Prime Mover Of Knee Extension
Int J Sports Phys Ther. 2012 December; 7(vi): 606–616.
MUSCLE ACTIVITY DURING Genu‐EXTENSION STRENGTHENING Practice PERFORMED WITH Rubberband TUBING AND ISOTONIC RESISTANCE
Markus Due Jakobsen
1U1.National Enquiry Centre for the Working Surroundings, Copenhagen, Denmark
Emil Sundstrup
1U1.National Inquiry Middle for the Working Environment, Copenhagen, Denmark
Christoffer H. Andersen
aneU1.National Research Centre for the Working Surroundings, Copenhagen, Denmark
Thomas Bandholm
twoClinical Enquiry Centre, and Departments of Orthopedic Surgery and Physical Therapy, Copenhagen University Infirmary, Hvidovre, Denmark
Kristian Thorborg
iiiArthroscopic Heart Amager, Amager University Hospital, Copenhagen Denmark
Mette K. Zebis
ivInstitute of Sport Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
Lars L. Andersen
1U1.National Enquiry Centre for the Working Environs, Copenhagen, Denmark
Abstract
Background/Purpose:
While elastic resistance training, targeting the upper body is constructive for forcefulness preparation, the upshot of elastic resistance training on lower trunk muscle activity remains questionable. The purpose of this study was to evaluate the EMG‐angle relationship of the quadriceps muscle during 10‐RM knee‐extensions performed with elastic tubing and an isotonic strength training machine.
Methods:
7 women and 9 men anile 28‐67 years (mean age 44 and 41 years, respectively) participated. Electromyographic (EMG) activity was recorded in x muscles during the concentric and eccentric contraction phase of a human knee extension exercise performed with rubberband tubing and in training automobile and normalized to maximal voluntary isometric contraction (MVC) EMG (nEMG). Knee joint angle was measured during the exercises using electronic inclinometers (range of motion 0‐90°).
Results:
When comparing the automobile and elastic resistance exercises there were no pregnant differences in summit EMG of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM) during the concentric contraction phase. Even so, during the eccentric stage, peak EMG was significantly higher (p<0.01) in RF and VM when performing knee extensions using the training car. In VL and VM the EMG‐bending pattern was unlike between the two training modalities (significant angle by exercise interaction). When using elastic resistance, the EMG‐angle pattern peaked towards total knee extension (0°), whereas angle at elevation EMG occurred closer to knee flexion position (90°) during the auto practise. Perceived loading (Borg CR10) was like during articulatio genus extensions performed with rubberband tubing (v.7±0.six) compared with knee extensions performed in training machine (5.ix±0.5).
Determination:
Human knee extensions performed with rubberband tubing induces similar loftier (>lxx% nEMG) quadriceps muscle activity during the concentric contraction phase, but slightly lower during the eccentric wrinkle phase, every bit articulatio genus extensions performed using an isotonic training machine. During the concentric contraction phase the two different weather condition displayed reciprocal EMG‐bending patterns during the range of movement.
Keywords: Electromyography, forcefulness training, quadriceps, perceived exertion
INTRODUCTION
Reduced knee‐extension strength is commonly reported in over‐use human knee pathologies, for instance, the patello‐femoral pain syndrome,1 and afterwards full genu replacement,2,3 suggesting that strength training of the quadriceps muscle is needed.iv Appropriately, articulatio genus articulation replacement and knee joint joint hurting is ofttimes associated with muscular cloudburst,five and central activation failureiii,6,seven resulting in reduced functional performance, potential for hereafter injury and increased risk for long‐term sickness and piece of work‐related absence.8,nine Heavy resistance training during a prolonged grooming period yields muscular hypertrophy,10–12 gains in forcefulness,13–xv increased neuromuscular (efferent) drive11,sixteen,17 and reduced pain.18 However, the availability of forcefulness training equipment is often a limiting cistron during rehabilitation and training interventions.xix
A growing involvement in developing unproblematic and effective training methods convenient for exercising at the workplace, in the hospital, at dwelling house or at the grooming field18–20 has been emerging for quite some time. Loftier‐intensity forcefulness training using elastic resistance has shown to be equally effective in activating smaller muscles in the neck, shoulder, and arm when compared to similar training exercises performed isotonically with dumbbells.21,22 The outcome of rubberband resistance grooming on larger muscle groups such every bit the quadriceps, however, remains largely unexplored. Furthermore, development of simple and effective grooming exercises feasible for use during rehabilitation of knee pathologies is needed.
