Physiological Demands of Rugby Union

ben bunting BA(Hons) PgCert Sport & Exercise Nutriton  Written by Ben Bunting: BA(Hons), PGCert. Sport & Exercise Nutrition. L2 Strength & Conditioning Coach.

Rugby union is a contact sport that blends aerobic with anaerobic demands on the body. As the game modernizes, the players become physically less defined by their positions.

This article looks to answer the physiological requirements of a modern-day rugby union player and covers the following areas:

  • What’s rugby union?
  • Nutritional requirements
  • Concerns for the female athlete
  • Supplements and ergogenic aids
  • Conclusion

What’s Rugby Union?

The game of rugby union consists of a blend of physiological demands, it consists of two halves of 40 minutes game time with lots of intermittent movement which is predominantly aerobic although features high-intensity efforts such as sprinting and high impact tackles. [1]

In terms of gameplay, there are two defined sets of players: the backs and the forwards. Duthie, et al identify that the game consists of high-intensity efforts with incomplete recovery periods, for the forwards this consists of more physical contact whereas the backs cover greater distances around the pitch. [2]

It is reported that elite female players will cover around 5.5-6.4 km during a game with an average heart rate of around 161bpm. [3]

It is reported that the players engage in a large number of high intensive bouts lasting between 5-15 seconds with less than 40 seconds of recovery. [4]

Due to the characteristics of the game, the anaerobic system is in high demand (glycolytic and phosphagen) and the aerobic system (carbohydrates and fats) is exploited for the periods in between (standing, walking, and jogging) and to assist with recovery. [5]

Bell, at al, [6] identify that the forwards display a higher mean heart rate throughout the game and a higher work rate frequency and more time above 90% of their maximum heart rate.

However, they also have higher periods of rest during gameplay which concluded that both sets of positions share similar anaerobic demands regardless of their positional and game-specific demands. [6]

Nutritional Requirements

physiological demands of rugby union

In addition to the anaerobic and aerobic pathways being employed during rugby, the incidence of direct impacts experienced throughout the game as outlined by Bayne et al. [7] need to be addressed.

Da Silva et al, [8] note that a single game of rugby union induces significant muscle damage which reduces performance and increases recovery time. Raised creatine kinase levels [9] increase metabolic cost [10] which need to be taken into account to reduce the risk of injury to the player. [11]

Nutritional intervention is accepted to enhance performance. Beck at al,[12] state that carbohydrate intake maximizes glycogen stores thus maintaining carbohydrate (CHO) oxidation, preventing hypoglycemia, and improving the central nervous system.

A meta-analysis of 2588 articles found that, in the majority, field-based female athletes’ energy, carbohydrate, and iron intake was insufficient to their demands. [13]

The female Triad must also be taken into consideration as part of the performance effects of a Relative Energy Deficiency in Sport. [14]

Athletes subject to around 18 hours of exercise per week require 40-70 kcals/kg/day. [15]

It is recommended that elite athletes consume around 6-10g/kg CHO daily to meet their nutritional requirements, in particular an athlete who has a moderate to a high-intensity exercise program. [16]

To aid with recovery, maintain nitrogen balance, prevent catabolism, illness, injury, and training intolerance it is recommended that an athlete consumes 1.2-2.0g/kg/day  [17] whereas a meta-review of studies concluded that 1.63g/kg/day was optimal. [18]

High-fat diets have not demonstrated any ergogenic benefit to athletes, [19] while it has been noted that female ‘tight-five forwards’ possess significantly greater skin-folds and trunk fat-mass that loose forward positions [20], it is optimal to promote lean mass and reduce fat mass to develop speed, power, and aerobic fitness. [21]

There is little research available into female rugby and whether additional cushioning provided by fat mass is advantageous [22], and due to females’ unique physiological differences and the effect of hormones, nutrition plans need to be carefully considered. [23]

However, general recommendations for fat intake are approximately 30% of calorie intake, yet when fat loss is preferred, this can be reduced to 20% which ranges from 0.5-1g/kg/day, [24] to risk restricting intake below 20% may prevent the absorption of fat-soluble vitamins and fatty acids. [25]

Nutritional Guidelines for Rugby

physiological demands of rugby union

Carbohydrates

In addition to the anaerobic and aerobic pathways being employed during rugby, the incidence of direct impacts experienced throughout the game as outlined by Bayne et al. [7] need to be addressed.

Professional rugby union players, particularly forwards are recommended to consume 6-10g/kg/bw daily of CHO (Buckley, et al 2019), the notion of periodized CHO intake has been identified as not maximizing glycogen storage for match demands (Anderson et al, 2017).

Protein

Insufficient PRO intake can lead to illness and injury. The ISSN recommendation for team sport athletes is 1.4-2.0g/kg/bw (Antonio, et al 2018).

This level of PRO intake is appropriate for those with a calorie deficit to maintain lean muscle mass and optimize body composition (Arciero, et al 2017).

Protein should align with these recommendations and not be consumed in excess, especially at the expense of CHO intake which could affect recovery and training adaptation (Croukamp, et al 2014).

Research from Byrne, et al (2015) suggests that excess PRO intake may reduce EI or CHO intake due to the satiety effects of PRO.

Fat

The recommended intake of fat is no more than 30% of the total energy.

Attention paid to the number of trans and saturated fats is important, amounts greater than 10% of total energy intake are linked to chronic diseases (Antonio, et al 2018).

Fluid

Euhydration is to be achieved prior to exercise at 5-10ml/kg within 2-4 hours (ACSM, 2007). For females at risk of hyponatremia, therefore monitoring fluid intake is critical.

A combination of fluids and water content from foods should equate to 35mL/kg daily to reach euhydration (Barasi, Combet, and Lean, 2017).

Nutritional Concerns for the Female Athlete

Food records for female athletes commonly reveal inadequate energy intake for female athletes which can then lead to mineral deficiencies such as calcium and iron (Gabel, 2006). Disordered eating habits may result in menstrual irregularities and low bone mass (Miller, 2001).

Supplements and ergogenic aids

Supplements can be a contentious subject, but they do have their place to improve performance.

Caffeine intake of 3-8mg/kg has been demonstrated to promote rapid glycogen restoration.

This should be accompanied by a high-quality protein source such as a whey protein shake immediately after exercise to stimulate MPS. [26] 20g every 3 hours post-exercise was found to maximize stimulation of protein-synthesis in resistance training, the main component of rugby training (Areta et al., 2013). [27]

Wyon et al, have suggested that vitamin D supplementation has demonstrated improvements in strength and a reduced risk of injury. [28]

Euhydration to be achieved prior to exercise at 5-10ml/kg within 2-4 hours. [29] For females at risk of hyponatremia, monitoring fluid intake is critical.

Beta-alanine should be considered, but doses individualized and no more than 800mg which has been associated with paresthesia. BA improves repeat sprinting ability alongside training program. [30]

Female athletes can be at risk of high iron turnover due to sweat, urine, and monthly menstruation, thus becoming deficient.

Iron intake may not be adequate, and it is difficult for the body to absorb. [31] The athlete’s consumption of iron should be monitored along with calcium to and a supplement can be used if required. [32]

In addition to this, nitrate supplementation has been shown to improve performance by 4.2% in team sports. [33]

Conclusion

Due to the unique demands on rugby union players, their nutritional intake needs to be highly specific to fuel and support their role.

Female players need to ensure their iron and energy levels are monitored to avoid deficiencies and every player must ensure their carbohydrate intake is sufficient enough to reduce injury, recover effectively and maintain the central nervous system.

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