Thursday, January 11, 2018

The Energetics of Beach Volleyball: How Collegiate Beach Athletes May Be at Risk for Low Energy Availability

Introduction

The number of women and girls playing sports in school is at an all time high.  Female sport participation in college has steadily grown for decades and now exceeds 217,600 athletes.[1] Increased participation has followed new opportunities for women to compete through sport sponsorship and athletic aid.[2]  As the NCAA's newest sport, beach volleyball is approaching its 7th season of competition and its second as a championship sport.  Since being added to the emerging sports list in 2009, the number of beach volleyball teams has grown steadily.  In 2012, there were fifteen Division I teams and 204 players, while in 2017, that number has increased to 64 teams across Divisions I, II and III and 1,070 players total.[3]  As sport sponsorship has grown so has the number of players.[4]  Sponsorship alone, however, is not the only factor driving growth.  Beach volleyball rosters have expanded 22.8% since the sport's first season in 2012.[5]  The average Division I roster size is now 16.7 players compared to 13.6 in the 2011-12 season.

Beach volleyball's growth has expanded access to the extraordinary benefits women and girls derive from athletic participation.[6]  It has also lead to a greater need to understand the unique health concerns of female athletes, including issues related to sex-specific physiology.  As nearly 60% of head coaches for Division I beach volleyball programs are men,[7] exploring the interaction of the demands of beach volleyball and women's health serves an important educational purpose.

In this article we'll explore the unique energy costs of playing beach volleyball to better understand the need for these female athletes to train and fuel properly for long term health and success.

Beach Volleyball - Physical Requirements and Physiological Demands

Beach volleyball is a physically demanding outdoor sport played in all weather conditions.[8]  Game tactics require players to move in multi-directional rapid bursts, across an 8x8 meter court, while explosively performing both vertical and horizontal jumping movements.  The game is played in a best-of-three-sets match format with matches lasting 40-54 minutes depending on the number of sets played.[9]  Sets to 21 points last approximately 18 minutes[10] and consist of about 38 rallies.[11]  A typical rally lasts about 7 seconds[12] during which players will jump on average 2.2 times, either blocking or attacking.[13].  Players compete in several matches over the course of a day and most events are contested over multiple days.[14]  Physiologically, the game actions, tempo, and movement patterns make beach volleyball a game of intermittent high intensity exercise interspersed by frequent periods of brief rest.[15]  At elite levels, players perform at approximately 75% of their maximum heart rate (about 146 bpm) throughout the match.[16]  A third of the match is played in excess of 80% of HRmax.[17]  According to data from Harvard Medical School, playing beach volleyball for 30 minutes burns between 240 and 355 calories, depending on playing weight.[18]

The physical demands of beach volleyball are heightened by the surface on which it is played.  Sand is difficult to maneuver in because it compresses and displaces at the point of contact.[19]  As the surface moves, athletes experience a loss of potential kinetic and elastic energy, which decreases the overall efficiency of movement for the energy being exerted.[20]  Some research has associated performing in sand with an increased load on the lower limb muscles because they work harder to stabilize the body as sand displaces during athletic movement.[21]  As anyone who has gone to the beach knows, there's a sensation of having to exert more effort to move in sand than on a firm surface.  The sand surface in beach volleyball is also highly unpredictable because it can vary in depth,[22] composition,[23] and temperature[24] from event to event.     

Perceived exertion while moving in sand is also associated with biomechanical adaptations during sand performance.  Research has shown several changes in the way the ankle, knee flexor, and hip joints work during the stride and jump mechanics of beach volleyball when compared to similar actions performed on a rigid surface.[25]  The biomechanical differences in the way the body functions in sand have been associated with a greater energy cost of performance. 

Lastly, there is a higher level of muscle activation and physiological strain associated with exercising on sand compared to a firm surface.[26]  The sand thus imposes an additional physiological component to the demands of beach volleyball above those associated with performing the technical and tactical skills of the game. 

