Effect of Induced Muscular Fatigue on Balance and Core Strength in Normal Individuals

Indian Journal of Physiotherapy & Occupational Therapy. July-September 2014, Vol. 8, No. 3

ABSTRACT

Background: Balance is the ability to maintain proper alignment of body segments with respect to each other. Muscular fatigue is a key factor which can influence performance via impaired joint proprioception and postural control. Fatigue alters the force generation capacity of the muscle and ultimately leads to task failure. The relationship between fatigue and balance is poorly understood.

The purpose of the present study was to assess if fatigue had an immediate effect on balance and core strength in healthy individuals, by checking the static and dynamic stability and the core muscle strength for spinal stability.

Aim: To find the effect of Induced muscular fatigue on Balance and Core strength in Normal Individuals.

Methodology: Functional reach tests, Single Leg Stance, Core strength were measured Pre and post Fatigue, which was induced by squats performed till RPE of 10. The data obtained was statistically analyzed using paired 't' test.

Results: A significant reduction was found in the mean single leg stance time from 10.05 seconds pre-fatigue, to 3.01 s post fatigue (p<0.05). The pre fatigue functional reach distance covered by individuals was 36.36 cms which was reduced to 29.48 cms post fatigue (p<0.05). There was also a reduction in the core muscle strength measured pre fatigue from 43.43 mmHg to 43.16 mmHg post fatigue statistically. (p<0.05)

Conclusion: Fatigue definitely has a significant reduction on Static balance, Dynamic balance & also on lumbar core strength as seen in normal individuals.

Keywords: Muscular Fatigue, Static Balance, Dynamic Balance, Core Strength

INTRODUCTION

Balance can be defined as the position of the body relative to the arrangement of the limbs and segments, for a specific activity, or the characteristic that one bears the weight of one’s body. It is the ability to maintain equilibrium in a gravitational field, and to react to destabilizing forces quickly and efficiently to regain stability via postural adjustments before, during, and after voluntary movement and in response to external perturbation. Balance, is maintained by the dynamic integration of internal and external forces and factors involving the environment. Specifically, balance can be classified as either static i.e. maintaining equilibrium with minimal movement, semi-dynamic i.e. attempting equilibrium while the base of support moves, or dynamic i.e. maintaining a stable base of support while completing prescribed movement. When an individual is in erect standing posture the integrity of stance is maintained by shifting body weight in multiple directions relative to corrective contractions of the muscles of the lower extremities and the trunk. Muscle fatigue is a complex phenomenon resulting in an exercise-induced reduction in the force-generating capacity of the muscles regardless of the task performed. The necessity of those con-tractions is expressed via the somatosensory, vestibular, and visual systems.

Impairments of the sensory systems have been associated with various pathological conditions, as well as transient physiological phenomenon, that increase the likelihood of fall or traumatic injury.

Fatigue, can affect the proprioceptive and kinaesthetic properties of joints, increase the threshold of muscle spindle discharge, which in turn disrupts afferent feedback and can alter joint awareness. The detrimental effect of fatigue on static balance has been established, but its effect on dynamic balance is unknown. To examine the ways in which fatigue affects balance, some authors have induced generalized muscle fatigue via strenuous aerobic exercise or selective muscle-fatiguing protocols. 

The relevance of fatigue to joint stability is evidenced by the relationship between postural control and the endurance of the ankle, knee and back muscles. Studies have shown the influence of foot mechanics on proximal structures i.e. core and have been studied extensively. The influence of proximal stability on lower extremity structure is known. One of the studies initially proposed that stabilization of the pelvis and trunk is necessary for all movements of the extremities. Studies have identified trunk muscle activity before the activity of the lower extremities, which authors felt served to stiffen the spine to provide a foundation for functional movements. This tendency for core instability has been suggested to predispose females to lower extremity injury. Stronger core muscles may help keep ground reaction forces (GRFs) within an optimal range. Based on previous literature and current thought, we hypothesized that fatigue would demonstrate effect on balance of the individual and significant difference in core strength. Therefore, the purpose of this study was to find out the relation between muscular fatigue and balance in normal individuals, by evaluating the static and dynamic stability and also to find if there was any change in the core muscle strength for spinal stability post induction of fatigue.

