Middle-East Journal of Scientific Research 12 (3): 376-381, 2012 ISSN 1990-9233 © IDOSI Publications, 2012 DOI: 10.5829/idosi.mejsr.2012.12.3.65105

Measurements of Injured Hamstring Muscle Volume Before and after Eccentric Exercises and Hamsprint Exercises with MR Observations 1

Parastoo Shamsehkohan, 2Maziar Meghdadi, 3Mohammad Yadegari and 4Yaghoub Moradi Department of Physical Education and Sport Sciences, Sports Biomechanics, Islamic Azad University, Karaj, Iran 2 Department of Physical Education and Sport Sciences, Sports Management, Tehran University, Tehran, Iran 3 Department of Physical Education and Sport Sciences, Sport Pathology and Corrective Exercise, Kharazmi University, Tehran, Iran 4 Department of Physical Education and Sport Sciences, Sport Pathology and Corrective Exercise, Razi University, Keramanshah, Iran 1

Abstract: Hamstring injuries occur frequently, with a high recurrence rate, in sports that require either high-speed skilled movement. A previous hamstring injury is the greatest risk factor for a future hamstring injury. 10 subjects performed the hamsprint exercises and 10 subjects performed the eccentric exercises for 1 month and 5 subjects which were control group did not do any special activity during this month. Athletes underwent magnetic resonance imaging before and after 1-month. Hamstring muscle volumes were determined for injured limbs using manual segmentation. One-way analysis of variance test was determined to comparison of injured muscle volume of pre-test and post-test of all three groups and the results did not show a significant difference. But, the results of this test showed a significant difference between the injured muscle volumes of post-test in three groups. The results of this study showed the reduction of muscle injuries after eccentric exercise program and hamsprint exercise program. In addition, the hamsprint exercise program was more effective than eccentric exercise program. The HamSprint program allows athletes to return to sports at less risk for acute re-injury than those who complete a more traditional isolated stretching and strengthening exercise program. Collectively, the study indicates that a training program consisting of neuromuscular control and proprioceptive, is a good way for recovery of hamstring strain. Key words: Magnetic Resonance Imaging Training Programs

Muscle Injury

INTRODUCTION

Proprioceptive

remains challenging, as evidenced by approximately 30% of individuals experiencing a re-injury within the first year after initial injury [10-12] and require more time away from sport than the initial injury [11, 12]. Magnetic resonance (MR) imaging provides an objective standard for confirming the presence of an acute muscle strain injury [8]. Recent studies have shown that the location and extent of abnormalities on MR images not only confirm the presence and severity of initial muscle fiber damage, but can also provide a reasonable estimate of the rehabilitation period [13-15]. In addition, re-injury rates have been shown to be higher among individuals that sustain a more severe original injury [8].

Muscle strain injuries may account for 30% of sports medicine practice [1-4], with hamstring injuries being particularly frequent among individuals participating in sprinting, kicking, or high-speed skilled movements [1, 4-8]. Various studies found that male athletes were 62% more likely to sustain a hamstring injury than female athletes and more common in field sports than in court sports [4, 9]. Hamstring strains were the second most common injury, only surpassed by knee sprains in football [4, 10] and injury rates varied by position [4]. The treatment and rehabilitation of hamstring injuries Corresponding Author:

Neuromuscular Control

Parastoo Shamsehkohan, Department of Physical Education and Sport Sciences, Sports Biomechanics, Islamic Azad University, Karaj, Iran. Tel: +9-89353861420.

