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Indian Journal of Physiotherapy and Occupational Therapy

Effectiveness of lateral and forward step-up exercises among selected muscles: An EMG study

Author(s): Mohan. N.

Vol. 2, No. 2 (2008-04 - 2008-06)

Mohan. N.

Department of Physiotherapy, Khalsa College , Amritsar

Keywords: electromyography, vastus lateralis, Rectus Femoris, Biceps femoris., vastus Medialis, Lateral step up, Forward step up.

Abstract:

Recovery of quadriceps strength is of primary concern during rehabilitation process following knee injury or surgery. The step up exercise is frequently used in rehabilitation protocol of knee which facilitate co-contraction of the quadriceps and hamstring muscle in a functional movement pattern and more importantly increase quadriceps strength without anterior translation of tibia on femur. The purpose of this study was to determine electromyographically of significant differences in level of electrical activity in vastus lateralis, rectus femoris vastus medialis and biceps femoris muscle occurred during the step up phase and step down phases of lateral step up and forward step up exercises at heights of 5, 8 and 11 inches. Twenty male subjects with no pathological condition of the knees participated in the study. Surface electrodes were used for recording, the muscle activity was taken in percentage to maximum voluntary contraction of each subject. For comparison between lateral step up and forward step up, step up phase and step down phase and comparison between different heights one tailed related ‘T’ test and ANOVA were used. Results revealed significant muscle activity of VM and VL during lateral step up than that of forward step up at heights of 5 inch [VL: T=3.43 (p<0.01), VM: T=3.21 (p<0.01)], 8 inch [VM: T=2.91 (p<0.01), VL: T=3.84 (p<0.01)] and at 11 inches height all muscles were significantly more active except for Biceps femoris [VL: T=2.22 (p<0.05), VM: T=4.06 (p<0.001), RF: T=2.12 (p<0.05)]. All muscles produced greater activity at the 11 inch height than the 8 inches and 5 inches at the level. In Lateral step up exercise, step up phase, produced significantly greater activity than step down, phase. In forward step up exercise, step up phase produced significantly greater activity than step down phase except for Biceps femoris.

This result of this study are discussed with respect to the limited role of shear force of tibia during step up exercise. We concluded that forward step up exercise had less motor firing than lateral step up exercise so lateral step up exercise is more effective in rehabilitation particularly in the vastii muscles. A gradual increase in bench height and addition of weights to the body would increase in strength performance.

Introduction

The knee joint is one of the most frequently injured joints in the body, especially in those engaging in athletic activity. Even though the knee appears to be a relatively simple joint, the biomechanics of the knee and treatment of injured knee have long been subjects of discussion in the literature and professional circles. Muscle weakness or atrophy of the extensor mechanism are major concern following knee injury or surgery (Antich et al., 1986, Baugher et al., 1984, Brunet, 1989, Paulos et al., 1981).

The prime aim of the rehabilitation program is to develop muscle strength to the pre injury status or atleast maintain the strength of the given muscle group to normal level. Strength is directly related to the efficiency of the neuromuscular system and the function of the motor unit in producing muscular force. Strength training in rehabilitation program will increase neuromuscular efficiency in three ways namely increasing the number of motor units being recruited. Increasing the firing rate of each motor unit, and increasing synchronization of motor unit firing (Bandy. et al., 1990). In most recent protocols of knee injury rehabilitation closed kinetic chain (CKC) activities such as squats, step ups, and leg press were incorporated (Case et al., 1991, Palmitier et al., 1992, Shelbrone, 1990). The promotion of closed kinetic chain exercise for rehabilitation is band on three main primary concepts (Hooper , 2001).

The first is the assumption that because closed kinetic chain exercises appear to better replicate functional tasks, they would enhance functional performance to a greater extent than open kinetic chain exercises (Palmitier et al., 1991, Prentice 1994, Shelbourne et al., 1992). The second reason was that the strain on ACL was greater during open kinetic chain exercises (Beynnon , 1998, Escamilla et al., 1998, Renstorm et al., 1986, Yack et al., 1993). The third reason has been favoured in belief that this exercise will be less harmful to the patellofemoral joint (Steinkamp et al 1993). Despite popular opinion favoring closed kinetic chain exercises, there is a lack of prospective clinical data. The step up exercise is one closed chain activity that is frequently utilized in rehabilitation protocols for the knee. Step up exercise simulates some of the activities of daily living and helps strengthen various muscle groups. Step up exercise is done in two ways namely lateral step up and forward step up exercise.