METHOD AND METHODOLOGY

The current study attempted to determine whether level of fatigue had any effect on balance & on core strength in normal individuals. To do so, experimental study design was used for this study and the study was carried out on general population in an urban region. Study approval was obtained by the institutional ethical board and an informed consent was obtained from all the subjects.

Sixty volunteers (30 men and 30 women; age range, 18-25 years; mean age, 20 ± 1.78 years) were included in the study, they were tested twice (pre and post) during same session. Any subject who had suffered a musculoskeletal injury to a lower extremity or a head injury in the 6 months before testing was excluded from the study.

The Functional reach test and single stance were used to measure the static and dynamic balance. Core strength was measured using aneroid sphygmomanometer. Subjects reported for test sessions were familiarised with the study followed by data collection for Functional reach test, single leg stance and the core strength.

Functional reach test is the measurement of difference between arm’s length and maximum forward reach in standing with a fixed base of support. (Figure 1) The subject was asked to reach as far as possible from comfortable standing posture without taking a step, losing balance and lifting the heel.

Excursion of arm from start to finish was measured with the subject standing parallel to the wall with 10 centimeters base of support. Instructions were given to avoid protraction of shoulder, flex arm near to the wall to 90 degrees and contra lateral upper limb in neutral. 1st point at tip of middle finger on wall was marked. Maintain of reach for three seconds and then again measure at tip of the middle finger. (Figure 2)

Distance between 1st and 2nd point was recorded. For the Single Leg Stance, subject was asked to perform single leg stance barefoot with the dominant leg and on the firm surface (dominant leg was found out by the ball kick test). Instructions were given to keep both the knees apart, not to touch hands to the body and to look straight and focus on any object at a distance of 1 meter. (Figure 3) Balance time was recorded until the subject could maintain the above mentioned posture without any movement.

Core Strength was measured by the pressure biofeedback method using an aneroid sphygmomanometer. Subject, in crook lying, the Cuff placed under the lumbar spine area and inflated to 40 mmHg. Subject were asked to activate core muscles (tuck in) and maintain it between 40 to 50 mmHg for 10 seconds (not more than 50 mmHg as rectus abdominis gets activated, and not less than 40 as it indicates arching of the lumbar spine.) If subject was not able to hold for 10 seconds, then rest was given for 3 minutes and asked to hold again at a lower value for 10 seconds.

Then muscular fatigue was induced. Subjects were asked to perform 90 degree squats with upper limbs in 90 degrees flexion and to be continued till rate of perceived exertion reaches 10/10 (Modified Borg Scale) that is extremely strong. The subjects were instructed to squat, as if sitting on a chair in which tibia remains relatively vertical. Subject may experience musculoskeletal or cardio respiratory fatigue. After this immediately single leg stance, functional reach test and core muscle testing was repeated.

Post fatigue measurements were compared with pre fatigue levels in single leg stance, forward reach test and core strength as well. Paired t test was used to measure pre and post performances to find any significant effects on the dependent variables with alpha set at p </=0.05.

The data thus obtained was analysed for further statistical purposes.

