Asymmetries in Flexibility, Balance and Power Associated with Preferred and Non-Preferred Leg

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1 World Journal of Sport Sciences 2 (1): 38-42, 2009 ISSN IDOSI Publications, 2009 Asymmetries in Flexibility, Balance and Power Associated with Preferred and Non-Preferred Leg H. Samadi, R. Rajabi, H. Minoonejad and A. Aghaiari 1 Department of Physical Education, Payame Noor University, Borujen Center, Iran 2 Department of Physical Education, Faculty of Physical Education, University of Tehran, Tehran, Iran 3 Department of Physical Education, Payame Noor University, Tehran Center, Tehran, Iran Abstract: The uninjured limb is commonly used as a pre-injury model because of the assumption that the limbs are symmetrical. However, this may not be true in all athletes. One-legged athletes (1LA) (e.g., jumpers) may develop bilateral asymmetries as a result of specific training. The purpose of this study was to determine whether asymmetries in flexibility, balance and power existed in the preferred and non-preferred legs of 1LA athletes. Three characteristics were measured in three groups of subjects: non-athletes (NAS) (n=10, age 21.0±1.2 y, height 170.1±6.8 cm, weight 68.5±13.1 kg); two-legged athletes (2LA) (n=10, age 21.4±1.4 y, height 169.9±8.6 cm, weight 66.3±10.0 kg) and one-legged athletes (n=10, age 22.3±1.4 y, height 179.7±11.0, weight 72.9±13.9 kg). Quadriceps and hamstring flexibility were measured using a Leighton Flexometer during a passive prone knee-flexion test and a supine passive straight-leg raise, respectively. Balance was assessed by stork standing test. One-legged hop distance (OLH) represented power. Leg preference was determined using soccer ball kicking task. 2x3 ANOVAs were used to determine if differences existed in the legs (preferred, non-preferred) by group (NAS, 1LA, 2LA) for flexibility, balance and OLH. Tukey s HSD post hoc test was performed to locate any significant differences. Results revealed no significant interactions in leg preference by group (NAS, 2LA, 1LA) for flexibility, stability and OLH. However, main effects among groups were revealed when the means of both legs were combined. Tukey s post hoc test revealed that 1LAs were jumped significantly farther compared to the NASs and 2LAs. The lack of significant asymmetries between preferred and non-preferred legs suggests that an inadequacy in training elicited asymmetrical adaptations. Therefore, a bilateral comparison is a valid pre-injury model for the injured lower limb allowing clinicians to accurately organize rehabilitation goal and return-to-play criteria. Key words: Asymmetry % Flexibility % Balance % Power INTRODUCTION In the lower extremity, the differences may not be as obvious in two-legged athletes [7-9] (e.g., sprinters and Sport injury rehabilitation centers on restoring swimmers) and non-athletes [10, 11] (e.g., sedentary functional abilities to normal, optimal, or a pre-injury state population). However, one legged athletes (e.g., long of health [1]. Using the uninjured limb as a pre-injury jumpers and high jumpers) may develop a significant model is very common because of the assumption that the bilateral asymmetry due to a constant training overload on limbs are physically and functionally symmetrical [1-3]. the jumping leg [12, 13]. Logically, superior physical Using a bilateral comparison, clinicians assume limb characteristics should be seen in the jumping leg of onesymmetry and use the uninjured limb as a comparison legged athletes like long jumpers, high jumpers and model for the injured limb. football kickers [12]. The limbs may not be perfectly symmetrical when Clinically, a bilateral comparison is performed observing left and right physical characteristics [3, 4]. between limbs with the assumption that the limbs are This is apparent in the upper extremity, where the symmetrical. However, pre-injury asymmetries between dominant arm is usually stronger and more versatile [5, 6]. the limbs may invalidate this bilateral comparison and Corresponding Author: H. Samadi, Department of Physical Education, Payame Noor University, Borujen Center, Borujen, Iran 38

