The Performance and Exercise Physiology of a Central Court Netball Player

The Performance and Exercise Physiology of a Central Court Netball Player

Introduction

Netball is a game played mainly by females, where successful participation depends on various factors. A player requires acceleration to ‘break free’ from an opponent, sudden and rapid changes in direction while jumping to receive a pass or intercept the ball (McGrath and Ozanne-Smith 1998). Allison (1978) described netball as an interval game consisting of sprinting, jumping and shuffling movements interspaced between periods of rest. I will discuss the physiological demands of a central court player and how participation affects her energy systems. I will investigate the most advantageous training methods to improve this athlete’s weaknesses, in-line with the team targets and discuss nutritional and ergogenic aids.

i) The physiological demands of netball

Netball requires good aerobic conditioning, but the high intensity actions associated with the sport, have greater implications on performance (Davidson and Trewartha, 2008). The majority of these actions take less than four seconds (s) (Otago, 1983), with a mean sprint duration of 1.4s (Davidson and Trewartha, 2008). These bursts will stress the adenosine triphosphate (ATP) and phosphocreatine (PCr) systems (McArdle, Katch and Katch, 2007).

A mean work: rest (W: R) ratio of about 1: 3 (Otago, 1983) was reported, with central court players having higher ratios (Davidson and Trewartha, 2008). ATP can re-synthesize in three to five minutes and complete creatine phosphate re-synthesis occurs in about eight minutes (Baechle and Earle, 2008). This ratio suggests that after subsequent high intensity bursts the rest interval may be insufficient to fully replenish the ATP-PCr stores. This will stress the anaerobic glycolytic pathway, which will result in a build up of lactate in the muscles. This lactate, along with hydrogen ions from ATP hydrolysis seems to advance peripheral muscle fatigue (McArdle et al., 2007).

Loughran and O’Donoghue, (1999) showed that players performed less high intensity actions as the game progressed. This suggests fatigue and complete lactate clearance is not occurring even during the quarter and half time breaks. The central positions are more active than other positions (McManus, Stevenson and Finch, 2005), however, there seems to be some discrepancy on whether they do more (Loughran and O’Donoghue, 1999) or less (Otago, 1983)   high intensity actions than the other positions. Both have implications on physiological demands.

There are a number of studies that have reported distances covered of up to 8 kilometres per game for central court players (McManus et al., 2005, Davidson and Trewartha, 2008). This will stress the player’s aerobic energy system. Woolford and Angove, (1991and 1992) showed that central players spent a significant amount of time with a heart rate (HR) of greater than 85% maximum and in some games a quarter of the time at above 95% maximum HR. Lactate threshold occurs at approximately 70%-80% in well trained individuals (Baechle and Earle 2008). Spending time above this level is going to accelerate exhaustion. With parts of the game played at close to maximal oxygen consumption, there will be a period of an oxygen deficit before the aerobic system adjusts to the required levels of oxygen uptake.

Although the studies revealed trends which occur in netball games, much of the information is an average taken over a small number of games. Individual data suggests that some games can be more or less intense than others. Although netball is highly anaerobic, aerobic patterns suggest that good conditioning is required in both for successful participation.

ii) Training practices to develop weak areas

Sprint speed – 10 metre flying and standing start

Speed is the ability to achieve high movement velocity (Sheppard, 2003). Netball players require the ability to accelerate, engage in play, decelerate and accelerate again. Although players sprint an average of 550 metres in a netball game, the average time per sprint is 1.4s (Davidson and Trewartha). This is insufficient time to achieve maximal velocity (Cronin and Hansen, 2006) before change in mode is required. Acceleration is combination of technique and force production capacity. In netball, a player is required to accelerate from different modes, not just a static position. This suggests that force production may be the more important of the two components (Cronin and Hansen, 2006).

