ABSTRACT
Background:
Physical fitness related to health is crucial for maintaining and enhancing an individual’s general health. In recent times, it has become crucial to be aware of fitness among adults due to its significance in reducing serious conditions and maintaining good health. However, there are insufficient data on the Indian population regarding the correlation among the components of physical fitness. Therefore, the main objective of this research was to examine the relationships among several aspects of fitness for health.
Methods:
In this research, a total of 419 respondents were screened after having approval from the institution ethical board. A Herpenden skinfold caliper was used to determine their body fat %, while a gas analyzer was used to determine their VO2 max. A computerized dynamometer was used to evaluate their handgrip strength and endurance. The Pearson correlation coefficient and student t-test were applied for statistical analysis.
Results:
The research found a positive relationship between VO2 max and handgrip strength (r = -0.465), and a negative association (r = -0.466) was observed between body fat percentage and VO2 max. Similarly, a negative association (r = -0.365) was observed between body fat percentage and grip strength.
Conclusion:
The study concludes that an individual’s cardiorespiratory and muscular fitness are negatively linked with body fat percentage but positively associated with each other. The research findings can be used to assess physical fitness and promote awareness about the benefits of fitness and lifestyle changes using measures of their cardiorespiratory and muscular fitness.
Keywords: Body fat percentage, cardiorespiratory fitness (CRF), maximal aerobic capacity (VO2 max), muscle strength, muscular endurance
Introduction
Health-related physical fitness has been defined as “the capacity to carry out everyday tasks with vigour, alertness, and without becoming exhausted, as well as the characterstics and capabilities that are linked with a minimal risk of chronic illness and early death.” The five factors are flexibility, muscle strength, endurance, cardiorespiratory fitness, and bodyfat content.[1]
Maximal aerobic power, also known as cardiorespiratory fitness, is the capability of the heart and lung as a whole and the capacity to engage in sustained, severe exertion.[2] The single best indicator of cardiorespiratory fitness is the ‘VO2 max’ attained throughout a progressive maximum activity to voluntary fatigue.[3]
Muscular Fitness: Muscular fitness is defined as the body’s capacity to generate and maintain muscle force through the contraction of skeletal muscles. Muscular endurance is commonly measured in muscle strength (maximum strength) and muscle endurance (maximum repetitions).[2]
Body composition is a health-related aspect of physical fitness that is concerned with the proportions of bone, muscle, fat, and other important body elements.[2]
Primary care physicians can use VO2 max and body fat % measurements to evaluate a patient’s general health and risk factors, especially for cardiovascular disease. In primary care, reducing constraints to exercise and motivating patients to participate in regular physical activity are key components of promoting health-related physical fitness. As part of this, patients’ levels of physical activity are evaluated, and appropriate exercise regimens, such as aerobic and muscle-strengthening exercises, are recommended.[4] Poor physical health is linked to both total mortality and life quality. Strength of hand grasp is a significant health biomarker. Its usefulness encompasses the detection of various health conditions and its potential as a novel vital sign for people of all ages.[5]
It is important to remember that physical fitness involves a variety of physical activities, including cardiorespiratory fitness, muscle fitness, and body composition. Nowadays, it has become very important to know about fitness among adults due to its important role in reducing the symptoms of conditions such as diabetes mellitus, metabolic syndrome, and coronary heart disease and in promoting overall good health. Cardiorespiratory fitness and muscular fitness share a common beneficial outcome in all-cause mortality and morbidity.[6]
However, no sufficient data on the Indian population are there, which entails the correlation among the abovementioned components of health-related fitness, that is, cardiorespiratory, muscle strength, muscular endurance, and body fat percentages. As a result, the current study’s goal was to examine and correlate VO2 max, muscular strength, and body fat % components of health-related physical fitness.
Methods
Study design and setting: The current ‘cross-sectional’ research was carried out at the Lab in the Physiology department with permission from the Institution Ethics Board, ‘RUHS-CMS/Ethics Comm-2018/148’ dated 21/12/2018.
Study duration: The study was conducted between January 2019 and January 2020.
Sample size and sampling: The sample size (419) was calculated on the basis on the prevalence of “45.6%” physically fit people in the ICMR-INDIAB (2014) research.[7] The study’s sample was compiled using the convenient method of nonrandom sampling.
