5. Availability of oxygen

resting muscle because it has acid reaction so it relaxes slowly unlike the fresh resting muscle which is alkaline.

Many muscle properties change during fatigue including the action potential, extracellular and intracellular ions, and many intracellular metabolites. A range of mechanisms have been identified that contribute to the decline of performance. Apart from the traditional explanation, that is, accumulation of intracellular lactate and hydrogen ions causing impaired function of the contractile proteins, alternative explanations considered are the effects of ionic changes on the action potential, failure of sarcoplasmic reticulum Ca2+ release by various mechanisms, and the effects of reactive oxygen species2. Muscle fatigue may be due to precise molecular changes that occur in vivo with sustained exercise. It has been found that the ryanodine receptor present in skeletal muscle undergoes a conformational change during exercise, resulting in "leaky" channels that are deficient in calcium release. These "leaky"

channels may be a contributor to muscle fatigue and decreased exercise capacity3.

So to summarize the main causes of fatigue, it can be due to:

1.Exhaustion of acetylcholine at motor end plate

2.Accumulation of metabolites like lactic acid and phosphoric acid

3.Lack of nutrients like glycogen

4.Lack of oxygen

During isotonic contraction, muscles get a chance for liberal blood flow during relaxation. That is why, circulatory occlusion hastens the onset of fatigue to a much greater extent4. It has been proved through various experiments that fatigue developing in maximal voluntary muscular effort first occurs in central nervous system followed by neuromuscular junction and lastly in the muscle proper. Thus, in the intact body, the sites of fatigue are in following order:

1.Betz(pyramidal) cells in cerebral cortex

2.Anterior gray horn cells ( motor neurons) of spinal cord

3.Neuromuscular junction

4.Muscle proper5

In the present era of modernization, human beings,

specially young adults have mostly restricted themselves to static lifestyle with lesser physical movement. This has led to an abnormal increase in weight which has been found to be associated with various diseases like cardiovascular diseases, type 2 diabetes mellitus, obstructive sleep apnea, certain

cancers and osteoarthritis in future. A reliable indicator for body fat is BMI6,7. The BMI is an attempt to

quantify the amount of tissue mass (muscle, fat, bone) in an individual and then categorize that person as underweight, overweight or obese based on that value. Thus, the present study was conducted to correlate body mass index (BMI) and muscle fatigability in young healthy adults using Mosso's Ergograph.

METHODOLOGY

STUDY DESIGN: The present study was conducted in the Department of Physiology of Era's Lucknow Medical College & Hospital (ELMC&H), Era University, Lucknow.The duration of this study was 6 months from the time of obtaining ethical clearance from the institute's ethical committee.

SAMPLE POPULATION

Both male and female young, apparently healthy attendants of patients visiting the OPD of Era's Lucknow Medical College & Hospital in the age range of 18-24 years8 were selected for the study. Subjects with a history of alcohol and tobacco consumption, history of chronic illness like cardiovascular, tuberculosis, hypertension etc, history of diabetes and subjects receiving drugs( corticosteroids, beta

blockers) were excluded from the study.

All the subjects fulfilling the inclusion criteria and not falling into the domain of exclusion criteria were invited to enroll in the study till the sample size requirements were fulfilled. All subjects were explained about the protocol of the study and a written informed consent was obtained.

SAMPLE SIZE

Sample size was calculated based on the study done by Smisha Mohan, Bagavad Geetha M and Padmavati R1 on the basis of the formula:

n= Zα2σ2 d2

Where, = 3.6, standard deviation of work done

detecting results with 90% power of stats.

Then sample size comes out to be: n=100

After enrolment, a general and systemic examination was done and a proper case history was recorded to confirm that the subjects selected were apparently healthy. These subjects then underwent recording of anthropometric parameters like height( in metres) and weight( in kilograms) and Body Mass Index(BMI) was calculated.

The WHO Criteria for various subgroups of Body

Mass Index was taken into consideration (9) i.e.

In this study the muscular fatigue was recorded as a function of the amount of work done by the exercising muscle using Mosso's Ergography.