Electromyography (EMG) and electro‐goniometry obtained during resistance training and concrete rehabilitation exercises provide valuable information on temporal and spatial muscle activation strategies during different angular phases of the exercise through range of move. Whereas the EMG ‐ articulation angle human relationship is well described for conventional (i.e. using dumbbell or auto) isoinertial force exercises,23 only ane recent report has investigated the EMG‐angle pattern during elastic resistance exercise.24 Aboodarda et al. compared the EMG angle‐relationship during articulatio genus extension using elastic resistance and a Nautilus isotonic machine (Nautilus, Vancouver, WA) and showed that the average vastus lateralis muscle activeness was similar during the two practise modalities. Nevertheless, the EMG‐angle relationship of multiple prime mover muscles (rectus femoris, vastus medialis and vastus lateralis) besides as the antagonist/synergists muscle activity during genu extensions remains un‐investigated. An imbalance in the synergetic activation ratio of the vastus medialis (VM) and vastus lateralis (VL) may contribute to genu injuries such as patellafemoral hurting syndrome.25,26 Appropriately, exercises with college VM to VL ratios may be preferred during rehabilitation.23 Although conventional knee joint extensions performed in an isotonic auto may non preferentially actuate the VM over the VL,23 the VM to VL activation ratio may differ throughout range of motion during articulatio genus extensions performed using elastic resistance.
The purpose of this study was to evaluate the EMG‐bending human relationship of the quadriceps muscle during x‐RM knee‐extensions performed with elastic tubing and an isotonic strength training car.
MATERIALS AND METHODS
Experimental Approach to the Problem
Muscle action and perceived loading (rated on a Borg CR10 scale) during leg strengthening exercises performed in a training automobile or with elastic resistance were evaluated using a cantankerous‐sectional design. For each individual musculus, EMG musculus activity of each of the dynamic musculus contraction was normalized to the amplitude elicited during a maximal voluntary isometric contraction (MVC).
Subjects
The study was performed in Copenhagen, Kingdom of denmark. A group of 16 untrained adults (7 women and nine men) were recruited from a large workplace with various job tasks. Exclusion criteria were claret pressure above 160/100, disc prolapse, or serious chronic disease. Tabular array 1 displays the subject field demographics. All participants performed both conditions of genu extension testing, with elastic resistance and in the isotonic preparation machine. All subjects were informed nearly the purpose and content of the project, and gave written informed consent to participate in the study, which conformed to The Declaration of Helsinki, and was canonical by the Local Upstanding Committee (H‐iii‐2010‐062).
Table i.
Demographics of the men and women of this study. Data presented equally hateful (SD).
| Men | Women | |
|---|---|---|
| n | 9 | vii |
| Age, yrs | 41(15) | 44(10) |
| Height, cm | 179(vi) | 167(8) |
| Weight, kg | 78(4) | 67(16) |
| BMI | 24(2) | 24(6) |
Exercise equipment
2 unlike types of knee‐extension forcefulness‐training equipment were used; 1) elastic tubing with resistances ranging from calorie-free to very heavy (red, green, blue, black, silvery/gray colors, TheraBand, Akron, USA) and ii) an isotonic knee‐extension automobile (Vertical seated knee joint extension, Technogym, Gambettola, Italy).
Practise description
A calendar week prior to testing, the participants performed a 10 repetition maximum (10 RM) test for the 2 exercises. During the elastic resistance do the x RM loading was found using i or a combination of several elastic tubes with resistances ranging from lite to very heavy (blood-red, light-green, blue, black, gray colors). All exercises were performed unilaterally using the dominant leg (preferred leg) as the exercising leg. A week later, on the day of EMG measurements, participants warmed up with submaximal loads, and then performed three consecutive repetitions for each do, using the predetermined 10 RM load, to avoid the influence of fatigue on the subsequent exercises. Exercises were performed in a controlled manner at a wearisome constant speed [participants attempted to perform each repetition in ∼3 sec (eccentric phase: ∼1.5 sec and concentric stage: ∼1.five sec)]. The order of exercises was randomized for each subject, and the balance menses between different exercises was approximately five minutes. The exercises are shown in Effigy 1 and described in item beneath:
(a) Start position for knee joint extension against elastic resistance. (b) End position for knee extension against elastic resistance. (c) Start position for knee joint extension performed on the isotonic machine. (d) End position for articulatio genus extension performed on the isotonic automobile.