2 complicate the rehabilitation process. Assuming pre- intrasession reliability was reported as 0.97 and 0.88, injury symmetry or asymmetry when the opposite exists respectively. Quadriceps flexibility was measured using sets erroneous functional progression criteria. the Leighton Flexometer during passive prone knee Establishing incorrect functional rehabilitation flexion. Intrasession reliability was established during a progression criteria may delay an athlete s progress pilot test by the primary investigator at All flexibility through the rehabilitation process. For the clinician, measures were recorded in degrees and used in the problems of misinterpretation arise when incorrect analysis. Power was represented by the distance hopped assumptions are made. Depending on the type of activity, during one-leg hop test (OLH) and was assessed as level of participation, or training regimen, the limbs may or described by Bolgla et al. [15]. Hop distance was may not be symmetrical. As a result, rehabilitating athletes measured using a standard tape measure secured to the are affected. Therefore, this study attempted to answer floor. The furthest hop distance of the 3 performed was the following questions: used in the analysis. Balance was assessed by stork Are there physical and or functional asymmetries standing test. For the stork stand the subjects completed between the right and left legs of one legged athletes? the test on the dominant and non-dominant foot. The And are these asymmetries associated with the preferred subjects kept their hands on their hips with the leg? uninvolved foot against the medial side of the knee of the stance leg. Each subject maintained this position while MATERIALS AND METHODS standing on the ball of the foot for the maximum possible time. The trial ended when the heel of the involved leg This investigation is a cross sectional, two-way touched the floor, the hands came off of the hips, or the ANOVA design. The dependent variables for this opposite foot was removed from the stance leg. The best investigation are flexibility (hamstring, quadriceps), of three trials was recorded for analysis. Outcome balance and power (OLH). The independent variables for measures were analyzed using 2 x 3 (leg preference x this investigation are leg preference (left, right) and group group) ANOVAs and Tukey s HSD Post Hoc Tests for (NAS, 1LA, 2LA). the dependent variables. Data were analyzed using SPSS Three groups of subjects: non-athletes (NAS) (n=10, 11.5 (SPSS, Chicago, IL). The level of significance was set age 21.0±1.2 y, height 170.1±6.8 cm, weight kg); a priori at p < two-legged athletes (2LA) (n=10, age y, height cm, weight kg) and one-legged RESULTS athletes (n=10, age y, height , weight kg) gave their informed consent and Table 1 shows descriptive statistics by group. The volunteered to participate in the study, which had the ANOVA revealed no significant interactions in leg approval of the University s Ethical Advisory preference (preferred, non-preferred) by group (NAS, Commission. All participants were informed verbally and 1LA, 2LA) for quadriceps [F (54,2) =0.30, p=0.967] and in writing about the nature and demands of the study as hamstring flexibility [F(54,2)=0.546, p=0.583]. The ANOVA well as the known health risks. Subjects completed a revealed no significant interactions in leg preference by health history questionnaire and were informed that they groups for balance F(54,2)=0.275, p=0.761]. Also the could withdraw from the study at any time, even after ANOVA revealed no significant interactions in leg giving their written consent. Athletes had trained for a preference by groups for OLH [F (54, 2) =0.07, p=0.925]. minimum of three years (part or full time) and all them However, a group main effect was revealed [F (54, 2) participated for at least 16 hours/week of training for the =35.18, p=0.000] when data for both legs were pooled. six months before testing. Tukey s HSD post hoc analysis showed that 1LA jumped After height and weight had been measured, the significantly farther than 2LA and NAS. subject completed a standardized warm up by riding a bicycle ergometer for five minutes at a comfortable speed. DISCUSSION The subject then stretched the lower extremity muscle groups. Leg preference was determined using soccer ball The results of this study show no significant kicking task [14]. Flexibility measurement of the hamstring differences in the preferred and non-preferred legs of 1LA, was measured using a Leighton Flexometer during the 2LA and NAS in any of the tests. Similar to Agre et al. passive straight-leg raise [13] which its intersession and [16], Rahnama et al. [17] and Knapik et al. [18] the present 39

