Introduction:

Field sports are the team sports, which are played in an open field, that include: football or soccer, baseball, cricket, field hockey, Gaelic football, rugby, softball, etc. One of the most important physical capacities that a field sport athlete requires is speed. Greater speed can assist with field sport–specific skill execution by allowing an athlete to become more involved in plays during a game, including those that can influence the final result. (Carson et al., 2020).

 Any gains made through strength and power training should be transferred into performance-specific motions, such sprinting, while preparing for field sports (Lockie et al., 2012). Many of the sprints completed in field sports are often short (i.e., less than 20 m), with efforts having a duration of 2 seconds or less. This places great prominence on the ability to accelerate, which is the capacity to generate as high a running velocity in as short a distance or time as possible (Lockie et al., 2013).

Attaining a high sprint velocity over a short distance is vital for successful performance in team and field sports (e.g., American football, rugby, soccer, Australian Rules football) (Lockie et al., 2012). Accelerating from a stationary position or a moving start requires high force generation capacity to overcome the body’s inertia. Thus, training techniques involving a high external resistance are useful for developing acceleration (Ebben et al. 2001). When training for field sports, it is important that any gains resulting from strength and power training are translated into performance-specific movements, such as sprinting. When playing matches, there are alternating demands for energy provision for bursts of high-intensity effort (such as several strokes, swift direction changes, brief accelerations, and in between accelerations and decelerations, energy is replenished and equilibrium is restored (by oxidative metabolism) by intramuscular phosphates and glycolysis (Fernandez-Fernandez, J et al. 2009; Glaister M et al., 2005; Smekal, G et al. 2001; Spencer M et al., 2005)

High-intensity interval training (HIIT) is as a time-efficient alternative to moderate- or low-intensity continuous exercise for improving variables related to endurance and anaerobic performance in young and adolescent athletes (Engel et al., 2018). High-intensity interval training (HIIT) embraces a variety of interval protocols with varying duration and interspersed recovery breaks involving (i) “repeated sprint training” (RST) with sprints of ∼3–7 s duration, interspersed with recovery periods of less than 60 s, (ii) “sprint interval training” (SIT) with ∼30 s all-out sprints, and 2–4 min of passive recovery periods, and (iii)  HIIT with either short (<45 s) or long (2–4 min) interval durations (Buchheit and Laursen, 2013).

 Adult endurance athletes are one category where HIIT has gained popularity for increasing variables related to performance (Kilen et al., 2014), team sports (Helgerud et al., 2011; Purkhs et al., 2016), individual sport competitions (Bonato et al., 2015; Fernandez-Fernandez et al., 2015; Monks et al., 2017), and team sports (Sperlich and Stöggl, 2014; Stöggl and Björklund, 2017).

Repeated sprints with little recovery time between sprint sessions (i.e., 10-20 maximum sprints or shuttle sprints of under 10 seconds, with short recovery intervals (under 60 seconds); work:rest ratio of 1:4–1:6 are

the hallmark of speed endurance and repeated-sprint ability (RSA)-based training. This type of training causes an increase in the activity of some anaerobic enzymes, which increases the rate at which anaerobic energy is turned over. It also increases the amount of muscle membrane transport proteins that are involved in pH regulation and muscle capillarization, and in some cases, it increases the muscle’s buffering capacity (Dawson, B et al. 1998; Edge et al. 2006; Harner et al. 2000). Additionally, performing maximal or nearly maximal short-term efforts can enhance VO2max values and the activity of aerobic enzymes (Bargomaster et al. 2006; Bargomaster et al., 2008; Bargomaster et al., 2005; Ferrauti, A et al., 2011; Gibala et al., 2006).

In recent years, there have been many studies on the training effect of SIT on sports performance in other intermittent sports such as soccer, basketball, volleyball and field hockey (Elly et al. 2018) Given the markedly lower training volume involved with SIT, this form of training may be used as a potential time-efficient strategy to increase V̇ O2max and endurance performance (Young et al., 2006). SIT causes physiological and biochemical changes that are often connected to increases in VO2max, such as improvements in muscle oxidative capacity, muscle buffering capacity, and nuclear abundance of PGC-1alpha (Gibala et al. 2006; Burgomaster et al. 2008; Little et al. 2010).

Research gap

Different studies had been used to compare the HRV, VO2 max and VO2 peak or Steady-state VO2 in High intensity training (HIIT) and other types of the trainings. Positive findings were reported in each of the HIIT training in increasing the running economy (steady state VO2), VO2 max, balance and agility. There is a lack of findings on the effects of changing the Work:Rest ratio of the HIIT and how the changes can affect on the running economy and the autonomic functions along with balance and agility. Till date, no study has been done to see the effects of the different protocols of HIIT on HRV and foot posture changes on an athlete. To fill this knowledge gap, this study aims to look upon the effects of changing the Work:Rest ratio of HIIT as RST and SIT on different physiological and physical components of an athlete such as- HRV, steady-state VO2 peak, foot posture, agility and balance on the university field sport athletes.

