Nutritional Strategies to Optimize Performance and Recovery in Rowing Athletes

Since rowing athletes train from 1–3 times a day and 5–6 times a week and the intensity of training is high, a sufficient amount of carbohydrates must be consumed prior to training in order to increase glycogen availability [13,14]. In fact, a group of athletes on a high-carbohydrate diet (10 g/kg/day) had more glycogen stored in muscle than a group of athletes on a moderate-carbohydrate diet (5 g/kg/day) and showed a higher level of enhancement in power output during a rowing training [13]. Some athletes skip breakfast and still participate in morning or afternoon trainings, which is an eating habit that can have negative effects on training performance. In a recent study, rowing athletes who skipped their carbohydrate-rich breakfast showed delays in their 2000-m time trial records measured in an afternoon training and reported high ratings of perceived exertion (RPE), which represents subjective training intensity [14].

The average calorie intake of rowing athletes is in the range of 2600 kcal to 4900 kcal. Depending on the training, it can reach up to approximately 7000 kcal (Table 1). Out of the total calorie intake, carbohydrate make up approximately 4.6–6.3 g/kg [4]. It is recommended that rowing athletes establish an individualized plan for their carbohydrate intake based on the intensity, duration, and type of training. For example, 3–5 g/kg/day of carbohydrate is recommended for a low-intensity training or a skill-based activity; 6–10 g/kg/day for a 1–3 h training with moderate–high intensity; and 8–12 g/kg/day for a 4–5 h training with moderate–high intensity [15]. If an athlete did not have a sufficient intake of carbohydrates in previous meals, an additional carbohydrate intake can be done 30–60 min before training (Table 1). In the past, an intake of carbohydrates 30–60 min before training was said to cause rebound or reactive hypoglycemia during training. However, a study reported that pre-training carbohydrate intake does not have a negative effect on performance [16].

Carbohydrate supplements for performance maintenance taken during training or competition must be easily digested and absorbed because the gastrointestinal (GI) tract plays an important role in transporting carbohydrates and fluid during training or competition [17]. However, not all types of carbohydrate are allowed. Athletes may intake carbohydrates such as glucose, sucrose, maltose, and maltodextrin [12]. In general, sports drinks and gel or low-fat, low-protein, and low-fiber solid bars are taken as supplements (Table 1). Sometimes, rowing athletes can use a carbohydrate mouth rinse during training [18]. As the term itself suggests, a carbohydrate mouth rinse is a method in which carbohydrates (sports drink or maltodextrin) are taken orally and used to rinse the mouth. It is regarded as an effective carbohydrate intake strategy during training [19]. In fact, Jensen et al. [19] let rowing athletes perform maximal isometric knee extensions. Then, athletes rinsed their mouths with 8% maltodextrin, repeated the same muscle contraction, and found that their performance improved due to diminished fatigue. Although the mechanisms that explain such changes have not been clearly identified, a theory has been put forward: Carbohydrate intake stimulates taste receptor cells distributed in the mouth, and taste cues then generate and transmit electrical activity to gustatory neurons, which leads to performance enhancement [20]. To perform a mouth rinse during training or competition using carbohydrates, the athlete must rinse their mouth with a sports drink or maltodextrin and spit it out after 5–10 s. Mouth rinses can be performed at 10–15 min intervals [18]. This method can be effective for a high-intensity training with a duration of less than one hour. A carbohydrate mouth rinse can be particularly helpful for rowing athletes who frequently experience gastrointestinal issues caused by drinks consumed during training.

Many athletes take various scientifically proven supplements in order to sustain high-intensity training, improve their records, and win competitions. Rowing athletes also take supplements for purposes such as enhancing performance (Table 2). Typical performance-enhancing supplements used by rowing athletes include β-alanine, among others [21]. Recently, Turnes et al. [21] claimed that the use of β-alanine is a popular and effective preconditioning strategy used to enhance performance among rowing athletes. It is known for its ability to maintain or enhance performance by increasing carnosine concentration in muscle to maintain muscle pH and delay exercise-induced fatigue [22]. In addition, since carnosine acts as a neurotransmitter, it improves response times and accuracy [23]. Several studies have investigated the supplementary effects of β-alanine on rowing athletes: Baguet et al. [23] found that muscle carnosine content significantly increased after taking 5 g of β-alanine supplement every day for seven weeks and showed a positive correlation with 2000-m performance enhancement, and Hobson et al. [24] showed that chronic supplementation of β-alanine (6.4 g per day for four weeks) in well-trained rowing athletes enhanced their 2000-m rowing performance. Rowing athletes can take β-alanine with meals, the typical side effect of which is minimizing paresthesia that subsides upon dividing the dose over time or stopping intake [25].