3 Table 1: Descriptive statistics by group. Data are means±sd 1LA (n=10) 2LA (n=10) NAS (n=10) Age (years) 22.3± ± ±1.2 Height (cm) 179.7± ± ±6.8 Weight (kg) 72.9± ± ±13.1 Quadriceps Flexibility (degree) Preferred leg 125.0± ± ±16.9 Non-preferred leg ± ± ±15.28 Hamstring Flexibility (degree) Preferred leg 69.1± ± ±10.5 Non-preferred leg 70.8± ± ±12.9 OLH test (cm) Preferred leg ± ± ±15.9 Non-preferred leg 211.5± ± ±20.6 Balance (sec) Preferred leg 24.6± ± ±2.46 Non-preferred leg 24.3± ± ±2.3 study found no significant differences in the preferred activity (manipulation) is typically lateralized regardless of and non-preferred legs for hamstring and quadriceps posture (e.g., standing or seated). Therefore, the inherent flexibility. However, neither Agre et al. [16] nor use of the support limb does not determine which leg one Knapik et al. [18] strictly examined NAS or 1LA. Both chooses to perform a task. Moreover during long jump, Agre et al. [16] and Rahnama et al. [17] used football high jump, or hurdle training, the 1LA does not focus on player athletes; however, Knapik et al. [18] only used improving single-leg standing balance. Therefore, female collegiate athletes. The present study is in contrast symmetry in stability performance in the legs is expected. to Sullivan et al. [19] who reported a significant difference The results of the present study are similar to those in the legs for hamstring flexibility. reported by Mangine et al. [25], Booher et al. [26] and Some ideas may explain why these adaptations did Jarvela et al. [27]. No studies reporting asymmetrical not occur in 1LA. The Overload Principle suggests that performance in the preferred and non-preferred legs were physical changes occur in tissues if imposed stresses are found. greater than what the tissues are accustomed [12]. The The results revealed that 1LA jumped significantly volume of exercise and the range of motion (R.O.M) of the farther than both the NAS and 2LA. This was probably movements needed to elicit changes in flexibility may due to the difference in training regimens among the have been inadequate. Additionally, the relative amount groups. The 1LA group consisted of varsity track athletes of work performed by one leg versus two is minute that actually trained 6 days per week, 2 hours per day. The compared to the relative amount of work performed by 2LA group consisted of athletes that varied weekly one arm versus two. Krahl et al. [20] noted significant volume between 3 and 6 days per week, 1 to 3 hours each structural asymmetries between the arms of tennis day. The large disparity among weekly volumes may have players. These athletes during training and activities of influenced this difference among groups. daily living (ADL) notably use one arm more than the Since no asymmetries were revealed in the present other. However, jumping and kicking athletes, even during study, the preferred leg could not be associated with training do not use one leg independently of the other for physical and functional characteristics. Therefore, leg long periods of time. preference does not influence or predict asymmetries in Similar to Harrison et al. [21], Ross et al. [22], flexibility, balance and power in the lower extremities. McCurdy and Langford [23], the present study observed The results of the present study demonstrated that no significant differences in the preferred and non- no asymmetries in flexibility, balance and power in the preferred legs. In contrast, Colby et al. [24] noted preferred and non-preferred legs existed in NAS, 2LA and significant differences. Contrasting results between 1LA. Hence, limb asymmetry is not associated with leg present study and Colby study could be attributed to preference. Therefore, a bilateral comparison is a valid different testing methods and subjects used. pre-injury model for the injured lower limb allowing Beling et al. [3] examined lower limb task performance clinicians to accurately organize rehabilitation goal and while standing and sitting and suggested that dynamic return-to-play criteria. 40

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