Electromyography is an appropriate tool to measure the relative intensity of muscle activity occurring during exercises or any functional activity. Surface EMG is being used not only in the study of human movement but also for diagnositic purposes and clinical settings.

The present study deals with anlaysis of superficial thigh muscles i.e. vastus lateralis (VL), Rectus femoris (RF), vastus medialis (VM), Biceps femoris (BF), during the step up phase and step down phase of lateral step up and forward step up exercise regime. The advantage of surface electromyography is that researcher can easily and reliably monitor myoelectrical activity of given muscle and it is a non invasive technique. EMG signals can be used as an indicator of intensity of each contraction when one is studying muscle functions. EMG also provides a technique to measure and compare muscle activity during phases of exercise performance.

Design and Methodology

The present study was conducted in the department of sports medicine and physiotherapy, Guru Nanak Dev University, Amritsar. A total of 20 healthy subjects (N=20) of the department with no history of hip, knee and ankle pain participated in the study. The study was done in only males. Their ages ranged between 19-29 years with a mean thigh girth of 45.5 cm (±4.5) and mean femoral length of 47.2 cm (±2.7).

Each subjects provided an informed consent prior to participation in the study. The data collection was undertaken during the period of July-August, 2003, under controlled environmental condition with temperature maintained at 24°.Subjects with present or past history of hip, knee or ankle injury.,previous or present knee pathology or surgery and positive findings on patellofemoral and tibiofemoral stress tests were excluded.The study was carried out on vastus lateralis, rectus femoris, vastus medialis and biceps femoris of the right lower limb which was the dominant leg of the subjects. The test for dominance was performed by making the subjects to kick a foot ball with the preferred leg.

Instrumentation

NORAXON INC. USA, Myosystem EMG machine was used to record the electromyographic signals. The EMG signals were collected using disposable bipolar silver chloride disc surface electrodes with a diameter of 5mm that were placed parallel to the muscle fibre with a center to center spacing of 2.5 cm.

EMG data processing

The raw EMG data was full wave rectified and low pass filtered. The signals were then normalized, the amplitude obtained during maximum voluntary isometric contraction (MVIC). The performance of MVIC allows the muscle activity measured during subsequent tasks to be reported in terms of percentage of MVIC. This method of reporting permits comparisons across subjects as well as comparison of the relative activation of muscles.

Subject preparation

In skin preparation hair were shaved off from the subjects skin overlying the area selected for electrode fixation.This skin was thoroughly cleaned with ethyl alcohol to reduce skin resistance.

Subjects were asked to wear shorts for the exercise session.

Electrode placement

For rectus femoris muscle electrode was placed at one half the distance between anterior superior iliac spine and superior pole of patella. For vastus medialis muscle the subject performed isometric contraction of quadriceps and surface electrode were placed four finger breadth proximal to the medial angle of the patella at the site of maximal bulge during contraction. For vastus lateralis muscle in the same type of vastus medialis the subject performed isometric contraction and electrode were placed a hand breadth proximal to upper pole of patella on the lateral aspect of thigh approximately at the site of maximal bulge during the contraction. For Biceps femoris muscle the electrode was placed one-third the distance between ischial tuberosity and the lateral knee joint space. Ground electrode was placed over the medial mallelous of the reference extremity.

Exercise performed

After an adequate initial warm up, each subject performed the following exercise in a randomized order. Manual muscle testing position was considered for calculation in the present study. For rectus femoris, vastus medialis and vastus laterals the subject seated upright on a plinth and knee flexed to 45-50° from full extension. The leg was restrained by manual resistance for 4 seconds. For Biceps femoris the subjects placed in prone lying position and knee flexed to 45-50° from full extension. The leg was restrained by manual resistance for 4 seconds

Lateral step up exercise

Lateral step up exercise is done by using stools of various heights. While standing on the stool, laterally the subject slowly raises and lowers himself using the involved leg. The foot on the uninvolved side is dorsiflxed and only the heel is allowed to touch the ground. Weight bearing on the uninvolved leg is not permitted, thereby forcing the involved leg to solely control the motion.

Forward step up exercise

In forward step up exercise the stool was kept in front of the subject. The subject slowly raises forward and lower himself backward using the involved leg. The forward step up exercise was similar to stair climbing. It is made sure that involved leg planted on the stool and that the body is lifted forward, than lowered with smooth motion.

Results

DATA ANALYSIS: A one way analysis of variance (ANOVA) is done to compare the activity of muscles at heights of 5,8 and 11 inches.To compare the difference in muscle activity of forward step up exercise and lateral step up exercise, step up phases and step down phases, t test was used.

