Many physiological and cardiovascular characteristics such as body weight (BW), lean body mass (LBM), percentage body fat (%BF), heart rate, blood pressure, muscle strength, etc. undergo adaptive changes as a result of training. Training also influences endurance, aerobic and anaerobic capacity, and physical performance (10,16). It has been known since long that exercise and training improve performance of individuals, especially in field sports (6,24). Different individuals need different training regimes for optimal performance according to their body type, current fitness status, physical requirements, and type of sport or physical activity. Currently, there is increased demand of personalized training regime to fit these criteria to promote physical fitness and performance. Previous research on soccer, basketball, baseball, handball, tennis, etc. show that different training regimes and programs may affect adaptations differently, and show different outcomes, as per the requirements and physiological demand of trainee and type of sports (4,30). Thus, studying and monitoring different training regimes of various durations and their outcomes become fundamental in the field of human performance and give an interesting area to explore.
Field hockey is an intermittent endurance sport that requires high aerobic fitness, anaerobic power, strength, and agility in addition to optimal skills and body composition (9,10,35,44,45). To meet these physiological demands for optimal performance and for promoting general health status, appropriate training along with repeated monitoring has to be performed. Coaches and health experts require effective training regimes to boost all the aforementioned relevant parameters of the players for optimal performance. Many studies on training adaptation have been published, but the effectiveness of short-term training on field hockey players has not been studied much, that too about sprint-strength and agility training (20,23,40). There is also a need for more precisely regulated, individual, and sports-based targeted training regimes and guidelines for coaches to improve the desired characteristics in players as well as in the general population (34). Hence, in this interventional study, we have tried to find the effects of a 6-week specialized program including sprint-strength and agility training on physiological, cardiovascular, and performance-related parameters of national-level field hockey players. We hypothesized that this short training of only 6 weeks should result in improvement in the studied parameters. To the best of our knowledge, no such study has been previously reported. The findings of this study will help coaches, sports management personnel, and trainees to design and incorporate effective and targeted training regimes of suitable duration for desired and better outcome of players.
Experimental Approach to the Problem
Specific short-duration (6 weeks) training regime was designed to include sprint-strength and agility exercises in this interventional study. The training intervention consisted of 2 sessions of 11–22 yards straight sprints per day; free weights and machine-based 8–10 isotonic resistance exercises affecting major muscle groups at 70–90% of 1 repetition maximum, 1–3 sets and 6–12 repetitions per day; and 2 sessions of 30-yard T-drills and Zig-Zag drills. The players were given rest of 3 minutes between each session of exercises (16). The training was of ≤3 hours duration per day and given 3 times a week for 6 weeks (July–August). Apart from the general warm-up exercises, no other training programs were given to the subjects during the study period. Selected anthropometric and physiological variables were measured at weeks 0 and 6.
The study was conducted at Sports Sciences & Fitness Center, North-East Regional Center (NERC), Sports Authority of India (SAI), Imphal, India. Twenty-four healthy male field hockey trainees (± SD age: 15.71 ± 1.60; range 13–20 years) of NERC-SAI, in the preparation phase and participated in any recognized national competition participated in this study. All the players stayed in the same hostel and were given similar diet and field hockey training under the same coaches. Purpose, methods, risks, and benefits of this study were communicated to all subjects. Informed consent was taken both from the players and their parents/legal guardians if the subjects were younger than 18 years old. The study was approved by the North-East Regional Center (NERC), Sports Authority of India. The trainees found unfit in preparticipatory physical and medical evaluation, and those with no written informed consent were excluded. This 6-week training program was started when all participants returned from 1 month holiday having rest period. Before holidays, they were given field hockey–related techniques and skills training and other training namely aerobic, anaerobic, and strength training as per the macrocycle of training and competition.
All parameters were measured according to previously reported standard procedures (17–19,42). All the tests were performed in the morning about the same time (±1 hour), after clearly explaining both the purpose and procedures to the players. The players reported after a sound sleep of 8 hours and light breakfast, with no physical exertion for 12 hours before the testing. No solid food intake or caffeinated drinks, however, were allowed within 4 hours of the tests. Wherever appropriate, familiarization sessions were given, and the best performance was taken from 2 to 3 attempts in each testing after maximal encouragement and motivation, and sufficient rest and recovery period in between. The measured parameters were subdivided into the following groups.