Beach Volleyball - Energy Costs

The energy costs of performing on sand have uniformly been shown to significantly exceed that of performing on a rigid surface.  When compared to firm surface activity, sand imposes a 1.8 to 2.7 times greater energy cost to walking,[27], a 1.2 to 1.6 times greater energy cost to running,[28], and a 1.2 times energy cost to jumping.[29] 

The energy cost of sand training means beach volleyball players exert greater energy pursuing the ball and jumping to serve, attack, and block than if they played indoors or on grass.  Beach volleyball thus imposes unique energy demands on its players.  The magnitude of the energy costs depends in part on the amount of sand displacement, which can vary based on the characteristics of the sand, including its granular composition, moisture content, and depth.[30]  This is why beach volleyball players find it easier to jump in shallow and wet sand than in deep and dry sand.  It also explains the difference players feel when they compete on traditionally "hard-packed" beaches, such as on the west coast of Florida, compared to deep sand beaches, such as in Hermosa Beach, California.

In short, beach volleyball athletes expend substantially more energy playing their sport in sand than their athletic counterparts playing on firm surfaces when performing lateral moves, running, diving, and jumping.

As collegiate beach volleyball attracts more women and girls into the sport, and the game itself continues to evolve, the unique physical and energy demands of the game must be understood within the context of the health and physiological needs of its female athletes.

Recent Study - Risk of Low Energy Availability in Beach Volleyball Athletes

In 2017, Gilchrist et al. examined the energy availability and muscle glycogen levels of 18 NCAA Division I beach volleyball players (ages of 19 and 22 years old; weight 63.3 to 68.4 kilograms, and height 174.5 to 180.1 centimeters). 

The authors examined the participants' dietary intake, energy expenditure, and energy availability by evaluating a 7 day food and activity log.  The players' resting metabolic rate (RMR) and muscle glycogen levels were measured before and after practice.  The analysis revealed that 55.6% of the players were not eating enough to meet the caloric needs associated with the RMR.  No players were eating enough carbohydrates, and 94.4% of the athletes were experiencing low energy availability.   Overall, the authors concluded that female collegiate beach volleyball athletes are at risk of experiencing low energy levels.[31] The findings were associated with the players' inadequate dietary habits for the high energy demands of beach volleyball.

Low Energy Availability - Physiological Function and Performance

Low energy availability among female athletes is a significant concern as it can inhibit an athlete's response to training and hinder her performance in competition.  More importantly, low energy can be symptomatic of disordered eating behaviors which, if not diagnosed and treated, can lead to serious long term health consequences.

LEA develops when athletes do not consume enough food to meet their specific energy requirements for training, competing, and normal physiological functioning.[32].  Adequate calorie intake is necessary to maintain lean tissue mass, immune and reproductive function, and optimal athletic performance.[33]  When supply is low the body works to conserve energy through a range of endocrine adaptations that alter its ordinary functioning.[34]  It also begins to burn fat and lean tissue as fuel, a process that decreases muscle mass and impairs strength and endurance.[35]  Female athletes with low energy intake have also been found to consume too few micronutrients and be at risk of experiencing deficiencies in calcium, iron, magnesium, zinc and the B-complex vitamins, among others.[36]  Similar to inadequate caloric intake, micronutrient deficiencies can impair biological functioning and contribute to sub-optimal athletic performance.[37]

Clearly, a beach volleyball player who is consuming less energy than is required to train and perform in her sport is at risk of suffering performance impairments.  For this reason it is essential that beach players' caloric intake be monitored and adjusted to properly fuel their bodies for the energy demands of the sport.[38]  This requires a coordinated effort among sports coaches, sport nutritionists, and team doctors.  While a number of studies indicate that female athletes are not consuming enough calories to meet their energy demands,[39] to date there is little research on the caloric burn or energy needs of female beach volleyball players in the collegiate game.  The work of Gilchrist and her colleagues is an important contribution to our understanding, and reliable evidence that collegiate beach players may be at risk for low energy availability.

