cant differences (p < 0.05) between subgroups

Size: px

Start display at page:

Download "cant differences (p < 0.05) between subgroups"

Stewart Weaver
6 years ago
Views:

1 /88/09ll-0365$02.00/0 THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright Q 1988 by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association lsokinetic Leg Flexion and Extension Strength of University Football Players TERRY J. HOUSH, PhD,* GLEN 0. JOHNSON, PhD," LEO MARTY, PT,t GEORGE EISCHEN, PT,* CLEM EISCHEN, PT,# DONA J. HOUSH, MPE* The purpose of this study was to evaluate the difference between positions for absolute and relative isokinetic leg flexion and extension strength as well as ipsilateral and bilateral ratios of NCAA Division I1 university football players. Fifty-five players (19.8 & 1.4 years) volunteered to be measured using a Cybex IP dynamometer at 180 and 300 /sec. The players were grouped into four positions: offensive backs and receivers (OB), offensive linemen (OL), defensive linemen (DL), and defensive backs (DB). One-way ANOVA with Scheffe post hoc comparisons indicated that for absolute flexion and extension strength the linemen (OL and DL) tended to be stronger than the backs (06 and DB); however, these relationships were reversed (backs were stronger than linemen) when differences in body weight were considered (peak torque/body weight). There were no significant (p c 0.05) differences between positions for ipsilateral comparisons at 180 or 300 O Isec. However, the magnitude of the ratio was specific to the speed of contraction. Significant differences between positions were found for bilateral strength ratios measured at 180 O/sec; however, all values were within 7% of equity and therefore were of little physiological consequence. The clinical uses of muscular strength profiles of this study was to evaluate the differences have been described by a number of investiga- between positions for absolute and relative isokitors.1-4.7,8~10 Imbalances in ipsilateral or bilateral netic leg flexion and extension strength as well as strength ratios have been associated with an in- ipsilateral and bilateral ratios of NCAA Division II creased risk of musculoskeletal inj~ries.'.~.~~~.'~ university football players. Health care professionals use muscular strength profiles to identify athletes with an increased po- MATERIALS AND IMETHODS tential for injury and to provide guidelines during ~ifty-fi~~ NCAA ~ i university ~ football i ~ ~ rehabilitation following injury.4310 In addition to the players (age: x SD = volunclinical applications, it is widely accepted that an teered as subjects for this study. All of the suboptimal level of muscular strength will contribute jects indicated that they had been involved in an to successful participation in most physical activ- off-season weight training program; however, ities. Previous investigators have concluded that there was no standardized protocol which was the demands of a particular Or the require- followed by the team as a whole. Furthermore, an merits a program may be respon- unknown percentage of the athletes had previsible for the dissimilarities in muscular strength ously suffered lower extremity injuries; however, characteristics between athletes who compete in all of the subjects were fully rehabilitated at the different sports and at different positions within a s ~ o ~. ~ ' ~ ' ~ ' ~ ' ~ ~ time of the strength testing. The subjects were differences suggest a need grouped into four positions based on nonsignififor comparative data which are specific to the cant differences (p < 0.05) between subgroups under the purpose within a position for the measured variables. There were no significant differences in age, height, weight, or peak torque values between offensive g'center for Youth Fitness and Sports Research, University of Nebraska-~incoln, Lincoln, NE backs [quarterbacks and running backs (N = 5)] t School of Health and Physical Education, Portland State University, and offensive receivers [split ends and flankers (" Portland. OR $ ~loyd Center sports Medicine Clinic, Portland. OR. = 9)]; therefore, the players were grouped to 365