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Middle-East J. Sci. Res., 12 (3): 376-381, 2012

Various studies have investigated structural changes immediately following an acute hamstring strain injury [11-13, 16]. However, it is unclear how repair processes may alter musculotendon morphology. It has been hypothesized that scar tissue formation, along with weakness or atrophy of the previously injured muscle may be contributing factors to re-injury [11, 12]. The other risk factors that predispose athletes to hamstring injury can be older age, decreased quadriceps flexibility and muscle imbalances of the thigh [4, 5, 17]. Studies have also find that a previous hamstring injury is a significant risk factor for recurrent injury, suggesting that post injury changes to the muscle and altered movement patterns may persist that contribute to this increased risk [3, 4]. Most hamstring injuries occur along the proximal musculotendon junction, where the muscle fibrils intersect with the tendon [14, 16]. In addition, atrophy and fatty replacement within the previously injured or surrounding muscles may also occur as part of remodeling process [11, 12]. Like most acute strain injuries, hamstring strains do not typically involve the muscle tearing away from the tendon. In fact, it is the muscle tissue adjacent that is damaged [16]. Immediately after injury, there is an acute inflammatory response that is followed by muscle and collagen regeneration [11, 12]. An injury such as this can result in fibrous scar formation. Structural changes within the muscle immediately after an acute hamstring strain injury have been investigated [4, 13]. The amount and extent of edema and hemorrhage on magnetic resonance images can confirm the presence and severity of initial muscle fiber damage and can also provide a reasonable estimate of the rehabilitation period [4, 7, 13]. The significance of these persistent musculotendon morphological changes to re-injury risk is not definitively known at the present time [18]. Silder et al. [11, 12] investigated the effect of scar tissue by assessing running kinematics at 4 speeds ranging from 60% to 100% of maximum sprinting speed and showed that peak stretch of the hamstring muscles might be reduced in the previously injured limb compared with the contralateral side as a compensation for the modified tissue. However, no significant asymmetries in overall hamstring musculotendon stretch were observed at any of the speeds tested [11, 12]. In response to eccentric exercise, an increase in serial sarcomeres has been suggested [19]. This would allow the muscle-tendon unit to operate at longer lengths and decrease the magnitude of the stretch absorbed by each sarcomere and likely the corresponding strain. Clinical investigations involving eccentric training have

also shown benefits in reducing the incidence of hamstring strain injuries. Despite the benefit of these programs, they can have significantly low compliance rates [3]. There are also authors who are critical of the training specificity of the Nordic curl, noting that it is a bilateral movement that only generates movement from the knees [20]. Cameron et al. [21] theorized that the HamSprint program could be an effective hamstring injury prevention program. Therefore, it is totally unknown whether these beneficial effect on hamstring strain during a certain period or not. The purpose of this study was to use MR imaging to investigate the changes in muscle and tendon morphology after a hamstring strain injury. And it will also help the reader understand what happens anatomically and physiologically after an acute hamstring injury. These items provide practical applications for the sports medicine and performance team that help return athletes to sport with reduced risk for recurrent injury. MATERIALS AND METHODS Subjects: Twenty-five previously injured athletes were volunteered to participate in the study. All subjects had experienced a clinically diagnosed between 2-6 months prior hamstring strain injury (grade I or II) and required being away from sport. This study was a quasi-experimental research with pre-test and post-test. The subjects were randomized into three groups, eccentrics exercise (n=10), hamsprint exercise group (n=10) and control group (n=5). They were free of other current or history of musculoskeletal impairments. Each subject provided written informed consent prior to participation in this study. Experimental Approach to the Problem: The present study was designed to investigate the effects of 2 types of exercises for improving the hamstring strain injury. By random, 10 subjects performed the hamsprint exercises and 10 subjects performed the eccentric exercises for 1 month (4 times a week) and the other 5 subjects were control group. 4 did not complete the exercise programs. One subject was involved in a motor vehicle accident and could not continue the exercise program. Three subjects did not follow up for their scheduled appointment. Of these 4 subjects excluded due to noncompliance, 2 were in the eccentrics group and 2 were in the hamsprint group. Athletes underwent MR imaging before and after 1-month. Initial and final data obtained from MRI images were compared in each exercise and also with each other. 377

