CONCUSSION IN PROFESSIONAL FOOTBALL: COMPARISON
WITH BOXING HEAD IMPACTS—PART 10
David C. Viano, Dr. Med., Ph.D.
Mild Traumatic Brain
National Football League,
New York, New York
Sports Biomechanics Laboratory,
Wayne State University
Pro Biomechanics LLC,
Bloomfield Hills, Michigan
Ira R. Casson, M.D.
Mild Traumatic Brain
National Football League
New York, New York,
Department of Neurology,
Long Island Jewish Medical Center,
New Hyde Park, New York,
Department of Neurology,
Albert Einstein College of
Bronx, New York
Elliot J. Pellman, M.D.
Mild Traumatic Brain
National Football League
New York, New York,
ProHEALTH Care Associates, LLP,
Lake Success, New York
Cynthia A. Bir, Ph.D.
Sports Biomechanics Laboratory,
Wayne State University
Liying Zhang, Ph.D.
Sports Biomechanics Laboratory,
Wayne State University
Donald C. Sherman, M.S.
Sports Biomechanics Laboratory,
Wayne State University
Marilyn A. Boitano, M.D.
Safety and Equipment Committee,
US Marine Corp,
United States Naval Reserves,
Hamilton Health Sciences,
Hamilton, Ontario, Canada
David C. Viano, Dr. Med., Ph.D.,
265 Warrington Rd.
Bloomfield Hills, MI 48304-2952.
Received, March 16, 2005.
Accepted, September 7, 2005.
OBJECTIVE: This study addresses impact biomechanics from boxing punches causing
translational and rotational head acceleration. Olympic boxers threw four different
punches at an instrumented Hybrid III dummy and responses were compared with
laboratory-reconstructed NFL concussions.
METHODS: Eleven Olympic boxers weighing 51 to 130 kg (112–285 lb) delivered 78
blows to the head of the Hybrid III dummy, including hooks, uppercuts and straight
punches to the forehead and jaw. Instrumentation included translational and rotational
head acceleration and neck loads in the dummy. Biaxial acceleration was measured in
the boxer’s hand to determine punch force. High-speed video recorded each blow.
Hybrid III head responses and finite element (FE) brain modeling were compared to
similarly determined responses from reconstructed NFL concussions.
RESULTS: The hook produced the highest change in hand velocity (11.0 ? 3.4 m/s)
and greatest punch force (4405 ? 2318 N) with average neck load of 855 ? 537 N.
It caused head translational and rotational accelerations of 71.2 ? 32.2 g and 9306 ?
4485 r/s2. These levels are consistent with those causing concussion in NFL impacts.
However, the head injury criterion (HIC) for boxing punches was lower than for NFL
concussions because of shorter duration acceleration. Boxers deliver punches with
proportionately more rotational than translational acceleration than in football con-
cussion. Boxing punches have a 65 mm effective radius from the head cg, which is
almost double the 34 mm in football. A smaller radius in football prevents the helmets
from sliding off each other in a tackle.
CONCLUSION: Olympic boxers deliver punches with high impact velocity but lower
HIC and translational acceleration than in football impacts because of a lower effective
punch mass. They cause proportionately more rotational acceleration than in football.
Modeling shows that the greatest strain is in the midbrain late in the exposure, after the
primary impact acceleration in boxing and football.
KEY WORDS: Boxing, Concussion, Impact biomechanics, Sport equipment testing, Sport injury
Neurosurgery 57:1154-1172, 2005
both sports are at risk for sustaining concus-
sions (?dinged,? ?knocked out,? cerebral con-
cussion, MTBI). Zazryn et al. (101) found 107
injuries to 427 professional boxing partici-
pants, 89.8% of the injuries were to the head,
neck and face with 15.9% concussions. For
amateur boxers, the incidence of concussion is
4.0% to 6.5% (19, 38, 98). The difference in
concussion rates between professional and
amateur boxing may be due to differences in
safety gear, and there have been recommen-
losed head injury is an occupational
hazard of many sports, and specifically
in boxing and football. Participants in
dations to analyze professional and amateur
boxers’ injury rates separately (41).
The clinical picture of more severe brain
injury is different in football and boxing (60–
64, 75, 88, 89). The pattern of brain injuries in
boxing has been extensively studied (2, 6, 7,
12, 13, 15, 18, 20, 22, 25, 26, 29–31, 36, 37, 44, 47,
51, 67–69, 72–74, 82, 85, 98). The pattern of
brain injury in professional football has been
recently studied and reviewed (60–64).
The medical literature is clear on the differ-
ence in the acute phase. Boxers are much more
likely to develop subdural hematomas and
brain-injury deaths than professional football
1154 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
players (40, 42, 66, 88, 89). Boxers are also prone to develop,
over the long term, a characteristic pattern of chronic brain
injury (chronic encephalopathy of boxers, pugilistic dementia,
?punch-drunk?) that has never been reported in professional
American football players (12, 39, 47, 75, 87, 89).
The biomechanical forces affecting the brain of professional
football players have been recently reported as part of the
ongoing studies of the NFL (58, 59, 64, 93–95). This study of
the biomechanical forces in boxing was undertaken to help
explain the similarities and differences between the clinical
overview of brain injuries in the two sports. A longer term
goal of this research is to study the effectiveness of protective
headgear and sport equipment, including helmets in football
and headgear and gloves in boxing. An understanding of the
biomechanical forces causing injury is the first step in address-
ing improved protection. Boxing gloves and headgear are
currently required in amateur boxing to prevent head injury
(98). The equipment may reduce some injuries, but it does not
eliminate the risk of knockouts (101).
The effectiveness of boxing safety equipment has been ad-
dressed by Schmidt-Olsen et al. (81) in a three-year study of
amateur boxers in Denmark. No decrease in injuries was
found with an increase from 8- to 10-ounce gloves, unlimited
hand-wrap and use of helmets for heavier boxers. The lack of
other data on this topic leaves boxing officials, athletes and
trainers uncertain as to what specific safety equipment is most
effective and what areas of improved safety needed additional
An improved understanding of the mechanisms of brain
injury and biomechanics of head responses in amateur boxing
is needed to lay the foundation for improvements in the
effectiveness of protective equipment in boxing. This study of
boxing and the biomechanics of the punch involves several
factors, including how much force is exerted during a punch
type, how that force is transferred to the opponent’s head,
how the opponent’s head responds to the punch and how the
opponent’s head responds to different punches.
Punch Forces in Boxing
The biomechanics of punches has been studied using sur-
rogates simulating the opponent (3, 83, 99). Atha et al. (3) and
Smith et al. (84) analyzed different surrogates that have been
used, including a ballistic pendulum, a uniaxial strain gauge
platform, instrumented punching bags, water-filled elastic
bags and boxing dynamometer. A consideration when choos-
ing a surrogate is its ability to mimic the human body in both
shape and impact response.
Atha et al. (3) used a single boxer and an instrumented
ballistic pendulum to evaluate a single straight punch. The
professional boxer punched the surrogate with 4096 N, which
the author estimated translated into 6320 N of force to a
human head. This force produced peak acceleration for 53 g’s
on the 7 kg ballistic pendulum.
Joch et al. (34) placed 70 boxers into one of three categories,
including 24 elite, 23 national and 23 intermediate boxers. The
force of straight right punches was measured with a water-
filled punching bag fit with a pressure transducer. The aver-
age maximum punch force was 3453 N, 3023 N and 2932 N,
respectively. In addition to the lack of biofidelity, there was a
need to stabilize the surrogate and de-gas the bag, which
made testing cumbersome (84).
