Body mass management practices of lightweight rowers and the impact of these on performance

Slater, Gary (2005). Body mass management practices of lightweight rowers and the impact of these on performance PhD Thesis, School of Human Movement Studies, The University of Queensland.

       
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Author Slater, Gary
Thesis Title Body mass management practices of lightweight rowers and the impact of these on performance
School, Centre or Institute School of Human Movement Studies
Institution The University of Queensland
Publication date 2005
Thesis type PhD Thesis
Supervisor David Jenkins
Anthony Rice
Total pages 258
Collection year 2005
Language eng
Subjects L
321401 Exercise Physiology
750203 Organised sports
Formatted abstract

The primary aims of the seven studies that comprise this thesis were to examine the body mass management practices of lightweight rowers and their impact on performance. In the first study (Study One), physique traits and their relationship to competitive success were assessed amongst lightweight rowers competing at the 2003 Australian Rowing Championships. Full anthropometric profiles were collected from 107 lightweight rowers (n= 62 males, n= 45 females) competing in the Under 23 and Open age categories. Performance assessments were obtained for 66 of these rowers based on results in the single sculls events. The relationship between physique traits and competitive success were then determined. It was found that lower body fat (race time estimate -8.4 s.kg-1, P < 0.01), greater total body mass (race time estimate -4.4 s.kg-1, P = 0.03) and greater muscle mass (race time estimate - 1 0.2 s.kg-1, P < 0.01) were associated with faster 2000 m heat times. It was concluded that success in lightweight rowing was most likely to be achieved by those athletes who had lower body fat and greater total muscle mass. Larger athletes were more successful than their smaller counterparts. 

Study Two examined the body mass management practices of lightweight rowers competing at the 2003 Australian Rowing Championships and compared these with current guidelines of the International Federation of Rowing Associations (FISA). Nutrient intake in the 1 -2 h between weigh-in and racing was also estimated. One hundred lightweight rowers completed a questionnaire that assessed body mass management practices during the four weeks prior to and throughout the regatta, and responded to questions relating to recovery strategies used following weigh-in. Biochemical data were collected immediately following weigh-in to validate questionnaire responses. Responses were categorised according to gender and age category ('Senior B' or less than 23 years old i.e. U23, 'Senior A' or OPEN i.e. open age limit) for competition.  Analysis revealed that most athletes (male U23 76.5%, OPEN 92.3%; female U23 84.0%, OPEN 94.1%) decreased their body mass in the weeks prior to the regatta at rates compliant with FISA guidelines. Gradual dieting, fluid restriction and increased training load were the most popular methods employed to manage body mass. While the importance of recovery following weigh-in was recognised by athletes, nutrient intake during recovery, and especially sodium (male U23 5.3 ± 4.9, OPEN 7.7 ± 5.9; female U23 5.7 ± 6.8, OPEN 10.2 ± 5.4 mg .kg- 1) and fluid intake (male U23 12.1 ± 7.1, OPEN 13.5 ± 8.1; female U23 9.4 ± 7.4, OPEN 14.8 ± 6.9 mL.kg- 1), were below current recommendations. It was concluded that few rowers were natural lightweights; the majority had to reduce body mass in the weeks prior to a regatta. Nutritional recovery strategies implemented by lightweight rowers following weigh-in were not consistent with current guidelines. 