Caffeine is a naturally occurring stimulant found in numerous plants. Thus, it is widely used as a supplement to increase strength and endurance and the glycogen sparing effect [26]. According to a study by Del Coso et al. [27] that investigated caffeine usage among athletes, rowing athletes were reported as one of the groups with the highest caffeine consumption. Several studies supported the performance enhancement effect of caffeine supplements in rowing athletes: Anderson et al. [28] divided oarswomen into two groups who differed in the amount of caffeine intake prior to rowing (6 mg/kg or 9 mg/kg) and showed that the performance of the 9 mg/kg intake group was enhanced; Bruce et al. [29] reported that both 6 mg/kg and 9 mg/kg reduced performance time and increased mean power; and Scott et al. [30] showed that taking caffeinated carbohydrate gel (21.6 g carbohydrate, 100 mg caffeine) 10 min before rowing reduced 2000-m rowing time. Results regarding the effect of caffeine intake on rowing performance are consistent: In their meta-analysis, Grgic et al. [31] suggested that caffeine effectively increases rowing ergometer performance, and another meta-analysis by Turnes et al. [32] reported that 6 mg/kg caffeine intake has the highest possibility of enhancing performance.

Sodium bicarbonate is often recommended for performance enhancement of rowing athletes as well. It has similar functions to β-alanine (the ability to buffer H +) [33]. Hobson et al. [34] reported intake of 0.3 g/kg sodium bicarbonate enhanced the athletic performance. However, several studies showed that sodium bicarbonate supplement has no effect on rowing performance enhancement [35,36] and that caffeine supplementation is more effective for performance enhancement [37,38]. Upon comprehensive review of various studies, there is no sufficient evidence to strongly encourage rowing athletes to take sodium bicarbonate supplements.

A metabolite of leucine, β-hydroxy-β-methylbutyric acid (HMB), has recently received attention in the field of sports nutrition [39]. HMB is shown to benefit athletes by increasing muscle mass and improving muscle recovery. However, in a study on rowing athletes that investigated variables related to endurance and body composition [40], Durkalec-Michalski and Jeszka showed that supplementing rowing athletes with a daily dose of 3 g of HMB for 12 weeks led to an increase in aerobic capacity and peak anaerobic power, and decrease in fat mass. Also, they suggested tentative mechanisms, such as mitochondrial biogenesis due to AMP-activated protein kinase (AMPK), Sirt 1 activation, and improved efficiency of carbohydrate, glycogen, and fat metabolisms, to explain the observed changes. A recent study [41] reported that supplementing rowing athletes with a combination of HMB (3 g/day) and creatine (0.04 g/day) for 10 weeks did not change muscle mass but significantly improved aerobic power. The authors suspected that the improvement in aerobic power was a result of a synergy effect between HMB that caused fiber transformation (driving fast-to-slow fiber switch) together with increased gene expression of gamma co-activator 1-alpha (PGC-1α) and creatine that increased energy availability during exercise via elevated phosphocreatine level in muscle [41]. This means that rowing athletes can save glycogen and gain energy via oxidative capacity when they need endurance. These results imply that HMB has a potential function to promote enhancement of variables related to aerobic capacity. Whereas there is a need for further studies on its combinatory supplementation with creatine, our review on current literature suggests that we can give HMB supplementation a shot with the purpose of enhancing the performance of rowing athletes in training or competition.

Meanwhile, several studies reported that beetroot juice, rich in nitrate (NO3-), can be helpful for rowing athletes [42,43]. Nitrate has a basic mechanism for vasodilation, in which it promotes the synthesis of nitric oxide (NO), and induces effects such as increased blood flow, promotion of ATP synthesis in mitochondria, and decreased ATP cost in muscle force production [44]. Also, beetroot juice has been introduced as a supplement with strong scientific evidence in the IOC consensus statement and the Australian Institute of Sport (AIS) and International Society of Sports Nutrition (ISSN) [45]. Bond et al. [42] showed that performance time improved in the later stages of rowing performance when well-trained junior male rowing athletes consumed beetroot juice that contained 5.5 mmol nitrate every morning (250 mL) and afternoon (250 mL) for six days. Hoon et al. [43] also observed that 2000-m rowing performance improved when highly trained male rowing athletes consumed 140 mL beetroot juice that contained 8.4 mmol of nitrate two hours prior to exercise. Maughan et al. [45] showed that 5–9 mmol (310–560 mg) of nitrate-rich beetroot juice had an effect on acute performance 2–3 h after its intake and that intake for more than three days may also be beneficial. These results suggest that nitrate-rich beetroot juice can be considered as an effective supplement for performance enhancement in rowing athletes.