Research question

·       Whether Sprint interval training (SIT) or Repeated Sprint training (RST) is effective to enhance physical performances such as agility in the athletes?

·       Whether Sprint Interval Training (SIT) or Repeated Sprint Training (RST) is effective to enhance the physiological performances such as autonomic functions, running economy and maximum aerobic capacity?

·       Whether Sprint Interval Training (SIT) or Repeated Sprint Training (RST) will show any changes on foot posture before and after the training program?

Objectives of the study

1.     To determine the effects of changing the work:rest ratio of high intensity interval training protocol on field sport athletes.

2.     To find out the effects of SIT on autonomic functions, running economy, maximum aerobic capacity, foot posture, agility.

3.     To find out the effects of RST on autonomic functions, running economy, maximum aerobic capacity, foot posture, agility.

Clinical significance of the study

·       As repeated sprints are an important component of field sports, repeated sprint-based training is very important for the athletes. Without the ability to sustain repeated sprints in a game, there is a greater chance of losing the game. Not only losing a game but it can also affect the various physical and physiological components of an individual. All these factors can contribute to decreased performance and also can gradually lead to overuse injuries or any cardiovascular and respiratory ailments.

·       These types of training will not only increase the repeated sprint ability (RSA) of an athlete but also work on the running economy, heart rate variability, agility, balance and maintaining the correct biomechanical factors required for a game thus, improving their endurance as well as the anaerobic capacity by maximizing their physical and physiological performance in field sports.

·       This study will demonstrate the effects of changing the work:rest ratio of HIIT on physical and physiological performances and whether it is a gain or a loss by interspersing the recovery periods in the training.

·       Studies on the comparison of sprint interval training (SIT) and repeated sprint training (RST) are scarce. The effects were seen separately but their effectiveness still needs to be explored to compare the effects of SIT and RST on physical and physiological performance that includes- HRV, running economy, agility, balance and repeated sprint ability. This study compares the effect of these interventions on field sport athletes.

Hypothesis

Null hypothesis:

·       There will be no significant changes on physical performance after RST and SIT.

·       There will be no significant changes on physiological performance after RST and SIT.

·       There will be no significant changes on foot posture after RST and SIT.

Alternate hypothesis:

·       There will be significant changes on physical performance after RST and SIT.

·       There will be significant changes on physiological performance after RST and SIT.

·       There will be significant changes on foot posture after RST and SIT.

Methods

Sample: A sample of healthy field sport (football, cricket and hockey) athletes will be taken from M.A.K Pataudi Sports complex, Jamia Millia Islamia.

Sample Size: The number of subjects (n=36) are determined using Software G. Power 3.1.9.2 using data based on the changes of running economy on athletes from the study of Fernandez-Fernandez et al., (2012) in which the effect of RST on running economy was assessed and effect size 0.68, alpha level of 0.05 and power (1-beta) of 0.95 and a sample size of 30 was calculated. Finally, the total sample size is 36 subjects (12 subjects in each 3 groups) considering 12% dropouts.

Eligibility:

Inclusion criteria

·        University male athletes of age group 18-32 years.

·       Foot Posture Index-6 should be within normal range (-1 to +6) of foot posture (Gabriel G et al., 2015).

·       Within normal range of BMI- 18.5 to 24.9.

·       Doing sports-specific training for at least 2 days/week (training volume: 8-16 hours per week)

·       Having at least 6 months of playing experience.

·       Working knowledge of English language.

Exclusion criteria

·       Any neuro-musculoskeletal deformities.

·       Recent fracture or injury or who had sustained any injury in the lower extremity within the past 6 months.

·       General medical conditions e.g., diabetes, hypertension, etc.

·       Any neurological disorder.

·       Diagnosed vestibular impairment.

·       Training in any other aerobic or anaerobic training program.

Procedure:

Research design: 3 arms, parallel, randomized controlled trial

Randomisation: lottery system

Allocation: 36 samples allocated in 3 groups- SIT, RST and control group

Concealment: In sealed envelops

Total time required: 6 weeks (3 days per week)

Location of study: CPRS and M.A.K Pataudi sports complex, Jamia Millia Islamia, New Delhi- 110025

Independent variables:

·       Repeated sprint training (RST)

·       Sprint interval training (SIT)

Dependent variables:

·       Autonomic function: will be measured by HRV

·       Running economy: will be measured with Steady- state VO2

·       Foot posture: will be measured by Foot Posture Index-6 (FPI-6)

·       Agility: will be measured by Hexagon Hop Test