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. 2004 Apr-Jun;39(2):146–150.

Collegiate Football Players Display More Active Cervical Spine Mobility Than High School Football Players

John Nyland *,✉, Darren Johnson †
PMCID: PMC419508  PMID: 15173865

Abstract

Objectives:

To compare the active cervical spine range of motion and resting cervical spine alignment (sagittal plane) of collegiate and high school football players using the Cervical Range of Motion (CROM) Measurement System and to identify normative values for these populations.

Design and Setting:

A 2 × 7 factorial design for main effects was used to evaluate the influence of level of play (college, high school) on the cervical spine range of motion of football players. Data were collected during preparticipation physical examinations.

Subjects:

A convenience sample of 189 unimpaired collegiate (n = 70, age = 19.5 ± 1.5 years) and high school (n = 119, age = 15.7 ± 1.4 years) football players participated.

Measurements:

Subjects were measured for active cervical spine range of motion using the CROM system and the manufacturer's recommended measurement techniques.

Results:

Collegiate football players had increased active cervical spine range of motion for flexion, extension, left cervical rotation, and left lateral flexion (overall mean increase = 4.3 ± 2°) compared with high school players. Collegiate players also assumed a more flexed resting sagittal-plane cervical spine posture (P = .001).

Conclusions:

Collegiate players generally displayed greater active cervical spine range of motion than high school players. The increased resting sagittal-plane cervical spine flexion alignment we report among the collegiate players suggests a change in the natural cervical spine lordosis, possibly due to a neutral-zone shift associated with combined increases in lower cervical spine flexion and upper cervical spine extension as an adaptation to football training or playing. Further study using radiographic or magnetic resonance imaging techniques is warranted. The CROM system is a useful tool for identifying aggregate hypomobile or hypermobile active cervical spine mobility among football players that might otherwise remain unrecognized during standard preparticipation physical examinations. In combination with manual segmental assessments of passive accessory intervertebral movements, CROM enables early identification of players with impaired or excessive cervical spine mobility, thus facilitating proactive injury-prevention intervention.

Keywords: goniometry, neck injury prevention, preparticipation physical examination

Age has been shown to contribute to active joint-mobility reductions.1–3 In studying the relationship between age and sex on the range of motion of 17 joint actions at 8 joints, Bell and Hoshizaki1 reported a general decline in joint flexibility with age. The cervical spine also displays decreased active mobility with increasing age,2,3 with the most dramatic decreases occurring between 30 and 39 and 40 and 49 years of age.4 In a detailed cadaveric study of cervical spine structural changes across the life span, Hirsch et al5 reported progressive degenerative changes, including osteophyte formation beginning as early as adolescence and continuing throughout life. They attributed the early onset of cervical spine degeneration to the absence of a direct blood supply to disk tissues.5 Cervical spine degeneration has widely been reported with advancing age among asymptomatic subjects5–10; however, the progression is accelerated with a history of excessive or repetitious loading secondary to sports7–9 or occupation.10 Maintenance of pain-free, unimpaired active cervical spine mobility during the life span is essential to quality of life.2,5

Using 2-dimensional video analysis in studying 22 unimpaired subjects per age group (11 males, 11 females), Netzer and Payne2 reported reduced active cervical spine rotation and lateral flexion among older adults (60–80 years old) compared with children (6–8 years old), adolescents (12–15 years old), young adults (20–30 years old), and middle-aged adults (40– 50 years old). However, older adults displayed increased measurement variability, and middle-aged adults had superior cervical spine rotation to adolescent subjects. Netzer and Payne2 suggested that lifestyle might have contributed to their study results, but lifestyle and exercise or sports histories were not evaluated during their subject screening. Age-group comparisons of 337 unimpaired, nonathletic subjects (approximately 20 male and 20 female subjects per age group) by Youdas et al3 using the Cervical Range of Motion (CROM) Measurement System (Performance Attainment Associates, Roseville, MN) showed that with each 10 years of age, subjects could expect a 5° reduction in active cervical spine extension and a 3° reduction in flexion, right and left cervical spine rotation, and left lateral flexion. However, subjects were not screened for lifestyle or exercise or sports history (Table 1).

Table 1.