Study Three assessed the performance implications of acute weight loss strategies popular among lightweight rowers (as indicated by Study Two) when generous nutrient intake was provided in 2 h of recovery after making weight. Competitive rowers (n = 17) completed four ergometer trials, each separated by 48 h. Two trials were performed after a 4% body mass loss in the previous 24 h and two were performed after no weight restrictions i.e. unrestricted. Two of the trials (one unrestricted and one following acute weight loss) were undertaken in a thermoneutral environment (mean 21.1 ± SD 0.7°C, 29.0 ± 4.5% relative humidity) and two were completed in the heat (3 2.4, ± 0.4°C, 60.4 ± 2.7% relative humidity) . Trials were performed in a counterbalanced fashion according to a Latin square design. Aggressive nutritional recovery strategies (2.3 g.kg-1 carbohydrate, 34 mg.kg-1 Na, 28.4 mL.kg-1 fluid; UNR ad libitum) were employed in the 2 h following weigh-in. Performance in the 2000 m time trial was compromised by both acute weight loss (mean 2.1, 95% CI 0.7 - 3.4 s; P = 0.003) and heat exposure (4.1, 95% CI 2.7 - 5.4 s; P < 0.001). While acute weight loss resulted in hypohydration, the associated reduction in plasma volume explained only part of the performance compromise observed (0.2 s for every 1% decrement). Moreover, acute weight loss did not influence core temperature or indices of cardiovascular function. It was concluded that acute weight loss compromised performance, despite generous nutrient intake in recovery, although the effect was small. Performance decrements were further exacerbated when exercise was performed in the heat. 

Study Four examined the influence of moderate, acute weight loss on rowing on-water performance when generous nutrient intake was provided during the 2 h following weigh-in. The same competitive rowers (n = 17) who participated in Study Three undertook three on-water 1 800 m time trials under cool conditions (8.4 ± 2.0°C), each separated by 48 h. No weight limit was imposed for the first time trial i.e. unrestricted body mass. However, one of the remaining two trials followed a 4% body mass loss in the previous 24 h. Aggressive nutritional recovery strategies (2.3 g.kg-1 carbohydrate, 34 mg.kg-1 Na and 28.4 mL.kg-1 fluid) were employed in the 2 h following weigh-in. It was found that acute weight loss had only a small and statistically non-significant effect on on-water time trial performance (1.0, 95% CI -0.9 - 2.8 s; P = 0.286) compared with the unrestricted trials. This was despite a substantial reduction in plasma volume at the time of weigh-in for the body mass restricted trial when compared to the unrestricted trials (-9.2, 95% CI - 12.8 - -5.6%; P <0.001). It was concluded that acute weight loss within the range of 4% over 24 h, when followed by aggressive nutritional recovery strategies, can be undertaken with minimal impact on on-water rowing performance, at least in cool conditions. 

Study Five extended the work of Study Three and examined the impact of acute weight loss on repeat 2000 m rowing ergometer performance during a simulated multi-day regatta. A comparison of two different body mass management strategies between races was also undertaken. Competitive rowers (n = 16) were assigned to either a control, a partial recovery or a complete recovery group. Volunteers completed four trials, each separated by 48 h. No weight restrictions were imposed for the first trial. Thereafter, athletes in the partial and complete recovery groups were required to reduce body mass by 4% in the 24 h prior to trial two, again reaching this body mass prior to the final two trials. No weight restrictions were imposed on the control athletes. Aggressive nutritional recovery strategies were employed in the 2 h following weigh-in for all athletes. These strategies were maintained for the 12- 16 h following racing for the complete recovery group with the aim of restoring at least three-quarters of the original 4% body mass loss. Post-race recovery strategies were less aggressive in the partial recovery group; these volunteers were encouraged to restore no more than half of their initial 4% body mass loss. It was found that acute weight loss increased time to complete the first ' at-weight' trial by a small margin (3.0, 95% CI -0.3 - 6.3 s, P = 0.069) when compared to the control group. This effect decreased when sustained for several days. Aggressive recovery strategies tended to eliminate the effect of acute weight loss on subsequent performance. It was concluded that acute weight loss resulted in a small performance compromise that was reduced/eliminated when weight loss was repeated over several days. The results indicate that athletes should be encouraged to maximise recovery in the 12- 16 h following racing in an attempt to optimise subsequent performance. 