LEA - Female Athlete Triad

The role of collegiate sport coaches is first to support and protect the long term health of athletes in their care.  LEA thus raises concerns that run more deeply than an athlete's impaired athletic performance.  Women and girls who experience low energy may be at risk for a triad of serious health conditions known collectively as the female athlete triad.   

The female athlete triad is a combination of interrelated conditions: (1) low energy availability, with or without disordered eating, (2) menstrual dysfunction, and (3) low bone mineral density.[40]  The triad is considered a spectrum disorder meaning each condition is evaluated on a range from low to higher levels of pathology and any one condition can meet the criteria for diagnosis.[41]  Low energy is widely considered the cornerstone, however, because it creates a risk of developing the other components of the triad.[42]

We've posited that the high energy demands of beach volleyball may contribute to female players' susceptibility for LEA and noted that the latest research supports the view.  In the following section we'll examine whether other aspects of collegiate beach volleyball contribute to the risk of LEA in female athletes. 

LEA in Beach Volleyball

Body Image

While female athletes in any sport can develop low energy availability, some sport settings contribute to a greater prevalence of the condition.  Studies have shown that athletes who perceive pressure to appear lean are more susceptible to the female athlete triad.[43]  Beach volleyball has not traditionally been considered a lean-athlete sport in the category of dancing, gymnastics, running, and diving.  However, the beach culture of the sport, in which participants traditionally have competed in bikinis, should not be ignored in a search for risk factors particularly in light of evidence that many female athletes report concern with the weight and shape of their body.[44]  As the sport has become more professionalized uniform requirements have prohibited (college) and no longer require (international and Olympic) bikinis.  The restrictions do not, however, apply to junior girls or collegiate players training outside of their school season.  The drive in some female athletes to improve their body image on the beach could be considered a risk factor in beach volleyball.[45]  

Time Demands - Eating Disruptions

As LEA is related directly to energy intake, collegiate beach volleyball athletes who skip meals to meet academic or training schedules (or simply to get more sleep) could be at risk of expending more energy than they are consuming.  Time demands on collegiate athletes are intensive and may disrupt optimal eating patterns and choices.[46]  The understanding of this risk for collegiate athletes suggests that it may be beneficial to monitor nutritional intake and educate players in time management skills that can mitigate the adverse impact of time demands on beach volleyball athletes' energy levels.

Dual Sport Athletes

As many as 50% of Division I beach volleyball players are dual sport athletes who train and compete both for their school's indoor and beach teams.[47]  Collegiate beach volleyball is thus unique in the high prevalence of athletes who have no official off-season and who may train and compete under different coaching and support staffs.  As the two sports impose distinct energy demands on players, and the continuous nature of training in-season adds hours of additional training time to players schedules, the dual sport status of many players raises a substantial risk that energy consumption may be inadequate to meet energy demands.

Sport coaches with dual sport athletes should implement energy and nutrition monitoring protocols to ensure female athletes are not at risk of developing low energy stores.  The services of a sports dietitian educated in the unique energy requirements and physiological demands of beach volleyball should also be made available to players as education has been shown to improve nutritional intake and knowledge in collegiate volleyball players.[48]

Conclusion

The presence of LEA in female beach players is particularly concerning given the unique energy demands of the sport and current diagnostic guidelines.  Low energy alone could meet the criteria for diagnosis of the female athlete triad and certainly should trigger further evaluation and monitoring.  Sport coaches should thus be educated in the risks of LEA, skilled in identifying symptoms, and prepared to seek professional assistance from outside the staff.  Identification and treatment requires a multidisciplinary, coordinated approach as early intervention and treatment are essential to the avoidance of long term health consequences for female beach volleyball players.

Acknowledgement

I am grateful to Mary Mulcahey, M.D., Director of the Women's Sports Medicine Program & Associate Professor in the Department of Orthopaedic Surgery at Tulane University, for reviewing an earlier draft of this article and providing invaluable editorial assistance.