Maximal Active Cervical Spine Range of Motion (Degrees) Reported by Youdas et al3

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Although the CROM system has been used for evaluating the active cervical spine range of motion of unimpaired male and female populations of widely varying ages3,11–13 and patients with cervical spine impairments including sprain, strain, spondylosis, degenerative disk disease, and disk herniation,14,15 our literature review failed to identify the use of this device for screening an athletic population. Stiffness at the cervical spine with or without pain may be reason enough to remove an athlete from football participation.16 Decreased active cervical spine range of motion with or without severe pain could be the only sign of a cervical spine lesion.16,17 Decreased cervical spine range of motion compromises the ability to move out of the way of the path of the torso during impact loading, increasing the neck injury risk.17 Having adequate cervical spine mobility is paramount to decreasing neck injury risk during impact loads.16,17 Normal active cervical spine mobility is also foundational to neuromuscular readiness (strength and kinesthetic awareness).18,19 Although neck injuries are an unavoidable part of football, effective preparticipation cervical spine screening may help to detect players who are at risk for sustaining a neck injury.20–22 Our purpose was to compare the active cervical spine range of motion and resting cervical spine alignment (sagittal plane) of collegiate and high school football players using the CROM system and to identify normative values for these populations.

METHODS

Subjects

A convenience sample of 189 high school (n = 119, age = 15.7 ± 1.4 years) and collegiate (n = 70, age = 19.5 ± 1.5 years) football players participated in this study. All participants were nonimpaired at the time of study participation. Subjects or parents or guardians of minors provided written informed consent as required by the university institutional review board (which also approved the study) before study participation. The high school group consisted of participants from 12 regional high schools, and the collegiate group consisted of participants from 3 colleges. The primary positions played by the high school players were offensive lineman (18%) and running back (18%), whereas the primary positions played by the college players were offensive lineman (17%) and defensive lineman (17%). Complete primary player positions are listed in Table 2. Resting sagittal-plane cervical spine alignment and maximal active cervical spine range-of-motion measurements were taken during preparticipation physical examinations.

Table 2.

Primary Player Positions

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Cervical Spine Range-of-Motion Measurements

The CROM system measures the cervical spine range of motion for flexion, extension, lateral flexion, and rotation using separate orthogonal inclinometers. These inclinometers are attached to a frame similar to that for eyeglasses: one in the sagittal plane for flexion-extension, a second in the frontal plane for lateral flexion, and a third in the transverse plane for rotation. Two of these inclinometers have a gravity-dependent needle (sagittal and frontal planes), and the other has a magnetic needle (transverse plane). A magnetic neck collar is worn by the subject to standardize the magnetic needle's starting location. The 2 primary advantages of the CROM system are its ease of use and its affordability (approximately $500). Using radiographic techniques, Tousignant et al23 reported excellent criterion validity for CROM cervical spine flexion and extension measurements. Subjects were measured for active cervical spine range of motion and resting sagittal-plane cervical spine alignment using CROM and the manufacturer's recommended measurement techniques. During each measurement, subjects sat with an erect low back positioned against a chair back to standardized thoracic spine position, with the hips and knees flexed to approximately 90° and the feet positioned flat on the floor. While in this position, active cervical spine range-of-motion measurements were recorded in the following order: resting sagittal-plane cervical spine alignment, flexion, extension, right lateral flexion, left lateral flexion, right rotation, and left rotation.3,11,14,15,23 During testing, subjects were instructed to move the head and neck in the desired motion pattern as far as they could at a slow, comfortable velocity. The use of a volitionally comfortable test velocity negated the influence of potential order effects. A consistent test order enabled data to be collected in a time-efficient manner without our having to otherwise modify the preparticipation physical examination station schedules. When the subject reached terminal active range of motion, displacement magnitude was recorded. The primary investigator and 2 physical therapy students who had been instructed in proper device use performed all CROM measurements. Pilot interrater reliability testing using these 3 testers and 10 subjects revealed overall good active cervical spine measurement reliability for resting sagittal-plane cervical spine alignment with intraclass correlation coefficient (ICC) (3,3) = 0.90 to 0.92, SEM = 2.2 to 2.3°; flexion ICC (3,3) = 0.87 to 0.96, SEM = 2.4 to 2.5°; extension ICC (3,3) = 0.92 to 0.98, SEM = 2.3 to 2.4°; lateral flexion ICC (3,3) = 0.89 to 0.94, SEM = 1.6 to 1.8°; and rotation ICC (3,3) = 0.91 to 0.93, SEM = 1.9 to 2.1°. The CROM system has widely been reported to be a valid11,12,23 and reliable13–15 tool for measuring 3-dimensional, active cervical spine range of motion.

Statistical Methods

We used a 2 (high school versus collegiate) × 7 (cervical spine range-of-motion measurements) factorial analysis of variance (main effects) to assess group differences. Independent variables included resting sagittal-plane cervical spine alignment and the following 6 maximal active cervical spine range-of-motion measurements: flexion, extension, right lateral flexion, left lateral flexion, right rotation, and left rotation. An alpha level of P < .05 was chosen to indicate statistical significance. All statistical tests were performed using SPSS (version 11.0; SPSS Inc, Chicago, IL) software.