RESULTS

DISCUSSION

The purpose of this study was to evaluate whether fatigue affects the balance which was tested by single leg test and functional reach distance for static and dynamic balance respectively. It shows that there is a significant reduction in the single leg stance time which means the ability of the individual to maintain a stable posture is reduced. Single leg stance represents a very important phase in a normal human gait cycle. Stance phase contributes to 40% of the gait cycle. Postural control or balance can be either static or dynamic, and refers to person’s ability to maintain a stable body and body segments in response to forces that threaten to disturb the body’s structural equilibrium. Reduction in the functional reach distance can be due to diminished ability to maintain balance when the Center of Gravity and Line of Gravity shift out of the base of support in a fatigued state. This requires eccentric and isometric muscle activity by both the type 1 and type 2 muscle fibers. The key elements of muscle performance are strength, power and endurance. Studies concluded the effects of fatigue appear to be condition specific, concurring with previously reported findings that showed fatigue had more of an effect with the tandem-foam and tandem-tremor conditions. Studies also concluded that local muscle fatigue is the diminished response of muscle to repeated stimuli and is reflected by a progressive decrement in amplitude of motor unit potentials. This occurs when a muscle repeatedly contracts either statically or dynamically against imposed load. Rate of perceived exertion is an individual’s potential limitation to fatigue and is the ability to quantify the amount of fatigue to which the subjects are subjected. It would be difficult to compare the effect of fatigue on postural stability if the degree of fatigue is varied across the investigations. To rectify this, we have used the Borg RPE scale in an attempt to quantify the amount of fatigue. The RPE scale may be used as a substitute to determine exercise intensity. Using the 15-point Borg RPE scale, study showed 10 to moderate work load.

In the present study, the imposed load was the persons own body weight. Ideal squat requires greater trunk flexion to maintain balance and stronger quads contraction to support the load of the pelvis posterior to the knee axis. In repetitive squatting there is fatigue of all lower limb muscles especially glutei, quadriceps femoris, hamstrings, planter and dorsi flexors. Fatigue of the calf and thigh muscles affect postural sway in standing. Hence, the force capacity of muscles was altered. The effect of moderate fatigue on dynamic balance requires control and additional demands. In later on assessing core strength there was a difference found in the lumbar core muscle strength from 43.43 mmHg to 43.16 mmHg which was statistically significant. Research showed a clear relationship between trunk muscle stability and activity and lower extremity movement. They concluded that Core stability may provide several benefits to the musculoskeletal system, from maintaining low back health to preventing knee ligament injury & also suggested that decreased core stability may predispose to injury and that appropriate training may reduce injury suggested to contribute to the etiology of lower extremity injuries. Studies concluded that Decreased lumbo-pelvic (or core) stability contributes to the etiology of lower extremity injuries. This prospective study compares core stability measures between genders and between athletes who reported an injury during their season versus those who did not. A combination of these strength measures could be used to identify athletes at risk for lower extremity injury.

Fatigue after prolonged exercise leads to reduction in muscle glycogen. This occurs even if sufficient oxygen is available to generate energy by aerobic pathways. Fatigue leads to increase level of blood and muscle lactic acid and increase in H+ concentration in the exercising muscles. All this alters the activity of myofilaments and impairs muscular performance even when the nerve impulses continue to fire. In all when all motor units are maximally activated, fatigue is accompanied by reduction in neural activity. Here as we also see that there is affection of the lumbar core muscles post squatting, thus local fatigue will have an effect at the same site but might also produce an effect at another site in the body. So this, if not considered can be harmful.

In our everyday life, fatigue can significantly affect our balance & stability function making us predisposed to falls & injuries. A reduced muscle support to the body post fatigue will also cause abnormal joint forces and thus markedly increase the frequency of strains, sprains etc. Fatigue at distal/ peripheral area also has an effect on our core stability making us at risk of back problems & spinal damage. Thus our everyday tasks & activities should be planned & organized so as to minimize the effects of fatigue on our musculoskeletal system as with our other systems. The level of fatigue should be considered and the person should not be pushed beyond their capacity as this will increase the chance of injuries and thus reduced performance.

CONCLUSION

Muscular Fatigue causes a significant reduction in Static & Dynamic balance and also has an effect on reduction in core strength as seen in normal individuals. These results highlight the importance of proximal stabilization for lower extremity.