Current coaching programmes use various forms of resistance training and plyometric training to improve acceleration. A study by Delecluse, Coppenolle, Willems, Leemputte, Diels and Goris (1994) found that high velocity (HV) training improved the acceleration phase over 100m. This is also more specific to netball due to the rapid changes in velocity and mode. The exercises should be sports specific and effect multi-group muscles. Cronin, Ogden, Lawton and Brughelli (2007) found no correlation between acceleration and maximal strength. Resisted sprint training using sleds and uphill running has shown to be an effective means of developing acceleration (Cronin and Hansen, 2006, Harrison and Bourke, 2008). This may be due to the characteristics specific to acceleration including longer stance phase and greater trunk angle. With training replicating these characteristics, greater enhancements can be achieved using the principle of specificity and overload.

Although not as important in netball, maximal velocity may occur. Improving flying 10m drills involves increasing muscle fibre recruitment and firing frequency (Gonzalez and Gaitan, 2009). This can be achieved using explosive exercises and a combination of foot drills (Brown, Ferrigno and Santana, 2000).

In designing a programme to develop acceleration and speed in a netball player, sport specificity, overload and speed seem to be the key. A combination of plyometrics, high velocity and explosive training, technique drills and sprint resisted tasks seem to be most appropriate.  In the four weeks leading up to the first match, the player’s improvements are likely to be due to neuromuscular adaptations.

Agility – Zigzag run

Baechle and Earle (2008) describe agility as the skills and abilities needed to explosively change movement velocities or modes. In most team sports, including netball, agility is the reaction to the ball, an opponent or a team mate (Young and Farrow 2006). Although agility uses components of speed, leg strength and power, it does not seem to be highly related to any of these factors (Young, McDowell and Bentley, 2001, Young and Farrow 2006). Plyometric drills which focus on single leg lateral and forward movements, showed improvements in lateral movement ability and four metre lateral and forward sprints in tennis players (Salonikidis and Zaferiridis, 2008). This can easily be applied to netball player’s who require lateral, forward and deceleration movements.

Although high level contextual tasks, such as open skill, mirror and shadow drills would be the most appropriate training for a netball player, Holmberg (2009) discusses the importance of introducing low level contextual tasks first, before moving to more advanced tasks. These include simple technique training, like, stepping drills and single directional changes. This would progress to closed skill pattern running, which combines predetermined agility tasks like the zigzag test. Closed skill exercises are not as useful developing agility in elite athletes, as most intermittent sports require a reaction to a stimulus (Dawes 2008). Tasks should be at high intensity and others at low intensity with minimal rest to stress different energy systems used in a game situation (Young and Farrow 2006).  

According to Young and Farrow (2006), due to the complex nature of agility, it is difficult to isolate which tasks are the most important. In this article they feel that decision making is the most important factor in improving agility performance in a game situation. A netball player could learn to react to specific cues to achieve an expected outcome. This can be achieved in a practice game situation where pre-determined actions are used to provoke a certain reaction. 

Although the zigzag test is used to test agility and allows for a reliable re-test, it does not seem to be highly representative of game agility. This test can be improved by participating in regular closed skill activities which resemble the test (Young, McDowell and Bentley, 2001). This along with a well developed plyometric programme using position specific exercises, would improve the zigzag re-test results.       

Power – Vertical jump

Power production and ability to rapidly change from one position to another over the shortest period of time is a vital component for success in netball. Power is an important component in speed, acceleration, deceleration and agility. The vertical jump height (VJH) is a good indicator of an athlete’s ability to produce power as well as a test to determine readiness for the upcoming season (Klavora, 2000). This anaerobic power test is performed at high speeds to produce maximal power output over a short duration. (Baechle and Earle, 2008).

Current literature shows that although, resistance training or plyometric training improve VJH, combination training shows significantly greater gains (Adams, O’Shea, O’Shea and Climstein, 1992; Fatouros, Jamurtas, Leontsini, Taxildaris, Kostopoulos and Buckenmeyer, 2000).  This indicates that maximal muscular power in the form of a vertical jump requires both maximum muscular strength and high speed muscular strength. Using the stretch-shortening cycle exercises seems to be more beneficial than concentric exercises. For greatest effects the overload principle needs to be utilised by slowly progressing the volume and intensity. Due to the volume and intensity restraints, this programme should only be used in pre-season or post-season (Baechle and Earle, 2008). Although the full effects will not be noticed during the four weeks preceding her first Super league match, combination training seem to be the most effective way to improve this player’s anaerobic power.