DETERMINATION OF FATIGUE BY MOSSO'S

ERGOGRAPHY

A spring loaded writing ball point pen and a paper on the platform underneath was arranged in the Mosso's Ergograph. The forearm of the subject was fixed on the ergograph by means of clamps. The middle finger was put in the loop to be pulled and the index and the ring fingers were inserted into the fixed metal tubes provided in the ergograph. The subject's position was adjusted at various adjustable points in the ergograph is such a way that the

Subject's forearm was properly fixed and at the same time the subject was comfortable.

With the middle finger extended, a weight of 1.5 kgs was suspended on the ergograph. The subject was asked to make a series of maximal contractions without moving the shoulder. The contractions were continued until fatigue was so great that weight could no longer be lifted.

Outcome of the procedure was noted in terms of work done in Kg.m.

Table 1. shows that the mean work done in the underweight subgroup was found to be 3.01±1.12 Kg.m, normal subgroup was 3.54±1.67 Kg.m, overweight subgroup was 3.78±1.68 Kg.m and in the obese subgroup was 3.84±1.29 Kg.m with the mean age being 20.03±2.19 years, 20.53±1.97 years, 20.81±2.26 years and 21.6±2.2 years respectively.

Fig.1 Mosso's Ergograph: Image

STATISTICALANALYSIS

∙The data so collected was subjected to statistical analysis using Statistical Package For Social Sciences (SPSS) version 20.0

∙To correlate BMI with muscle fatigue ( which is a function of work done by the specific muscle) Pearson's Correlation was applied.

∙To analyze any statistically significant differences between the means of different categories of BMI i.e. underweight, normal, overweight and obese, in both males and females separately and also combined, One- Way ANOVA was used.

∙The confidence limit of the study was 90% hence a 'p' value less than 0.05 was considered to be statistically significant.

∙Generation of graphs and tables were done by Microsoft Excel and Microsoft Word version 2007.

OBSERVATION AND RESULTS

The study was carried out to observe correlation between Body Mass Index (BMI) and muscle fatigue in young adults.

Table 1 : Shows comparison of demographic and

clinical characteristics amongst underweight, normal,

overweight and obese subjects.

Values are Mean±SD; BMI=Body Mass Index; Analyzed

with one way ANOVA

Fig 2: shows overall scatter plot correlation of

work done(Kg.m) with BMI

DISCUSSION

Skeletal muscle is a fascinating biological tissue able to transform chemical energy to mechanical energy. The production of movement and force is the mechanical outcome of skeletal muscle contraction1.

Physical inactivity contributes to weight gain in adults7. Several studies suggest that an active lifestyle during childhood and adolescence can play an

important role in optimizing growth and development(10,11). Muscle function testing is used to

measure muscle contraction, fatigue, endurance, strength and physical capacity under varying conditions.

During exercise, it has been observed that defects in Ca2+ release from the sarcoplasmic reticulum impairs muscle function. Andrew M. Bellinger et al in 20083 suggested a possible mechanism by which Ca2+ leak via calstabin1-depleted Ryanodine (RyR1) channels leads to defective Ca2+ signaling, muscle damage and impaired exercise capacity.

With this background, the present study was carried out to correlate Body Mass Index (BMI) and muscle fatigue in young adults.

Kader NA et al in the year 201512 found a positive correlation of work done with Body Mass Index ®= 0.44) which was statistically significant(p<0.001) which coincides with the results of the present study that also shows a positive correlation in the Normal(r=0.05) and Obese( r=0.21) subgroups of BMI. These results also stand in accordance with Mafffiuletti et al in 200813 who reported significant higher absolute voluntary muscle strength in obese

adolescents which was attributed to working at a shorter muscle length to avoid excessive stress during an activity or sport or to avoid injury. However, the results are in contradiction to the study conducted by Blimkie et al in 199014 who reported no significant difference between obese and non-obese groups. This may be attributed to a comparatively smaller sample size. Besides, it may also be attributed to the fact that a fixed weight of 1.5 kg was used for lifting by the exercising muscle to calculate the work done which cannot clearly define the degree of fatigueness in various subgroups of Body Mass Index.

Smisha Mohan et al in 20161 reported that sedentary individuals goes into fatigue sooner because of inadequate supply of nutrients like oxygen, creatine phosphate, ATP and depletion of neurotransmitters and accumulation of metabolites in the muscles earlier than the exercising individuals. Robert Fitts in 199415 suggested that factors which influence onset of fatigue are type of muscle fibres, training and blood flow.