2 366 HOUSH ET AL JOSPT Vol. 9, No. 11 gether as offensive backs and receivers (OB: N = 14). The offensive linemen (OL: N = 13) included centers, guards, tackles, and tight-ends, while the defensive linemen (DL: N = 14) included nose guards, tackles, ends, and linebackers. The defensive backs (DB: N = 14) included cornerbacks and safeties. Right and left leg peak torque for flexion and extension movements at the knee joint were measured during spring football practice (March) with a Cybex IIm isokinetic dynamometer (Cybex, Division of Lumex, Ronkokoma, NY). The subjects were seated on an adjustable chair with the thigh stabilized by a velcro strap. The axis of rotation of the Cybex II dynamometer was aligned with the anatomical axis of rotation of the knee joint and the lever arm apparatus was attached just proximal to the malleoli in accordance with the Cybex II instruction manual. Leg flexion and extension movements were performed at 180 and 300 /sec through a 90 range of motion. Following a 3-4 trial submaximal warm-up, three consecutive maximal efforts were performed by each subject with the highest peak torque for each movement being taken as the representative score. Test-retest reliability for isokinetic measurements using the Cybex II have been reported at r = 0.97 and greater; therefore, duplicate measures were not taken.2 The dampening on the Cybex II was set at 2. One-way ANOVA with Scheffe post hoc comparisons were used to determine the location of significant (p < 0.05) differences between positions for age, height, body weight, absolute peak torque, relative peak torque, and ipsilateral and bilateral ratios. Related t-tests were used to evaluate differences in absolute peak torque values for the right versus the left side of the body. RESULTS The descriptive characteristics of the subjects are presented in Table 1. There were significant (p < 0.05) differences between positions for height and body weight but not for age. The linemen (OL and DL) tended to be taller and heavier than the backs (OB and DB). There were significant differences in peak torque between positions for absolute flexion and extension at 180 and 300 /sec for the left leg only (Tables 2 and 3). There were no differences by position in absolute peak torque values of the right leg. The extension strength of the left leg of the DL was significantly greater than the DB when measured at both 180 and 300 /sec. The flexion strength of the left leg measured at 1 80 /sec was significantly greater for the OL than the DB, while at 300 /sec the OL were stronger than both the OB and DB. When peak torque values were divided by body weight (Tables 2 and 3) there were significant differences between positions for right and left leg flexion and extension at 180 and 300 / sec. In general, the backs (OB and DB) were stronger than the linemen (particularly the OL) per kilogram of body weight. The range of correlations between body weight and peak torque measured at 180 and 300 /sec were r = and r = , respectively. Table 4 describes the ipsilateral strength ratios (flexion/extension) for the right and left legs measured at 180 and 300 /sec. There were no significant differences between positions for any of the ipsilateral comparisons (Table 4). The range of ipsilateral ratios measured at 180 and 300 /sec were and , respectively. Table 5 presents the bilateral (leftlright) ratios for flexion and extension at 180 and 300 /sec. Significant differences were found between positions for bilateral ratios measured at 180 /sec only. The bilateral ratio for flexion was significantly greater for OL than DB while the ratio for extension was greater for DL than DB. However, all bilateral ratios were within 7% of equity. The correlations between peak torque values comparing the right versus the left side of the body for flexion and extension at 180 and 300 /sec were r = 0.85,0.68,0.80, and 0.67, respectively. There were no significant (p < 0.05) differences between the right and left side of the body for flexion or extension peak torque values at 180 or 300 /sec. DISCUSSION The ratio of muscular strength for leg extension measured at 180 /sec to body weight for the university football players (n = 55) in the present study (2.13 nm/kg) was greater than samples of sedentary subjects (1.9), orienteers (1.7), and race walkers (2.0) but less than downhill skiers (2.3), alpine skiers (2.2), and sprinter/jumpers (2.7).5*11 Furthermore, the flexion and extension strength values (absolute and relative to body weight) of the university athletes in the present study were substantially greater than those of high school football players reported by Gilliam et al3 [absolute right leg flexion at 1 80 /sec = versus nm, extension = versus 132.7, and relative (nm/kg) for flexion = 1.66 versus 1.42,

