|Year : 2020 | Volume
| Issue : 1 | Page : 26-30
The effect of strength training of the calf muscle pump on cardiovascular parameters
Andrew Lalchhuanawma1, Divya Sanghi2
1 Department of Physiotherapy, Manav Rachna International Institute of Research and Studies, Faridabad, Haryana, India
2 Faculty of Applied Sciences, Manav Rachna International Institute of Research and Studies, Faridabad, Haryana, India
|Date of Submission||09-Mar-2020|
|Date of Decision||18-Apr-2020|
|Date of Acceptance||21-Apr-2020|
|Date of Web Publication||20-Jun-2020|
Dr. Andrew Lalchhuanawma
C-47, Ramhlun Venglai, Aizawl - 796 001, Mizoram
Source of Support: None, Conflict of Interest: None
Background: The heart pump allows blood to flow where the network of arteries, capillaries, and veins throughout the body regulates the rate of circulation of the blood. Parameters that determine the fitness level of the cardiovascular system include heart rate (HR), blood pressure (BP), VO2 max, fatigue, etc., The calf muscle pump is the most important of the lower limb, as it is the most efficient and has the largest capacitance. It has been suggested that increased leg strength, independent of cardiovascular training, may augment an aerobic endurance performance. Aim: The aim of this study is to determine the effect of strength training of gastrocnemius and soleus muscles on cardiovascular parameters. Materials and Methods: An experimental study carried out at MRIIRS Institution for 1 year. Forty-five recreational players aged between 20 and 30 years were selected after obtaining informed consent. Participants were divided equally into three groups by a convenient chit method. They were assessed for cardiovascular parameters of HR, BP, VO2 max, fatigue, and FI at baseline and after 8 weeks training program. Group A participated in gastrocnemius and soleus; Group B participated in gastrocnemius, and Group C participated in the soleus muscle training program. Results: Paired t-test for pre–post training shows a significant difference P < 0.05 for all the groups. ANOVA used between groups pre–post training were found to be significant for HR and systolic BP (SBP), and nonsignificant for diastolic BP (DBP) and VO2 max. Kruskal–Wallis test used between groups before and after training was found to be significant for fatigue and fitness index (FI). Jonckheere-trend test Post hoc analysis showed that Group A performed better than Group C and B. Wilcoxon signed-rank test for fatigue and FI showed a significant difference for all the groups. Conclusion: Eight weeks of leg muscle training on cardiovascular parameters have an effect on cardiovascular parameters of HR, SBP, FI, and fatigue. The results showed no significant effects on DBP and VO2 max.
Keywords: Calf muscle, cardiovascular parameters, fitness, pump, strength training, VO2 max
|How to cite this article:|
Lalchhuanawma A, Sanghi D. The effect of strength training of the calf muscle pump on cardiovascular parameters. Arch Med Health Sci 2020;8:26-30
|How to cite this URL:|
Lalchhuanawma A, Sanghi D. The effect of strength training of the calf muscle pump on cardiovascular parameters. Arch Med Health Sci [serial online] 2020 [cited 2020 Oct 27];8:26-30. Available from: https://www.amhsjournal.org/text.asp?2020/8/1/26/287357
| Introduction|| |
The cardiovascular system, in its simplest form, is a system that consists of a pump, pipes, and a fluid system. The system is a closed circuit, which is elastic, thereby allowing movement and stresses to occur without damaging it. The pump in this system is the heart which allows the blood to flow in. The network of arteries, capillaries, and veins throughout the body regulates the rate of circulation of the blood. There are parameters that determine the fitness of the cardiovascular system, among these are heart rate (HR), blood pressure (BP), VO2 max, fatigue, etc.
In athletes, the heart undergoes changes in response to systematic athletic training. These changes result in morphological function and electrophysiological alteration, which have collectively been recognized as athletic heart syndrome. The heart becomes more hypertrophic and performs better in getting blood to working muscle, referred to as cardiac output. Regular training causes the heart to enlarge, resulting in the combination of left ventricular enlargement (dilatation) and increased wall thickness (hypertrophy), clinically known as the athlete's heart.
Maximal oxygen consumption, also known as VO2 max is the amount of oxygen consumed under maximal aerobic metabolism. It has long been considered the gold standard for determining cardiorespiratory fitness level. In athletic events, a large amount of energy is needed to perform the task, which is produced through the use of oxygen. It is estimated that 25% of total energy comes from oxygen in events lasting 40–60 s, whereas in longer events such as distance running 90%–95% of the energy comes from the aerobic source. In general, athletes participating in endurance sports possessed higher VO2 max than those individuals associated with short duration, high intensity oriented sports such as weightlifting and sprinting.