Smith et al. (84) developed a boxing dynamometer to mea-
sure punch force. Twenty-three boxers were sorted into elite,
intermediate, and novice boxer categories. Boxers were in-
structed to punch the head region of a pear-shaped bag
mounted to a wall. Boxers threw straight punches using both
their lead and rear hands. Punches were thrown singularly
and in two and three punch combinations. The elite boxers
had a mean rear-hand punch force of 4800 N and a front-hand
punch force of 2847 N. The intermediate boxers’ rear and front
hand punch forces were 3722 N and 2283 N, respectively, and
the novice boxers’ mean rear and front hand punch forces
were 2381 N and 1604 N (84). The researchers developed a
surrogate, but the faceless pear-shaped device lacked the hu-
man response provided by the neck.
Walilko et al. (97) recently studied the biomechanics of
straight punches to the jaw causing translational and rota-
tional head acceleration. This was a precursor study to the
present investigation. Seven Olympic boxers from five weight
classes delivered 18 straight punches to the compliant face of
the Hybrid III dummy. Instrumentation included hand accel-
eration and pressure distribution on the jaw. The punch force
averaged 3427 ? 811 N, hand velocity 9.14 ? 2.06 m/s and the
effective punch mass 2.9 ? 2.0 kg. The jaw load was 876 ? 288
N. The peak translational acceleration was 58 ? 13 g, rota-
tional acceleration 6343 ? 1789 r/s2and neck shear 994 ? 318
N. They found that boxers deliver straight punches with high
impact velocity and energy transfer to head rotation. The
severity of the punch increased with weight class primarily
due to a greater effective mass of the punch.
Assessing Head Injury Risks
Following the methods of Pellman et al. (58), the risk of
head injury was determined by the methods of Gadd (21) and
Hodgson et al. (32) using a human surrogate that has biofi-
delity in its impact response. Biofidelity reflects the ability of
the surrogate to simulate the essential biomechanical charac-
teristics of the human impact response. The Hybrid III dummy
used in this effort is currently the most advanced, validated
biomechanical surrogate, particularly for the head and neck
areas. Sensors placed in the surrogate collect biomechanical
data that are related to risk of injury. Previous studies have
developed criteria to estimate the risk of head injury from
various impacts (24, 28, 55).
One of the earliest head injury criteria was based on re-
search conducted at Wayne State University (46). By investi-
gating the relationship between the level of acceleration and
duration of the impact, the Wayne State Tolerance Curve
(WSTC) was developed (27). Impacts to the head that were
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1155
lower in acceleration required a longer pulse duration to cause
the same injury as those higher in acceleration.
From this initial research, Gadd (21) expanded the analysis
by including other human tolerance data from Eiband (17) and
plotted the effective or average acceleration versus duration of
impact on a log-log scale. The result was a straight line that
had a slope of –2.5. Based on this result, the Severity Index (SI)
was developed relating head acceleration to risk of injury:
SI ? ?a?t?2.5dt
where a(t) is the resultant translational acceleration at the head
center of gravity (cg) and T is the duration of the acceleration.
SI depends on the time history of the resultant translational
acceleration. From the existing data, an SI tolerance of 1000
Versace (90) presented a new method for determining a
head impact injury that took the SI one step further by opti-
mizing the formula over the duration of impact. The final
result was the Head Injury Criterion (HIC):
HIC ? ??t2? t1???
where t1and t2are determined to give the maximum value to
the HIC function and a(t) is the resultant translational accel-
eration of the head cg. In practice, a maximum limit of T ? t2
? t1? 15 milliseconds is used.
Risk of head injury is calculated from accelerations at the
head cg in three orthogonal directions. The resultant acceler-
ation is calculated from these measurements and is used to
determine HIC. As summarized by Walilko et al. (97), the final
value provided a maximum acceptable value. The US delega-
tion to Working Group (WG) 6 provided an estimate of the
percent of the adult population expected to experience a life-
threatening brain injury (AIS 4) for various HIC levels due to
frontal head impacts (70). The delegation’s best estimate is that
16% of the adult population would experience a life-
threatening brain injury at a HIC level of 1000. In a recent
study of concussions in the NFL, Pellman et al. (58, 59) rec-
ommended a value below 250 to minimize the risk of Mild
Traumatic Brain Injury (MTBI or concussion).
Holbourn (33) worked with gel models of the brain and
showed that rotational acceleration was an important mecha-
nism in head injury. Ommaya and Hirsch (55) scaled primate
head injury data to humans and predicted that a level of head
rotational acceleration in excess of 1,800 r/s2would have a
50% probability of cerebral concussion in man. Analysis of
injuries produced in rhesus monkey experiments resulted in
Gennarelli et al. (23) estimating a 16,000 r/s2rotational accel-
eration tolerance threshold in man.
In a recent survey of rotation head injury criteria, Ommaya
et al. (54) found that the rotational acceleration of 4,500 r/s2
was required to produce concussion in an adult and that
severe diffuse axonal injuries (DAI) occurred at 18,000 r/s2.
The range is from scaling of animal impact data and indicates
the difficulty in developing a precise injury-prediction crite-
rion for rotational motion, since the shape and mass of the
animal brains are different from human and scaling laws
assume geometric similarity. This makes extrapolating animal
data to humans difficult. Also, the low mass of the animal
brain requires very high rotational accelerations to produce
closed head injuries (55). The combination of these factors
makes predicting injuries in humans difficult. Furthermore,
Pellman et al. (58, 59) found concussion was related to trans-
lational acceleration of the head.
In an effort to understand the relationship between forces
delivered in boxing and risk of head injury from linear and
rotational accelerations, the biomechanics of four different
types of boxing punches was studied. The punches included
straight punches to the forehead and jaw, a hook and an
uppercut. Olympic boxers threw punches at an instrumented
Hybrid III headform with their dominant hand, except for the
hook. Correlations were made between the biomechanics of
the Hybrid III head responses for the boxing punch and hel-
met impacts in professional football with attention to concus-
sion. This study shows the similarities and differences be-
tween the head impacts.
Eleven Olympic boxers weighing 51 kg (112 lb) to 130 kg
(285 lbs) were included in the study. They were tested while
participating in the 2004 United States Boxing National Cham-
pionships. The research received approval from the Wayne
State University’s Human Investigation Committee and each
boxer read and signed an informed consent prior to testing.
Since their involvement was voluntary, they could withdraw
from the study at any time. A certified boxing trainer was
present for the tests even though the risk of injury was mini-
mal. The boxers were not compensated for their participation.
Each boxer was evaluated for four punches. After a boxer
warmed-up, they were instructed to strike the instrumented
Hybrid III head with their gloved fist two times with four
different punches, straight punches to the forehead and jaw
and a hook and uppercut. Based on the method of Walilko et
al. (97), three of the four punches were delivered with the
dominant hand, including a straight punch to the jaw, a
straight punch to the forehead and an upper cut to the jaw. For
the fourth punch, the boxers’ non-dominant hand was instru-
mented and they were asked to deliver a hook to the temple.
Impact location of the punch was determined by high-speed
Measurement of Effective Hand-Arm Mass
Height and weight of each boxer were measured and an-
thropometric data for the dominant hand was collected. Vol-
ume measurements were obtained by submerging the domi-
nant fist up to the styloid process in a water bath (97). The
displaced volume of water was measured. Boxers then sub-
merged their fist and forearm up to the epicondyles of the
humerus bone. The effective mass of the fist and forearm were
VIANO ET AL.
1156 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
calculated from the anthropometric and volumetric measure-
ments by estimating the density of the body and converting
densities of the forearm and hand. The segmental forearm and
hand densities were multiplied by the segmental volumes to
determine mass. Density estimates (d) were made using d ?