References

[1]  National Collegiate Athletic Association. 1982-2007 NCAA Sports Sponsorship and Participation Report. Indianapolis, IN: National Collegiate Athletic Association; 2007.  Sports Sponsorship, Participation and Demographics Search [Data file]. Retrieved from http://web1.ncaa.org/rgdSearch/exec/main.  Participation rates are only for female athletes enrolled in NCAA member institutions and participating in sports for which the NCAA conducts championships.  Participation and sport sponsorship data used throughout this article is through the 2016-17 academic year and as of October 2017.

[2]  In 2016-17, there were 149 women's team added at NCAA institutions and 87 women's teams dropped, making it a slow year of growth for women's sports.  Since 1988-89, more than 5,609 women's teams were added to NCAA athletic programs, resulting in a net gain of 3,390 teams after adjusting for changes in sports sponsorship.  The average net gain for women's sports teams over the last 18 years is 188.3 teams per year.  Compared to 1981-82 (when the detailed records began), the average NCAA campus has approximately 96 more female athletes.  National Collegiate Athletic Association.  1982-2007 NCAA Sports Sponsorship and Participation Report. Indianapolis, IN: National Collegiate Athletic Association; 2007.  Title IX of the Education Amendments of 1972 requires that scholarship dollars be spent proportional to participation.  20 U.S.C. §§ 1681 et seq.; 34 C.F.R. § 106.37(c).

[3] National Collegiate Athletic Association. 1982-2007 NCAA Sports Sponsorship and Participation Report. Indianapolis, IN: National Collegiate Athletic Association; 2007 (64 teams).  Sports Sponsorship, Participation and Demographics Search [Data file]. Retrieved from http://web1.ncaa.org/rgdSearch/exec/main (65 teams).  Participation rates are limited to female athletes enrolled in NCAA member institutions.  As many as 392 additional women compete on 32 NAIA and junior college beach volleyball teams.  American Volleyball Coaches Association.  College Beach Volleyball By the Numbers.  Lexington, KY: American Volleyball Coaches Association; July 2017.  Retrieved from https://www.avca.org/res/uploads/media/CollegeBeachVB-ByTheNumbers-6-17-.pdf.

[4]  According to the American Volleyball Coaches Association (AVCA), 50% of Division I rosters are comprised of dual sport athletes - athletes who play both indoor and beach volleyball.  American Volleyball Coaches Association.  2017 AVCA College Beach Volleyball Survey Results - 64 Teams.  Lexington, KY: American Volleyball Coaches Association; June 22, 2017.  Sport sponsorship therefore provides new collegiate participation opportunities to approximately 50% of the female athletes on beach volleyball rosters and new sport participation opportunities to 100% of those athletes. 

[5] Compare the average roster size of 13.6 in 2011-12 (15 D-I teams and 204 players) to the average roster size of 16.7 in 2016-17 (64 teams and 1070 players).

[6]  Girls who participate in organized sports have a more positive self image and are at lower risk for teen pregnancy, substance abuse, suicide, and depression.  Sports participation by young girls also positively correlates with improved academic achievement in math and science.  Staurowsky, E.J., DeSousa, M.J., Miller, K.E, Sabo, D., Shakib, S., Theberge, N., Veliz, P., Weaver, A. & Williams, N. (2015).  Her life depends on it III: Sport, physical activity and the health and well being of American girls and women.  East Meadow, NY: Women's Sports Foundation.

[7]  Independent survey of NCAA D-I beach volleyball coaching staffs conducted by Shane Spellman, Assistant Coach, Beach Volleyball at Tulane University.  Data is based on 50 programs currently staffed by a head coach.  Four programs currently in the process of hiring have been excluded.  Also excluded are three programs that have publicly announced an intention to add beach volleyball to their athletic programming commencing with the 2018-19 academic year.  Exclusion of putative future teams was made regardless of whether a coaching staff was announced as part of the sport sponsorship plan.