Middle-East J. Sci. Res., 12 (3): 376-381, 2012

Materials: MR images were obtained of subjects on a 1.5 Tesla MR scanner (SIEMENS AG 2006, Germany) and a flexible circularly polarized phased-array torso coil was used with the patient in a supine position. At first, we acquired axial T1-weighted turbo spin-echo MR images (TR/TE: 802/12, section thickness: 10 mm, FOV: 3032 × 40-42.7 cm, echo-train length: 3, matrix: 213 × 512, intersection gap: 20%, acquisitions: 2) and axial inversion recovery T2-weighted turbo spin-echo images (TR/TE: 5032/30, section thickness: 10 mm, FOV: 30-31.9 × 40-42.5 cm, echo-train length: 7, matrix: 182 × 256, inversion time: 150 msec, intersection gap: 20%, acquisitions: 1). Additionally, we obtained sagittal T1-weighted turbo spin-echo images (TR/TE: 676/12, section thickness: 7 mm, FOV: 24 × 32 cm, echo-train length: 3, matrix: 213 × 512, intersection gap: 20%, acquisitions: 2), sagittal inversion recovery T2-weighted turbo spin-echo images (TR/TE: 5000/30, section thickness: 7 mm, FOV: 24 × 32 cm, matrix: 189 × 256, echo-train length: 7, inversion time: 150 msec, intersection gap: 20%, acquisitions: 1) and axial gradientecho images (TR/TE: 610/18, flip angle: 20°, section thickness: 10 mm, FOV: 30-31.4 × 40-41.9 cm, matrix: 192 × 512, intersection gap: 20%, acquisitions: 1). Also a computer checked the signals and converted them into 3 dimensions images which investigated in different directions (Symphony; syngo MR A30). The patient should change to MR gown and remove any clothing with any metal.

warm-up before training. The HamSprint program were running, marching, skips, short stride cariocas, side shuffles, leg cycling, leg pawing, ankle pops, quick support running, forward falling running and explosive starts [21]. And the eccentric exercises were the eccentric box drops, eccentric loaded lunge drops, eccentric forward pulls, split-stance Zerchers and singleleg dead lift [20]. The drills were repeated 10 times in both limbs (3 times) and running drills were 30 meters (3 times). After 1-month training program, all subjects had a 48 hours rest. Then the post-MR imagines were obtained, to estimate the hamstring strain after training programs. Also the post-MR imagines were obtained from the control group. Statistical Analyses: Hamstring muscle volumes were determined for injured limbs using manual segmentation [22]. We quantified injured volumes of the biceps femoris long head, biceps femoris short head, proximal conjoint biceps femoris and semitendinosus tendon and proximal semimembranosus tendon by the prolate ellipsoid method based on the formula: volume = length x width x height x 0.52 on three dimensions [23]. Volumes were calculated as the product of the inter-slice distance and the summed cross-sectional areas from all slices containing the muscle of interest (Fig. 1). All measurements were conducted for all 3 groups. SPSS 16.0 (SPSS, Inc., Chicago, IL, USA) was used for all statistical procedures. To assess whether any significant differences existed in the pre-test scores across the three groups, a one-way ANOVA was

Protocol: MR imaging data were collected at the first of study. And then, 20 patients started their specific training programs. Athletes incorporated a 10 minutes dynamic

Fig. 1: a) 24-year-old male sprint player with hamstring strain injury, b) Cronal T2-weighted turbo spin-echo MR image, c) Axial T2-weighted turbo spin-echo MR image shows the injury in long head of biceps femoris muscle which is marked by green. 378

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calculated. This analysis was performed to assess whether any significant difference existed between the three groups prior to the initiation of the study. Next, a one-way ANOVA was calculated across the post test scores of the three groups to assess if any difference existed in the posttest scores. This analysis was performed to assess whether any difference existed between the three groups (including the control group). Significance for all statistical tests and all follow-up tests was accepted at the 0.05 level of probability. All data were screened for normality assumptions using the Shapiro-Wilk test and Levine.

The result of Shapiro-Wilk test showed a randomize distribution and the homogeneity of variances was determined by Levine statistic test. One-way analysis of variance test was determined to comparison of injured muscle volume of pre-test and post-test of all three groups and the results did not show a significant difference (P = 0.22) (Table 2). However, the results of this test showed a significant difference between the injured muscle volumes of posttest in three groups (p = 0.007). So post-hoc tukey test was performed on each variable to find differences between the groups and the results showed no significant difference between control group and eccentric exercise program group and also eccentric exercise program group and hamsprint exercise program group (p = 0.18, p = 0.15), however there is a significant difference between control group and hamsprint exercise program group (p = 0.006) (Table 3). The difference of pre-test and post-test of the three groups are shown in Figure 2.