0.6905 ? 0.0297c with c ? h/w1/3, where h ? height (inches),
w ? weight (lbs), conversion factor for hand density (1.08) and
conversion factor for forearm density (1.06). The equations
have been shown to be suitable for estimating segmental body
masses (8, 10, 100).
The test methods follow those described by Walilko et al.
(97). A Hybrid III dummy with a frangible face was used to
represent the response of the jaw and realistically transfer
acceleration to the head. For the tests, a cork insert was used
to give facial compliance for the straight jaw punches. The
straight blow to the forehead and hook to the temple were on
regions of the Hybrid III with known biofidelity. The uppercut
was to the jaw, which has less biofidelity.
The tests used the compliant face of the Hybrid III head (50).
This design has an improved biomechanical response in the
facial region over the standard molded Hybrid III and more
accurately reproduces the force and acceleration of the head
for impacts in the frontal, zygomatic, maxillary and mandib-
ular regions. Other devices used either a stiff load-measuring
face or deformable structures in regions other than the jaw (1,
52, 92). The head and neck of the dummy were attached to the
upper torso, which was fixed to the table by the flexible
lumbar joint. This gave realistic head and upper body motion.
For the straight punch to the forehead, hook and uppercut,
the punches were directly to the Hybrid III head. The straight
punch to the jaw loaded the compliant face. Headgear was not
placed on the dummy. The upper torso was attached to a rigid
table with a foam pad placed below the Hybrid III abdomen
insert so that the dummy remained in an upright position after
each punch. Scaffolding was used to adjust the height of each
boxer to a minimum 175 cm (69?) to ensure the punches were
in the horizontal plane.
The Hybrid III simulates a tensed neck so the head is nor-
mally upright. The segmented neck includes flexible polymer
discs to simulate the flexion-extension and lateral bending
responses. A cable inside tightens the assembly to give the
right neck response in calibration testing and during head
acceleration (77, 80). While the Hybrid III neck was utilized in
the study, it is unknown how it represents the strength of a
boxer’s neck. Boxers undergo extensive training to develop the
neck muscles necessary to resist punch forces from an oppo-
nent. However, Johnson et al. (35) demonstrated that neck
muscle tension has little effect on the oscillation of the head
under sinusoidal excitation from a shaker.
Instrumentation was placed in the boxer’s clenched hand.
Two Endevco (San Juan Capistrano, CA) 7264-2k accelerome-
ters were secured to a semicircular cylinder, which was
wrapped with the boxer’s hand to measure hand acceleration
in a biaxial arrangement. Integration of acceleration gave the
velocity change of the hand during the punch. The Hybrid III
was equipped with the standard triaxial accelerometers
(Endevco 7264-2k) at the head center of gravity (cg) and six
more accelerometers in a ?3-2-2-2 configuration? to determine
rotational acceleration (56). Processing of the nine accelera-
tions determined the complete three-dimensional motion of
the head. Rotational accelerations were computed from linear
accelerations in the head. The analysis is valid for accelerom-
eters coincident with the origin of the system or coincident
with one of the axes. Deviations from this were required in the
Hybrid III head, and a correction for centripetal and Coriolis
acceleration was made according to DiMasi (16). Data was
collected at 10,000 Hz using the TDAS PRO (DTS, Inc.) data
acquisition system (SoMat, Co, Urbana, IL) and post processed
according to SAE J211-1 (78).
Video Film Analysis and Target Location
A target was placed on the glove to digitize its motion and
calculate impact velocity. Additional targets were attached to
the head of the Hybrid III to measure the overall kinematics of
the dummy during impact. Images were captured with a
Kodak HG2000 high-speed video camera. The camera re-
corded the event at 4500 images per second. Digitization of the
data was completed using the Image Express for video record-
ing and processed according to SAE J211-2 (79).
Data Collection Procedure
After an appropriate warm-up period, the boxer was asked
to lightly punch the head of the instrumented dummy with
their wrapped and gloved hand. If there was no pain or
discomfort, they were asked to increase their punch strength
until they reached a point where they were throwing ?normal?
punches. Once the boxer was comfortable throwing punches,
they were asked to deliver four different punch types to the
dummy. Each punch type was performed twice for a total of
eight punches per boxer. The order of punch placement was
varied randomly; however, all of the punches for a particular
hand were completed before the alternate hand was tested.
Punch and Head Inertial Forces
Impact forces were determined by two methods. First, the
hand acceleration was measured for each punch and multi-
plied by their effective punch mass, which was determined
separately. This estimated the impact force for the punch.
Second, the resultant head acceleration of the Hybrid III was
multiplied by the head mass of 4.45 kg to estimate the inertial
force on the head. The punch force includes the inertial force
on the head and neck loads, so it was always higher than the
inertial force. The severity of the impacts was further quanti-
fied using translational and rotational acceleration, head in-
jury criterion (HIC), severity index (SI) and change in head
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1157
Concussion Risks from Boxing Punches
Pellman et al. (58) determined concussion risks using the
Logist function in the Statistical Analysis Package (SAS). This
function relates the probability of concussion p(x) to a re-
sponse parameter x based on a statistical fit to the sigmoidal
function p(x) ? [1?exp(?-?x)]?1, where ? and ? are parame-
ters fit to the NFL response experience from the laboratory
reconstruction of game impacts. The risk of concussion was
determined for Olympic boxer punches using the NFL risk
functions based on all football players exposed to helmet
collisions. The parameters for the Logist functions were ? ?
2.677 and ? ? 0.0111 for HIC, ? ? 4.678 and ? ? 0.0573 for
translational acceleration and ? ? 5.231 and ? ? 0.000915 for
FE Modeling of Brain Responses
Head accelerations from the Hybrid III dummy were used
as input to a finite element (FE) model of the boxer’s brain.
This analysis follows the approach reported by Viano et al.
(95) in the study of brain responses in NFL concussions. The
brain responses for three punches from the heaviest boxer
were simulated and compared with the patterns of brain
deformation determined with NFL concussions. Early and
mid-late strain responses and brain displacement were deter-
mined to show timing and areas of greatest brain deformation
from the punches.
Effective Impact Radius
During a punch, the head experiences translational and
rotational acceleration from the impact force. The accelera-
tions are coupled. The impact can be resolved into a force at
the head cg and a moment. The moment is related to the
punch force times a radius between the impact axis and head
cg. The radius (r) of impact causing rotational acceleration can
be approximated by a simplified 2D relationship: r ? ?I/F ?
(?/a)(I/m), where the head mass (m) is 4.45 kg and moment
of inertia (I) about a lateral axis through the head cg is 0.022 kg
m2(45). The impact radius is proportional to the ratio of
rotational to translational acceleration, where the constant of
proportionality is the ratio of head moment of inertia to mass,
or 0.0049 m2. If the simplified analysis assumes the head and
neck are acting together to resist the impact, the mass is 5.80
kg and the average moment of inertia is 0.035 kg m2(4). This
gives a ratio of head-neck moment of inertia to mass of 0.0059
m2and the effective radius increases 20%.
Boxer Anthropometry and Effective Punch Mass
Table 1 shows anthropometric data on each boxer. It also
gives the volume of the hand and forearm, which were used to
determine the effective punch mass. The average weight of the
11 boxers was 76.5 ? 22.1 kg (167.7 ? 48.5 lb) and their height
was 177.2 ? 9.2 cm (69.8 ? 3.6 inch). The hand mass increased
with boxer weight and averaged 1.67 ? 0.28 kg.
Punch Force and Biomechanical Responses
Figure 1 shows an example of the punch kinematics for the
four different blows. These are images from the high-speed
video and show the progression of the punch to the head of
the Hybrid III dummy. The left column shows the straight
punch to the jaw, which initially causes flexion of the upper
neck and extension of the lower cervical region (third image).