For refueling after training, carbohydrate intake is necessary (Table 3). Since the average glycogen replenishment in muscle is generally about 5-6 mmol per hour, recovery after a high level of depletion takes about 24 h [11]. Hence, carbohydrate intake after a high-intensity training must be done as soon possible. The high level of glycogen synthase and insulin sensitivity right after training facilitate a faster and increased storage of glycogen [49]. This is particularly important when the recovery period is short due to consecutive rowing training sessions (e.g., training throughout a day such as morning, afternoon, and evening sessions). Carbohydrate products with a high glycemic index (GI) can give an advantage in glycogen storage [50]. Burke et al. [51] found that carbohydrate products with a moderate or high GI resulted in increased glycogen storage during the recovery period compared to those with a low GI. Also, it has been reported that carbohydrate products can be taken in the liquid or solid form or as a meal or a snack [52,53]. The recommended carbohydrate is about 1.2 g/kg [4]. For instance, a rowing athlete who weighs 60 kg needs an intake of 72 g of carbohydrates right after a training. By focusing on glycogen replenishment through the planning of the form, type and amount of carbohydrate intake during the recovery period, and based on the intensity and duration of the training, athletes can prepare for the next training or competition while full of energy.

Rowing athletes also need to pay attention to rehydration during the recovery period, as it is the area of nutrition that is most easily neglected during recovery (Table 3). Fluid must be consumed right after training. However, rather than drinking a very large amount within a short period of time, multiple intakes spread across the recovery time are better [15]. In general, weight loss after training reflects a loss of fluid. Monitoring weight loss is the easiest and best method to measure hydration status [54]. After a 2000-m rowing competition, an athlete experiences a weight loss of approximately 1.5–2 kg. The amount of fluid intake must be 1.5-times the amount of weight loss after a competition or training [55]. The recommended multiplication factor used to be 1, but taking into account the fluid loss from urination and other activities after exercise, an intake of 1.5-times the amount of weight loss is effective in improving and maintaining hydration status. If there has been a marked weight loss from sweating after a competition or training, a rowing athlete can drink commercially available sports drinks or eat food with sodium (Na⁺) and water [56]. Based on the environmental conditions during trainings or competitions, a rowing athlete should be able to decide on the type of fluid to intake.

Repair is related to protein intake, which is definitely necessary for protein synthesis (Table 3). According to scientific evidence, the amount and type of intake and the interval between intakes affect recovery after training [57,58]. The recommended amount of protein intake in the early stage of recovery is about 20–25 g, which can increase up to 40 g based on factors such as age and muscle mass [58]. The amount of protein intake can be converted into a relative value. For recovery, 0.3–0.4 g/kg protein can be consumed immediately after a training or competition [59]. The most important considerations in the selection of protein food for recovery include whether it can be easily digested and absorbed and how much essential amino acids and leucine it contains [60]. A rowing athlete can consume various foods with essential amino acids. Further, if intake of protein through diet is difficult, an athlete may consume whey protein, which is the protein fraction of the byproducts of cheese production using milk. Due to its fast absorption rate, whey protein is already consumed as a source of protein among many athletes [60]. It can be easily absorbed and digested and has a rich essential amino acid content, especially leucine, which activates a regulator of protein synthesis called ‘mammalian target of rapamycin’ (mTOR) in muscle to help recovery [61]. In general, 20–25 g protein (as part of a meal or snack) should be consumed every 3–5 h for recovery [62]. In order to maximize protein synthesis, the intake of casein protein before sleep can be recommended [63,64]. Casein protein comprises 80% of the proteins in milk and is considered in pre-sleep nutritional strategies because, due to its slow digestion and absorption rates, it can constantly supply amino acids in the body [58]. Therefore, an intake of 40 g casein protein before 30 min prior to sleep, a period lacking in nutritional supply, can bring a number of advantages for recovery [65].