The muscle pumps of the lower limb include those of the foot, calf, and thigh. Among these, the calf muscle pump is the most important, as it is the most efficient, and has the largest capacitance and generates higher pressures. With a single contraction, the normal limb has a calf volume ranging from 1500 to 3000 cm 3, a venous volume of 100–150 cm 3, and ejects over 40%–60% of the venous volume., Evidence suggests that dynamic exercise increases blood flow as compared to continuous isometric exercise. During dynamic exercise, the muscle pump plays an important role in the initial increase and the maintenance of blood flow as blood flow increases between contractions, even for low-intensity exercises.,
Researchers suggest an increased leg strength, independent of cardiovascular training, may augment VO2 peak and aerobic endurance performance. Conley and Rozenek reported that high volume resistance training, consisting primarily of multi-joint exercise movements of the leg musculature, increases aerobic metabolism between 8% and 10%. Although the exact physiological mechanisms responsible for the change in aerobic metabolism are unknown, it could be attributed to the skeletal muscle improvement in oxygen delivery and utilization of the periphery, vascular, or cardiac.
A single contraction of the calf muscle pump ejects over 40%–60% of the venous volume into the popliteal and femoral veins. Walking reduces venous pressure from 100 mmHg to 22 mmHg in a few steps. Similar changes in pressure are observed in the heel raise, and the hydrostatic pressure (venous fill time) is restored after 30 s of contraction. On heel raise with knee extension, the maximal work is done by gastrocnemius as compared to soleus muscle, and the maximal work is done by soleus on heel raise with knee flexion and a 70% drop in gastrocnemius action.,, In clinical practice, evaluating the calf muscle pump function helps athlete maintain their endurance to the optimal level, increase their tolerance to fatigue, and assist in cardiac rehabilitation.
To the best of our knowledge, the contribution of calf muscle strength on the cardiovascular system and its parameters has not been determined. Only a relative handful of researchers have specifically determined the effects of intensive leg strengthening combined with aerobic training on VO2 max, short- and long-term aerobic endurance, and aerobic power.,,, The aim of the study was to identify the effect of strength training of gastrocnemius and soleus muscles on cardiovascular parameters and to determine which calf muscle performed better.
| Materials and Methods|| |
The study was performed at the Institutional outpatient department, physiotherapy unit, Faridabad for a period of 1 year (October 2018–September 2019). A total of 45 male recreational players aged between 20 and 30 years who were able to attend all training sessions were selected for the study after obtaining informed consent. Permission for the study was obtained from the Institutional Ethical Committee, Manav Rachna International Institute of Research and Studies. Individuals with acute and chronic injuries of the ankle and foot, knee, hip, abdominal and back pain pathology, history of acute or chronic peripheral vascular disease, smoking history for 3 months, on any cardiorespiratory program, any recent calf strains, and compartmental leg syndrome and on any medications such as muscle relaxants, histamines were excluded from the study.
All the individuals were divided equally into three groups by a convenient chit method. The entire group was assessed for cardiovascular parameters on HR, systolic BP (SBP), diastolic BP (DBP), VO2 max, fatigue, and fitness index (FI) at baseline before and after 8 weeks training program. Subjects in Group A participated in gastrocnemius and soleus muscle training program with sitting and standing calf raise, Group B participated in the gastrocnemius training program with standing calf raise and Group C participated in soleus training program with sitting calf raise 3 sessions per week for all the groups.
For soleus seated calf raise, individuals feet were placed at the edge of a wooden block, dumbbell was placed on the thigh, and then slowly, the heels were raised off the floor. For gastrocnemius standing calf raise, barbell was placed on shoulders, and then slowly heels were raised up onto tiptoes. One repetitive maximum of each subject was taken before the start of training program and progressed weekly in the intensity and sets of exercise till the end of study. Exercise routine comprises 3 sets of 8 reps, 3 sets of 10 reps, 3 sets of 12 reps, 3 sets of 15 reps, 3 sets of 20 reps, 3 sets of 25 reps, 4 sets of 20 reps, and 4 sets of 25 reps. The same clinician administered the training program and evaluated participants on the same day, 3 days a week for 8 weeks throughout the study.
Harvard step test
It is a test of aerobic fitness used to measure HR, BP, fatigue and FI. The individuals steps up and down on the platform of 45–50 cm height at a rate of 30 steps per minute (every 2 s) with the help of metronome for a duration of 5 min or until exhaustion. Exhaustion is defined as when the subject cannot maintain the stepping rate for 15 s. On completion of the test, the total number of heart beats are counted between 1 and 1.5 min, 2 and 2.5 min, and between 3 and 3.5 min.