This happens because the punch is below the head cg. The
TABLE 1. Anthropometry of the Olympic boxersa
aSD, standard deviation.
VIANO ET AL.
1158 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
hook produces lateral bending of the neck and twists the head
about its vertical axis. The uppercut is shown in the last
sequence at the right.
Table 2 summarizes the average biomechanical responses for
the four different punch types. The full data is given in the
Appendix. The hook produced the greatest impact force (4405
? 2318 N) and inertial load on the head (3107 ? 1404) with an
average neck load of 855 ? 537 N. It also had the highest
change in hand velocity (11.0 ? 3.4 m/s). The lowest forces
occurred with the uppercut to the jaw. Because of the range in
boxer weight, the overlap in responses does not produce
significant differences when the punches are grouped by type.
The hook also produced the largest head translational and
rotational accelerations, reaching an average 71.2 ? 32.2 g and
9306 ? 4485 r/s2, respectively. The straight punch to the jaw
resulted in the largest neck loads (1088 ? 381 N) as the neck
flexes as the jaw is driven rearward. This also resulted in the
greatest bending moment of 81.9 ? 23.8 Nm about the y-axis
Even though the hand velocity change was in the range of
6.7 to 11.0 m/s on average, the change in velocity of the
Hybrid III head was only 2.8 to 3.1 m/s on average for the
various punches. This reflects the relatively low punch mass
during the momentum exchange in the punch, although the
change in hand velocity includes some effects of rebound from
Comparing Boxer Punches to NFL Concussions
Figure 2 shows the average and standard deviation in head
inertial force (head mass times acceleration) for the four punches
from the Olympic boxers and three conditions from NFL helmet
impacts. The highest force is for NFL players experiencing con-
cussion. Lower forces were measured in the NFL reconstructions
for players struck without injury and for the striking players in
helmet-to-helmet tackles. The force from the boxer’s hook ex-
ceeded that of the non-injured NFL players and was within the
statistical range for concussion. The jaw and forehead impact
forces were lower and the uppercut produced the lowest inertial
loads on the Hybrid III head.
Figure 3 compares the head biomechanical responses for the
NFL game reconstructions and the boxer punches to the Hy-
FIGURE 1. Sequences from high-speed video of a boxer throwing a
straight punch to the jaw (left column) and forehead (second column),
a hook (third column) and an uppercut (right column). Time is shown in
the top left of each image and the number in the top right is the frame count.
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1159
brid III dummy. The HIC was higher for NFL players experi-
encing concussion. The NFL players not injured or striking
without injury had HICs slightly higher than the range of
boxer punches. A similar trend can be seen in the translational
acceleration, but the hook shows levels in the range for a risk
of concussion based on the NFL experience. Interestingly, the
boxers deliver more rotational acceleration to the Hybrid III
dummy head for the hook and jaw punches than occurred in
NFL concussions. However, the duration of impact is shorter
for the boxing punch, so the rotational velocity of the head is
similar to that in NFL concussion impacts with longer dura-
tion but lower rotational acceleration.
Figure 4 shows the peak rotational and translational accel-
erations for the NFL concussions and the boxers punches to
the Hybrid III dummy. The closed circles represent concussed
players in the NFL and the open symbols biomechanical data
from players struck without injury or the striking players. The
boxer data is included showing that jaw and hook punches
have impacts in the range of the concussions experienced in
the NFL. On average the boxers produce more rotational than
translational acceleration with their punches.
Concussion Risks in Boxing and NFL Head Impacts
Table 3 shows the average and standard deviation in con-
cussion risk using biomechanical responses from the Hybrid
III dummy. Risk functions were used for concussion, where
HIC had the strongest statistical correlation with NFL concus-
sions (58). Based on HIC, the hook had a 13.8% ? 14.3% risk
of concussion. On average, the predicted risks were in the
range of 7 to 14% for the various punches. Similar concussion
risks were predicted by peak translational acceleration, which
was also a good predictor of concussion for the NFL impacts.
The risk averaged 11 to 97% based on the peak rotational
For comparison, the average and standard deviation in NFL
concussion risk is shown from Pellman et al. (58, 59). Based on
28 players struck with 22 concussions, the average risk of
concussion was 58.2% ? 33.0% based on HIC. While no strik-
ing player experienced concussions, the head responses were
high enough to estimate a risk of 23.4 ? 20.7%, which obvi-
ously overstates the incidence based on the field experience.
Nonetheless, the Logist risk functions were determined as a
FIGURE 2. Inertial force on the Hybrid III head for NFL game impacts
and four different boxing punches.
TABLE 2. Summary punch forces and biomechanical responses of the Hybrid IIIa
aHIC15, head injury criterion for 15 ms duration; SI, severity index; Res, resultant; Acc, acceleration; Rot, rotation; SD, standard deviation; Vel, velocity.
VIANO ET AL.
1160 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
probability relationship between measured biomechanical re-
sponses and physician observed concussions.
FE Modeling of Brain Responses
Figure 5 shows the simulated brain responses for a hook
from the heaviest Olympic boxer (boxer #6). This was a sub-
stantial blow and the strain ?hot spots? show an early pattern
in the temporal lobes with the highest strain occurring late in
the midbrain. The maximum strain occurred about 10 milli-
seconds after the peak impact force.
Effective Impact Radius
Figure 6 shows groupings of peak accelerations for NFL
concussions, striking players without concussion, struck play-
ers without injury and the four boxer punches. The lines are
based on the relationship: r ? ?I/F ? (?/a)(I/m). The average
radius between the punch axis and head cg was 57 to 71 mm
with 57 mm for the forehead punch, 65 mm for the hook, 66
mm for the uppercut and 71 mm for the jaw punch. In con-
trast, NFL concussions occur at a higher translational acceler-
ation and force on the head, but lower rotational acceleration.
The average radius varied from 32 to 36 mm for the NFL
players struck and injured (35 mm), those struck and not
injured (36 mm) and the striking players (32 mm).
The ratio of head rotational to translational acceleration is
higher in boxing than in NFL helmet impacts and results in a
larger effective radius. The effective radius in football is 48%
smaller than in boxing on average (34 mm v 65 mm). If the
simplified analysis assumed the head and neck was acting to-
gether to resist the impact, the effective radius increases 20%.
FIGURE 3. HIC and peak translational and rotational acceleration for
NFL game impacts and four different boxing punches.
FIGURE 4. Individual data points for translational and rotational acceleration
of the Hybrid III head for NFL game impacts and four different boxing punches.
FIGURE 5. Strain ?hot spots? in the brain for a hook (Test 6h) showing
the early, mid and late response pattern. The punch is to the right side of
the Hybrid III head. The peak translational acceleration occurred at 5 mil-
liseconds and the duration was about 8 milliseconds. The strain and
strain-rate responses are shown for tissue in the brain.
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1161
This study compares the biomechanical forces affecting the
head and brain from boxing punches with football helmeted
impacts occurring in the NFL. There were three significant dif-
ferences noted. The boxers’ punches resulted in lower transla-
tional accelerations in the struck head, as compared to the foot-
ball impacts. The boxers’ punches applied a higher moment to
the struck head than did the football impacts. This necessarily
resulted in higher rotational accelerations in the head struck by
the boxers’ punch. Boxers therefore sustain brain injury by two
mechanisms, translational and rotational accelerations of the
brain, with a preponderance of the rotational component. Pro-
fessional football players, on the other hand, sustained MTBI
mostly by translational accelerations. These differences in the
biomechanical forces may help explain the clinical differences
between head injury in boxing and professional football.