Anthropometry and Body Composition Parameters
Body heights (HT in cm) of the players were measured using a stadiometer (Seca; United Kingdom) nearest to 0.1 cm. A bioelectrical impedance machine (TANITA Body Composition Analyzer, TBF310 Model; Japan) was used to measure BW (in kg), %BF, and LBM (in kg). Age and height of the players were entered in the instrument; then, they were asked to stand erect barefoot on the foot pad of the instrument with minimum clothing till the values showed on the panel and recorded paper came out with full data. Body mass index (BMI) (kg·m−2) was calculated as BW·HT−2.
The players were trained and instructed to take their own resting heart rate (rHR) manually from carotid pulse just after waking up, while still in bed, and from a relaxing night's sleep (42). Resting blood pressure (rBP), resting systolic blood pressure (rSBP), and resting diastolic blood pressure were measured using a mercury sphygmomanometer after a sitting rest of 10 minutes, before commencing other testing: An average of 3 readings was taken. Resting double-product (rDP in mm Hg·min−1) was calculated as rSBP multiplied by rHR (16).
Aerobic and Anaerobic Capacity
Running-based Anaerobic Sprint Test (RAST) was used to measure the maximum power (Pmax in W), average power (Pavg in W), and fatigue index (FI in W·s−1) following the standard methodology reported earlier (1,18,49). Briefly, the players were instructed to do 6 sprints with maximum efforts on a distance of 35 meters. A 10-second passive recovery pause was given between each sprint. The power and FI were calculated according to the following equations: power = body mass × distance2 ÷ time3, and FI = (maximal power − minimum power) ÷ total time of 6 sprints.
Aerobic variable (maximal oxygen uptake or V̇o2max in ml·kgBM−1·min−1) was predicted using Beep test or 20-meter multistage shuttle run test, following the standard methodology (29). The players were asked to run 20 meters back and forth along with touching the 20-meter line. A prerecorded sound signal was played at the same time, with the frequency of the signal increasing from a starting speed of 8.5 km·h−1 by 0.5 km·h−1·min−1. The stage number when the players could no longer maintain the pace was noted. The following equations were used for estimation of V̇o2max in ml·kg−1 BM per minute: (a) V̇o2max = 31.025 + 3.238X − 3.248Y + 0.1536XY (for <18 years), and (b) V̇o2max = −27.439 + 6.0028X. Here, X is the speed in km·h−1 and calculated as 8 + 0.5 multiplied by the stage number, and Y is the player's age in years (43). Beep test is an accurate and reliable test (28,29). Aerobic variable was analyzed in absolute (aV̇o2max in l·min−1) or relative value (V̇o2max and V̇o2max/LBM). The same was performed for anaerobic and strength variables.
Strength- and Performance-Related Parameters
Best score of vertical jump test (VJ in cm) was used to assess lower limb muscle strength and explosive power (38,47), following the standard methodology (41). Upper limb muscle strength was assessed using seated shot put throw test score (SP in cm), after conducting the test as per the standard methodology (11). The angle of shot put released was not controlled. Performance of trainees was assessed by measuring the best average ball-hitting speed (BS in m·s−1). The players were instructed to hit a hockey ball as fast as possible in a straight line with minimum vertical distance from the ground. They hit the ball from the center line toward the goal line, and the time taken was noted. The best timing was used to calculate BS as distance traveled by time taken (17).
It is the ability to rapidly change direction without losing balance and speed, and is another important factor for sports performance. The 505-agility test was used to measure best score of left (Tl in s) and right (Tr in s) feet. Mean score (Tm in s) was calculated as (Tl + Tr)/2. The test was conducted as per the standard methodology (8,19,48). All subjects were instructed to do warm-up before test. Then, the subjects were made to stand in split stance on the start line and instructed to accelerate maximally to 15-m line on go signal, and then turn on the right leg and sprint back on 5-m line for measuring Tr. The test was repeated for turn on the left leg for Tl. Time was recorded with a stopwatch that was started when the players passed the 5-m line on the way to the 15-m line, and stopped when the players passed the 5-m line on return. All participants completed 3 efforts with 2–3 minutes of rest in between. Mean value for each foot was calculated by taking the average of 3 efforts.