Hence, a positive correlation between Body Mass Index and amount of work done by the exercising muscle suggests that the level of fatigueness in an individual is related to his/her physical fitness, socio- economic status and nutritional status. A poorly nourished individual with a lower BMI(<18.5 kg/m2) showed a significant decrease in the work done capacity while a higher BMI(>=30 kg/m2) showed a greater absolute maximal muscle strength suggesting that increased adiposity possibly acts as a chronic overload stimulus on the exercising muscles.

CONCLUSION

Thus, this study prompts for aiming at maintaining physical fitness which can result from a healthier lifestyle in young adults which includes regular exercise, healthy dietary habits and refrainment from tobacco smoking and alcohol consumption that shall go a long way in increasing their work efficiency and productivity with lesser fatigability.

STUDY LIMITATIONS AND FUTURISTIC

PERSPECTIVES

Though , it is a small study, but on the basis of the conclusions drawn, further research work can be undertaken with a larger sample size to ascertain any significant relation between subgroups of Body Mass Index viz. underweight, normal weight, overweight and obese with the degree of fatigability in these subgroups.

REFERENCES

1.Mohan S, Geetha M B, Padmavathi R; Study of

m u s c l e f u n c t i o n i n y o u n g a d u l t s : Sch.J.App.Med.Sci 2016; 4(7A): 2348-2352

2.Allen D G, Lamb G D, Westerblad H; Skeletal Muscle Fatigue: Cellular Mechanism: Physiol Rev 2008; 55: 2, 88-332

3.Bellinger A M, Reiken S,Dura M, Murphy PW,

Deng S, Landry DW et al; Remodeling of

ryanodine receptor complex causes leaky channels: A molecular mechanism for decreased exercise capacity: Proceedings of the National Academy of Sciences of the United States of America 2008; 105(6): 2198- 202

4.Jain AK. Textbook of Physiology. 6th Edition. Sirmour. Avichal Publishing Company; 2016;Ch.21: 750-751: ISBN 978-81-7739-476-4

5.Ghate US, Indapurkar KV; Study Association between Dhatu Sarata and Mosso's Ergography: Int J Ayu Pharm Chem 2017; 6(1): 150-158

6.Holzbaur KRS, Delp SL, Gold GE, Murray WM; Moment generating capacity of upper limb muscles in healthy adults: J Biomech 2007; 40(11): 2442-2449

7.Andersen RE, Crespo CJ, Bartlett SJ, Cheskin LJ, Pratt M; Relationship of physical activity and television watching with body weight and level of fatness among children: results from the Third National Health and Nutrition Examination Survey: JAMA 1998; 279: 938-942

8.About the Youth Programme| United Nations Educational, Scientific and Cultural Organization [Internet]. Unesco.org.2018[ cited 15 September 2018].Available from: http://www.unesco.org /new/en/social-and-human-sciences/themes/ youth/about-youth/

9.Mean Body Mass Index (BMI)[ Internet]. World Health Organization.2018[ cited 15 September 2018].Available from: http://www.who.int/gho/ ncd/risk_factors/bmi_text/en/

10.Physical Activity & Health: A Report of the Surgeon General (1996) [Internet]. Profiles.nlm. nih.gov.2018[ cited 15 September 2018]. Available from: https://profiles.nlm.nih.gov/ ps/retrieve/ResourceMetabase/NNBBHB

11.Cooper D M; Evidence for and mechanisms of exercise modulation of growth: Med Sci Sports Exerc. 1994; 26: 733-740

12.Kader NA, Hasan AK, Kamal HM, Hussein ZA; Relation between body mass index percentile and muscle strength and endurance: The Egyptian Journal of Medical Human Genetics 2016; 17: 367-372

13. Mafiuletti N A, Jubeau M, Agosti F, De Col A, Sartorio A; Quadriceps muscle function

characteristics in severely obese and nonobese adolescents: Eur J Appl Physiol. 2008; 103(4):481-4.

14.Blimkie C J R, Sale D G, Bar-Or O; Voluntary strength, evoked twitch contractile properties and

motor unit activation of knee extensors of obese and non obese adolescent males: Eur J Appl Physiol 1990; 61: 313-318

15.Fitts RH; Cellular mechanism of muscle fatigue: Physiol. Rev 1994; 74: 49-94

▄▄ ▄