Comparison of Kettlebell and Cycling Exercise on Heart Rate Variability

Abstract

Background:

Kettlebells, dating back to 1703 in Russia, offer a full-body workout for strength, endurance, and flexibility. They activate back and hip musculature, reduce low back injury risk, and improve postural coordination. Cycling induces muscle hypertrophy, guiding exercise prescription.

Objective:

The study evaluates the impact of kettlebell and cycling exercise on heart rate variability (HRV) in healthy young adults, assessing lifestyle, body mass index (BMI), and relationship with HRV.

Methods:

A pilot study at King George’s Medical University’s Department of Physiology in Lucknow, Uttar Pradesh over a period of 1 year, involved 64 participants, including healthy adults aged 18–35, consenting individuals, and those under 35 diagnosed with any medical conditions were excluded.

Results:

The study examined the impact of kettlebell and cycling exercise on HRV in 64 healthy individuals. The participants were divided into two groups, with no significant differences in height, weight, BMI, waist circumference, or blood pressure. After exercise, heart rate (HR) increased by 55%, but low frequency (LF) power and high frequency (HF) power decreased.

Conclusion:

The study found that combining kettlebell and cycling exercise can improve cardiovascular health and overall physical fitness in 64 healthy individuals, increasing HR by 55% but decreasing LF and HF power.

INTRODUCTION

Exercise alters the balance of the parasympathetic and sympathetic systems in the heart, leading to acute changes in heart rate variability (HRV).[1] During exercise, the body undergoes cardiovascular adjustments, with parasympathetic control at rest and reactivation during recovery. Factors influencing sympathetic and parasympathetic involvement during exercise include exercise intensity and duration. This study focuses on the effect of 20 min of stationary cycling exercise at mild-to-moderate intensity on HRV in a normal individual.[1,2,3,4,5]

HRV is a noninvasive measure that assesses autonomic nervous system function during exercise. Physical exercise, particularly aerobic exercise, promotes positive adjustments in cardiac autonomic modulation, resulting in reduced sympathetic and increased vagal modulatory influences on the heart, increasing HRV. Several methodological tools have been used to assess the degree of these adjustments.[5]

Kettlebells, dating back to 1703 in Russia, are an ancient training implement with unique ergonomic benefits. They can be safely moved between legs in swings and snatches, enabling ballistic eccentric loading. Kettlebell exercises offer a full-body workout that improves strength, endurance, and flexibility. Studies show that kettlebell training can lead to significant improvements in muscular strength, power, and aerobic capacity. Kettlebell swings can be divided into three phases: Explosive initial phase, coasting phase, and the deceleration phase. Kettlebell training is effective in activating the back and hip musculature, reducing the risk of low back injury, and improving arabesque esthetics in dancers. It also improves postural coordination, jumping performance, power and strength performance, cardiovascular fitness, and sympathovagal balance.[6,7,8,9,10,11,12]

Cycle training is widely performed as a major part of any exercise program seeking to improve aerobic capacity and cardiovascular health. Cycle training induces muscle hypertrophy in both young and older adults, with strength gains favoring older adults. Young adults may need higher-intensity intermittent cycling for strength gains. Muscle hypertrophy is influenced by positive changes in muscle protein net balance.[13] Cycling, an aerobic exercise, offers cardiovascular benefits and endurance. Continuous cycling at varying intensities can improve HRV, especially when performed at moderate intensities for prolonged periods. The rhythmic nature of cycling contributes to its positive effects on HRV. A study comparing kettlebell exercises and cycling on HRV should consider factors such as intensity, duration, and frequency, as well as individual fitness levels, training status, and age. Understanding these effects can guide exercise prescription and optimize training protocols for cardiovascular health and fitness.[14]

The study compares the effects of kettlebell training and cycling exercise on HRV, a crucial indicator of autonomic nervous system function and cardiovascular health. Kettlebell training, which combines strength and aerobic conditioning, may offer unique benefits compared to traditional aerobic exercises. This research can inform personalized exercise prescriptions and contribute to sports science by highlighting kettlebell training’s versatility in improving overall heart health.