Brain injury resulting in death is mostly due to acute subdural
hematomas, which is much more common in boxing than in
professional football. This difference can be explained by the
differing effects on the bridging veins and other fragile brain
structures resulting from the biomechanical forces. In addition,
boxers are susceptible to a specific, unique pattern of chronic
brain damage that has never been seen in American football
players. The relative prepon-
derance of rotational accelera-
tions and the lower transla-
tional accelerations seen in
boxing impacts may set the
stage for boxers to sustain this
type of long term brain injury.
This study also demonstrates
one significant similarity be-
tween the head impacts in box-
ing and professional football. In
both cases, the FE modeling in-
dicates that the highest strain
suggests that high midbrain
strain in the late timeframe
might be a final common path-
cussion from a variety of head
Boxing and NFL Brain
Acute head injuries in box-
ing can be more serious and
devastating than those seen in
professional football. There
were over three hundred box-
ing deaths recorded in England due to brain injury before 1937
(66). Between 1945 and 1980, there were over 335 documented
fatalities due to boxing (38–40, 66, 86–89). There have been many
more deaths due to boxing in the years since 1980.
Approximately 75% of brain injury deaths from boxing are
due to subdural hematoma (40, 66, 75, 89). Most of the other 25%
subdural hematomas that account for the majority of boxing
deaths are due to tearing and rupture of the bridging veins that
run between the dura and the surface of the brain (40, 66, 89).
animals as well as clinical experience in humans indicate that
almost all of the subdural hematomas are due to the effects of
rotational forces stretching the bridging veins (89). One would
expect that tearing of the bridging veins and subsequent sub-
dural hematoma would be seen more commonly after head
blows in a sport such as boxing with a preponderance of rota-
tional acceleration as compared to professional football in which
translational forces predominate.
The data from these tests on boxers shows proportionately
higher rotational accelerations than translational acceleration
in boxing. There is another possible explanation for tearing of
the bridging veins in boxing. The present study indicates that
TABLE 3. Estimated risk of concussion for boxer punches based on the National Football League
Risk of concussion
HIC Trans acc. g Rot. acc r/s2
Olympic boxer punchesForehead
NFL Helmet Impacts
aHIC, head injury criterion; Trans acc, translational acceleration; Rot acc, rotational acceleration; SD, standard
VIANO ET AL.
1162 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
punches directly to the jaw cause flexion of the head and neck
resulting in stretching (high strains) of the bridging veins. In
contrast, punches impacting the forehead cause extension of
the head and neck with resultant compression (low strains) of
the bridging veins.
Although there have been 433 fatalities due to head injury in
football between 1945 and 1984 (337 cases due to subdural
hematoma), almost all of these have occurred in high school or
college players (66), where neck musculature and abilities are
not as well developed as in the professional athlete. The
authors are aware of one head injury related death in a pro-
fessional Canadian football player and no brain injury related
deaths in American professional football players since 1945.
There was one case of subdural hematoma occurring in an
American professional football player during those years but
this was successfully removed without fatality.
The occurrence of subdural hematoma is consistent with the
relatively larger translational accelerations and inertial force
on the head in professional football than in boxing. This also
raises the possibility that rotational head accelerations may be
more predominant among college and high school players
than in professional football players. It is also possible that the
younger high school and college athletes’ brains are more
susceptible to tearing of the bridging veins than the more
mature adult brains of the professional players. Although the
absolute number of head injury related fatalities are similar in
boxing and amateur levels of football, the incidence is in fact
much higher in boxing because of the much larger number of
annual participants in football at all levels compared to the
number of annual participants in boxing.
Another clinical difference between the patterns of brain
injury seen in boxing and football is the chronic brain damage
seen in boxers but not in football players. A chronic enceph-
alopathy of boxers has been well known to physicians since its
initial description in 1928 (39, 47, 49, 75, 89). The clinical
syndrome of pyramidal, extra pyramidal and cerebellar dys-
function combined with organic mental syndromes with cog-
nitive and memory impairments and personality changes has
been well documented (75, 89). The chronic encephalopathy
may range from very mild to very severe.
During the past 25 years, studies have documented a pattern
of cognitive and memory impairments in boxers ranging from
subclinical to clinical dementia of varying degrees from chronic
brain injury (5, 76). Studies have also defined a specific pattern of
neuropathology which constitutes the chronic encephalopathy of
boxers. This consists of abnormalities of the septum pellucidum,
the cerebellum, the substanta nigra and the cerebral hemispheres
(11, 89). The abnormalities of the septum pellucidum region
include tears and fenestrations with resultant CSF leakage into
the septum resulting in cavum septum pellucidum. The cerebel-
lar findings consist of scarring and loss of Purkinje cells. In the
substantia nigra there is depigmentation and loss of neurons.
There is cerebral scarring as well as the presence of neurofibril-
lary tangles without senile plaques. There is enlargement of the
third and lateral ventricles. This distinct neuropathological pat-
tern is diagnostic of chronic encephalopathy of boxers. Studies
have demonstrated that this chronic encephalopathy of boxers is
related to the accumulation of multiple subconcussive blows to
the brain over a long period of time. Its occurrence is directly
related to the length of a boxer’s career and the number of bouts
fought, not to the number of times the boxer had been knocked
out (5, 75, 76).
Roberts’ (75) study suggested that chronic encephalopathy
was more prevalent in heavier weight class boxers. This cer-
tainly would be consistent with the findings of the present
study that heavier fighters delivered blows with higher forces
than those generated by the lighter boxers. Critchley’s (14)
earlier paper, however, found that chronic encephalopathy
occurred equally across all weight classes thus raising a cau-
tionary note to interpreting the findings of this present study.
This syndrome has never been reported in American football
players. The present study may give some insight into why
this syndrome is seen in boxers but not in other athletes such
as professional football players. The present results indicate
that boxers’ brains sustain translational forces which are
largely at or below the threshold for MTBI in NFL players and
are likely to be subconcussive in nature when encountering an
alert opponent rather than the stationary Hybrid III dummy.
As a result, boxers are infrequently knocked out and thus able
to continue fighting even though there may be substantial
force in the punches landed.
In the course of training or a bout, a boxer may sustain large
numbers of such blows in a repetitive manner. Repetitive head
impacts with relatively high translational and rotational acceler-
ation sustained over a period of time may cause tearing of
structures such as the septum pellucidum resulting in cavum
septum pellucidum, damage to the deep midline structures of
the brain such as the substantia nigra and damage to the cere-
bellum and cerebral hemispheres. The nature of the forces im-
FIGURE 6. Peak translational and rotational acceleration for Olympic boxing
punches and NFL helmet impacts. The lines are a constant distance between the
axis of impact force and head center of gravity (cg) using a simplified formula
linking translational and rotational acceleration.
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1163
long term chronic brain damage (39, 71). The professional foot-
ball player’s head, on the other hand, is occasionally subject to
much higher translational accelerations which are more likely to
result in cerebral concussion and more likely to result in the
player being removed from play or at least limited in his game
activities for at least a short period of time. Professional football
players do not sustain frequent repetitive blows to the brain on a
regular basis. In addition, the relative preponderance of transla-
tional forces in professional football players may make them less
susceptible to chronic injury than does the relative preponder-
ance of rotational accelerations in boxing.
Difference Between the Biomechanics of Boxing and
NFL Head Impacts
Figure 2 shows the inertial force on the head (58, 59) from
reconstruction of helmet impacts in the NFL. They collected
data from Hybrid III dummies simulating impacts recorded
on game video. The laboratory reconstructions provided data
on the biomechanical responses associated with recorded con-
cussions in the players, and other severe impacts without
injury. No concussion occurred in six struck players, and none
of the striking players was injured. Interestingly, the boxers in
this study generated impact forces that are similar to the
non-concussion forces on the helmeted heads of NFL players.