In comparison between lateral and forward step up exercises at 5 and 8 inch heights, VM and VL produced significantly greater activity in lateral step up phase than forward step up phase (p<.01)(Table 1,2). At 11 inches height VM, VL, and RF produced significantly greater activity in lateral step up phase than forward step up phase(p<.05) (Table 3). No significant differences were seen between the lateral and forward step down phase at all 3 heights in all muscles. The step up phase of lateral step up exercise was significantly greater than step down phase in all three heights as well as in all muscles (p<.05). In the forward step up exercise same results were seen (p<.05) except for BF muscle where there was no significant difference in activity.

Table 1: Comparative analysis of selected muscle activity of VL, VM, RF and BF during lateral step up phase and forward step up phase at a height of 5 inches

  Lateral 5 inch step up phase Forward 5 inch step up phase % change ‘t’ value ‘p’ value
Mean S.D. S.E. Mean S.D. S.E.
VL 32.59 6.15 1.37 26.10 5.76 1.28 19.91 3.43 p<0.01
RF 13.93 6.09 1.36 11.44 4.94 1.10 17.87 1.41 NS
VM 32.91 6.08 1.36 26.88 5.75 1.28 18.32 3.21 p<0.01
BF 9.22 5.22 1.16 8.52 6.02 1.34 7.59 0.38 NS

Table 2: Comparative analysis of selected muscle activity of VL, VM, RF and BF during lateral step up phase and forward step up phase at a height of 8 inches

  Lateral 5 inch step up phase Forward 5 inch step up phase % change ‘t’ value ‘p’ value
Mean S.D. S.E. Mean S.D. S.E.
VL 41.57 10.16 2.27 33.39 7.39 1.65 19.67 2.91 p<0.01
RF 18.35 8.13 1.81 14.41 5.52 1.23 21.47 1.79 NS
VM 42.09 7.12 1.59 34.42 5.36 1.19 18.22 3.84 p<0.001
BF 12.69 7.81 1.74 10.04 6.63 1.48 20.88 1.15 NS

ALL muscles showed an increase in activity with increase in step height.

Discussion

In conservative method of treatment and strengthening, the knee joint and muscles surrounding it are always a point of great concern for the physiotherapist. In the clinical practices, choice of treatment through different exercise, different protocols becomes a point of contradiction and varies from one school of thought to another. The present study was to anlayze electromyographically selected muscles such as vastus lateralis, vastus medialis, rectus femoris and biceps femoris during lateral step up and forward step up exercises at height of 5, 8 and 11 inches. This study documented the difference in muscle activity between the step up phase and step down phase for both lateral step up and forward step up exercises at height of 5, 8 and 11 inches. It also include difference in muscle activity between. Lateral step up exercise and forward step up exercise during both phases, the step up phase and step down phase and at all three heights namely 5, 8 and 11 inches. Inter muscle activity comparison was also done during step up phase and step down phase of forward and lateral step up exercise.

Table 3: Comparative analysis of selected muscle activity of VL, VM, RF and BF during lateral step up phase and forward step up phase at a height of 11 inches

  Lateral 5 inch step up phase Forward 5 inch step up phase % change ‘t’ value ‘p’ value
Mean S.D. S.E. Mean S.D. S.E.
VL 48.37 14.71 3.28 39.60 9.72 2.17 18.13 2.22 p<0.05
RF 22.89 8.98 2.00 17.44 7.13 1.59 23.80 2.12 p<0.05
VM 51.31 5.57 1.91 40.56 8.16 1.82 20.95 4.06 p<0.001
BF 16.60 9.89 2.21 12.64 8.07 1.80 23.85 1.38 NS


The main findings of this study are

  • In lateral step up exercise, the step up phase produced significantly greater muscle activity (VL, VM, RF and BF) than the step down phase at all three heights (5, 8 and 11 inches).
  • In forward step up exercise, the step up phase produced significantly greater muscle activity than the step down phase, except for BF at all three heights (5, 8 and 11 inches).
  • On comparing between lateral step up exercise with forward step up exercise at both 5 and 8 inches height VM and VL produced significantly greater muscle activity in lateral step up activity.
  • At 11 inches height VM, VL and RM produced greater muscle activity in lateral step up phase than forward up phase.
  • During step down phase there is no significant difference in muscle activity between lateral step up exercise and forward step up exercise at all three heights (5, 8 and 11 inches).