 Shimpi Apurv P, Kharkar Supriya A, Talreja Ankita A

References and Article at:

http://www.indianjournals.com/ijor.aspx?target=ijor:ijpot&volume=8&issue=3&article=036

Skills of Treatment Goal Setting in Physiotherapy Practices

This article is dedicated to all my little friends, my students who are the aspirant Physiotherapists of tomorrow and the constant source of our learning and motivation.

And also to all my teachers, professional colleagues and friends who have been working hard towards our professional enrichment, development and enhancement.

Have a happy friendships day.

The commonest dilemma we encounter in clinical practise as a physiotherapy student is planning the treatment concept for our patients. Although we know the general line of management, planning the detailed treatment sometimes becomes a challenge. Setting the treatment goal for the patient depends a lot on the patients’ assessment. But even here, the assessment has to be a physiotherapeutic assessment involving the patients’ functional diagnosis rather than purely the medical diagnosis. I don’t mean to say that the medical diagnosis of the patient is not important, but it does not lead us to the physiotherapy treatment. Rather, it helps us understand the red flags and the yellow flags for the patients’ treatment.

E.g., we routinely talk about OA knee, stroke, Grade III B fracture femur, PA shoulder, CABG, ACL reconstruction, TKR, Bronchitis, Spinal cord injury, GBS etc. But as Physios, we do not treat any of these problems. Rather we treat the functional impairments associated with these problems. In fact, many times, the diagnosis is purely functional based, e.g. Low back pain, neck pain, weakness etc. In short, Physiotherapy treatment is more functional impairment driven rather than structural impairment driven. Again, it’s not that we physios don’t manage any structural impairment at all. We do work on the tightness (stiffness) of the muscles, we do mobilise the joints (bread & butter of us manual therapists), we do help in clearing the chest of secretions or working on the consolidated/ fibrosed lungs to reduce the pathology, or reduce swelling (Oedema) or help in accelerating wound healing and in infection control by actinotherapy etc. But these are just a few examples of the application of physiotherapy in structural impairment. At least, to my knowledge, I have never heard of fracture healing, ACL repair, stroke management (of the infarct/ ischemia in the brain), coronary blockage clearance, articular degeneration treatment by physiotherapy.

Thus, the most crucial part is working on the functional aspect of the patient, working on the functional impairments as well as enhancing the activities and participation of the patient. This part cannot be understood without being clear in the International Classification of Functioning (ICF) aspect. ICF deals with a global, holistic approach to the patient. Rather than looking at the assessment on observation, palpation and examination in parts, it unites them together to understand the problems in totality.

E.g. Rather than observing chest movements or swelling, palpating for chest symmetry or type of swelling (pitting or non-pitting), examining for chest expansion or amount of swelling by measuring tape in isolated parts, ICF looks at the Impairment ‘reduced chest mobility’ (functional impairment) confirmed by observing chest movements, palpating for chest symmetry and examining for chest expansion by measuring tape or ‘presence of swelling/ oedema’ (structural impairment) confirmed by observing site of swelling, palpating for type of swelling (pitting or non-pitting) and examining for amount of swelling by measuring tape. This helps in identifying problems faster and planning the treatment goals with more accuracy.

Setting the treatment goals of the patients are often done looking at the patients’ short term goals. But this does not make sense as we need to know the final goal, the treatment end point. For this, the easiest method of treatment planning is the A B C D E method for goal setting:

A – Actor: Describes the patient

B – Behaviour: Describes the need of the patient. It is an important factor as it describes the level of involvement of the patient, whether the patient wants to or does not want to be compliant towards rehab.

C – Condition: Describes the need of the task the patient has to be involved in.

D – Demands of the task: Describes the demands of the task the patient has to be involved in.

E – Event time: Describes the times needed to complete the planned goal.

Example: I may have a 30 year old postman who is from a village and underwent a traumatic trans-tibial amputation on his right leg. Now the final treatment goal of this patient can be:

The patient, a 30 year old male (actor), wants to (behaviour) go back to his job as a postman (condition) and should be able to deliver the letters to all the houses by riding his cycle on the rough village roads (demands of the task) in a period of 4 months (16 weeks) (event time).