3 JOSPT May 1988 MUSCULAR STRENGTH OF FOOTBALL PLAYERS TABLE 1 Physical characteristics of the subjects (x f SEM) Offensive Backs Offensive Defensive Defensive and Receivers Linemen Linemen Backs IN = 141 fn = 13) 1N = 14) fn = 14) Total (N = 55) Age (years) 20.0 k k Height (cm)' 72.4 k k k r 0.3 Body Weight (kg)? k k O 94.1 f 1.9 ' One-way ANOVA significant between positions: F(3.3, = 2.79, p < Scheffe post hoc comparisons indicated a significant tp < 0.05, Scheffe = OL and DL versus OB and DB. TABLE 2 Absolute (nm) and relative (nmlkg) leg flexion and extension strength by position at 180 /sec (x f SEM) R~ght leg Left leg Position Flexion/ Extension/ Flexion Flexion/ Extension/ body weight body weight 8o01sec* F$gG body weight bcdy weight 800/sec 800/sec 1 800/sec* 1 800lsec /secji 1 80 /sec7 Offensivebacks k k k k k k k k0.06 and receivers Offensivelinemen 163.3e k k k f k k0.06 Defensive linemen k k k k k k 0.04 Defensivebacks 148.9k k k k k f k Total k k k k k k k k 0.03 'One-way ANOVA significant between positions: F(3.51) = 2.79, p < Scheffe post hoc comparisons indicated a significant t p < 0.05, Scheffe = OL and DL versus OB and DB. * p < 0.05, Scheffe = OL versus DB. p < 0.05, Scheffe = DL versus DB. 11 p < 0.05, Scheffe = OL versus OB. I p < 0.05, Scheffe = OL versus OB, DL and DB. Position TABLE 3 Absolute (nm) and relative (nmlkg) leg flexion and extension strength by position at 300 /sec (x k SEM) Flexion 3o00/sm ~~~~ Right Leg Left Leg Flexion/ Extension/ Flexion Extension Flexion/ Extension/ body weight W weight 3oo.lsec. 3000~sec+ body weight MY weight 30O01sec' 300 1sec' 300 1sec* 300 1sec' Offensive backs k k k k k k k k 0.05 and receivers Offensivelinemen 135.5f f k k r f0.04 Defensivelinemen 130.3k k k k k k k0.04 Defensive backs k k Total k f k k f f f 0.03 One-way ANOVA significant between positions: F(3.51) = 2.79, p < Scheffe post hoc comparisons indicated a significant tp < 0.05, Scheffe = DL versus DB. extension = 2.13 versus 1.801; however, both studies indicated that in terms of absolute peak torque, the linemen (OL and DL) tended to be stronger than the backs (OB and DB). This was particularly true in the university players for flexion and extension strength of the left leg at 180 and 300 /sec. There were no differences, however, between OL versus DL or OB versus DB. It is interesting to note that while there were no significant differences and only moderate correla- tions for peak torque comparing the right versus left sides of the body, differences between positions were found for comparisons involving flexion and extension strength of the left leg only. Previous investigators have reported small (2-3%) differences between the peak torque values for the right versus left legs.3 Therefore, in some cases data have been reported for only one side of the body (i.e., right side, dominant sides, etc). While this procedure is appropriate for correla-

4 HOUSH ET AL TABLE 4 lpsilateral ratios (flexion/extension) by position Right Leg Left Leg JOSPT Vol. 9, No. 11 Position Flexion/extension Flexion/extension Flexion/extension Flexion/extension Offensive backs and re ceivers Offensive linemen 0.80 Defensive linemen 0.80 Defensive backs /sec 30O0/sec 1 80 /sec 300 /sec Total Position TABLE 5 Bilateral ratios (leftlright) by position Flexion Extension 1 80 /sec' 300 /sec sect 3OO01sec Offensive backs and receivers OO OO Offensive linemen Defensive linemen Defensive backs OO Total OO 1.03 One-way ANOVA significant between positions: F,,,,, = 2.79, p < 0.05, Scheffe post hoc comparisons indicated a significant difference for OL versus DB. tp < 0.05, Scheffe = DL versus DB. tional or related measures designs, it would have led to erroneous findings in the present study. Therefore, additional research is necessary to further evaluate differences between independent samples for peak torque measured on the right and left sides of the body. The moderate correlations between peak torque and body weight (r = ) in the present study as well as the significant relationships reported by previous investigators suggest that muscular strength is, in part, a function of body eight.^.^ The influence of body weight is significant for isokinetic strength measurements at slow, moderate, and fast speeds of contracti~n.~,~.~ Furthermore, the measurement of absolute peak torque may not accurately describe the functional abilities of athletes involved in dynamic sports which require the movement of body weight. Comparisons between positions for absolute peak torque revealed that the linemen tended to be stronger than the backs. However, per kilogram of body weight, the backs tended to be stronger than the linemen. Therefore, to fully evaluate differences between athletic samples, it is useful to express muscular strength values relative to body weight as well as in absolute terms. The ipsilateral strength ratios of the university football players in the present study (180 /sec = 0.77, 300 /sec = 0.89) were similar to those reported for collegiate distance runners (180 /sec = 0.76, 300 /sec = 0.87) and high school football players (180 /sec = 0.77), but greater than male ballet dancers (180 /sec = 0.64).3-8s9 These findings support the conclusions of Morris et a1.' that hamstringlquadricep ratios reflect the demands of the sport and are specific to the speed of contraction. However, the competitive demands of a football lineman are quite different from a backfield player, yet no significant differences were found between positions for ipsilateral comparisons. Therefore, further investigations are necessary to determine the relative contribution of factors such as the testing and training protocols as well as the competitive demands of specific sports to ipsilateral strength ratios. Statistical analysis of the bilateral strength ratios (leftlright) in the present study revealed significant differences between positions at 180 / sec. However, the ratios for all positions were within 7% of equity and the mean ratios (N = 55) for flexion and extension at 180 and 300 /sec were within 3% of equity. These values are consistent with acceptable ranges proposed by previous investigator^.^ Therefore, although statistical significance was found, the differences be tween positions for bilateral strength ratios are of little physiological consequence.