Improving the vertical jump with improving anaerobic power in mind, should come in the form of resistance training and plyometric training. The resistance training should take the form of squats or cleans depending on the player’s level of resistance training experience, using the squat as the safer option. Pate (2000) suggests resistance training twice a week and plyometric training twice a week on different days as pre-season/pre-competition guidelines. Ford, Myer, Smith, Byrnes, Dopirak and Hewett (2005) showed that by using a ‘goal’ as a motivating tool they could improve the vertical jump performance in male and female soccer players in a test situation. Introducing a ball into training sessions as a motivating aid could help illicit maximal effort during anaerobic power exercises.   

Her training status is of particular concern as no resistance or plyometric training history is supplied. If she is not at a reasonable level as indicated by the NSCA positional statement for plyometric training, the volume and/or the intensity may need to be adjusted in accordance with her current abilities. Channell and Barfield (2008), report that neural factors will contribute to the improvements during the initial period of training, especially in untrained individuals.  

High intensity endurance – Yo-yo test

The Yo-yo intermittent recovery level one (Yo-Yo IRL1) test focuses on the capacity to carry out intermittent exercise leading to maximal activation of the aerobic system (Bangsbo, Iaia and Krustrup, 2008). The Yo-Yo IRL1 test has been shown to be a valid test for many sports including basketball (Castagna, Impellizzeri, Rampinini, D’Ottavio and Manzi, 2008) and soccer (Castagna, Impellizzeri, chamari, Carlomagno and Rampinini, 2006) for the assessment of aerobic-anaerobic fitness and game related endurance. Similarities can be seen between these sports and netball.

Castagna, et al, (2006), found no correlation between  O2max and ventilation threshold (VT) with the Yo-Yo IRL1 test. There are other studies (Krustrup, Mohr, Amstrup, Rysgaard, Johansen, Steensberg, Pedersen and Bangsbo, 2003), where a correlation was found between  O2max and the Yo-Yo IRL1 test. It is suggested by Bangsbo (2008) that the Yo-Yo IRL1 test is a useful test to assess sports characterised by intermittent exercise, for seasonal changes in athletic physical capacity.

A recent study by Iaia, Rampinini, and Bangsbo (2009) found that both aerobic high-intensity running training (>85% HRmax) and speed endurance interval training can be used during the season to improve high-intensity intermittent exercise performance. Speed endurance training performed twice a week showed significantly greater improvement in Yo-Yo IR test results after eight to twelve weeks in footballers. Similar results would be expected in netball players. 

Wong, Chaouachi, Chamari, Dellal and Wisloff (2009) compared concurrent muscular strength and high intensity interval training in professional soccer players. The results showed significant improvements in distances covered in the Yo-Yo IR test. The training was performed twice a week on the same day with five hours between sessions. The results support the correlation between improvements in vertical jump height and the Yo-Yo IRL1 test. This information is useful in designing an effective training programme. Iaia et al (2009) say that the training should be game related, and specific to the technical, tactical, and physical demands imposed on each player. This would also be true for netball.

The netball player’s training seasons should consist of explosive strength training with progressive overload. The exercise selected should be as closely related to the skills required in netball. The explosive training should come in the form of plyometrics. Although high intensity and interval training were both effective in improving the results, interval training seemed to be the favoured methods. This can be implemented in a practice game situation, using high intensity work periods interspaced with active rest periods. 

iii) Nutrition and ergogenic aids

All athletes need to consider proper nutrition to achieve optimal performance as they have different requirements to participate in different sports and activities. Carbohydrates serve primarily as an energy source in human physiology (Baechle and Earle 2008). Carbohydrates are used to maintain blood glucose levels, recover glycogen stores, maximize protein balance and help with fuelling and repair (Wildman, Kerksick and Campbell, 2009). The ingestion of carbohydrate is dependent on the energy expenditure. What seems to be more important is the timing of ingestion to maximise the glycogen stores and the recovery effect. In a literature review by Wildman, Kerksick and Campbell, (2009) they discuss the importance of pre-exercise loading with 1-2g/kg three to four hours prior to exercise to raise glycogen stores. During exercise they suggest 30-60g per hour of a carbohydrate sports drink and 1.5g/kg immediately post exercise using about 1.2g/kg ever 30min for five hours. This is sufficient to completely replenish glycogen stores within 24 hours.  