[8]  See, e.g., Ulmer, A., "Beach Volleyball: It Even Rains on Copacobana."  10 Aug. 2016, www.reuters.com/article/us-olympics-rio-bvolleyball-weather/beach-volleyball-it-even-rains-on-copacabana-idUSKCN10L24Q (describing rainy, windy, and cold conditions during beach volleyball events of 2016 Summer Olympic Games in Rio); Robertson, L., "No matter the weather in London, beach volleyball goes on."  31 July 2012, http://www.miamiherald.com/sports/article1941619.html (describing rainy, cold conditions during beach volleyball events of 2012 Summer Olympic Games in London); Martin, D.E. (1998).  Measurement of climatic heat stress at outdoor venues for endurance events at the Atlanta Olympic Games, 1996.  Sports Medicine Training & Rehabilitation, 8 (4), 321-46 (describing relationship between temperature and beach volleyball players' health and performance during 2008 Summer Olympic Games in Atlanta).

[9]  Hayrinen, M., & Tampouratzis, K. (2012).  Technical and tactical game analysis of elite female beach volleyball.  KIHU Research Institute for Olympic Sports Pub. No. 37, 10.  Two set matches averaged 39 minutes 42 seconds.  Three set matches averaged  53 minutes 41 seconds.

[10]  Hayrinen, M., & Tampouratzis, K. (2012).  Technical and tactical game analysis of elite female beach volleyball.  KIHU Research Institute for Olympic Sports Pub. No. 37, 10.  Set duration for 15 point third sets averaged 14 minutes 24 seconds.  Id. We've chosen to include data only from the women's game as the physical demands of women's beach volleyball are more relevant to the issue under discussion than the different requirements of the men's game.

[11]  Hayrinen, M., & Tampouratzis, K. (2012).  Technical and tactical game analysis of elite female beach volleyball.  KIHU Research Institute for Olympic Sports Pub. No. 37, 10.

[12]  Palao, J.M., Lopez-Martinez, A.B. & Ortega, E.  (2015).  Physical actions and work-rest time in women's beach volleyball, International Journal of Performance Analysis in Sport, 15, 424-429 (mean rally length of 6.46 during 2008 Olympic Games); Hayrinen, M., & Tampouratzis, K. (2012).  Technical and tactical game analysis of elite female beach volleyball.  KIHU Research Institute for Olympic Sports Pub. No. 37, 10 (average rally length of 6.9 seconds in FIVB World Tour and European Championships).

[13]  Palao, J.M., Lopez-Martinez, A.B. & Ortega, E.  (2015).  Physical actions and work-rest time in women's beach volleyball, International Journal of Performance Analysis in Sport, 15, 424-429.  Jumping requirements are slightly higher for blockers than defenders.

[14]  Collegiate and domestic professional beach volleyball events are most commonly contested over two (2) days.  International events are played over a period of 2-3 days (excluding the qualifier event preceding the main draw competition).  The Olympic beach volleyball tournaments for each gender are contested over a period of two (2) weeks.

[15]  Magalhaes, J., Inacio, M., Oliveira, E., Ribeiro, J.C. & Ascensao, A. (2011).  Physiological and neuromuscular impact of beach-volleyball with reference to fatigue and recovery.  Journal of Sports Medicine and Physical Fitness, 51, 66-73.

[16]  Magalhaes, J., Inacio, M., Oliveira, E., Ribeiro, J.C. & Ascensao, A. (2011).  Physiological and neuromuscular impact of beach-volleyball with reference to fatigue and recovery.  Journal of Sports Medicine and Physical Fitness, 51, 66-73 (approximately 75% - male players); Jimenez-Olmedo, J.M., Pueo, B, Penichet-Tomas, A., Chinchilla-Mira., J.J. & Perez-Turpin, J.A. (2017).  Physiological work areas in professional beach volleyball: a case study.  Retos: Federacion Espanola de Asociaciones de Docentes de Educacion Fisica (FEADEF), 31, 94-97  (players' median max heart rate between 71.71% and 84.78%).