During the comparison of heights all muscles produced higher muscle activity proportionately with increase in heights but only some muscles showed significant difference in muscle activity at 5, 8 and 11 inches height. Such as in lateral step up exercise during step up phase, the VL muscle showed significantly greater muscle activity in 8 inch step height than 5 inch step. Also the muscle activity produced by the VM muscle at 11 inch step was significantly greater than the 8 inch block and that of 8 inch step was significantly greater than 5 inch step. During step down phase of lateral step up exercise, the VL muscle produced significantly greater muscle activity at the 8 inch than that of the 5 inch step. The VM muscle produced greater muscle activity at 11 inch step than 8 inch step height.

In forward step up exercise during step up phase, the muscle VL and VM produced greater muscle activity at 11 inch step height than 8 inch step and that of 8 inch was significantly greater than 5 inch step height. In step down phase of forward step up exercise, the muscle VL and VM produced greater muscle activity at 11 inch step height than 8 inch step and that of 8 inch was significantly greater than 5 inch step height. In inter muscle activity comparison, the muscle VM and VL produced no significant difference in both lateral step up and forward step up exercises at all heights (5, 8 and 11 inches). The maximum activation was produced by VM muscle followed by VL muscle in both forward and lateral, lateral step up exercise.

In comparative anlaysis of selected muscles during lateral step up phase and step down phase at heights of 5, 8 and 11 inches. It is seen that all muscles have mean values significantly greater in step up phase than step down phase. Bent Brask et al (1984) determined the electrical activity in vastus medialis, rectus femoris, biceps femoris and semimembranosus/ semitendinosus muscle during concentric and eccentric phases of lateral step up exercise.

They found concentric phase (step up phase) produced significantly greater activity than eccentric phase (step down phase) at each height except for semimembranosus/ semitendinosus muscle where no difference existed, as the bellies of this muscle were less distinct than other muscle studied.

The EMG force relationship has also been examined in terms of eccentric and concentric contractions, eccentric or lengthening utilize elastic elements and metabolic process more efficiently than concentric contraction. Therefore for the same amount of muscle tension, an eccentric will require fewer motor units (less EMG activity than a concentric contraction (Susan Sullivan, 2001). This might be the reason of greater muscle activity during step up phase than step down phase.

In comparative analysis of selected muscle during forward step up phase and step down phase at heights of 5, 8 and 11 inches. All muscles had mean value significantly greater in step up phase than step down phase except for biceps femoris. Zimmermann et al (1994) had similar findings and noted that there was increased peak activity of gluteus maximums, quadriceps and gastrocnemius and no apparent difference in EMG activity of hamstring during stair stepping exercise. They also recommended that stair stepping exercise would not be helpful in strengthening hamstring musculature.

In comparative analysis of lateral step up phase and forward step up phase at heights of 5 and 8 inches. VM and VL had significantly greater mean value than forward step up phase. In comparative analysis of lateral step up phase and forward step up phase at height of 11 inches it is seen VM, VL and RF had significantly, greater mean value than forward step up phase.

Wang et al (2003) found that lateral step up exercise produced greater knee flexion angle and ankle dorsiflexion angle than forward step up phase. They found that lateral step up exercise generated greater impulse, work and power at knee and ankle. The lateral step up exercise places greater demand on knee extensor and ankle plantar flexors, while forward step up exercise places greater demand on hip extensor. This might be the reason that VM and VL produced greater muscle activity in lateral step up phase than forward step up phase. With increase in height the difference in activity of RF between forward and lateral step up showed consistent increase which might be due to greater difference between knee flexion angle in lateral step up exercise and forward step up exercise, and rectus femoris is a two joint muscle.

It was observed that VM and VL activity increased with increase in step height in both lateral and forward step up exercise than other muscles. There can be several reasons for this. As centre of gravity of body has to go greater distance to attain erect position, the amount of work done by muscle VM and VL also increase proportionately this would lead to greater motor units activation and thus greater EMG activity (Thomas et al, 1992). As the height of step increases there is greater gravitational torque in knee and increased knee flexion angle therefore more motor units are recruited to overcome gravitational torque (Zimmermann et al, 1994).Tata et al (1983) analyzed EMG activity of quadriceps femoris muscle during stair cycle. They found that quadriceps components demonstrated a regular sequence of recruitment. EMG amplitude obtained was higher in ascending than descending which had a implication of designing lower extremity prosthesis and in application of functional electrical stimulation. It was lastly concluded that lateral step up exercise had greater motor firing than forward step up exercise, so lateral step up exercise would be more effective in any rehabilitation program.