Articulatio genus extension with elastic resistance (Fig. 1a & 1b).
The participant was sitting on a high chair, facing abroad, from a wooden bar (rubberband fixation betoken located 10 cm in a higher place the flooring and with a horizontal altitude of ∼1.5 thousand from the chair to the bar) with both legs flexed at ∼xc° knee joint angle and a xc° hip flexion. The elastic tubing was fixated to the participant'southward talocrural joint on ane end (1 finger to a higher place the medial malleoli), and the other end was attached to the bar. The elastic ring was then stretched to ∼200% of the initial length. The participant started extending the human knee from the flexed knee position (∼90° knee joint angle) (concentric phase) until full extension (∼0° knee articulation angle), and then returned to the flexed knee position (eccentric phase).
Isolated knee extension in motorcar (Fig. 1c & 1d).
The participant was seated in a Technogym human knee extension machine with the leg flexed at ∼ninety° knee joint angle and a 100° hip flexion. The machine's lever arm was fixated i finger above the medial malleoli. The participant started past extending the knee (concentric phase) until total extension was accomplished (∼0° human knee joint angle), and then flexed the genu (eccentric phase) returning to the ∼90° knee joint angle.
Inclinometer sampling and assay
Knee joint angle was continuously measured using ii electronic inclinometers (2nd DTS inclination sensor, Noraxon, Arizona, USA) placed at the lateral side of the tibia and femur, respectively. The inclinometer information were synchronously sampled with the EMG data, using the sixteen‐channel 16‐bit PC‐interface receiver (TeleMyo DTS Telemetry, Noraxon, Arizona, U.s.). The dimension of the probes was 3.four cm × 2.4 cm × 3.5 cm. During subsequent analysis, the inclinometer signals were digitally lowpass filtered using a ivth social club zip‐lag Butterworth filter (3 Hz cutoff frequency).
The momentary knee joint angle was calculated as the departure in athwart position, with respect to the gravitational line, betwixt the tibia and femur inclinometers. Knee articulation angles ranged from a 908 flexed position to a 0° total articulatio genus extension. The concentric and eccentric phases were defined as periods with negative or positive athwart velocity, respectively, (going from 90°‐0° or 0°‐xc°, respectively). Bending at superlative EMG was calculated inside the concentric and eccentric phase.
EMG signal sampling and analysis
EMG signals were recorded from 10 leg, intestinal, and lower dorsum muscles, including: vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) (prime movers for knee joint extension) and biceps femoris, semitendinosus, adductors, gluteus medius, right erector spinae, right external oblique and the right rectus abdominis (non‐prime movers for knee extension). A bipolar surface EMG configuration (Blue Sensor N‐00‐S, Ambu A/Southward, Ballerup, Denmark) with an inter‐electrode distance of 2 cm were used.23,27 Before affixing the electrodes, the peel of the respective surface area was prepared with scrubbing gel (Acqua gel, Meditec, Parma, Italy) to finer lower the impedance to less than ten kΩ.21 Electrode placements for all muscles followed SENIAM recommendations (world wide web.seniam.org).
The EMG electrodes were connected directly to wireless probes that pre‐amplified the signal (gain 400) and transmitted data in existent‐time to a sixteen–channel sixteen‐chip PC‐interface receiver (TeleMyo DTS Telemetry, Noraxon, Arizona, Usa). The dimension of the probes was 3.4 cm × 2.4 cm × iii.5 cm. Information was collected at a sampling rate of 1500 Hz. Common mode rejection ratio was higher than 100 dB.