FI = (100 × test duration in seconds) divided by (2 × sum of heart beats in the recovery periods). Ratings of FI is given by; below 54 denotes poor, between 54 and 67 is low average, between 68 and 82 is average, between 83 and 96 is good, and >96 as excellent. Borg scale of rate of perceived exertion is most commonly used to assess fatigue or intensity levels of physical activity. The scale developed by Swedish psychologist Gunnar Borg consists of 15 categories which ranges between 6 and 20 where 6 denotes no exertion and 20 indicates maximal exertion. Digital BPs monitor (citizen CH-432B) was used to measure BP and HR.
The Balke test
It is a treadmill walking test where the speed was set at 3.3 mph (5.3 kph) until it reached a gradient of 25%. Thereafter, the grade remained constant and the speed increased to 0.2 mph (0.32 kph) each minute. The starting gradient was at 0% for the 1st min and raised to 2% at the end of the 1st min, and increased by 1% per minute thereafter until it reaches 25%. The total time of the test was recorded by a stopwatch for estimation of the individuals VO2 max. It can be calculated as; VO2 max = 1.444 × T + 14.99 where “T” is the total time of the test expressed in minutes and fractions of a minute).
Standard statistical analysis (one-way ANOVA, Paired t-test, Kruskal–Wallis test, Jonckheere trend test, Wilcoxon signed-rank test) were used to analyzed data using the SPSS software packages version 17.0 (IBM, Chicago, IL, USA).
| Results|| |
Paired t-test was used for comparison of HR, SBP, DBP and VO2 max in Group A, B and C between the variables at pre and post training level. The results were 10.942, 7.168, 2.948, −9.110 for Group A; 4.016, 4.611, 3.537, −7.490 for Group B and 7.418, 7.529, 3.066, −6.164 for Group C, respectively, and were found to be significant for all the groups. Refer to [Table 1].
|Table 1: Related t-test for heart rate, systolic blood pressure, diastolic blood pressure and VO2 max for Group A, B and C|
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One way ANOVA was used between Group A, B, and C before and after training for variables HR, SBP, DBP, VO2 max. The results were found to be statistically significant (P < 0.05) for HR and SBP, and nonsignificant for DBP and VO2 max (P > 0.05). Refer to [Table 2].
|Table 2: One-way ANOVA and Scheffe's test for HR, SBP, diastolic blood pressure, and VO2 max at pre- and posttraining between Group A, B, and C|
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The results between Group A versus B for HR and SBP was −11.93 and −12.66, respectively, and was found to be statistically significant (P < 0.05), whereas for DBP and VO2 max, the results (−3.73 and 2.90, respectively) show a nonsignificant difference (P > 0.05). The results between Group A versus C for HR, DBP, and VO2 max was −5.73, −4.40 and 2.41, respectively, and was found to be nonsignificant (P > 0.05), whereas the result (−8.66) was found to be statistically significant (P < 0.05) for SBP. The results between Group B versus C for all the variables of HR, SBP, DBP, and VO2 max, i.e., 6.20, 4.00, −0.66 and −0.48, respectively, was found to be nonsignificant (P > 0.05). Post hoc analysis showed Group A performed better than both Group C and Group B, and Group C performed better than Group B.
Kruskal–Wallis test was used for comparison between Group A, B, and C before and after training for variables of fatigue and FI. The result shows a nonsignificant (P > 0.05) difference between the groups at pretraining for fatigue and FI, posttraining results between the groups were found to be statistically significant (P < 0.05) for fatigue and FI [Table 3].
|Table 3: Kruskal-Wallis and Jonkheere test for fatigue and FI at pre, post and MD (pre-post) interval between Group A, B and C and Jonkheere test at pre-post fatigue and FI|
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Jonckheere trend test was used between Groups A, B, and C to find out which group perform better after training for variables of fatigue and FI. Post hoc analysis showed that Group A performed the best followed by Group C and Group B.