HOW????

Treatment Options can be multiple but always rationalise and choose the best possible option including the details of the therapy, dosage etc. Always have an evidence backing for your management with recent literatures from reputed journals. Best possible option means the best and most effective treatment that we can give to our patients in the given possible situation. It may or may not be the most ideal treatment. But it has to be the most practicable and realistic option being offered to the patient.

A] Short term OR Phase I/ Maximum protection phase/ (0 – 4 weeks):

1) Wound care – wound healing by IR (luminous) for 15 minutes x 2times/ day [1-2 weeks cryotherapy for controlling inflammation and pain]

2) Pain relief (VAS was 8/10) – GOAL: Pain should be VAS 2/10 in 4 weeks: TENS at 150 Hz, 4 electrodes, 2 over sciatic nerve course & 2 over L4 – S1 nerve roots on right side [Even a IFT can be used with same arrangement]

3) Strengthening (Strength was grade 3 on MMT) – GOAL: Strength should be grade 4 in 4 weeks: Active resistive exercises [Here calculating the 1RM or the RPE would be very important rather than just 10 reps x 10 count holds which is non-specific to treatment. Also rather than only strength, training for ENDURANCE is more important.]

Left lower limb closed chain strengthening (squats by holding the bed end/ railing) till RPE 6/10 on modified Borg scale.

Bilateral upper limb closed strengthening by scooting/ push ups on the bed till RPE 6/10 on modified Borg scale.

[Initiation of the strength/ endurance training can be done by open chain PRE by calculating the 1RM by dynamometer/ spring balance or calculating RPE and train the patient to 50-60% of it]

4) Range of Motion (Knee flexion was 15 – 65 degrees) – GOAL: ROM should be 0 – 90 in 4 weeks: Active ROM exercises for the knee [in intra articular stiffness/ hypo mobility, manual therapy concept with dosage (grade of mobilisation) and direction of glide to be mentioned]

5) Gait training – with axillary crutches 3 point NWB gait. Start with standing and swing-to gait progressed to swing-through gait.

B] Long term OR Phase II/ Moderate Protection phase (4 – 8 weeks)

1) Stump shaping and conditioning – Weight bearing on the stump, pressure bandaging/ shrinker for compression, bridging exercises for gluteal and back extensor strengthening.

2) Strengthening – GOAL: Strength should be grade 5 in 8 weeks by closed chain exercises till RPE 6/10 on modified Borg scale.

3) Range of motion – GOAL: Full ROM should be obtained. Active ROM exercises for the knee to be done 3-4 times in the day.

4) Pre prosthetic training – GOAL: Should be able to use PTB prosthesis with a SACH foot.

5) Gait training – with temporary prosthesis using a pylon and walker/ crutches

C] Phase III/ Minimum Protection phase (8-12 weeks)

1) Prosthetic training – Gait training with PTB prosthesis for all functional activities

2) Strengthening – Maintenance of strength by closed chain exercises till RPE 6/10 on modified Borg scale. Also focus on endurance training.

3) Proprioception training – For lower limb by single leg stance, eyes closed standing for 10 sec x 5 sets

4) Gait training – walking on even surface in controlled environment. Begin ambulation as per patients’ needs. E.g. Begin with 10 meters progressing to 100 meters in 12 weeks.

D] Return to the work training phase (12-16 weeks)

1) Gait training – uneven surface in real environment

2) Training for cycling on static cycle (12 – 14 weeks) – cycling for ½ hour x 4 times/ day x 5 days/ week

3) Training for cycling on moving cycle on controlled surface (14 – 16 weeks) – cycling for ½ hour x 4 times/ day x 5 days/ week

The treatment goal of being able to ride the cycle on the rough village roads for 8 hours/ day (intermittent) to deliver the letters should be achieved by the end of the 16 weeks. This is only an outline which can be hindered with factors like patient landing with infection/ fever due to reasons other than infection/ got transferred etc. But the minimum time frame and treatment plan is extremely important.