During after off‐line analysis, all raw EMG signals obtained during MVCs as well as during the exercises were digitally filtered by a Butterworth 4th gild high‐pass filter (10 Hz cutoff frequency). For each individual muscle, maximal moving root mean square (RMS) (500 ms constant) EMG was used to identify peak EMG within the concentric and eccentric stage whereas the RMS of the highpass filtered EMG indicate was calculated within each 10° angle interval (0°‐10°, 10°‐twenty°,… 80°‐90°) of the concentric and eccentric phases and so normalized to the maximal moving RMS (500‐ms fourth dimension constant) EMG obtained during MVC.21,27,28 Contraction time was calculated according to procedures previously described in.27
Maximal voluntary isometric wrinkle (MVC)
Prior to the dynamic exercises described above, isometric MVCs were performed, according to standardized procedures during ane) static knee extension and two) flexion manoeuvres (positioned in a Biodex dynamometer: human knee bending: 70° and hip angle: 110°), 3) hip adduction (lying flat on the back and pressing the knees confronting a solid brawl), 4) hip abduction (lying apartment on the back and pressing the knees outwards confronting a rigid ring) and 5) hip extension (lying flat on the tummy with the knee flexed (90°) and pressing the human foot upwards against the instructors hands), and 6) trunk extension and 7) body flexion (in continuing posture and pelvis fixated the trunk was extended against a rigid ring) to induce a maximal EMG response in the tested muscles.29 Two MVCs were performed for each muscle, and the trial with the highest RMS EMG value was subsequently used for normalization of the RMS EMG signals obtained in the resistance exercises. During the MVCs, subjects were instructed to gradually increment muscle wrinkle force towards maximum over a period of ii seconds, sustain the MVC for three seconds, and then slowly release the strength again. Strong and standardized exact encouragement was given during all trials.
Perceived loading
Immediately after each set of exercise, the Borg CR10 calibrationxxx (Appendix 1) was used to rate perceived loading during the resistance practice. We have previously validated this scale in the evaluation of neck/shoulder resistance exercises with elastic resistance.21
Statistical assay
A ii‐way repeated measures assay of variance (Proc Mixed, SAS version 9, SAS Institute, Cary, NC) was used to determine if differences existed between exercises and range of human knee articulation motion for each muscle and wrinkle style (concentric or eccentric), vastus medialis to vastus lateralis activation ratio, perceived loading (BORG) and contraction time. Factors included in the model were Practice (rubberband resistance and machine) and knee joint angle (0‐90 degrees), likewise as Practise by human knee angle interaction. The analysis was controlled for gender and historic period. Normalized EMG was the dependent variable. Values are reported equally least foursquare means (SE) unless otherwise stated. P‐values ≤0.05 were considered statistically significant.
A priori power analysis showed that 16 participants in this paired design were sufficient to obtain a statistical power of 80% at a minimal relevant difference of 10% and a blazon I error probability of i%, assuming standard deviation of 10% based on previous research in the authors laboratory.31
RESULTS
Normalized EMG
Figure 2 shows the normalized EMG‐angle human relationship for the quadriceps muscles during knee extension exercises performed in machine or with rubberband resistance during the 0‐90° knee joint range of motion. There was no meaning difference in maximal EMG between car and elastic resistance exercise for the prime movers for genu extension (rectus femoris, vastus lateralis, vastus medialis) during the concentric contraction phase (Table ii). However, during the eccentric phase, peak EMG was significantly higher (p<0.01) in RF and VM when performing knee joint extensions using the training machine compared with elastic resistance.
Table two.
Maximal nEMG (% of max) and angle at maximal nEMG obtained during the concentric and eccentric phase of genu extensions performed with machine and elastic resistance.