Inclusion Criteria: Students between 18 and 25 years old who appear healthy and who agree to consent must be of both genders.
Exclusion criteria: The study excluded people who smoked or drank or had diabetes, heart disease, lung disease, musculoskeletal disease, or a history of being hospitalized during the prior 3 months.
Data collection tools:
The ‘’National Health and Nutrition Examination Survey (NHANES)’’[8] was used to measure the anthropometric measurements, which comprised height, bodyweight, and skinfold thickness. Body fat % was calculated using the Durnin and Womersley (1974) body fat percentage chart[9] after skin-fold measurements were taken from four locations, including the biceps, triceps, sub-scapular, and supra-iliac.
Assessment of cardiorespiratory fitness: VO2 max was directly measured using the Gas Analyzer from AD Instruments (model-ML206). The detailed descriptions were explained and shown to the participants before proceeding. The participants had to put on a mask that was attached to a device that kept records of the total volume of gas they breathed and expired throughout the test. Subjects were first instructed to walk for 3 minutes at a level grade, followed by 3 minutes of jogging at the speed they preferred (between 4.3 and 7.5 mph). The ‘treadmill grade’ was increased by 2.5% every minute until the subject became too exhausted to carry out the test, as per the ‘treadmill graded exercise test protocol’[10] [Figure 1].
Figure 1.
Recording of maximal oxygen consumption using the Gas Analyzer of AD Instrument (ML-206)
Figure 1 shows a subject exercising on a treadmill wearing a mask whose airflow is being recorded on the monitor display through a gas analyzer.
Muscular fitness assessment: The muscular fitness assessment was done as per the guidelines given in the hand grip strength Procedures Manual published by “the National Health and Nutrition Examination Survey (NHANES)”.[8] The subjects were asked to sit erect on the stool with the arm in a mid prone position and the elbow flexed at 90 degrees. Maximum hand grip strength and static and dynamic endurance parameters were measured using a digital physiograph (model-MLT004/ST Grip Force) sequentially with a rest period of 3 min between each maneuver[11] [Figure 2].
Figure 2.
Measurement of maximal handgrip strength
Figure 2 shows that a subject is given a hand grip strength measurement.
Data analysis: Data are entered into Microsoft Excel after collection. To ascertain if the data distribution was normal or not, the Smirnov test was utilized. Using an independent t-test, the ‘mean differences’ and ‘standard deviation’ of the variables between the participants were examined. Significant value was defined as a 0.05 P value or lower. For correlation analysis on VO2 max, grip strength, and body fat percentage, Karl Pearson’s correlation coefficient was applied.
Ethical consideration: The research was conducted after obtaining approval from the institution’s ethical board (RUHS-CMS/Ethics Comm-2018/148). The participants were informed that they could withdraw from the study at any point without any negative consequences. All participants’ personal information was kept confidential throughout the study period survey.
Results
419 students who appeared to be in good health participated in the current investigation (275 males and 144 females).
Table 1 depicts a comparative analysis of study parameters among male and female participants. The result shows that significant differences were found in weight, height, BMI, body fat %, physical activity, VO2 max, and hand grip strength. Males were found to have considerably higher mean values for BMI, physical activity, VO2 max, and hand grip strength than females, while females had higher mean body fat percentages than males.
Table 1.
Demographics and physiological parameters of participants
| Parameters | Gender | Mean | t | P |
|---|---|---|---|---|
| Age | M | 20.34±2.02 | 0.57 | 0.566 |
| F | 20.22±2.02 | |||
| Body weight (kg) | M | 65.45±9.68 | 11.65 | <0.00 |
| F | 54.28±8.54 | |||
| Height (cm) | M | 172.70±5.61 | 22.16 | <0.00 |
| F | 159.99±5.50 | |||
| BMI (kg/m2) | M | 21.94±2.99 | 2.33 | <0.02 |
| F | 21.21±3.09 | |||
| Body fat % | M | 14.51±4.74 | 15.19 | <0.00 |
| F | 22.82±6.27 | |||
| Physical activity (METs) | M | 1433.82±721.98 | 7.99 | <0.00 |
| F | 909.58±431.74 | |||
| VO2 max (ml/kg/min) | M | 45.30±7.35 | 13.87 | <0.00 |
| F | 35.71±5.29 | |||
| Hand Grip strength (kg) | M | 41.53±7.49 | 15.26 | <0.00 |
| F | 29.94±7.14 | |||
| Static endurance (sec) | M | 16.66±6.20 | 0.67 | 0.499 |
| F | 16.24±5.42 | |||
| Dynamic endurance (sec) | M | 136.411±26.65 | 0.87 | 0.382 |
| F | 133.90±29.97 |
*P: Probability value, P<0.05 (significant), M - Male, F - Female
Table 2 shows the Pearson’s correlation between various parameters. A positive association between VO2 max and hand grip strength is shown. However, there was a moderate inverse relationship between body fat percentage, VO2 max, and hand grip strength.