Objectives

The study aims to assess the impact of kettlebell and cycling exercise on HRV in healthy young adults. It also aims to evaluate the effects of these exercises on lifestyle, body mass index (BMI), and lifestyle through the subjective Exercise Experience Scale, and to determine their relationship with HRV.

METHODS

A pilot study at King George’s Medical University’s Department of Physiology in Lucknow, Uttar Pradesh over a period of 1 year, involved 64 participants, including healthy adults aged 18–35, consenting individuals, and those under 35 diagnosed with any medical conditions were excluded.

A study was conducted to measure HRV and anthropometric parameters such as height, weight, BMI, waist circumference, hip circumference, and neck circumference. Two groups of 32 participants were formed, one for kettlebell exercise and the other for cycling. Participants were required to abstain from stimulants 24 h before the test. Participants performed a set of American kettlebell swings and 10 min of moderate-intensity cycling. HRV was recorded immediately after each group’s exercise. The study involved a personal history, including height, weight, mid-arm circumference, waist circumference, hip circumference, blood pressure, total body fat, family history, and socioeconomic status. The study aimed to provide valuable insights into the effects of exercise on HRV and overall health.

The study compares the effects of kettlebell and cycling exercise on HRV using statistical analysis version 26^th. Baseline and postexercise data will be collected, and differences between groups will be compared using paired t-tests, independent t-tests, and regression analysis.

RESULTS

This study categorized 64 healthy individuals into two groups: Group K, which consisted of 32 individuals using kettlebells, and Group C, which consisted of 32 individuals using cycling. The frequency of males and females in Group K was 71.88%, whereas in Group C, 65.63% were males and 34.38% females. Both groups were comparable in terms of sex and mean age, with the mean age of the patients being 28.16 ± 4.87 years in Group K and 27.31 ± 4.50 years in Group C [Table 1].

Table 1.

Comparison of demographic profile between Group K and Group C

	Group K (n=32), n (%)	Group C (n=32), n (%)	χ 2	P
Male	23 (71.88)	21 (65.63)	0.07	0.787
Female	9 (28.13)	11 (34.38)
Age (years)	28.16±4.87	27.31±4.50	0.072	0.475

The study compared the height, weight, and BMI of two groups: Group K and Group C. Both groups had similar heights, weights, and BMIs. The waist circumference, hip circumference, and waist-to-hip ratio were similar. The mean systolic blood pressure was 117.34 mmHg in Group K and 119.84 mmHg in Group C [Table 2].

Table 2.

Comparison of mean height, weight, body mass index, waist circumference, hip circumference, waist-to-hip ratio systolic blood pressure, and diastolic blood pressure between Group K and Group C

	Group K (n=32), mean±SD	Group C (n=32), mean±SD	t	P
Height (cm)	166.97±7.98	167.75±6.51	−0.43	0.669
Weight (kg)	63.19±6.46	65.19±8.35	−1.34	0.185
BMI (kg/m2)	22.77±2.80	22.89±3.07	−0.83	0.408
Waist circumference (cm)	78.17±11.04	81.91±7.20	−1.60	0.114
Hip circumference (cm)	89.39±10.66	92.34±7.56	−1.28	0.206
WHR	0.87±0.03	0.89±0.05	−1.56	0.123
SBP (mmHg)	117.34±12.15	119.84±10.57	−0.88	0.383
DBP (mmHg)	79.13±8.07	80.56±8.51	−0.69	0.491

SD=Standard deviation, BMI=Body mass index, WHR=Waist-to-hip ratio, SBP=Systolic blood pressure, DBP=Diastolic blood pressure