| Muscle | nEMG(%of max) | Angle at pinnacle EMG (°) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Rubberband | Machine | Elastic | Machine | ||||||||
| Mean | SE | Mean | SE | P | Hateful | SE | Hateful | SE | P | ||
| Rectus femoris | CONCENTRIC | 76.7 | iv.6 | 83.nine | 4.vi | .24 | 38.9 | 4.3 | 55.0 | 4.3 | <.01 |
| ECCENTRIC | 45.1 | 3.half-dozen | threescore.7 | 3.v | <.01 | 15.5 | 4.9 | 52.four | 4.9 | <.01 | |
| Vastus lateralis | CONCENTRIC | 83.7 | 4.6 | 84.vii | four.6 | .87 | 33.eight | 4.3 | 60.2 | 4.3 | <.01 |
| ECCENTRIC | 53.1 | three.six | 61.6 | iii.v | .08 | 12.vii | 4.nine | threescore.v | 4.9 | <.01 | |
| Vastus medialis | CONCENTRIC | 71.v | 4.half-dozen | 81.viii | 4.6 | .10 | 34.3 | iv.3 | 64.3 | 4.3 | <.01 |
| ECCENTRIC | 43.2 | 3.6 | 57.iii | 3.5 | <.01 | 15.half-dozen | iv.9 | 59.6 | 4.ix | <.01 | |
| Adductors | CONCENTRIC | 17.2 | 4.5 | 20.2 | four.6 | .61 | 31.0 | four.3 | 58.3 | four.3 | <.01 |
| ECCENTRIC | eleven.4 | iii.four | 15.2 | 3.5 | .43 | xviii.1 | 4.viii | 49.nine | 4.9 | <.01 | |
| Gluteus medius | CONCENTRIC | 13.ii | 4.5 | 13.2 | four.six | .99 | xxx.0 | 4.3 | 42.ix | iv.3 | <.01 |
| ECCENTRIC | 8.5 | iii.4 | 8.4 | 3.5 | .98 | 12.4 | iv.8 | 24.6 | 4.9 | .04 | |
| Erector spinae | CONCENTRIC | 13.3 | 4.five | 21.2 | 4.6 | .19 | 31.9 | four.3 | 62.four | four.three | <.01 |
| ECCENTRIC | 12.0 | 3.4 | 17.2 | 3.v | .28 | 39.7 | four.8 | 48.8 | 4.ix | .12 | |
| Obliques externus | CONCENTRIC | 13.2 | 4.5 | 20.0 | iv.6 | .26 | 29.4 | iv.3 | 46.8 | 4.3 | <.01 |
| ECCENTRIC | 9.3 | 3.four | 12.8 | iii.5 | .46 | 20.6 | iv.eight | 36.ix | iv.9 | <.01 | |
| Rectus abdominis | CONCENTRIC | 7.0 | 4.5 | xi.3 | 4.vi | .47 | 27.2 | 4.3 | 48.1 | 4.3 | <.01 |
| ECCENTRIC | 4.vi | 3.4 | 6.two | 3.five | .74 | 23.6 | iv.8 | xl.7 | 4.nine | <.01 | |
| Biceps femoris | CONCENTRIC | thirteen.vi | 4.5 | 17.three | iv.6 | .53 | 43.ii | iv.3 | 68.5 | 4.three | <.01 |
| ECCENTRIC | 8.6 | iii.four | thirteen.2 | 3.5 | .34 | 24.8 | 4.eight | 64.8 | iv.9 | <.01 | |
| Semi tendinosus | CONCENTRIC | 7.9 | 4.5 | 7.3 | 4.6 | .93 | 36.i | 4.3 | 67.0 | 4.3 | <.01 |
| ECCENTRIC | 5.iii | 3.4 | 5.4 | 3.5 | .97 | 16.4 | 4.viii | 62.viii | iv.9 | <.01 | |
EMG data for Quadriceps during the 4 dissimilar conditions, represented as means and standard deviations.
There was a meaning exercise past knee joint articulation angle interaction (P<0.01). The EMG‐human knee articulation angle relationships for the 2 investigated vasti were different betwixt preparation modalities. For the car, the concentric phase EMG‐amplitude peaked near maximal knee flexion (60.ii°±4.3 and 60.5°±4.3 for the VL and VM, respectively) and decreased towards total genu extension, whereas the opposite design was seen for the elastic tubing (angle at elevation EMG: 33.8°±4.3 and 34.three°±4.3 for the VL and VM, respectively). Irrespectively of training condition, angle and wrinkle fashion, the VM to VL EMG ratio never exceeded 1.00 and was similar between the two exercise conditions.
All muscles as well the prime movers RF, VL and VM demonstrated depression peak EMG values (<21% of nEMG). However, these followed a comparable EMG‐angle pattern every bit VL and VM of their respective training status (i.east. using rubberband resistance the EMG increased towards articulatio genus extension whereas EMG increased towards knee flexion during the machine exercise). Appropriately, significant differences (p<0.01) were observed in bending at peak EMG between the two practice weather.