The super-heavy weight boxer generated inertial forces of
3633 ? 1196 N and punch forces of 5352 ? 2775 N, which is at
the average impact force causing concussion in NFL players.
Since a majority of NFL players are injured by facemask or
lateral impacts on the helmet, the loading direction is consis-
tent with directions of the boxing punches, although straight
anteroposterior impacts are an uncommon cause for NFL con-
cussions. Boxer weight correlated with punch force, HIC and
head acceleration in tests on Olympic boxers (97). While
weight was a good predictor, punch force had a stronger
correlation with HIC and translational acceleration. This
means the effective mass of the boxer’s punch is more impor-
tant in increasing the severity of a blow.
There are probably two means by which boxers deliver con-
cussive blows. The first means involves the boxer delivering
enough translational acceleration. The hook involves a blow to
the temple, which is just above the head cg. The forehead punch
delivers force frontally above the head cg and the jaw impact
applies force below the head cg. These impacts translate the head
cg, and the forces can reach levels consistent with NFL concus-
sions. The damaging mechanism is translational acceleration
where the greater the mass of the punch, the greater the head
HIC and translational acceleration. The second means involves
rotational acceleration, which occurs with the impacts taking
advantage of the offset from the head cg. During the punch, the
axis of impact moves away from the head cg and introduces
proportionately more rotational acceleration during the punch.
The hook, for example, is always thrown with the elbow bent
(43). This necessarily results in the axis of impact moving away
from the cg after impact, thus imparting a significant amount of
rotational acceleration to the opponent’s head. The rotational
nature of the hook has led sports writers to describe this punch
as ?whirling? and ?tornadic? (43).
Increasing the effective mass behind a punch is the best way
to increase the force of the punch. Increased acceleration of the
punch may also result in increased force but it would seem
difficult to increase the acceleration in the actual scenario of
throwing a punch. Boxers and trainers intuitively realize that
increasing the effective mass behind the punch increases its
force. Champion boxer Jack Dempsey wrote that when he
threw a straight left hand punch he began his attack ?with a
falling step forward toward the target with his left foot? (43).
This ?started the weight transfer which was the power source.?
He continued, ?as you take your falling step forward, you
shoot a half open left hand straight along the power line chin
high? (43). The emphasis on keeping the arm and hand
straight is consistent with the results from Walilko et al. (97)
indicating that keeping the wrist straight and not flexed in-
creases the force of the punch. By falling forward into the
punch, Dempsey was increasing the effective mass behind the
punch and thus increasing its force. Dempsey also knew that
it was very difficult to deliver a knockout punch without
throwing the entire weight of his body behind the punch. He
wrote that it would be very difficult to throw a knockout
punch by just turning the shoulders (43).
Presumably, other champion fighters and trainers have
learned the same lessons that were known to Dempsey (96).
The results of the present study lend scientific validity to this
Figure 3 shows the HIC and translational and rotational
accelerations from Pellman et al. (58, 59) on the biomechanics
of NFL concussion. The boxers cause HIC and peak transla-
tional accelerations in the lower range of concussions in the
NFL, but the head rotational accelerations can be higher from
boxing punches. This means the boxers do not transfer as
much energy in their punch as the collisions in the NFL. Figure
4 shows more of the trend in the peak translational and
rotational acceleration. In this case, there is a greater overlap
in the peak rotational accelerations of the boxing impacts with
concussion levels found for NFL players. However, the peak
translational accelerations are lower than what occurs in the
NFL. GAMBIT is a head injury criterion that limits the com-
bination of rotational and translational acceleration (53). The
tolerance line is shown.
With the use of football helmets, the striking player must line
up his impacts closely with the head cg of the other player. This
allows the impact to transfer energy. If the impact vector is at an
angle, the blow will glance off due to the smooth plastic shell of
the helmets. Players realize that they need to align their impact
transfer to the other player. Severe helmet impacts that cause
concussion involve high translational acceleration and change in
head velocity (?V). NFL concussions involve an average impact
velocity of 9.3 ? 1.9 m/s; and, the ?V is 7.2 ? 1.8 m/s for the
concussed player. Since the duration of impact is nominally 15
milliseconds, the peak head acceleration is high at 98 ? 28 g. In
football, there is a strong correlation between translational and
VIANO ET AL.
1164 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
rotational acceleration due to the impact alignment and subse-
quent head-helmet motion.
In boxing, the punch and glove conform more to the head of
the opponent allowing punches to induce high rotational ac-
celeration without high translational acceleration. The effec-
tive mass of the boxer’s fist is 1.67 ? 0.28 kg, which is more
than an order of magnitude lower than the 25 kg effective
mass of the helmeted football player who strikes an opponent
(64, 93). With concussion, the striking player lines up their
head, neck and torso so their effective mass is considerable,
and only the head and part of the opponent’s neck resist the
blow. In boxing, the most efficient energy transfer involves
more rotational acceleration than translational acceleration.
The punch velocity of the boxers averaged 6.7 to 11.0 m/s for
the four different punches. These levels are essentially similar to
the impact speed in football concussions; but, the head ?V after
a punch was only 2.8 to 3.1 m/s on average, well below half that
of the punch. Boxers cannot deliver high translational accelera-
tion and ?V to the opponent because of the low punch mass in
comparison. Obviously, the effectiveness of punches is greater
when the opponent is dazed and their neck muscles are more
relaxed, since this lowers the effective head mass resisting the
punch. Many of the well known boxing fatalities in the modern
era have involved a fighter who has been dazed and stunned by
multiple blows from his opponent. He is in a defenseless state
with resultant marked diminution of muscle tone in the cervical
paraspinal muscles (89). The resultant decrease in effective head
mass results in increased translational and rotational accelera-
tions of the head with every further punch. These increased
accelerations are more likely to result in high strains to the brain,
including the bridging veins, leading to severe injury or death.
While this discussion is theoretical, it is based on the me-
chanics of two different sports that can deliver neurocognitive
effects to the brain in the form of memory, cognitive and
functional problems. What is critical to the logic is that striking
players in the NFL do not experience concussion even though
they have head ?V of 4.0 ? 1.2 m/s and the same impact
velocity as the concussed player. Their ?V and peak transla-
tional acceleration are above what the boxer can deliver in
their punches. This indicates that rotational accelerations may
be a factor in boxing knockouts, since translational effects are
Obviously, boxers can deliver rotational accelerations in
and above the range where NFL players are concussed. How-
ever in both sports, we have not determined the root cause of
concussion or knockouts. The underlying injury mechanism
may depend on yet unknown combinations of translational
and rotational acceleration, or factors of the brain response to
skull accelerations associated with the impact. It is clear that
head accelerations displace the skull in a complex kinematic,
which loads the brain and causes internal stresses that deform
neural tissues (45, 93). Brain and spinal cord tissues are sen-
sitive to the rate and extent of strain in an impact (91). A
sufficient combination of strain and strain rate can bruise the
tissue and cause dysfunctions in neural function.
FE modeling of the brain response to a hook is shown in
Figure 5. The responses are similar to the patterns of strain ?hot
spots? found in NFL concussions (95). Strain migrates from the
temporal lobes early in the response to the midbrain, where
the largest strain occurs late after the primary impact force of
the punch. Since most of the NFL concussions involve lateral
acceleration of the head, the hook has a similar direction of
head loading. The boxers claim the hook is their knockout
blow, but it is hard to deliver in a bout. Obviously, more
analysis of the FE responses is needed to determine strategies
for improving head protection in boxing and football; but,
these results offer new insights into the biomechanical re-
sponses of the brain during head impact.
Effective Impact Radius
the striking and struck players who were not injured. The aver-
age radius was 34 mm for the three groups (range 32-36 mm).