In intermuscle comparison of muscle activity of VM, VL RF and BF during lateral and forward step up exercise VM showed maximal activation followed by VL muscle. Simon et al (2001) found that in closed kinemtic chain exercises VMO activation was obtained at 60° knee flexion and found maximal VMO/VL ratio was observed at this knee flexion angle and muscle contraction intensity was also greatest.

Conclusion

Lateral and forward step up exercises could be given to improve functional activity in elderly patients as these exercises require greater muscle activity in functional household chores.

For rehabilitation of VM and VL muscles, lateral step up exercises could be chosen over the forward step up exercises, as these muscles had greater activation with the former.

Using biofeedback mechanism, if VM is isolated and stimulated during lateral step up exercise, it can be used in patellar malalignment problems as VM had the maximal activation compared to other muscles.

References

  1. Antich TH, Brewster CE, Modification of quadriceps femoris muscle exercise during knee rehabilitation exercises. Phys Ther 66 (8): 1246-1250, 1986.
  2. Baugher WH, Warren RH, Marshall JL, Joseph A: Quadriceps atrophy in the anterior cruciate insufficient knee. Am J Sports Med 12(13): 192-195, 1984.
  3. Bent Brask, Robert H, Lueke Gary L, Soderberg. Electromyographic analysis of selected muscles during the lateral step up exercise. Physical Therapy. 64(3): 324-329, 1984.
  4. Bandy W., Lovelace, Chandler, V. Bandy: Adaptation of selected muscle to resistance training. J. Ortho. Sports Phys. Ther. 12(6): 248-255, 1990
  5. Beynnon BD, Johnson RJ, Flemming BC. Anterior cruciate ligament during squatting and active flexion and extension. A comparison of open and closed kinetic chain exercises. Am J Sports Med 25: 823- 829, 1997.
  6. Brunet ME, Stewart GW: Patellofemoral rehabilitation. Clinic Sports Medicine 8(2: 319-329, 1989.
  7. Case JG, Depalma BR, Zelco RR. Knee rehabilitation following antrerior cruciate ligament repair. J Athl Train 26: 22-31, 1991.
  8. Donald K, Shelbourne Paul Nitz. Accelerated Rehabilitation after ACL ligament reconstruction. JOSPT. 15(6): 256-64, 1992.
  9. Hooper DM, Mathew C, Morrissey. Open and closed kinetic chain exercise in early period after ACL ligament reconstruction. Am J Sports Med 29:2, 2001.
  10. Palmitier RA, Ank-N, Scott SG, Chao EYS. Kinetic chain exercise in knee rehabilitation. Sports Med 11(6): 402-412, 1991.
  11. Paulos L, Noyes JR, Grood E, Butler DL: Knee rehabilitation after anterior cruciater ligament reconstruction and repair. Am J Sports Med 9(8): 140- 147, 1987 Prentice WE et al. Rehabilitation techniques in sports medicine. Mosby, 1994.
  12. Renstrom P, Arms SW, Stanwyck Ts, Strain with in the anterior cruciate ligament during hamstring and quadriceps activity. Am J Sports Med 14: 83-87, 1986.
  13. Simon FT, Tang Chih Kauang Chen, Robert HSU. Vastus medialis obliqus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patello femoral pain syndrome: An electromyographic study. Arch. Phys. Med. Rehab. 82: 1441-1445, 2001.
  14. Steinkamp LA Dillingham MF,Markel MD, Biomechanic consideration in patellofemoral joint rehabilitation. Am J Sports Med 21: 438-444, 1993. Sullivan SO Physical rehabilitation (Assessment and Treatment). Jaypee Brothers, 4th ed., 2001.
  15. Thomas M, Cook Chvis L, Zimmermann Varin. EMG comparison of lateral step up and stepping machine exercise. JOSPT. 16(3): 108-113, 1992.
  16. Wang MY, Flanagan S, Song JE. Lower extrimity biomechanics during forward and lateral stepping activities in older adults. Clinic Biomech. 18(3): 214- 21, 2003.
  17. Yack HJ, Collins CE, Whieldon TJ. Comparison of closed and open kinetic chain exercise in the ACL deficient knee. American Journal of Sports Medicine. 21(1): 49-54, 1993.
  18. Zimmermann CL, Cook TM, Braward MS. Effects of stair stepping exercise direction and cadence of EMG activity of selected lower extremity muscle groups. JOSPT. 19(3): 173-80, 1994.
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