Also treatment has to be realistic in relation to the pathology. E.g. Instead of a Trans tibial, if this patient had a Trans femoral amputation, this above mentioned final outcome will not be possible (considering the limited technology and resources) and alternative treatment options have to be realised by both the therapist and the patient in the final goal and return to work phase.

Similar treatment plan can be done for any condition considering the pathology, healing phase, patients’ age and requirements. The part B, C & D should be based on re-assessment ensuring that the patient participates equally and is well informed of the goals of the treatment and also of the expectations from them in the rehab process. Details of the phase II, III and IV can be based on these re-assessments, but the treatment outline, goals and plan should definitely be ready even before initiation of the 1^st treatment session.

In our professional training we are typically taught the problem solving approach. We are trained to look at what is wrong with the patient and patch it up. Typically like patching the roads with tar which has developed potholes rather than focussing on making a stronger and better road right at the beginning. In ICF, the functional impairments help us formulate our short term goals which are definitely important to make the patient normal again to his pre injury status. I always like to give example of the movies ‘Koi Mil Gaya’ and ‘Krishh’. In KMG, the mentally challenged hero becomes a powerful hero at the movie end. This is typically what we do for our patients. It’s like the patient has become a zero and you are making the patient hero again. But just stopping at this phase is not good as the patient is at a risk of re-injury once again going back to his zero status, maybe with a higher level of disability. In Krishh, the lead actor becomes a superhero from his hero state. This should be the objective from our Phase III treatment onwards. Along with the problem solving approach, we should also perform something called as ‘appreciate enquiry’. We need to know what is good in the patient as well and should enhance these qualities. This will help us take the patient to a level where he learns not just to compensate for his weakness (for which we are treating and training them) but also to reach such a level of fitness and health by which he is never at a risk of landing with the injury again. This can only be obtained by knowing and focussing on the structural and functional integrity of the patient and also on the activities and participation levels of the patient. This can be further enhanced by knowing the contextual factors of the patients, especially the environmental facilitators including the architectural, technological, support systems, family and policies available for health.

We are many times ruled by the treatment protocol in patient treatment. Every protocol is extremely important in patient care as it help us keep in line each and every part of the treatment spectrum. In absence of a protocol, there is always a risk of missing out a crucial treatment link. In the example cited above, it is very important to follow the steps and sequences of the treatment. But we cannot forget the individualisation in the patients’ needs and requirements considering the patients goals. Thus protocols should form the basis of patient treatment, but it should also be individualised using the therapists’ knowledge of the patient, the condition, the pathology, and the sciences of tissue healing and the needs of the patient.

Again, in the example cited above, nowhere are we treating the structural or medical pathologies. We are looking and treating the movement dysfunction, dyskinesia’s, abnormal muscle recruitments, sensory dysfunction, functional loss and loss of involvement in daily life’s situations. Thus, as physiotherapists, we should be more trained in understanding and assessing these problems and managing them rather than conditions and medical diagnosis. There may be surely other views and opinions on the same and they all are respected and welcomed. No way is medical diagnosis lesser important to be learnt and understood. It, many times, helps us in re-assessment or understanding the problem being treated. It also helps us all to speak the same common language of patient care between all the care giving professionals. But as physiotherapists, we should also be focussing more on physiotherapeutic assessment and diagnosis and treatment as well.

Thus, I would again like to say that planning the clients treatment plan is an art, a science and also a commerce as it involves not only the skills of treatments, the evidences and the logics behind it backed by an efficient research methodology and publications but also involves the financial management of treatment expenses, of learning to have a proper documentation of the treatment procedures and also of the financial transactions, payment receipts and bills, legal knowledge of the laws and legislature of the state in relation to Physiotherapy practices, partnering with the professional councils and associations governing profession and the professionals and very important, being accountable and answerable to your clients, your own self and finally to GOD who blessed us all in this noble and honourable profession.