[17]  Magalhaes, J., Inacio, M., Oliveira, E., Ribeiro, J.C. & Ascensao, A. (2011).  Physiological and neuromuscular impact of beach-volleyball with reference to fatigue and recovery.  Journal of Sports Medicine and Physical Fitness, 51, 66-73.

[18]  "Calories burned in 30 minutes for people of three different weights."  Harvard Health Publishing, 2004, July.  (Updated, 17 March 2017), www.health.harvard.edu/diet-and-weight-loss/calories-burned-in-30-minutes-of-leisure-and-routine-activities.

[19]  Binnie, M.J., Dawson, B., Pinnington, H., Landers, G. & Peeling, P.  (2004). Effect of sand versus grass training surfaces during an 8-week pre-season conditioning programme in team sports athletes.  Journal of Sports Science, 32(11), 1001-1012 (overcoming the lack of initial fixed resistance in sand requires greater exertion of effort and expenditure of energy).

[20]  Gaudino, P., Gaudino, C., Alberti, G., & Minetti., A. (2013).  Biomechanics and predicted energetics of sprinting on sand: Hints for soccer training.  Journal of Science and Medicine in Sport 16, 271-275; Zamparo, P., Perini, R., Orizio, C., Sacher, M., & Ferretti, G., (1992).  The energy cost of walking or running on sand.  European Journal of Applied Physiology and Occupational Physiology, 65(2), 183-187.  See Lejeune, T.M., Williams, P.A., Heglund, N.C. (1998).  Mechanics and energetics of human locomotion on sand.  Journal of Experimental Biology. 201(Pt 13), 2071-2080.

[21]  Zamparo, P., Perini, R., Orizio, C., Sacher, M., & Ferretti, G., (1992).  The energy cost of walking or running on sand.  European Journal of Applied Physiology and Occupational Physiology, 65(2), 183-187; Lejeune, T.M., Williams, P.A., Heglund, N.C. (1998).  Mechanics and energetics of human locomotion on sand.  Journal of Experimental Biology. 201(Pt 13), 2071-2080.

[22]  Sand must be at least 40 centimeters deep and comprised of fine, loosely compacted grains for international competition.  Federation Internationale de Volleyball (FIVB), Official Beach Volleyball Rules, Rule 1.2.2 (2001-2020); USA Volleyball Beach Domestic Competition Regulations, Rule 1.2.2 (2015-17).  Maximum depth is unregulated.

[23]  The sand should be "levelled . . . as flat and uniform as possible" on a playing surface "free of rocks, shells and anything else, which can represent risks of cuts or injuries to the players."   Federation Internationale de Volleyball (FIVB), Official Beach Volleyball Rules, Rule 1.2.1 (2001-2020);  USA Volleyball Beach Domestic Competition Regulations, Rule 1.2.2 (2015-17).

[24]  The sand reportedly reached 107 degrees (F) during the 2004 Summer Olympic Games (Athens, Greece).  "Sand Reaches 107 Degrees."  ESPN, 22 Aug. 2004, http://www.espn.com/olympics/summer04/volleyball/news/story?id=1864959.

[25]  Giatsis, G., Panoutsakopoulos & Kollias, I.  (2017).  Biomechanical differences of arm swing countermovement jumps on sand and rigid surface performed by elite beach volleyball players.  Journal of Sports Sciences, 36, 997-1008 (compliance of sand adversely impacts coordination of lower limb joints);  Giatsis, G., Kollias, I., Panoutsakopoulos, V. & Papaiakovou, G.  (2007).  Biomechanical differences in elite beach volleyball players in vertical squat jump on rigid and sand surface.  Sports Biomechanics, 3, 145-158; Pinnington, H.C., Lloyd, D.G., Beiser, T.F. & Dawson, B.  (2005).  Kinematic and electromyography analysis of submaximal differences running on a firm surface compared with soft, dry sand.  European Journal of Applied Physiology, 94, 242-253 (greater hip and knee flexion angles observed while running on sand); see also Muramatsu, S., Fukudome, A., Miyama, M., Arimoto, M., & Kijima, A. (2006). Energy expenditure in maximal jumps on sand.  Journal of Physiological Anthropology, 25(1), 59-61 (decreased efficiency in coordinating body segments to jump in sand could be associated with greater energy expenditure).