RESULTS

Although the mean age difference between our groups was only 3.8 years, collegiate football players had increased active cervical spine extension, flexion, left lateral flexion, and left cervical rotation compared with high school players, and collegiate players also displayed a mean 2.7° more flexed resting sagittal-plane cervical spine postural alignment (Table 3) (Figure). These findings contrasted with the trends of a steady decrease in active cervical spine mobility with each decade of life as reported by Youdas et al.3 Statistically significant differences were not observed between groups for right lateral flexion and right cervical spine rotation. Statistical power estimates were .87 or greater for all measurements except right lateral flexion and right cervical rotation; however, the combined eta-squared values indicated that only 35.3% of the total variance could be explained by the level of play.

Table 3.

Cervical Spine Range-of-Motion (Degrees) Comparison Between High School and Collegiate Football Players

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Active range-of-motion comparisons.

DISCUSSION

Our findings that collegiate football players had greater active cervical spine range of motion and a more flexed resting sagittal-plane cervical spine alignment than high school players supports the findings of Netzer and Payne,2 who reported increased active cervical spine rotation among young adults compared with adolescents and suggested that activity level contributed substantially to the active cervical spine range-of-motion variability observed with increasing age.

Similar to rugby, in football the cervical spine is repeatedly exposed to potentially injurious energy inputs. Most of these forces are effectively dissipated by the energy-absorbing capabilities of the cervical paravertebral muscles and the intervertebral disks through controlled intersegmental spinal motion. In contrast to rugby, the advent of improved head protection with the modern football helmet has led to periodic use of the top of the helmet as the initial point of player-to-player contact.20 In moving from the normal sagittal-plane cervical spine alignment of slight lordosis to a more flexed neck alignment, the cervical spine assumes the physical characteristics of a segmented column, reducing its normal energy dissipation function.20 In this scenario, impact energy is dissipated almost entirely through the aligned vertebrae rather than through neuromuscular mechanisms. The increased resting sagittal-plane cervical spine flexion alignment we report among the collegiate football players suggests a change in the natural cervical spine lordosis. Panjabi et al24 reported that sagittal-plane head and neck alignment affected 3-dimensional upper cervical spine motions, with the motion at one level sometimes occurring in a direction opposite to that at the adjacent level. Penning25 noted that during anterior translation of the skull (with the chin out), the upper cervical spine is maximally extended and the lower cervical spine is moderately flexed, whereas during posterior translation (chin in), the upper cervical spine is maximally flexed and the lower cervical spine is moderately extended. Panjabi et al26 also identified the 3-dimensional cervical spine neutral zone locations where regions of low osteoligamentous stiffness necessitate optimal neuromuscular stabilizer function. Although axial rotation at the articulation between the first and second cervical vertebrae displayed the neutral zone with the largest range of motion (39.6 ± 7.5°), extension between the occiput and the first cervical vertebra provided the second largest range of motion (13.9 ± 4.1°).

Conceivably, the increased resting cervical spine flexion angle we report among the collegiate players may represent combined increases in lower cervical spine flexion and upper cervical spine extension as an adaptation to football training or playing. This may effectively shift the neutral zone location; however, we cannot confirm this with the methods employed in our study. Because CROM provides only an aggregate measurement of active cervical spine range of motion, the increased resting sagittal-plane cervical spine flexion we observed may actually represent combined increases in lower cervical spine flexion and upper cervical spine extension. Further study using radiographic or magnetic resonance imaging techniques in combination with CROM would be useful to validate this possibility. Wojtys et al27 evaluated the relationship between thoracic and lumbar spine alignment and the sports training histories of 2270 children between 8 and 18 years of age using radiographic and photographic stereography. They reported increased thoracic kyphosis and lumbar lordosis angles with increased training history, whereas the smallest curves were associated with a lack of sports participation. Although Wojtys et al27 did not evaluate cervical spine alignment, increased thoracic kyphosis and lumbar lordosis are known to be associated with compensatory changes in cervical spine lordosis.28 The findings reported by Wojtys et al27 may partially explain the increased resting cervical spine flexion angle we report among the collegiate players.

