Researches for the evaluation of strength in the hip abductors, biceps brachi and quadriceps in the dominant and non-dominant limb have been done but the data for calf muscle strength has yet not been evaluated in normal adults.

To form a normative data of isokinetic testing of calf muscle strength in dominant and non-dominant lower extremity in young Indian adults.

83 normal young collegiate males and females were tested for isokinetic peak torque production during plantar flexion on the isokinetic dynamometer.

Strength for the dominant calf muscle was 73.17±26.44 N and for the non-dominant calf muscle was 56.65±21.27 N. The paired t test was used to analyse the data to evaluate if there is a significant difference between the dominant and non-dominant calf muscle. Paired t-tests (p-value-0.000) indicated significant differences in peak torque among dominant versus non-dominant calf muscle group strength.

These results suggest that peak torque of dominant calf muscle group was more than peak torque of non-dominant calf muscle group.

Keywords: Strength, Isokinetic Testing, Peak Torque, Calf muscle

The calf muscle is a very important muscle in the human body because the contribution of this muscle more than just being a simple muscle is that it works as a second heart. It plays a very important role in blood pumping from legs to heart and maintains a good venous return flow. This muscle is actually a group of seven muscles arranged into superficial and deep muscle groups. The superficial group includes the gastrocnemius, plantaris, soleus and the deep group includes the popliteus, flexor digitorum longus, flexor hallucis longus and the tibialis posterior. Contracting these muscles helps in plantar flexion of ankle, curling of toes, knee flexion, walking, running and biking. The Achilles tendon is the strongest and thickest tendon in the body. It attaches the calf muscles (soleus and gastrocnemius) to the heel bone (calcaneus). The tendon transmits force from the contracting calf muscles to the calcaneus to cause the foot action of plantar flexion (foot pointed down) that is important in walking, running, jumping and change of direction activities. Although the Achilles tendon is the strongest tendon in the body, it is also the tendon most commonly torn or ruptured. The most common cause of rupture is a sudden plantar flexion (such as taking off to jump.

Direct trauma over the Achilles tendon or doing forceful dorsiflexion (foot moving upward) such as landing from a jump, stepping into a hole may cause injury to the Achilles tendon. [1] To do such type of work, calf muscle has to be strong enough to carry the body weight. Researches show that during running and jumping the Achilles tendon is subjected to load as high as 6 to 12 times of body weight. [2-4]

The limb dominancy is very important for good body dynamics or maintaining static balance as well as control of the body. Due to this the person feels more stable on his/her dominant body side. The limb dominance is defined as one limb demonstrating increased dynamic control as a result of an imbalance in muscular strength and recruitment patterns. Dependence on the dominant limb can increase stress on the joints of that extremity [6, 7, 8] and because of over-reliance on the dominant limb, weakness of the contralateral limb muscles may occur, which can further decrease the non-dominant extremity’s ability to absorb large forces associated with activities.[9]

But as there is no numerical data available for strength difference between dominant and non-dominant calf muscle that may suggest the marginal strength gap or ratio of strength difference between both (calf muscle) the legs, these numerical values will be very helpful for the planning of making effective physiotherapy and rehabilitation protocol in calf muscle weakness cases and provide the target strength level for both the legs as well.

Newton RU (2006) conducted a study for determination of functional strength imbalance of the lower extremities. They concluded that a significant strength imbalance can exist even in collegiate level athletes. [9] Jones PA (2010) compared the isokinetic and functional methods of assessing bilateral strength imbalance. Significant differences (p<0.01) were found between strength in the dominant (D) and non-dominant (ND) limbs for all strength measures, ranging from 4.5% (hop test) to 12.4% (eccentric extension). No significant differences between the right and left limbs were found (p>0.05). No significant relationships between strength of D and ND ratios of isokinetic variables and the field tests were evident (p>0.05).[10]

Hans E. Berg et al and Ola Eiken et al 2007, conducted a study on hip, thigh and calf muscle atrophy and bone loss after 5-week bed rest inactivity. They concluded that a substantial loss in hip extensor strength and a smaller, yet significant atrophy of these muscles, demonstrate that hip muscle deconditioning accompanies losses in thigh and calf muscle mass after bedrest[11].

A total of 83 subjects were taken from Jamia Hamdard University, New Delhi. Sample of convenience was used for subject selection. The subjects were screened and selected for the study according to the following inclusion and exclusion criteria:

Data Analysis was performed by using SPSS 17 for windows software. Data was tabulated in the master chart. Descriptive statistics was used to analyze subject’s characteristics such as age, BMI, calf muscle circumference and mean scores of peak torque in dominant and non-dominant calf muscle strength in young adults. Paired sample t test was used to find the comparison of peak torque between dominant and non-dominant lower limb. P-value of 0.005 was taken as significant value.

83 subjects had given their consent to participate in the study. The isokinetic calf muscle torque of dominant and non-dominant leg was measured and the value of dominant torque was put into group A [PTLLD] and peak torque value of non-dominant lower limb (PTLLND) was put into group B.

The mean age of 83 subjects was 23.40±2.33 and the mean BMI of subjects was 21.70±1.98. Group A contains 83 dominant lower limb calf muscle strength in young adults subjects. The mean score of peak torque in dominant lower limb was 73.17±26.44.

Group B contains 83 non-dominant lower limb calf muscle strength in young adults, the mean score of peak torque in non-dominant lower limb was 56.65±21.27.

The mean score of strength difference in dominant and non-dominant lower limb calf muscle was 16.52±5.17.

BMI- Body mass index; PTLLD- Peak torque of dominant lower limb; PTLLND- Peak torque of non-dominant lower limb

*RT CC- Right calf circumference; LFTCC- left calf circumference

Figure 1.1. Descriptive statistics of subject’s characteristics.

Figure 1.2. Descriptive statistics of subject’s characteristics.

Table 2- Paired t-test analysis for dominant v/s non-dominant peak torque

Comparison between dominated lower limb calf muscle strength and non-dominant lower limb calf muscle strength is t = 11.66 and p = 0.000 which is statistically significant.

The purpose of the study was to find out the difference in calf muscle strength between dominant & non-dominant lower limb in normal young adults. Upon analysis of the data, it was revealed that there was a significant difference in the calf muscle strength between dominant & non-dominant lower limb. The calf muscle of the dominant limb were stronger than that of the non-dominant lower limb.

The subject’s dominant lower limb calf muscle peak torque was 73.17±26.44 and non-dominant lower limb calf muscle peak torque was 56.65±21.27 (p= 0.876). This indicates that the difference was statistically significant. The average side to side strength difference was approximately 22.58%, which indicates imbalance in calf muscle strength. The side-to-side strength imbalances in the range of 10% to 15% in other muscle groups have been associated with increased injury rates.

Knapik et al reported increased lower extremity injury rates in female athletes demonstrating 15% strength deficits of either the left quadriceps or hamstring muscles. Burkett reported that a 10% side-to-side strength difference in the hamstrings was associated with an increased incidence of hamstring strains. Cale Jacobs et al showed that hip-abduction strength differences exist between the dominant and non-dominant legs. Measures of strength and fatigability were poorly related; therefore, clinicians may opt to assess hip strength and fatigability independent of each another.