[26]  Pinnington, H.C., Lloyd, D.G., Beiser, T.F. & Dawson, B.  (2005).  Kinematic and electromyography analysis of submaximal differences running on a firm surface compared with soft, dry sand.  European Journal of Applied Physiology, 94, 242-253.

[27]  Lejeune, T.M., Williams, P.A., Heglund, N.C.. (1998).  Mechanics and energetics of human locomotion on sand.  Journal of Experimental Biology. 201(Pt 13), 2071-2080;  Zamparo, P., Perini, R., Orizio, C., Sacher, M., & Ferretti, G., (1992).  The energy cost of walking or running on sand.  European Journal of Applied Physiology and Occupational Physiology, 65(2), 183-187.

[28]  Gaudino, P., Gaudino, C., Alberti, G., & Minetti., A. (2013).  Biomechanics and predicted energetics of sprinting on sand: Hints for soccer training.  Journal of Science and Medicine in Sport 16, 271-275; Pinnington, H.C. & Dawson, B. (2001).  Running economy of elite surf iron men and male runners on soft dry beach sand and grass.  European Journal of Applied Physiology, 86, 62-70; Pinnington, H.C. & Dawson, B. (2001).  The energy cost of running on grass compared to soft dry sand.  Journal of Science and Medicine in Sport, 4(4), 416-430; Lejeune, T.M., Williams, P.A., Heglund, N.C.. (1998).  Mechanics and energetics of human locomotion on sand.  Journal of Experimental Biology. 201(Pt 13), 2071-2080; Zamparo, P., Perini, R., Orizio, C., Sacher, M., & Ferretti, G., (1992).  The energy cost of walking or running on sand.  European Journal of Applied Physiology and Occupational Physiology, 65(2), 183-187.

[29]  Muramatsu, S., Fukudome, A., Miyama, M., Arimoto, M., & Kijima, A. (2006). Energy expenditure in maximal jumps on sand.  Journal of Physiological Anthropology, 25(1), 59-61.

[30]  Pinnington, H.C. & Dawson, B. (2001).  Running economy of elite surf iron men and male runners on soft dry beach sand and grass.  European Journal of Applied Physiology, 86, 62-70.

[31]  Gilchrist, M., Torres-McGehee, T., Minori, M., Emerson, D., & Pritchett, K. (2017).  Energy Availability and Muscle Glycogen Levels in Division I Beach Volleyball Athletes.  Medicine & Science in Sports & Exercise, 49(5S) Supplement I, 13-14.  Previous research focused only on indoor volleyball.  Woodruff, S.J. & Meloche, R.D. (2013).  Energy Availability of Female Varsity Volleyball Players.  International Journal of Sports Nutrition and Exercise Metabolism, 23, 24-30.

[32]  There is some evidence that female athletes' energy needs increase above normal levels for her physical activity during the luteal (premenstrual) phase of the menstrual cycle.  Thomas, D.T., Erdman, K.A. & Burke, L.M. (2016).  Position of the academy of nutrition and dietetics, dietitians of Canada, and the American college of sports medicine: Nutrition and athletic performance.  Journal of the Academy of Nutrition and Dietetics, 116(3), 501-528 (citing Manore, M. & Thompson, J., Energy requirements of the athlete: Assessment and evidence of energy efficiency. in: L. Burke, V. Deakin (Eds.) Clinical Sports Nutrition. 5th ed. McGraw-Hill, Sydney-Australia: 2015, 114-139.).

[33]  American College of Sports Medicine, American Dietetic Association; Dietitians of Canada. Joint Position Statement: Nutrition and Athletic Performance.  Medicine & Science in Sports & Exercise. 2000, 32, 2130-2145.

[34]  Female Recreational Exercisers At Risk For Low Energy Availability, Slater, J, McLay-Cook, R., Brown, R. & Black, K. (2016).  International Journal of Sport Nutrition and Exercise, 26(5), 421-427.