57–71 mm). The lines are constant radii. The impact radius is
proportional to the ratio of rotational to translational acceleration
with the ratio of moment of inertia to mass a constant of propor-
tionality. The ratio of head rotational to translational acceleration
is larger in boxing than in NFL impacts. This simplified analysis
seems to point to rotational acceleration as a possible factor in the
severity of knockout punches, whereas the NFL concussion stud-
ies found the strongest correlation with translational acceleration
and that the impacts had to be aligned with the head cg to
prevent the helmets from sliding off. The duration of impact is
shorter for boxing punch.
This analysis points to two different biomechanics of head
injury in boxing. One associated with high translational accel-
eration and HIC, and another related to high rotational accel-
eration with low translational acceleration and HIC. Obvi-
ously, more study is needed to determine the underlying
causes of boxing knockouts and football concussions. The
simplified analysis assumed average values for a complex
three dimension event. Also, the radius varies with time, the
punch can be at varying orientation to the head cg and the
flexibility of the neck is a factor. Nonetheless, the simplified
analysis shows that a punch produces proportionately larger
rotational than translational accelerations than in football by
having a larger effective radius. The analysis also shows that
rotational acceleration depends on the translational accelera-
tion; they are inextricably coupled in an impact.
The data generated by this present study has been compared
to the data from MTBI in the National Football League. The
translational accelerations to the Hybrid III dummy head than
are similar or higher to those seen in NFL concussions. This
indicates that there may be a greater role for rotational accelera-
tion in boxing blows compared to translational accelerations in
helmet impacts in professional football. These results suggest
that rotational acceleration of the head may be a factor in chronic
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1165
of brain injury is not seen in football players.
Comparing Concussion Risks in Boxing with NFL Head
Previous studies have primarily determined the force of a
boxer’s punch using a heavy bag or instrumented pendulum.
The current study is a continuation of the effort started by
Walilko et al. (97) to collect head impact responses using the
Hybrid III dummy to determine head injury risks from boxer
punches. The head-neck assembly of the Hybrid III closely
represents the mass and compliance of the human head and
neck. With this system, the risk of injury in terms of HIC, and
translational and rotational acceleration can be explored from
the momentum transfer of a punch to the head.
Because the dummy has humanlike impact responses and
there are risk functions for concussion, the results of this study
are relevant to determining the concussion risks from the
punches of boxers. Although the knockout punch is a dramatic
part of the sport, it is a relatively uncommon event. Studies have
shown that knockouts occur in less than 5% of professional fights
and probably in less than 2 to 3% of amateur level fights and in
less than 1% of all amateur fights (40, 48).
The present results are consistent with this data. The trans-
lational accelerations resulting from these punches were at
levels that one would expect to see relatively few clinical
concussions, particularly for the uppercut and forehead im-
pacts. The rotational accelerations are relatively higher and
perhaps closer to the levels that one might see with clinical
concussion. Most of the rotational accelerations were at or
above levels expected to cause cerebral concussion in football.
The uppercut is the exception. Therefore the laboratory results
are consistent with a measurable but low incidence of knock-
out in the sport of boxing.
High rotational accelerations were found. The average peak
rotational acceleration varied from a high of 9308 rad/s2for
the hook to 3181 to 6898 rad/s2for the other punches. Om-
maya et al. (54) indicated a rotational acceleration of approx-
imately 4500 rad/s2were required to produce concussion. He
also stated severe DAI occurs at 18,000 rad/s2, and moderate
and mild DAI occur at 15,500 r/s2and 12,500 r/s2, respec-
tively. Earlier studies by Pincemaille et al. (65) measured
rotational accelerations of 13,600 rad/s2and rotational veloc-
ities of 48 rad/s during boxing. There were no cases of con-
cussion in the tests. The current tests with the Hybrid III also
show high rotational accelerations, however, the data reflect
higher tolerances than specified in the literature otherwise
knockouts would be much more common in boxing matches.
Since the rotational acceleration tolerances are based on scal-
ing of animal data, a question may be raised about the ade-
quacy of the technique, which assumes similar geometry and
equivalent material characteristics between animal and man.
Using risk functions for concussion in NFL players (58), the
boxer impacts in this study show the highest risks with peak
rotational acceleration (Table 3). The average risk was 11 to 97%
for the four boxing punches. However, the NFL data showed the
most significant correlation of concussion with HIC and peak
head acceleration. Based on those biomechanical responses, the
boxing data indicate a concussion risk of 7 to 14% for HIC and 3
to 36% for translational acceleration. Interestingly, the boxers do
not generate enough head ?V to reach much of a concussion risk
based on the NFL data. HICs were low for the four punches with
a risk of severe traumatic brain injury ?2% (70). The average
threshold of 250 (58, 59).
Force delivered to the jaw loads the dummy in an area with
responses that are similar to the human, so the reported trans-
lational acceleration and HIC reflect what occurs in boxing
(50). However, it is uncertain how force from the uppercut to
the jaw is related to risk of MTBI or if the Hybrid III dummy,
in its current form, has sufficient similarity to the human
response to measure risks with this punch. Development of
human surrogate with an articulating jaw may improve the
response of the head in this region and may show different
biomechanical responses for the uppercut.
Before applying the results of this study to actual boxing
experience in the ring, one must be aware of other limitations.
The boxers that participated in this study were Olympic level
amateur boxers. Although these boxers are at the higher ech-
elon of amateur boxers, they most likely have not attained the
proficiency or power levels of professional boxers. It is prob-
able that more accomplished professional boxers can deliver
punches with significantly higher force than those that were
generated by these boxers.
It also must be pointed out that only four specific punches
were evaluated in this study, including a straight punch to the
jaw, uppercut to the jaw, hook to the temple and forehead
punch. Other punches and uppercuts, hooks and crosses to
other regions of the head may have different characteristics
than the punches studied here; and, therefore may result in
different translational and rotational accelerations in the op-
ponent’s brain than were seen in this study.
Furthermore, the data in this study was collected in a con-
trolled laboratory setting, not during an actual boxing match.
Factors such as fatigue, excitement and the effects of ?adren-
aline? on the boxers may significantly alter the forces of the
punches delivered. Also, in an actual boxing match, the move-
ments and defensive maneuvers of the opponent may affect
the forces of the punches delivered to the opponent’s head. In
the present study, the punches were delivered to a stationary
dummy head. The punch forces that were measured may be
different than those that are seen in an actual boxing match.
VIANO ET AL.
1166 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
APPENDIX: Measured and determined results from testing of Olympic boxersa
type HIC15SI acc. gm/s
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1167
aHIC15, head injury criterion for 15 ms duration; SI, severity index; g, gravity; Res acc, resultant acceleration; Res rot acc, resultant rotational acceleration; N,
newton; SD, standard deviation.
VIANO ET AL.