External load and contraction time
The average load of the car do was 28±2.31 kg, ranging from fifteen‐50 kg. The 10 RM elastic resistance ranged from a combination of 1xSilver, 1xBlue and 1xGreen to 3xSilver, 1xBlack, 1xBlue, 1xGreen and 1xRed (TheraBand elastic tubes).
Irrespectively of training status there was no significant divergence in contraction time (i.east. fourth dimension nether tension) during the knee extension exercise. Wrinkle times for car and elastic resistance were 1824±111 ms and 1834±103 ms respectively, and for wrinkle modes concentric vs. eccentric were 1733±80 ms and 1572±75 ms, respectively.
Perceived loading and influence of age and gender
Perceived loading assessed with the Borg CR10 rating scale was like (p=0.67) during articulatio genus extensions performed with rubberband bands (5.72±0.57) compared with human knee extensions performed in training automobile (five.87±0.47). There were no meaning effects of age and gender on muscle activeness (p=0.71 and p=0.72, respectively).
Discussion
The main finding of this study was that knee extensions performed with elastic tubing induces similar quadriceps EMG muscular activity equally knee extensions using an isotonic training machine. However, different EMG‐angle patterns existed between exercise conditions.
Irrespectively of loading modality (motorcar or elastic), there was no meaning deviation in maximal quadriceps (rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM)) EMG during the concentric contraction phase. The EMG‐angle pattern of the VL and VM, however, demonstrated quite a dissimilar design when comparing the two exercise weather. When using elastic resistance, the EMG activeness of the concentric stage increased from knee joint flexion position and peaked towards full knee extension whereas a reciprocal behavior was observed during the machine practice, where the EMG activity increased from extension and peaked closer to human knee flexion position. This difference may be explained by the elastic strength generation (i.east. external loading) being greatest at the more extended genu angles whereas the intramuscular forcefulness induced by the external loading may be greater at the more flexed knee joint angles during the machine exercise.
A recent study by Aboodarda et al. compared the EMG bending‐relationship of knee extensions performed using elastic resistance and a Nautilus motorcar and showed that the average vastus ‐lateralis muscle activeness was like during the two exercise modalities.24 As previously indicated, Aboodarda et al. demonstrated that the practical force exerted during the elastic resistance exercise increases from human knee flexion to genu extension, while the Nautilus machine provided a more than constant load throughout ROM.24 Although, Aboodarda et al. observed significantly higher exerted forces in the first 66% of ROM (44°‐100°) using the Nautilus, the EMG‐angle pattern was quite similar (in intensity and shape) displaying an increase towards full genu extension during both exercise modalities. Accordingly, the present EMG‐angle pattern using elastic resistance seems comparable with the findings of Aboodarda et al., whereas a reciprocal EMG‐angle design seems to be when comparing the Nautilus motorcar with the car used in the present study.
Open‐chain exercises are by and large better tolerated in early rehabilitation of postoperative patients when airtight‐chain exercises such every bit a squat are not viable. Despite alien guidelines regarding the impact of patellofemoral stress in extended knee positions32–34 studies have shown that open up‐chain protocols are effective and safe about full articulatio genus extension.35,36 Accordingly, greater quadriceps muscle action during extended genu positions, as observed using rubberband resistance compared with machines, may exist peculiarly benign for rehabilitation of knee pathologies such every bit ACL injury and following total knee joint arthroplasty where forcefulness deficits have been observed to exist nowadays during the well-nigh extended knee angles.37,38 Thus, the observed reciprocal EMG‐angle design between the two grooming modalities may take clinical relevance when designing specific rehabilitation and strengthening programmes.
When comparing the two practise modalities, the RF muscle demonstrated a somewhat similar curvilinear EMG‐angle relationship peaking in the mid region (39‐55°) of the concentric phase. This similarity in RF EMG‐angle pattern betwixt the two types of exercise indicates less dependence on the specific type of regional external loading. This beliefs may be explained by the bi‐articular function of the RF working as a knee extensor likewise every bit a hip flexor consequently leading to enhanced activation in the heart role of range of move irrespectively of exercise modality.