RESULTS Table 1 showed baseline characteristics of the subjects. There was no statistical significant difference between three groups according to age, weight and height period by one-way analysis of variance test. Table 1: Baseline characteristics of subjects

Variable

Statistical Parameters ----------------------------------------------------------------------------------------------------------------------------------------------------Group N Mean Standard deviation

Age (year)

Eccentric exercise program Hamsprint exercise program Control

8 8 5

27.50 24.62 24.60

5.61 5.40 3.21

Hieght (centimeter)

Eccentric exercise program Hamsprint exercise program Control

8 8 5

1.75 1.76 1.78

7.80 6.62 4.57

Weight (kilogram)

Eccentric exercise program Hamsprint exercise program Control

8 8 5

68.50 71.12 76.60

7.18 10.25 12.05

Table 2: The comparison of injured muscle volume between pre-test and post-test of the three groups Pre-test -------------------------------------------------------------------Eccentric Hamsprint Control (mean±SD) (mean±SD) (mean±SD)

Post-test -------------------------------------------------------------------Eccentric Hamsprint Control (mean±SD) (mean±SD) (mean±SD)

Injured muscle volume (mm3)

28.11±17.39

22.14±12.43

ANOVA Sig.

0.22

19.79±19.68

37.50±11.95

9.68±11.75

35.60±14.58

0.007

Table 3: The result of Tukey Post Hoc (Post-test) Group ---------------------------------------------------------I J Control Eccentric Hamsprint

Eccentric Hamsprint Control Hamsprint Control Eccentric

Mean Difference

Std. Error

Sig.

13.46 *25.92 -13.46 12.46 *-25.92 -12.46

7.23 7.23 7.23 6.34 7.23 6.34

0.18 0.006 0.18 0.15 0.006 0.15

*Statistical significance at P < 0.05

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Middle-East J. Sci. Res., 12 (3): 376-381, 2012

Fig. 2: The difference of pre-test and post-test of the three groups DISCUSSION

acute re-injury than those who complete a more traditional isolated stretching and strengthening exercise program. In addition, doing a regular and moderate exercise is a useful way for a rapid recovery of hamstring strain. Protection against muscle strain is provided not only by strong muscles but also by the appropriate timing and magnitude of neural control. Thus, according to the results of this study, it is suggested that the athletes who suffer hamstring strain, do hamsprint exercises or similar exercises which prevent a recurrent injury and keep athletes in the game.

The main purpose of this study was to compare the effect of eccentric exercises and hamsprint exercises on the athletes who had hamstring strain. The results of this study showed the reduction of muscle injuries after eccentric exercise program and hamsprint exercise program. In addition, the hamsprint exercise program was more effective than eccentric exercise program, but there were no significant differences between two exercise programs. The findings of this study about the effect of hamsprint exercises and eccentric exercises on hamstring strain recovery were in agreement with Kraemer and Knobloch [6], Stanton and Purdham [24], Cameron et al. [21] and Sherry and Best [4]. The results of this study indicated significant differences between two exercise program groups. One of the possible reasons for recovery of injury, is the training program of neuromuscular control and proprioceptive in promoting return to sports and in preventing injury recurrence in athletes who have sustained an acute hamstring strain. Although the findings suggested that a simple program of eccentric exercises could reduce the incidence of hamstring injuries but widespread implementation of this program is not likely because of poor compliance [21]. In comparison with functional eccentric strengthening exercises; dynamic agility drills, integrating neuromuscular control and lower body stabilization exercises (hamsprint exercises) have shown more potential to prevent a recurrent injury and keep athletes in the game. In conclusion, the results of this study demonstrated that a training program consis of progressive agility and stabilization exercises was effective in promoting return to sports and in preventing injury recurrence in athletes who had sustained an acute hamstring strain. The hamsprint program allows athletes to return to sports at less risk for

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