1168 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
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This testing was funded by United States Amateur Boxing Association and
Wayne State University. The analysis was funded by the National Football
League and NFL Charities, which is funded by NFL Player’s Association and
League. Their support and encouragement to conduct research on concussion is
greatly appreciated. The authors would like to acknowledge all the athletes who
took time from their busy training schedules to participate in our study. Thanks
are also extended to Ta-Ying Wang and Biren Patel for their technical assistance.
eration of the head is proportionately greater after boxing punches, whereas
translational acceleration tends to predominate in football impacts. As the
the higher incidence of both acute injuries, such as acute subdural hema-
toma, and chronic brain injury in boxing.
iano et al. continue their fascinating biomechanical studies of sports-
related traumatic brain injury by investigating boxing punches and
Alex B. Valadka
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1170 | VOLUME 57 | NUMBER 6 | DECEMBER 2005
acteristics of the impact to the head from an amateur boxer’s punch
with the physical characteristics of head injuries sustained in profes-
sional football. As they point out in the discussion section, the clinical
applicability of their results is limited. For example, the forces applied
to the head as measured in their laboratory would be expected to
cause a much higher incidence of concussion than is actually seen on
the playing field. It also is likely that professional boxers sustain
significantly greater translational and rotational displacement of the
head than do amateur boxers. Because of the more severe rotational
forces sustained by boxers compared with football players, and the
much higher incidence of lethal brain injuries in boxing, I completely
agree with the statement by Viano et al. that “boxers are susceptible to
a specific, unique pattern of chronic brain damage that has never been
seen in American football players.” Their study underscores the need
for studies that clearly define the histopathology of chronic traumatic
encephalopathy in professional football players, and cautions against
generalizing the autopsy findings in boxers to other sports.
iano et al. carefully studied the biomechanics of boxing injuries
using finite element modeling, and compared the physical char-
Donald W. Marion
game, athletes develop hitting strategies to gain an advantage. In
many cases, this strategy involves head impacts. This article provides
insight into what, until now, has largely been ignored. Depending on
the situation, athletes are able to use different strategies to create
concussions. Even though it is obvious that a number of factors
contribute to head injuries in sport, helmet designs have, for the most
part, focused on preventing subarachnoid bleeds. This has primarily
been accomplished by managing a 40 to 80 joule impact under 275 gs
of linear acceleration. Recently, cerebral concussion has become more
of a concern, whereas subarachnoid bleeds have become relatively
rare. Although the threshold for protecting the brain against concus-
sive injuries is not well established, it has been estimated at approx-
imately 4500 r/s2for angular acceleration and 75 to 80 gs of linear
acceleration. Football helmets are primarily designed to manage im-
pacts to prevent subarachnoid bleeds and although they do provide
some protection against concussion, they are not designed to do so.
The objective of these and many other sports is to manage physical
interactions in such a way as to enrich the competitive environment of the
activity without undue risk of injury to participants. This thin line is man-
risk of player injury. Coaches, players, and game officials all have incentives
to allow increased hitting. Examples of this are numerous and include
coaches having to gain an advantage over other teams, especially when the
team is under pressure to win, players fighting to win a spot on the team,
and league officials under pressure to increase fan attendance. Professional
is attractive to a broad audience.
This article demonstrates the need for research to better understand the
can use any number of strategies to take advantage of their opponents. Just
how athletes receive concussions in sport is still not well understood. The
recent National Football League study identified linear acceleration as the
very limited data set and should be interpreted accordingly. More extensive
research directed at understanding the mechanism of head injuries in indi-
n sports, such as American football, ice hockey, boxing, rugby,
lacrosse, and martial arts, in which contact is an integral part of the
vidual sports would be extremely valuable in managing head injuries in all
T. Blaine Hoshizaki
Ottawa, Ontario, Canada
potential relationships between the impact biomechanics of boxing and
football. To do so, 11 Olympic-level boxers (weight range 112–285 lbs)
delivered 78 blows (inclusive of four types including hooks, uppercuts, and
jabs) to the head of a Hybrid III Dummy. Recorded variables included
translational and rotational head acceleration and neck load. Punch force
was measured using a biaxial acceleraton model. The most significant
punch force (4405 ? 2318 N). The authors found that boxing punches have
proportionately more rotational than translational acceleration than what is
observed in football cuncussions.
This is useful information and indirectly addressed a number of
questions. It is interesting to note that the NFL Mild Traumatic Brain
Injury Committee has yet to identify an example of dementia pugilis-
tica (or variants thereof) in retired NFL players. Obviously, this is
quite the contrary in professional level boxing. Exposure obviously
differs significantly both with regard to the quantity of head impacts
and the likely associated force in the absence of headgear.
The importance of head-gear will need to be defined at the amateur
level before any consideration at the professional level. Even then, the
more spurious elements involved in the management and promotion
of the sport will likely be slow in adopting any suggested guidelines
regarding headgear use at the professional level. The perception is the
possible impact on the fan base and the associated income. Initial
work continues at the Olympic Training Facility in Colorado to eval-
uate responses in the presence and absence of headgear in boxing.
Evaluation of impact at varying distance will also be required.
The consideration of headgear is important at the professional level. A
related to central nervous system injury and short- or long-term disability
remain unknown. Conceptually, the understanding of the force associated
with “Heavy Hands,” or lack thereof, in athletes susceptible to concussion
(Glass Jaw) will also need to be determined. An important first step would
be to evaluate the potential myth of the big punch. Obviously, the only
chance an individual may have in a fight in which, based upon points, the
individual has no chance of winning the fight. The damage sustained by
individuals who are losing in these competitions tends to be consistent. We
would suspect that the suggestion of an early end to a 12-round champion-
ship fight given an inability to win based on the 10 point scale would be as
well received as the use of head gear. A final caveat. There are a number of
n a further contribution from the National Football League (NFL) Mild
Traumatic Brain Injury Committee, the authors sought to evaluate the
‘I am going to kill him good. I do not care about styles. Styles do not
mean anything. I have seen every style in the world. I have been in this
game for 18 years. I have been a world champ for 12. He cannot even
touch that. I am going to be the WBA heavyweight champ of the world.
I am ready to go no matter what. I do not care: you want to play rough,
I will play rough. Boy, you have no idea. I tell you, I will hurt you.’
Michale L. Levy
San Diego, California
CONCUSSION IN PROFESSIONAL FOOTBALL
VOLUME 57 | NUMBER 6 | DECEMBER 2005 | 1171
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III test dummy and accelerometers, 11 Olympic boxers were studied deliv-
test mannequin. Using finite element analysis, the kinetic energy and head
responses were compared with similarly determined impacts from video
documented and reconstructed concussions in NFL players. Any study that
analyzes the biomechanical forces imparted during contact sports is a wel-
come addition to the literature. As the authors note, closed head injury is an
occupational hazard of many sports, particularly in boxing and football, in
which neurocognitive effects to the brain can occur in the domains of
memory, cognitive, and functional injury. The ability to carefully visualize
and measure the various aspects of the contact athlete’s torso and head
response to high velocity impacts increases our understanding of the issues
This study also adds insight and helps clarify the fact that
translational and rotational accelerations are major components of
the human body’s response in contact sports. In my opinion, the
effective radius of the impact and the relative contribution of the
supporting musculature in the thorax, head and neck are most
his study by Viano et al. investigates the biomechanical forces involved
in boxing punches in comparison with football impacts. Using a Hybrid
Our computerized video analysis of various types of boxing matches
has led to the conclusion that there is little difference between the fights
which are considered “classic” versus those that result in a lethal out-
come. Unquestionably, the most significant contributing factor in lethal
boxing outcomes is the absorption of multiple blows to the cranium,
especially during long-duration fights and with a fighter who is progres-
sively impaired, resulting in relaxation of the supporting neck muscula-
ture and lowers the effective head mass against the punch.
Surprisingly, the dramatic single-punch knockout rarely results in a
lethal outcome or significant brain injury in a boxer. The chronic effect
seen in boxers is related to an accumulation of blows to the cranium,
accentuated with years in the sport and in heavier weight classifica-
tions. the authors note the limitations of their study, which was
performed in a controlled laboratory setting with Olympic-level am-
ateur boxers, looking at a limited number of punches, and those
delivered to a stationary test mannequin. This is an important study
with comparative data between two contact sports which are associ-
ated with potential for brain injury.
Julian E. Bailes
Morgantown, West Virginia
Hoard unearthed from a bog in Norway containing a gold trefoil brooch from France, a large golden neckring from Russia,
and coins from Arabia, Byzantium, and England. (Courtesy of Museum of Cultural Heritage, Oslo).
VIANO ET AL.