Table 2.
Karl Pearson’s correlation coefficients
| Parameters | Body fat % | VO2 max (ml/kg/min) | Grip strength (kg) | Static endurance (sec) | Dynamic endurance (sec) | |
|---|---|---|---|---|---|---|
| Body fat % | r | 1 | -0.466 | -0.465 | -0.151 | -0.032 |
| p | <.001 | <.001 | 0.002 | 0.517 | ||
| VO2 max (ml/kg/min) | r | -0.366 | 1 | 0.433 | 0.065 | -0.086 |
| p | .<001 | <.001 | 0.184 | 0.079 | ||
| Handgrip strength (kg) | r | -0.365 | 0.433 | 1 | 0.057 | -0.009 |
| p | <.001 | <.001 | 0.244 | 0.860 | ||
| Static endurance (sec) | r | -0.151 | 0.065 | 0.057 | 1 | 0.103 |
| p | 0.002 | 0.184 | 0.244 | 0.035 | ||
| Dynamic endurance (sec) | r | -0.032 | -0.086 | -0.009 | 0.103* | 1 |
| p | 0.517 | 0.079 | 0.860 | 0.035 | ||
* p-value: Probability value, r = Correlation coefficient
Graph 1 depicts a significant moderate correlation (r = -.466, P = .000) between body fat % and VO2 max.
Graph 1.
Correlation between body fat % and VO2 max
Graph 2 depicts a moderate significant correlation (r = -.465, P = .000) between body fat % and hand grip strength.
Graph 2.
Correlation between body fat % and grip strength
Graph 3 depicts a moderate significant correlation (r = 0.433, P = 0.000) between maximal oxygen consumption (VO2 max) and hand grip strength.
Graph 3.
Correlation between VO2 max and hand grip strength
Discussion
To examine the association between VO2 max, grip strength, endurance, and body fat percentage, the current study included 419 participants aged 18 to 25 years. Adequate levels of cardiorespiratory capacity and handgrip strength may help reduce risk factors for diseases in future.[12]
According to Table 1, the average body fat % for the male and female participants was 14.51 ± 4.74 and 22.82 ± 6.27, respectively. This is comparable to a study by Sharma HB et al.,[13] which found that the average body fat percentage for men and women was 17.42 ± 4.30 and 26.02 ± 3.06%, respectively.
Male participants in the present study had significantly higher mean VO2 max values than female participants, 46.83 ± 9.48 and 35.94 ± 9.8 ml/kg/min, respectively. Similar to the findings of the current investigation, Srivastava S et al.[14] found that the VO2 max of the males was substantially greater than that of the females (52.37 ± 8.78 vs. 40.96 ± 4.06 ml/kg/min). Due to hormonal, physiological, and behavioral influences, men have higher levels of blood hemoglobin, lower fat percentages, more lean mass, a large heart with a greater ability to deliver oxygen, a faster maximum heart rate, a larger maximal stroke volume, and a higher physical activity compared than women.[15]
In the present study, male and female hand grip strengths differ significantly (41.53 ± 7.49 kg; 29.94 ± 7.14 kg), which is similar to research done by Koley S et al.[16] that found that the grip strength in males and females was 41.31 ± 6.39 kg and 28.82 ± 3.71 kg, respectively. A study done by Uz Zaman et al.[17] also has similar findings.