Genu extensions using the isotonic auto resulted in higher eccentric activation values compared to rubberband resistance. During the machine do the eccentric EMG‐pattern was rather constant throughout ROM, whereas the elastic resistance showed an increase in EMG towards knee extension. This may bespeak that the higher and more constant eccentric activation during the machine exercise makes this a more effective training modality for rehabilitation of muscular strain injuries.39,40 Nonetheless, this assertion should be tested in a randomized controlled trial.
An imbalance in the synergetic stabilization ratio of the VM and VL may contribute to knee joint injuries such every bit patellofemoral pain syndrome.25,26 Atrophy of the VM is oftentimes the cause of an imbalance in the VM to VL ratio,41–43 consequently, making the VM muscle an important target for achieving a counterbalanced genu articulation. Thus, exercises with higher VM to VL ratios may be preferred during rehabilitation.23 Nevertheless, in line with previous findings of conventional knee extensions performed in auto23 the VM:VL‐ratio never exceeded 1:00 throughout ROM and was quite like in the two grooming modalities. Although none of the exercises seems to preferentially activate VM over the VL, the VM:VL‐ratio never fell below 0:85 making both exercises optimal for maintaining patellar articulation alignment.
The activation of the not‐prime movers (all muscles besides RF, VL and VM) was rather low for both exercise modalities, still, these followed a comparable EMG‐angle pattern every bit VL and VM during their respective training weather condition. Accordingly, this indicates that increases in prime mover activity during knee joint extension are accompanied past a simultaneous increase in synergetic and adversary muscle activation to preserve fixation and control of the articulatio genus and surrounding joints.
Perceived loading was similar between auto and elastic resistance exercises. This is in line with the comparable tiptop EMG and contraction time (fourth dimension under tension) values observed during performance of the 2 exercises. Importantly, the exercises induce loftier musculus activity regardless of gender and historic period. Thus, these exercises tin can be used beneficially for both younger and elderly individuals, also as men and women.
The knee extension exercise performed with elastic resistance seems to be a feasible and uncomplicated method, regardless of age and gender, for achieving loftier muscle activity potentially stimulating muscular hypertrophy and strength gains in the quadriceps muscles. Its portability makes information technology ideal for work site training, rehabilitation in hospitals, at home or in training fields where there may exist few resources for large preparation equipment. A future randomized controlled study is needed to investigate the ability of elastic resistance exercise to increment knee‐extension force over time.
Limitations
The fact that the chair has to exist high (or raised), to forestall pes and ground contact when performing the genu extensions using elastic tubing, may limit the feasibility of the exercise. Alternatively, the do can be performed with the distal femur elevated east.m. with a pillow or triangular box beneath the thigh to ensure free motility of the lower leg. As this slightly changes the articulation angles, it should be noted, that this may change the muscle activity pattern. However, when considering this suggestion, the difference in hip angle between the elastic and machine exercise (90° vs. 100°) as well as the alter in the elastic's angle of pull throughout the ROM should exist considered when interpreting the EMG‐bending pattern of the two do conditions.
CONCLUSION
In untrained individuals, knee extensions performed with rubberband tubing induces similar quadriceps EMG muscle activity during the concentric contraction phase, just slightly lower action during the eccentric wrinkle phase, as knee extensions using an isotonic training machine. During the concentric wrinkle phase the ii modalities displayed reciprocal EMG activity patterns during the range of movement. This reciprocal behaviour may take clinical relevance when designing specific rehabilitation and strengthening programmes.
APPENDIX 1
Borg CR10 scale
Use this scale to rate the load you experience (i.e. weight in the automobile or resistance of the elastic band) in relation to your muscle strength.
0= Nothing at all
10= The maximal load that yous can imagine if you utilize all your muscle force
| Number | Load |
|---|---|
| 0 | Nothing at all |
| 0.3 | |
| 0.5 | Just noticeable |
| 0.vii | |
| ane | Very light |
| 1.5 | |
| 2 | Light |
| ii.5 | |
| three | Moderate |
| 4 | |
| v | Heavy |
| 6 | |
| 7 | Very heavy |
| eight | |
| nine | |
| 10 | Maximal |
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Prime Mover Of Knee Extension,
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