The aim of Study Six was to compare the effectiveness of different nutritional recovery strategies between weigh-in and racing on rowing performance among oarsmen undertaking acute weight loss prior to competition. Competitive rowers (n = 12) completed four ergometer trials, each separated by 48 h. No weight restrictions were imposed for the first trial. However, in subsequent trials, athletes were required to reduce their body mass by 5.2% in the 24 h prior to trial two, again reaching that body mass prior to the final two trials. Athletes were provided with one of three different nutritional recovery strategies in the 2 h between weigh-in and racing in a counterbalanced fashion according to a Latin square design: fluid (2.8 kJ.kg-1 , 0.0 g.kg-1 carbohydrate, 0.6 mg.kg-1 sodium, 28.5 mL.kg-1 fluid), carbohydrate/sodium (45 .3 kJ.kg-1 , 2.2 g.kg-1 carbohydrate, 32.9 mg.kg-1 sodium, 7.2 mL.kg-1 fluid) and a combination of water, carbohydrate and sodium ( 44.8 kJ.kg-1 , 2.3 g.kg-1 carbohydrate, 33 mg.kg-1 sodium, 28.5 mL.kg-1 fluid). Results indicated that performance was slower for the carbohydrate/sodium formula compared to both the combination of water, carbohydrate and sodium (4.13, 95% CI 1.37 - 6.88 s, P = 0.003) and fluid alone (2.88, 95% CI 0.13 - 5.63 s, P = 0.039). However fluid ingestion alone was not significantly different to the combination of all three nutrients ( 1.24, 95% CI - 1.41 - 3.90 s, P = 0.474), indicating the fluid content of the recovery formula was most critical among this population of athletes who presented at weigh-in in a hypohydrated state. It was concluded that appropriate nutrition intake (including adequate fluid, carbohydrate and sodium in accordance with current guidelines) in the recovery period between weigh-in and racing may be critical to performance outcomes among rowers who undertake acute weight loss prior to competition. 

The aim of Study Seven was to assess the impact of chronic body mass reduction on performance. This investigation also sought to strengthen the depth of lightweight rowing talent in Australia by identifying experienced heavyweight rowers who possessed physique traits that predisposed them to excellence as a lightweight. Three 'naturally small' heavyweight oarsmen were monitored over 16 weeks during which time they were encouraged to decrease their body mass in an attempt to achieve the specified body mass limit for the lightweight division. Variables measured included performance, anthropometric indices and selected biochemical and metabolic parameters. All athletes decreased body mass during the investigation (range 2.0- 8.0 kg), with muscle mass accounting for a large proportion of the loss (31.7 - 84.6%). Two athletes were able to maintain their performance despite reductions in body mass. However, performance was compromised for the athlete who experienced the greatest weight loss. Consequently, it was concluded that smaller heavyweight rowers can successfully make the transition into the lightweight category, being nationally competitive in their first season as a lightweight. However, for optimal results, weight loss should be undertaken over an extended time frame. 

In conclusion, the studies presented in this thesis have confirmed that the majority of lightweight rowers do undertake acute weight loss prior to competition. Given the competitive advantage afforded to larger, more muscular rowers over their smaller counterparts, the use of moderate, acute weight loss may be justified, at least among larger, leaner athletes who struggle to achieve the specified body mass requirement and have limited potential for further body mass loss via reductions in body fat. The performance implications of acute weight loss appear to be small on the ergometer and may be even less on-water, at least when aggressive recovery strategies are adopted between weigh-in and racing. Furthermore, any performance implications of acute weight loss are not exacerbated when such weight loss is undertaken repeatedly throughout the course of a regatta, and may even be eliminated when aggressive recovery strategies are introduced before and after racing. The combination of adequate sodium, fluid and carbohydrate in line with current guidelines resulted in the best performances. Finally, while the performance implications of modest acute weight loss may still need to be considered in regard to competition outcome, chronic body mass strategies may also not be without performance implications. This is especially the case for athletes who have very low levels of body fat and/or athletes who decrease their body mass too quickly. Further studies are needed to address the degree of weight loss that can be tolerated with minimal health and/or performance implications, and the optimal time frame over which this should be undertaken. Possible adaptation to the physiological state that accompanies acute weight loss also warrants investigation. 

Keyword Rowers
Body weight -- Measurement

 
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