5 JOSPT May 1988 SUMMARY MUSCULAR STRENGTH OF FOOTBALL PLAYERS REFERENCES The results of this investigation provide descriptive and comparative information which can be valuable to therapists, trainers, coaches, and athletes. These data can be useful to therapists and athletic trainers as guidelines for determining appropriate ipsilateral and bilateral muscular strength ratios. Systematic evaluations of athletes and comparisons to reported values can help identify those athletes at an above normal risk of musculoskeletal injury. Coaches, athletes, therapists, and trainers can use this information for defining the goals of a conditioning program to meet the demands of a particular sport and level of competition. While it should be recognized that many factors contribute to successful participation, high school players could use this information to aid in the selection of an appropriate level of intercollegiate competition and the prediction of the likelihood for future success. However, a degree of variability exists between competitors within a sport. Therefore, it should not be assumed that modest differences in muscular strength characteristics will necessarily preclude successful participation. 1. Burkett LN: Causative factors in hamstring strains. Med Sci Sports 2:39-42, Clarkson PM, Johnson J, Dextradeur D, Leszczynski W, Wai J. Melchiondia A: The relationships among isokinetic endurance, initial strength level, and fiber type. Res Q Exerc Sport 53:15-19, Gilliam TB, Sady SP. Freedson PS. Villanacci J: lsokinetic torque levels for high school football players. J Sports Med 60:llO-114, Gleim GW. Nicholas JA, Webb JN: lsokinetic evaluation following leg injuries. Phys Sports Med 6:74-82, Haymes EM, Dickinson AL: Characteristics of elite male and female skiracers. Med Sci Sports 12: , Housh TJ, Thorland WG, Tharp GD, Johnson GO. Cisar CJ: lsokinetic leg flexion and extension strength of elite adolescent female track and field athletes. Res Q Exerc Sports 55: , Mwre M: Scouting the elite, unbreakable football player. Phys Sports Med 9: , Morris A, Lussier L, Bell G, Dwley J: Hamstring/quadriceps strength ratios in collegiate middle-distance and distance runners. Phys Sports Med 11 :71-77, Mostardi RA, Porterfield JA, Greenberg 8, Goldberg D, Lea M: Musculoskeletal and cardiopulmonary characteristics of the professional ballet dancer. Phys Sports Med 11:53-61, Sapega AA, Nicholas JA: The clinical use of musculoskeletal profiling in orthopedic sports medicine. Phys Sports Med , Thorstensson A, Larsson L. Tesch P, Karlsson J: Muscle strength and fiber composition in athletes and sedentary men. Med Sci Sports 9:26-30,1977

Effect of cold treatment on the concentric and eccentric torque-velocity relationship of the quadriceps femoris

Effect of cold treatment on the concentric and eccentric torque-velocity relationship of the quadriceps femoris By: Kerriann Catlaw *, Brent L. Arnold, and David H. Perrin Catlaw, K., Arnold, B.L., & Perrin,