[35]  American College of Sports Medicine, American Dietetic Association; Dietitians of Canada. Joint Position Statement: Nutrition and Athletic Performance.  Medicine & Science in Sports & Exercise. 2000, 32, 2130-2145.

[36] Thomas, D.T., Erdman, K.A., Burke, L.M. (2016). Position of the academy of nutrition and dietetics, dietitians of Canada, and the American college of sports medicine: Nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics, 116(3), 501-528;  Silva, M-R.G. & Paiva, T. (2014).  Low energy availability and low body fat of female gymnasts before an international competition. Applied Sport Sciences, 15(7), 591-599.

[37] Lukaski, H.C., Vitamin and mineral status: Effects on physical performance. (2004).  Nutrition, 20 (7-8), 632-644.

[38]  Monitoring athletes' energy intake may be particularly effective as there is evidence that athletes with low energy availability do not experience increased appetite.  Hubert, P., King, N.A., Blundell, J.E. (1998).  Uncoupling the effects of energy expenditure and energy intake: Appetite response to short-term energy deficit induced by meal omission and physical activity.  Appetite, 31(1), 9-19.

[39] Shriver, L.H., Betts, N.M., Wollenberg, G.  (2015).  Dietary Intakes and Eating Habits of College Athletes: Are Female College Athletes Following the Current Sports Nutrition Standards?  Journal of American College Health, 61, 10-16 (75% of participants not consuming enough carbs to minimally support energy for training); Hoogenboom, B., Morris, J., Morris, C., Schaefer, K. (2009). Nutritional knowledge and eating behaviors of female, collegiate swimmers.  North American Journal of Sports Physical Therapy, 4, 139-148.

[40]  American College of Obstetricians and Gynecologists, Committee on Adolescent Healthcare. Committee Opinion 702: Female Athlete Triad. Obstetrician Gynecologist, 2017, 129(6), e160-e167; Nattiv, A., Loucks, A.B., Mannore, M.M., Sanborn, C.F., Sundgot-Borgen, J., Warren, M.P.  (2007).  American College of Sports Medicine Position Stand.  The female athlete triad, Medicine and Science in Sports and Exercise, 39(10), 1867-1882.

[41]  DeSousa, M.J., Nattiv, A., Joy, E. et al. (2014). Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play of the Female Athlete Triad: First International Conference held in San Francisco, California, May 2012 and Second International Conference held in Indianapolis, Indiana, May 2013.  British Journal of Sports Medicine, 48(4), 289.

[42]  Nattiv, A., Loucks, A.B., Mannore, M.M., Sanborn, C.F., Sundgot-Borgen, J., Warren, M.P.  (2007).  American College of Sports Medicine Position Stand.  The female athlete triad, Medicine and Science in Sports and Exercise, 39(10), 1867-1882.  The International Olympic Committee proposed renaming the triad the "relative energy deficiency in sport" or "RED-S."  Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., et al. (2014).  The IOC consensus statement: beyond the Female Athlete Triad--Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine, 48(7), 491-497.

[43]  American College of Obstetricians and Gynecologists, Committee on Adolescent Healthcare. Committee Opinion 702: Female Athlete Triad. Obstetrician Gynecologist, 2017, 129(6), e160-e167.  Reinking, M.F., Alexander, L.E. (2005). Prevalence of disordered-eating behaviors in undergraduate female collegiate athletes and nonathletes.  Journal of Athletic Training, 40(1), 47-51.

[44]  Frederic, D.A., Peplau, L.A., Lever, J. (2006).  The swimsuit issues: Correlates of body image in a sample of 52,677 heterosexual adults.  Body Image, 3, 413-419.

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3 comments:

  1. Interesting article! I've asked myself some of the questions addressed by the conducted research and honestly am not surprised by the findings. Thanks for this Wayne!

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  2. Thanks for reading, Jess. Great to get feedback from a player in the trenches!

    ReplyDelete