Wilcoxon signed rank test was used for comparison of improvement in mean within Group A, B and C between pre and posttraining for variables of Fatigue and FI. Comparison of pre- and posttraining for variables of fatigue and FI within Group A −3.578, −3.420, Group B −2.530, −3.311 and Group C were −3.419, −3.413, respectively, and the results were found to be statistically significant [Table 4].
|Table 4: Wilcoxon signed ranks test for fatigue and fitness index at pre and post interval within Group A, Group B and Group C|
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| Discussion|| |
The possible mechanism which has been attributed to the lowering of HR and SBP could be due to small nerve endings located in the thigh and calf musculature. These small nerve endings in skeletal muscle perceive the metabolic milieu inside the muscle and influence HR response through links to the cardiac control center in the brain. Therefore, resistance training-induced changes in cardiovascular adaptations such as a reduced HR response to known work rates. The lowered HRs to known work rates may be positively correlated to increased leg strength. This lowered HR due to strength training increased diastolic filling time and increased coronary blood supply.
The mechanisms of lowering HR and SBP involved enhanced cardiac filling (preload) in diastole due to increased venous return, which results in increased stroke volume (SV), to supply the muscles oxygen demands in the body. Increased SV is accompanied by a reduced HR and BP. Second, the mechanism for the exhibition of vagal tone secondary to training is by neuro-chemical secretion of acetylcholine from nerve endings, which stimulates the receptors on SA and AV nodes of heart, resulting in slowing of HR. The parasympathetic division of the autonomic nervous system (ANS) has control over these nodes, supplied by the right and left vagus nerves, respectively. Another potential mechanism is the decreased sympathetic drive in response to training, which can be attributed to lower plasma nor-adrenaline levels, thereby reducing the peripheral resistance of vessels. BP is the product of cardiac output and peripheral resistance, and training helps in lowering the SBP due to the influence of the parasympathetic division of ANS.
Improvement in fatigue can be attributed to the change in the type of muscle fiber in response to leg training. The cumulative effect of strength training results in greater recruitment of Type IIa over Type IIb muscle fibers. Furthermore, resistance training may also enhance the oxidative (aerobic) production of adenosine triphosphate (ATP), and therefore, short-term endurance capacity increased without a complementary increase in VO2 max.
The density and volume of mitochondria in Type I skeletal muscle fibers increases as is found in elite runners. Staron et al. observed the effects of 4-weeks heavy-resistance training in females and found a significant increase in the percentage of Type I skeletal muscle fibers. Fast-twitch oxidative glycolytic (FOG) Type IIa skeletal muscle fibers allows it to be moderately resilient to muscular fatigue. In addition, the FOG fibers have the ability to use metabolites from blood to sustain the metabolic activity required during muscular contraction.
Another mechanism which can be attributed to increasing strength-endurance capacity is the improvement in muscular recruitment pattern as it influences blood lactate turnover rate. Fast-twitch type IIa skeletal muscle fibers also have a high density of mitochondria. It has been proven that high repetitive and progressive resistance-training regime increases the number of capillaries per muscle fiber, thus increasing the capability of skeletal muscle to sustain a given force for extended periods.
Hickson et al. observed that during sub-maximal cycle ergometer exercise, each pedal thrust ensued an increase in the recruitment of slow-twitch fibers accompanied by diminished recruitment of fast-twitch fibers in the thigh musculature. The reduced reliance on fast-twitch fiber recruitment with each pedal thrust would result in a reduced rate of ATP consumption per muscle fiber, and a subsequent sparing of muscle glycogen with prolonging resistance to fatigue.
There were no significant changes in VO2 max. The leg-resistance training program employed in our study had no effect on VO2 max. due to the peripheral adaptations, which may favorably impact aerobic fitness status. These peripheral adaptations may be attributed to instantaneous high volume (performed to volitional fatigue) leg resistance training. If oxidative and nonoxidative skeletal muscle tissue increases, then any work rate will represent a lesser percentage of that muscle's maximal capacity to complete both aerobic and anaerobic work. Therefore, the workload will be perceived as less stressful, thereby lowering HR and allowing one to exercise for extended durations without fatiguing. In this study, improvement in FI can be attributed to the lowering of HR after strength training, as HR is inversely proportional to FI.
Limitations of the study include the absence of a control group, a relatively small sample size consisting of 45 subjects, a homogenous population (consisting only male subjects), and anthropometric data (height, weight, BMI) were not considered in the study. Same study with a larger sample size and heterogeneity of samples could be incorporated for future scope. Based on our experimental study, it can be concluded that 8 weeks of leg muscle training on cardiovascular parameters has an effect with improvement in variables of HR, SBP, FI, and fatigue. On the contrary, the results showed no significant effects on DBP and VO2 max. The present study also shows that strength training of the calf muscle pump helps in improving cardiovascular fitness, and the soleus muscle has an effect over the gastrocnemius muscle.
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[Table 1], [Table 2], [Table 3], [Table 4]