.
This result may indicate that slowing the body in general decreases the head accelerations experienced12 or increases the time of approach, allowing the tackler to achieve better form as they apply the tackle.13
Other portions of the QYTS may show higher odds of head accelerations above 15 and 20g, however these data were limited to few impacts above those levels possibly due to the laboratory design as well as the age of the participants.
Linear accelerations and rotational acceleration/velocity have been proposed as the causative factors of concussive injuries,14 with a significant relationship between linear and rotational components.15
Previously only impacts that resulted in a concussion were seen as dangerous.16As knowledge regarding head injuries increases, the role of subconcussive blows in long term health effects has become better known.17
Some research has indicated the effect of subconcussive impact includes increased risk of mild cognitive impairment and chronic traumatic encephalopathy (CTE).18
Providing a form structure that limits both high level impacts and subconcussive blows may lead to reduced concussive injury rates and long term cognitive issues.
The results of this study indicate a training program in tackling form is capable of significantly decreasing the number of head contacts over 10g.
The goal of many programs and rule changes has been the reduction of the number and severity of head contacts10 through decreasing the number of contact practices,19 coach’s education,8 and implementation of form instruction20 and cervical strengthening.21
These studies have utilized a number of mechanisms including conducting drills with helmets removed to create a risk adverse environment22 and a comprehensive coaches’ education framework to limit the head impact exposure of football players.3,23
The 2016 Berlin Consensus Statement on Concussion in Sport recognizes prevention as a key component of concussion management, but also references the limited scope and the need for “A clear understanding of potentially modifiable risk factors is required to design, implement and evaluate appropriate prevention interventions to reduce the risk of SRC.”24 ,p.8 To date both coach education and helmetless tackling programs have shown promise in reducing the impact exposure of players.
Limitations to this study include a restricted age range and the use of a laboratory environment. Additional work should expand the scope both in number of participants and age range.
The translation of these results to both a controlled dynamic and real life environment should be completed.
Additional regression analysis could identify the components of the tackling form that influence the head accelerations experienced by the tackler in order to determine the source of changes in head accelerations found in this study.
CONCLUSION
The performance of a tackle that minimizes head accelerations is critical to the safety of the athletes in youth football.
The results of this study indicate training in a head up vertical style tackle reduces the head accelerations experienced by tacklers in a laboratory setting against a stationary target.
These results are critical to determining a form that minimizes the head accelerations experienced.
These results provide a baseline from which additional research should be planned to translate these results to a field based dynamic environment.
Provided by American Academy of Neurology