The physiological rationale for this is that males have more muscular mass, are taller, and have longer forearms than females, which results in more contractile tissues and a stronger grip.[18] Increased satellite cells have been linked to the male hormone testosterone (precursors of skeletal muscle cells). Males have a large proportion of type 2 fibers, which are rapid fibers with higher glycolytic enzyme activity and have the capacity to produce more force. Testosterone also boosts type II fibers.[19]
In the present study, it was observed that static (16.16 ± 6.20 sec; 16.24 ± 5.42 sec) and dynamic endurances (136.41 ± 26.65; 133.90 ± 29.97 sec) of males and females have no significant difference. On the contrary, a study conducted by Baxi G et al.[20] in the 18–25 years age group found a significant difference among males (38.66 ± 20.24 s; 48.63 ± 24.34) and females (45.05 ± 20.81; 59.95 ± 25.02 s) for static and dynamic endurance; this difference can be attributed to differences in muscle fiber composition in both genders. Compared to men, women have a higher % of type 1 muscle fibers, which exhaust more quickly. On the other hand, a study conducted by Gupta M et al.[21] reported that males (43.55 ± 28.84 s) have higher static endurance than females (32.38 ± 21.25 s).
According to the current study, there is a moderate and positive association between hand grip strength and maximal oxygen consumption (VO2 max) (r = 0.436, P = 0.000), which is similar to a study by Vaidya SM et al.[22] that also found a moderate and positive association between maximal oxygen consumption and hand grip strength (r = 0.720, P = 0.05) and another study by Mandal N et al.[23] that found a significant positive relation between VO2 max and handgrip strength (r = 0.925, P = 0.05). The findings of the current study are further supported by Dag F et al.[24] observation that grip strength was favorably connected with VO2 max (r = 0.36).
The theory is that changes in muscle protein balance caused by more mitochondria can explain the physiological basis for decreased handgrip strength in people who exercise less aerobically. Muscular strength is decreased because a lack of aerobic exercise increases inflammatory mediators including tumor necrosis factor-alpha (TNF-alpha) and cytokines. Reduced IGF-1 results in a loss in muscle mass because inflammation and insulin-like growth factor-1 (IGF-1) levels are inversely correlated, and TNF causes cell death in muscles, impairing muscle function. Muscle protein balance is maintained during aerobic exercise by regulating the production and degradation of muscle protein and increasing skeletal muscle development. A lack of aerobic activity also causes an increase in body fat, which is then stored inside muscle fibers and impairs skeletal muscle performance.[25]
Body fat percentage and maximum oxygen uptake (VO2 max) were found to be negatively correlated in the current study (r = -0.407), which is similar to a study by Mondal H et al.[26] that found VO2 max and body fat percentage to be negatively correlated (r = -0.750). It is believed that having a lot of body fat places an unfavorable strain on cardiac function and the uptake of oxygen by working muscles, which is why there is a negative correlation between VO2 max and body fat. Additionally, this connection has shown that adipose tissue’s decreased capacity to utilize oxygen during exercise lowers total VO2 max. An increase in type II muscular fibers and a decrease in type I fibers in individuals with higher body fat percentages are contributing factors to decreasing VO2 max.[27]
Similar to a study by Lad UP et al.[28] on healthy young adults, who found a moderate and negative correlation (r = -0.461, P = 0.05) between handgrip strength and body fat%, the current study found a negative and moderate correlation between the study population’s body fat% and hand grip strength in dominant and nondominant hands (r, -0.465 and -0.485). A study by Saini S et al.[29] also found a modestly negative relationship between hand grip strength and body fat percentage, which is consistent with the findings of the current investigation. This is due to the physiology of obesity, which involves changes in the distribution of type I and type II muscular fibers as well as infiltration of fat.[30]
In summary, VO2 max and hand grip strength tests can provide important information about a patient’s health condition, offering more accurate risk assessments and focused interventions in primary care settings.
Conclusion
We can assess an individual’s physical fitness and spread awareness of physical activity and lifestyle change using estimated VO2 max, hand grip strength, endurance, and body fat percentage. Present study results conclude that body fat percentage affects cardiorespiratory and muscular fitness. The present study concludes that though the cardiorespiratory and muscular fitness of an individual are positively coupled with each other, they both are negatively associated with body fat percentage. Thus, the present study suggests that the cardiorespiratory and muscular fitness of an individual can be enhanced by focusing on decreasing the body fat percentage. This will lead to a definite improvement in the overall physical fitness of an individual.
Limitation
The current study was conducted on a limited age group; therefore, additional research in a larger age range is necessary to fully understand the correlation between the components of fitness.
Conflicts of interest
There are no conflicts of interest.
Acknowledgment
We would want express our gratitude to thank all the physiology experts and participants.
Funding Statement
Nil.
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