Greene DL, Hamson KR, Bay RC, Bryce CD. Effects of protective knee bracing on speed and agility. Am J Sports Med 2000;28:453–459.
ObjectiveEffects of Knee Braces on Speed and Agility of Football Players
To assess the effects of 6 different types of prophylactic knee brace on speed and agility in young football players.
DesignEffects of Knee Braces on Speed and Agility of Football Players
Randomized controlled crossover trial.
SettingEffects of Knee Braces on Speed and Agility of Football Players
Phoenix Junior College outdoor football practice facility.
ParticipantsEffects of Knee Braces on Speed and Agility of Football Players
30 junior college football players (age range, 18 to 22 years; 6 linemen, 5 linebackers/tight ends, and 19 skill players) were volunteers from the active roster of the 86-member team. No player had a current knee injury or evidence of any knee instability.
InterventionEffects of Knee Braces on Speed and Agility of Football Players
Participants were assigned to 6 off-the-shelf brands of knee brace and a control (no braces) condition. The braces were models 1 and 2 of the Air Armor Knee and Thigh Protection System (Air Armor, Inc.), Breg Tradition (Breg, Inc.), DonJoy Legend (DonJoy), McDavid Knee Guard (McDavid), and OMNI-AKS 101W (OMNI Life Science). Participants wore full football gear, and the braces were fitted and applied to both legs according to the manufacturer's instructions. Participants were asked to complete 2 drills, a 40-yard dash and a 4-cone agility drill, wearing the 6 braces and no braces in random order. Each drill was run before the afternoon practice on separate occasions ≥1 week apart. The 7 runs of the drill were separated by ≥10-minute rest periods.
Main outcome measuresEffects of Knee Braces on Speed and Agility of Football Players
Time taken to complete each run of the dash and the cone drill was recorded. Brace migration was measured by marking the skin before the run. Players were asked for their preferences among the braces. 25 players (83%) completed ≥1 drill. 7 players were injured during the period of study, and 6 players did not attend a second drill session.
Main resultsEffects of Knee Braces on Speed and Agility of Football Players
Compared with control, the Air Armor 1 and the OMNI did not affect mean time for the 40-yard dash, whereas all other braces increased time for the dash (p < 0.008). In the cone drill, none of the braces except the Breg significantly slowed the players (p = 0.001). The Air Armor 2 and the OMNI cone-drill times were faster than those for other braces (p < 0.001). The DonJoy and Air Armor 2 rotated on the leg less than other braces and the OMNI rotated more. The Air Armor 1 and 2 and the McDavid braces migrated up or down less than other braces and the OMNI migrated more. There was no consensus among the athletes on brace preference: 32% favored Air Armor 1; 32%, McDavid; 20%, Air Armor 2; and 16%, OMNI.
ConclusionsEffects of Knee Braces on Speed and Agility of Football Players
The knee braces varied in their effect on the speed and agility of football players. Some braces migrated more than others. Players' preferences were not clearly related to the effects on performance of the braces.
Source of funding: (in part) Air Armor, Inc., and (brace supply) Hanger Prosthetics and Orthotics, Inc.
For article reprint: D. L. Greene, MD, Brown University, Department of Orthopaedics, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, U.S.A.
CommentaryEffects of Knee Braces on Speed and Agility of Football Players
The study by Greene et al. is a randomized, controlled, crossover trial designed to assess the effect of prophylactic knee braces on function (specifically speed and agility tests in college football players). The study has an appropriate design and has taken care to minimize most potential sources of bias. However, we do not know about the participants' previous brace use, which could affect their performance and brace preferences. The tests were relevant to football and realistic (performed in full equipment).
There was no clear consensus as to which brace was preferred by the players, but on reviewing the data, it seems that the braces that migrated the least on the knee were the most favored. Interestingly there was an inverse relationship between players' brace preference and their perception of the protective value of the brace.
It is important to recognize that the investigators only addressed one aspect of the “Prophylactic Knee Brace Performance Triad,” the on-field performance aspect, but not the questions of injury reduction or biomechanical protection. The best-designed study on clinical outcomes (effectiveness in preventing injury) was the study by Sitler et al. 1 They showed a statistically significant, position dependant, reduction in knee injuries in the braced group. Unfortunately the brace they used, the DonJoy Protective Knee Guard, was not evaluated in the study by Greene et al.
Many football athletes use prophylactic braces, and in the absence of clear information on the relative protective value of the braces on the market, often the choice is based on the perceived effect on performance. This study provides information that is of value to physicians and trainers who are asked for recommendations.