The study analyzed the heart rate (HR), low-frequency (LF), high-frequency (HF), and total power (TP) (ms²/Hz) before and after the Kettlebell Exercise and Cycling Exercise. The average HR was measured in beats per minute before and after exercise, with no significant changes between groups. However, there was a significant increase in HR in both groups, with Group K experiencing a 55.61% increase and Group C experiencing a 58.64% increase. The average LF power was measured in ms²/Hz before and after exercise, with no significant changes in LF power. The mean HF power was measured in ms²/Hz before and after exercise, with no significant changes in HR (ms²/Hz) between groups. The mean TP (ms²/Hz) was also measured before and after exercise, with no significant changes in TP between groups. The mean LF/HF ratios were also measured before and after exercise, with no significant changes in the ratio between groups. The study concluded that the HR, LF, HF, and TP were all measured before and after exercise [Table 3].

Table 3.

Comparison of the heart rate, low-frequency, high-frequency, low-frequency/high-frequency, low-frequency, high-frequency, and total power of Groups K and C before and after exercise

	Group K (n=32), mean±SD	Group C (n=32), mean±SD	t	P
HR (beats/min)
Pre	85.69±5.80	84.41±5.10	0.94	0.352
Post	133.34±6.87	133.91±5.66	−0.36	0.722
LF (ms2/Hz)
Pre	325.50±202.57	328.63±206.55	−0.06	0.951
Post	258.41±163.00	265.00±164.06	−0.16	0.872
LF (nu)
Pre	47.88±9.45	48.78±9.83	−0.38	0.708
Post	38.28±7.81	39.03±7.88	−0.38	0.704
HF (ms2/Hz)
Pre	496.09±271.07	522.03±296.63	−0.37	0.716
Post	444.84±269.76	480.19±297.96	−0.50	0.621
HF (nu)
Pre	38.03±11.01	39.69±11.75	−0.58	0.563
Post	30.19±9.47	30.06±6.08	0.06	0.950
TP (ms2/Hz)
Pre	913.13±120.07	877.50±50.10	1.55	0.126
Post	189.09±27.13	171.13±24.36	2.79	0.007
LF/HF
Pre	1.16±1.50	1.21±1.89	−0.10	0.920
Post	1.17±1.60	1.24±2.15	−0.14	0.887

HR=Heart rate, LF=Low-frequency, HF=High-frequency, TP=Total power, SD=Standard deviation

The study reveals that after kettlebell training, HR increased by 55%, whereas LF power and HF power decreased significantly. TP also decreased significantly, with no significant change in the LF/HF ratio before or after exercise. The study highlights the importance of maintaining proper HRV during exercise [Table 4].

Table 4.

Changes in mean heart rate variability from pre- and post-exercise in Group K

Group K	Preexercise, mean±SD	Postexercise, mean±SD	Percentage change	t	P
HR (beats/min)	85.69±5.80	133.34±6.87	55.61	−30.13	<0.001
LF (ms2/Hz)	325.50±202.57	258.41±163.00	−20.61	8.75	<0.001
LF (nu)	47.88±9.45	38.28±7.81	−20.04	10.85	<0.001
HF (ms2/Hz)	496.09±271.07	444.84±269.76	−10.33	65.19	<0.001
HF (nu)	38.03±11.01	30.19±9.47	−20.62	12.84	<0.001
TP (ms2/Hz)	913.12±120.07	189.09±27.13	−79.29	43.17	<0.001
LF/HF	1.16±1.50	1.17±1.60	0.68	−0.25	0.802

HR=Heart rate, LF=Low-frequency, HF=High-frequency, TP=Total power, SD=Standard deviation

The study reveals that after cycling exercise, HR increased significantly by 58.65%, whereas LF power and HF power (RF) decreased significantly by 19.36%, 19.99%, 8.01%, 24.25%, and 80.50%, respectively. The TP also decreased significantly by 80.50%. The LF/HF ratio showed no significant change before or after exercise [Table 5].

Table 5.