SPSS (Statistical Package for Social Science) version 20 was used for data analyses. The effect of training was assessed using paired t-test. The absolute values of change (d) in interested variables (posttraining minus pretraining value without sign) were evaluated. Association among absolute changes and with pretraining values was determined using Pearson zero-order correlation, and using partial correlation, controlling for the corresponding pretraining values. Statistical significance was chosen at p value (2-tailed) ≤0.05.
All measured parameters at 0 weeks and after the sixth week of training are depicted in Table 1, which shows improvement in most parameters at the end of training. On analysis, we found significant changes in BF, LBM, rHR, rBP, rDP, Pmax, Pmax/BW, Pavg, Pavg/BW, FI, VJ, VJ/BW, VJ/LBM, SP, SP/BW, BS, Tl, Tr, Tm, aV̇o2max, and V̇o2max (Table 1). When anaerobic power, upper limb strength, and aerobic parameters were expressed relative to LBM, the significant differences disappeared, showing the major contribution of change in LBM on them. However, VJ increased significantly even when expressed relative to BW or LBM (Table 1).
Table 2 compiles correlations of measured variables. It was observed that decrease in rHR, rBP, and rDP was associated with increase in aerobic variables. When initial value of V̇o2max/LBM was controlled for, change in it was also positively associated with increase in BS. Increase in anaerobic variables was associated with decrease in FI. Increase in lower limb and upper limb strength was associated with increase in agility and aerobic variables, respectively. However, those with lower changes in BF and LBM had more decrease in Tr and Tm (initial Tm controlled), which might be a coincidental finding.
Correlation analysis of absolute changes in selected variables with pretraining values also indicated that those with lower BM, BMI, and BF had more improvement in BS (Table 2). Those with higher initial BS had more increase in SP (initial SP controlled, Table 2) and more improvement in aerobic variables (Table 2). Lower initial rSBP and rDP were associated with more decrease in Tr (Table 2).
However, certain seemingly irregularities in associations were also observed. Negative correlation was seen between initial anaerobic power, aerobic variables, and SP (initial BS controlled) with dBS (Table 2), and initial HT and aV̇o2max with dV̇o2max/LBM (Table 2). Initial rHR positively correlated with change in SP (Table 2) and relative V̇o2max variables (initial values controlled, Table 2).
Although this training program was of short duration, we found it to be effective in improving various physiological parameters of the participants. The training improved LBM significantly (Table 1) most probably due to the strength training component of the regime (27), which is favorable, as field hockey requires players with leaner body (35,48). It has been reported earlier that weight training with sprint and agility training brings more substantial gain in muscle size than agility or sprint-agility training alone (39). Increased LBM might not only elevate basal metabolic rate and energy expenditure, but also cause considerable excess after exercise oxygen consumption (EPOC) (2,3), even greater than that by aerobic exercise (5), causing considerable fat loss, which might explain the significantly reduced BF in our study (Table 1). This combined with the relatively short training duration might cause nonsignificant changes in BM and BMI (Table 1) (27).
All measured cardiovascular parameters showed significant improvement after training, showing positive effects of such regime and improved fitness of the trainees. The significant reduction in rHR and rBP (Table 1) is possibly due to training-induced increased parasympathetic activity and decreased sympathetic activity (15,26). Reduction in BF might also reduce rBP (13). Increase in nitric oxide formation due to repetitive episodic increase in the shear stress of endothelial cells (33) and reduced sensitivity to vasoconstrictor effects of norepinephrine as a result of training (7) might be another reason. Reduction in total peripheral resistance can also result from less vascular occlusion during muscular contraction after strength training, which decreases the percentage of maximal voluntary contraction necessary to obtain a submaximal absolute workload as a result of increased maximal strength (32).
This significant reduction in rHR and rBP resulted in decreased rDP (Table 1) (14,25,46), indicating decrease in myocardial O2 consumption (12). Training induced reduction in total peripheral resistance, and hence after load (32), and myocardial wall tension might be another reason (22).