In focusing on isolated uniplanar sagittal-, frontal-, or transverse-plane cervical spine measurements in each of the 3 cardinal motion planes, the CROM system does not fully evaluate the coupled motions associated with functionally relevant, multiplanar movement patterns as described by Panjabi et al24,26 and Penning.25 Additionally, although CROM provides a reliable measurement of aggregate 3-dimensional cervical spine mobility, it does not measure the contributions of individual cervical spine segments to this overall value. Within this scenario, cervical spine components that lie adjacent to a hypomobile segment may become hypermobile, thereby enabling seemingly unimpaired active cervical spine range of motion but creating the potential for cervical spine injury at both the hypomobile and hypermobile segments. Recent studies have combined CROM use for active mobility assessments with more qualitative manual segmental assessments of passive accessory intervertebral movements using a 3-point scale (normal, slight hypomobility, severe hypomobility) to provide a comprehensive assessment of both aggregate and component segmental cervical spine mobility.29,30 After neck injury, primary cervical spine motions and associated coupled motions also may be affected, with the coupled motions potentially being more sensitive indicators of impaired cervical spine kinematics.24

In studying the influence of different cervical spine postures on the isometric neck-extensor moment and electromyographic activation amplitude ratios of unimpaired subjects, Mayoux-Benhamou and Revel31 substantiated the influence of cervical spine alignment on neck-extensor muscle function. They reported increased neck-extensor muscle efficiency when subjects assumed a neutral cervical spine alignment compared with flexed or extended postures. By compromising sarcomere function, either muscular lengthening from excessive cervical spine flexion or shortening from excessive cervical spine extension decreases the mechanical properties needed for optimal function.31 Conceivably, the neutral zone shift in resting sagittal-plane cervical spine alignment toward greater flexion with football participation and training as players transition from high school to college play may influence neuromuscular function around the cervical spine. However, further study is warranted.

Players with insufficient active cervical spine range of motion may benefit from segment-specific joint-mobilization interventions and generalized stretching activities to improve arthrokinematic (component) and osteokinematic (aggregate) function, respectively.18,19 Players with excessive aggregate or component active cervical spine range of motion may particularly benefit from dynamic joint stabilization and kinesthetic awareness training within functionally safe ranges of motion. Progressive neck-muscle strengthening programs should be designed upon the foundation of normal, active cervical spine range of motion.16 Highland et al32 reported significant active range-of-motion and strength improvements when 90 subjects with cervical spine impairments, including degenerative disk disease, disk herniation, and cervical muscle strain, participated in an 8-week multiple-angle isometric exercise program. Watkins16 emphasized the importance of training appropriate dynamic cervical spine postures in relationship to trunk posture and core muscle strength for safe football participation. Winkelstein and Myers17 reported that behavioral changes such as using a “heads-up” football hitting style have helped to decrease neck injury incidence by enabling the head and cervical spine to move into extension.

Because the dorsal neck muscles and cervical facet joints have high densities of muscle spindle proprioceptors33 and mechanoreceptive nerve endings,34 respectively, football players may benefit from active cervical spine range-of-motion and strength-training interventions that include kinesthetic awareness challenges, particularly after neck injury. Using the CROM system, Loudon et al35 identified deficits in target position replication among 11 subjects with a history of whiplash injury compared with 11 age-matched, asymptomatic subjects. Similar methods of evaluation and intervention may be of use in football athletes as they rehabilitate after cervical spine injury.

Our finding of generally increased active cervical spine range of motion and increased resting sagittal-plane cervical spine flexion alignment among collegiate football players compared with high school players supports the influence of activity level and sport requirement on active cervical spine range of motion. The CROM is a useful tool in helping to identify football players with aggregate cervical spine range-of-motion hypomobility or hypermobility that might remain unrecognized during standard preparticipation physical examinations. Early identification of players with impaired or excessive active cervical spine range of motion facilitates proactive injury-prevention intervention. Collegiate football players approximately 4 years older displayed increased active cervical spine range of motion (mean increase = 4.3 ± 2°) and a more flexed resting sagittal-plane cervical spine postural alignment than high school players. Thus, factors other than age, such as lifestyle, sports participation, and training, may influence active cervical spine mobility and postural alignment.

CONCLUSIONS

Unimpaired collegiate football players displayed greater active cervical spine range of motion and an increased resting sagittal-plane cervical spine flexion alignment than high school players, supporting the influence of activity level and sport requirement. The CROM system provides the athletic trainer with a portable, valid, and reliable method of measuring aggregate active cervical spine range of motion. In combination with manual segmental assessments of passive accessory intervertebral movements, CROM provides a detailed evaluation of cervical spine mobility.

ACKNOWLEDGMENTS

We thank Timothy Brindle, PhD, PT, ATC; Gina Motley, MS, PT, ATC; and Jason Myers, MS, PT, for their assistance with data collection.

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