Changes in mean heart rate variability from pre- and post-exercise in Group C

Group C	Preexercise, mean±SD	Postexercise, mean±SD	Percentage change	t	P
HR (beats/min)	84.41±5.10	133.91±5.66	58.65	−38.34	<0.001
LF (ms2/Hz)	328.62±206.55	265.00±164.06	−19.36	8.30	<0.001
LF (nu)	48.78±9.83	39.03±7.88	−19.99	28.27	<0.001
HF (ms2/Hz)	522.03±296.63	480.19±297.96	−8.01	16.30	<0.001
HF (nu)	39.69±11.75	30.06±6.08	−24.25	8.18	<0.001
TP (ms2/Hz)	877.50±50.10	171.12±24.36	−80.50	121.58	<0.001
LF/HF	1.21±1.89	1.24±2.15	2.69	−0.70	0.488

HR=Heart rate, LF=Low-frequency, HF=High-frequency, TP=Total power, SD=Standard deviation

DISCUSSION

Kettlebell training, a popular method for increasing muscle strength and aerobic capacity, involves short sessions lasting <30 min, involving multiple muscle groups.[15,16,17,18] Kettlebell protocols can achieve high intensities, ranging from 73% to 93% HRmax to 56%–75% VO₂max, making them an effective alternative to high-intensity interval training to 56%–75% VO₂max.[19,20] However, there is limited data on the effects of kettlebell training on the ANS and cardiac autonomic recovery.[19,20,21,22,23,24] The postexercise recovery period can reveal the extent of exercise-induced cardiac stress by identifying changes in cardiac autonomic activity and monitoring its recovery to basal levels. The postexercise period is crucial for investigations into the effects of kettlebell training on cardiac health.

HRV is a noninvasive method used to measure cardiac autonomic recovery and exercise-induced cardiovascular overload.[25,26] Delayed recovery of autonomic cardiac activity to baseline indicates increased sympathetic activity and an increased risk of cardiovascular events, which can prevent untrained individuals from performing high-intensity activities, as per Task Force 1996.[26,27]

Higher loads increase the mechanical demand of kettlebell training, but the effects of load manipulation on autonomic activity are unknown.[28] Wong et al. investigated the acute autonomic response to kettlebell training in physically active novices (8 kg women and 16 kg men) with a fixed kettlebell load.[18] After a 30-min exercise session (12 rounds/30:30 s [s] work-to-rest ratio; 80%–90% expected HR), the authors observed a decreased HF index (HF-parasympathetic activity) and an increased LF index (LF – sympathetic and parasympathetic activities). The sympathovagal balance ratio (LF/HF) increased. During this period, there was no recovery of baseline autonomic activity.

The study assessed the accuracy of HRV measurements during exercise, finding differences in accuracy depending on the duration of the HRV analysis and exercise intensity.

The study found a 55% increase in HR after kettlebell training, with a significant decrease in LF power, LF power, and LF (RF) power. TP also decreased significantly. No significant change was found in the LF/HF ratio before and after exercise. The changes in average HRV parameters during physical activity were consistent with previous studies, showing a decrease in frequency domain indices during exercise. Previous studies have shown a decrease in LF and HF components.[29,30]

The study found a decrease in parameters during kettlebell and cycling training, but the average LF/HF change either decreased or remained constant with increased exercise intensity, which is commonly used to measure sympathetic nervous system activity or balance.[31] However, it has been suggested that detecting changes in autonomic nervous activity during exercise can be difficult.[32]

The study found a discrepancy between the change in HR to HR (LF/HF) and the increase in catecholamine concentration during exercise, contradicting the hypothesis that LF/HF is an indicator of sympathetic nervous system activity. A stronger correlation was found between HR to LF and noradrenaline levels.[33] Tanoue et al. investigated the changes in the HR/LF ratio during exercise. They suggested that HR/LF could serve as an alternative indicator of LF/HF in the assessment of sympathetic nervous system activity.[33]

The study found that after cycling, HR increased by 58.65%, whereas AF power decreased by 19.36%, LF power decreased by 19.99%, HF RF power decreased by 8.01%, RF power decreased by 24.25%, and TP decreased by 80.50%. There was no significant change in the LF/HF ratio before and after exercise. However, significant changes were observed in the frequency domain characteristics of TP, HR (ms²), very LF (VLF) (ms²), LF (ms²), and VLF (%).