Protein is required to maintain the balance between muscle protein synthesis and break down. For athletes training at high intensity levels 1.2g/kg/day – 1.6g/kg/day of protein is suggested (Phillips, Moore and Tang, 2007). More has not been proven to be beneficial. Antonio (2008) reports, that the timing and quality of the protein ingested is important and suggests a pre and post exercise meal. This has been shown to enhance performance and muscle

fibre size. This seems relevant for the netball player, who will be participating in high levels of training leading up to her first game. Schilling, (2008) reports, the female athletes often neglects high quality protein intake due to misconceptions that it is high in fat. 

Fat is an important macronutrient which must be considered carefully. Many female athletes develop a sigma with regard to fat intake (Schilling, 2008). Fat content in the diet should not exceed 30% in most cases with less than 10% consisting of saturates (McArdle, Katch and Katch, 2007). According to Schilling (2008) it is important to educate female athletes on the benefits of fat. These include providing energy, transport of vitamins, production of hormones needed to maintain a regular menstrual cycle and a proactive layer for organs. In a study by Elliott and Smith (1983), the mean average fat percentage in netball players was just above 24%, which is average for females participating in similar sports (Baechle and Earle 2008). This athlete has been out of intense training for a period of 12 weeks before returning to gym and pool training for four weeks. It is possible to assume that she may not have modified her eating patterns as a result of the injury. This coupled with boredom and limited training could have lead to a possible increase in her fat percentage and loss of lean muscle mass (Baechle and Earle 2008). This may not have changed her mass but skin fold analysis may reveal any increases in fat percentage.

Along with the normal vitamins and minerals, female athletes need to consider calcium and iron more carefully (Hickson and Schrader, 1982). According to Schilling (2008), many females fall short of their 1,300 mg/day calcium due to misconceptions regarding calcium rich foods being high in fat. Iron is another problem. Females are at a higher risk of developing anaemia from a combination of poor diet and menstruation, leading to fatigue and more serious physical problems.  

Although netball players are not considered a high risk group it is worth considering the possibility of the female athlete triad or components of the condition. If this player is highly motivated to succeed without the correct intervention, certain issues can occur (Pantano, 2009). Although her fracture was traumatic in nature, it is worth considering whether there may have been an innate weakness in the tibia. A symptom of the female athlete triad is stress fractures (Brandstater 1995) normally associated with an eating disorder, menstrual dysfunction and bone density issues. There are no other indications of this condition but it may be worth discussing her per-injury status with regard to eating habits and menstruation.  

There are a number of possible ergogenic interventions which can be utilised to aid in this players return to competition. Some actions may not be as important as others. Bishop, Jones and Wood, (2008) did a brief review on recovery strategies. They conclude that although good nutrition, rehydration and rest are important components of recovery, actions like massage or ice therapy may come down to personal preference.

Conclusion

The programme over the next 4 weeks will consist of resistance training and plyometric exercises, concentrating on speed of execution and maximal effort. Running technique, fast foot drills, speed resisted training and intermittent speed endurance interval training can be introduced into sport specific training sessions as preparation drills and on-court fitness sessions. This will improve the weaknesses highlighted. It is important to make all the exercises as sports specific as possible and allowing sufficient recovery between exercise and training sessions. A well balanced diet and a good understanding of recovery strategies are vital in any performance enhancing process. Considering common preventable effects is imperative in developing a sustainable, healthy athlete.

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By: N.Brink