Field hockey requires good aerobic fitness that also delays fatigue and quickens recovery from intermittent strenuous efforts with short rest intervals, which are very common in the game (10,26). This 6-week training regime also improved aerobic and anaerobic fitness of the players. Significant improvements in RAST parameters (Table 1) are most probably due to the training induced increased in anaerobic power and capacity (26). The strength gained might enable the player to perform a given task with less effort, thereby reducing the risk of fatigue and ultimately improving the performance, without risk of injury (26). Improvement in calcium kinetics after training might lead to development of speed and acceleration in sprint training (37). Because field hockey is associated with a high number of short sprints and accelerations-decelerations, a high anaerobic power with the ability to accelerate-decelerate efficiently is essential for better performance (44,45). Although aerobic training, especially high-intensity interval training, has been reported to be more effective than others in improvement of V̇o2max (21), the addition of resistance training lessens the volume of aerobic training required to raise V̇o2max (36). V̇o2max also increases after sprint training (31). Our training improved aerobic parameters significantly, except for V̇o2max/LBM (Table 1). The increase in aerobic variables was associated with decrease in rHR and rBP, and increase in SP (Table 2). The former is understandable because low rHR and rBP (and hence rDP) have been reported to be associated with high aerobic fitness (26). Those who improved more aerobically also had more reduction in myocardial O2 consumption (drDP) (Table 2).
Strength, agility, and performance parameters also improved at the end of our 6-week training regime, as a demand in the sport. Because many activities in field hockey are forceful and explosive, strength and power training are thus essential (9,45). Significant increment in VJ indicated improvement in lower limb and hip muscle strength, and explosive power (38,47). Positive association of dVJ with dTl, dTr, and dTm (Table 2) indicated a possible favorable effect of improvement in lower limb strength and explosive power for improving agility. There is high importance for agility in hockey that involves a lot of quick turning movements (44,45). Agility was improved significantly after the training (Table 1). There was also significant improvement in speed-strength quality and power of the upper limb musculature as indicated by SP (11). Significant improvement in the strength of both lower and upper limb with insignificant change in BW (Table 1) suggested training induced increment in strength-to-weight ratio, which might improve performance (35,48).
The seemingly irregular findings of those with lower initial anaerobic-aerobic variables and SP (initial BS controlled) having more BS improvement (Table 2), and those with higher rHR having more SP (Table 2) and relative V̇o2max variables improvement (initial values controlled, Table 2) might be coincidental and related to the small sample size and initial characteristics of our nonrandomly selected subjects. Subjects who were taller and had higher initial aV̇o2max also showed less V̇o2max/LBM improvement (Table 2). An earlier study did report lower improvement in V̇o2max at higher fitness levels (21).
This specialized 6-week training program proved to be “short yet effective” in improving many physiological parameters of study subjects. It is notable in the study that the 6-week sprint-strength and agility training resulted in significant improvement in body composition, aerobic, anaerobic, strength, agility, cardiovascular parameters, and performance of male field hockey players. Because these parameters are major determinants of not only sports performance but also for general health and fitness, the study will thus help in designing short duration yet effective training programs for both athletes and general population. Specific physiological parameters improvement targeted training can be designed based on this research. Sports, strength, and conditioning coaches can include such training programs without the fear of time constraints for targeted improvement of cardiovascular, body composition, agility, aerobic, and anaerobic characteristics of trainees and hence their performance. With ever increasing demand of quick result in the world of fitness, this study holds a good scope. This study also aids in understanding physiological adaptations to short-duration exercise training.
The authors express their sincere gratitude to NERC-SAI for providing facilities for the study; and to the Director In-charge, NERC-SAI; and Konthoujam Kosana Meitei, HOD, Sports Sciences & Fitness Center, NERC-SAI, for their valuable contribution. They acknowledge the contribution of P. Jhalajit Singh and Ch. Shakuntala Devi, field hockey coaches; Th. Malvia, physiotherapist; E. Ranitombi, staff nurse of Sports & Exercise Medicine Department, Sports Sciences & Fitness Center of the institute for data collection; and finally the participating players. The authors did not receive funding for this research. Instruments and resources available at North-East Regional Center (NERC), Sports Authority of India (SAI), Imphal, Manipur, India, were used for this study. The authors have no funding or conflicts of interest to disclose. The authors contributed equally to the article.
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