The standard deviation of NN intervals (SDNN), which represents the standard deviation of variations between adjacent RR intervals, is influenced by the relative power of the VLF, LF, and HF components. Based on the findings of the present exercise routine, the VLF and LF bands have more power than the HF band, resulting in a greater contribution to SDNN.[34] The SDNN values after exercise did not return to resting values, suggesting a delayed recovery of HRV. This delay could be due to the fact that the participants had not completed any sports training, which requires a longer recovery period after exercise. The decreasing trends observed in HRV parameters can be attributed to the further reduction in respiratory sinus arrhythmia, which is controlled by the parasympathetic nervous system and is weakened during exercise.

pNN 50% and root mean square of successive differences mainly assess parasympathetic activity, which remains unaffected by respiration. The decrease in parasympathetic activity during exercise was mainly reflected in a decrease in these time domain characteristics. More intense exercise is associated with a nonlinear decrease in time-domain characteristics. The exercise intensity function is a curvilinear decline characterized by a rapid and steep decrease in time-domain parameters.[35] Previous studies have documented a nonlinear decline in a time domain parameter that reaches a minimum value of 3–10 ms at high exercise intensity until a HR of 160 bpm is reached.[36] Due to the low intensity of the exercise, in which the participants only reached 30%–50% of their maximum HR, we could not detect a significant decrease in these parameters. This could be due to the fact that the subjects had not trained as athletes.[36]

Malhotra et al.[37] found a decrease in HR, VLF, and LF power proportions during the first 5 min of exercise. VLF power showed a sudden increase, whereas HF and LF power showed negligible decreases. Similar results were found in literature for TP, HF, and LF.

As exercise intensity increases, the respiratory rate also increases, leading to a decrease in HR. Similarly, HR power (nu%) is often used as a measure of the parasympathetic index of the heart, which decreases with exercise.[38,39] However, no statistically significant decrease in HR power (nu%) was found in the current study.

The study indicates that the balance between the sympathetic and parasympathetic nervous systems changes after light exercise, favoring the sympathetic nervous system. The LF: HF ratio varies with exercise intensities and durations, indicating a more optimal balance.[40]

The primary application of this study is HRV biofeedback. HRV biofeedback is widely recognized as beneficial for a variety of diseases and for improving performance.[41] HRV biofeedback has been shown to be beneficial for improving exercise endurance.[42] There is HRV biofeedback software for smartphones that allows the user to wear a fitness band while exercising. The band provides visual feedback and allows the user to monitor and control the intensity and duration of activities such as jogging or cycling. Hunter et al.[43] conducted a randomized experimental trial to evaluate the effects of brief biofeedback through a smartphone app on the process of stress recovery. It is often considered beneficial for overall well-being, especially in athletes who have established a regular exercise routine. The HRV data collected in this study while a normal person was exercising could be valuable for the development of similar HRV applications.

The study’s limitations include potential variability in fitness levels and exercise adherence, which could impact HRV outcomes, and not considering differences in exercise intensity and duration between kettlebell training and cycling, potentially affecting comparability.

CONCLUSION

The study examined the effects of kettlebell and cycling exercise on HRV in 64 healthy individuals. Results showed no significant differences in height, weight, BMI, waist circumference, or blood pressure. After kettlebell exercise, HR increased by 55%, but LF power and HF power decreased. The study suggests that combining kettlebell strength training with cycling for aerobic exercise can improve cardiovascular health and overall physical fitness.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.