Results and Discussion
A total of 210 injuries were reported by the 10 participating schools. Of these injuries, 96 occured in varsity or junior varsity (JV) games, 4 in practice games, and 110 during scheduled practices. Of these injuries, 152 were classified as monor, 58 were significant. Of the significant injuries reported, 23 were major. No severe injries were reported. The 10 schools had a total of 35, 5155 exposures during the football season (31,816 and 3, 339 in practices and games, respectively). Rates of injuries per 1000 exposures were 4.21 for minor injuries, 1.59 for significant injuries, and 0.65 for major injuries. A breakdown of these injuries, as reported by school, is presented in Table 1.4
Numbers and percentages of reported injuries, by type field, are presented in Table 2. Although the number of injuries sustained in practices was about the same as that in games, the number of exposures during practices, based on the average size of squads (practice or game) and the number of sessions (practice of games), was nearly 10 times as great as the number of game exposures. However, the severity of contact and the intensity of play during the game probably were considerably greater than for the practice sessions.
Of the 210 injuries reported, 12 (5.7 percent) were definitely field-related, 15.2 percent were considered possibly field-related, and 76.7 percent were definitely not field-related (Table 3.) In the judgement of the trainers responsible for recording the data on location at the time of injury, a total of 44 injuries (20.9 percent) may have been caused by poor field conditions. On the basis of these data, it can be estimated that as many as 20 percent of the reported injuries could have been prevented or perhaps rendered less severe by more favorable field conditions. Safety considerations should thus be an incentive for the construction and maintenance of high-quality playing surfaces, for practice as well as for games.
Injuries are listed, according to the body-parts involved, in Table 4. Within each body-part category, injuries are further classified according to their relation to field conditions. As would be expected, most of the injuries judged to be related to field conditions involved the lower extremities (i.e. hip/leg, knee, and ankle/foot). Also, it should be noted that the majority of injuries to lower extremities were classified as definitely not field-related or, in other words, they were considered by the athletic trainers in attendance at the time of occurence to be injuries likely to have been sustained regardless of field conditions.
Field Maintenance. Data collected on maintenance of game and practice fields indicated considerable variation between fields at a particular school as well as among fields at different schools. Although practice fields were much more intensively used than were the game fields, they received less care.
Mowing heights wer similar on game and practice fields, but game fields received more nitrogen fertilization and more aeration than practice fields (Table 5). Game fields averaged 2.0 lb N/1000 ft² compared to 0.2 lb N/1000 ft² for practice areas.
Herbicides were used for weed control on 25 percent of the game fields; not one school reported use of weed killers on practice fields. All fields receiving weed-control chemicals were treated with a pre-emergence crabgrass herbicide and a combination herbicide for broadleaf weed control.
Eighty-three percent of the 24 fields involved in this study were overseeded in the spring. Only 75 percent of the 12 playing fields and 25 percent of the 12 practice fields were aerated. Not one of the schools had access to a disk seeder, and only a few of the schools had access to aerators. Some of the fields were thus overseeded without adequate seedbed preparation. Without the seed-to-soil contact provided by proper preparation of the seedbed, success of the seeding is highly unlikely.
Field Conditions. Game fields were in better condition than practice fields. In general, game fields had smoother surfaces, lower bulk densities (less compact soil), fewer weeds, more vegetative cover, and more dense turf (Table 5). The better conditions on the game fields are no doubt a reflection of better construction and maintenance practices. Soils on all fields were medium or fine textured and were distributed among the following textural classes: loam, silt loam, clay loam, silty clay loam, silty clay (Fig. 1). Kentucky bluegrass was the predominant turfgrass species on most fields. Perennial ryegrass had been used to overseed fields; in some instances, the ryegrass population approached or exceeded that of Kentucky bluegrass.
Weed cover decreased during the season primarily because of the poor wearing qualities of species such as clover and knotweed, and loss of summer annuals such as crabgrass, goosegrass, and knotweed. Lower ratings for vegetative cover during the second of two evaluations were associated with reductions in weed populations. Turf density likewise decreased during the season; most practice and some game fields were nearly or entirely without vegetative cover between the inbound hash marks at the second of two field evaluations.
Additional or more effective maintenance practices (i.e., aeration, fertilization, overseeding, and weed control) were needed on most of the game fields and on all practice fields surveyed in this study. Practice fields were used more than game fields, but received lower levels of maintenance. All practice fields in this study were considered to be in poor condition, thus presenting surfaces potentially more conducive to player injury.
Relationships between Various Field Variables
Correlations wer used to indicate a relationship between two variables. Two variables may be correlated because on directly affects the other, or because both are influenced by an external factor. A negative correlation coefficient indicates that one variable decreased as the other increased.
Statistically significant correlations based on data from all fields are listed in Table 6. In general, correlations indicated that the fields with better maintenance practices also had better field conditions. Good maintenance practices seemed to be a carryover of good construction methods. For instance, factors associated with higher rates of nitrogen (N) fertilization were fewer undulations and depressions, more aeration, lower bulk density, fewer weeds, and greater cover early in the season. Fields with the most depressions also had more undulations, a rougher surface, more stones, less dense turf, less cover, less N fertilization, and severer use.
Good cover prior to the season was associated with higher N fertilization, more aeration, greater density, less roughness, fewer depressions and stones, and less use. At the conclusion of the season, better cover was associated with good cover in August and November, smoothness, fewer depressions and undulations, lack of stones, less use, and fewer weeds in August.
The highest correlations with use ratings were the negative correlations with density in August and with cover in August and November. Cover in November gave the best correlation with the overalll field rating.
Correlations were also determined for game fields only (Table 7) and practice fields only (Table 8). Fewer significant correlations occured when the sample was limited to either game of practice fields; however, the results tended to support the relationships found when all fields were considered. The complexity of interpreting correlations can be illustrated by the negative correlation between aeration and November density for game fields. One might question the result because it seems that a better-aerated field should better support a turfgrass stand. On the other hand, fields that have a less-dense cover are in greater need of aeration, and the data suggest that they are getting more.
Recommendations for Field Improvement
Good field conditions were associated with good management programs. Some fields, however, were poor because of construction methods and needed renovation beyond that provided by normal maintenance practices. Suggestions for maintenance and renovation programs were sent to each school following the second field evaluation. Subsequent visits have indicated that those schools that followed these suggestions have substantially improved their fields.
Methods of getting information about construction, maintenance, and renovation of fields to those in charge of field management must be implemented or improved. Valuable information is published in various forms (Beard, 1984; Daniel, 1982; Harper, 1983; Schmidt, 1984; Shearman, 1982), but it may not be reaching those having the greatest need. Chalmers (1982) reported that a survey of football field managers in Virginia indicated that 78 percent were not happy with the turf quality on their fields and 94 percent wanted to improve the quality of the fields. County extension personnel, Extension specialists, turf consultants, representatives of turf equipment and supply companies, and others involved in turfgrass management can and usually are quite pleased to provide guidance and information about athletci field maintenance problems.
The quality of construction and maintenance used for school fields may be related to socioeconomic factors within the community. Our results indicated a trend for better maintenance practices on the better constructed fields. Such a trend may have been coincidental, but it also could have been related to income or administrative knowledge and interest within a school district. The subject would be a worthwhile inclusion in future studies of high school athletic fields.