When the diet lacks enough calories to support the body during periods of intense training, nutrients may be sourced from within the body to support physiological functions. For example, when dietary protein is inadequate, skeletal muscle may be broken down to fuel protein requirements, thus reducing lean muscle mass and increasing muscle injury risk.

It is important for adequate energy intake to provide the nutrients required to fuel exercise and recover optimally. Recovering from exercise is essential to help repair any damaged tissues and replenish energy stores to fuel repeated exercise performance.

Dietary protein is known for its role in lean tissue repair and growth so it is recommended to consume g after training, as part of a daily intake of 1.

Alongside protein, post-exercise carbohydrate ingestion is also advocated to promote muscle glycogen synthesis to perform subsequent high-intensity training. For sports performance dietary protein and carbohydrates get the headlines for their role in protein synthesis and energy availability, however dietary fat is equally important for performance health.

Overconsumption of certain fats may negatively influence injury risk, due to the pro-inflammatory properties of excessive trans and omega-6 fatty acids. Anti-inflammatory omega-3 fatty acids should be prioritised to promote immune function, protein synthesis, brain function and recovery from exercise.

Saturated fat intake should also be controlled; it is important for anabolic hormone production and structuring cell membranes, but too much may impair performance and increase fat mass due to its high calorie value.

Diets that lack important nutrients leave the body in a state of nutrient deficiency that can impair physiological function and cause injury. When blood levels of nutrients are low, the body will source it from internal stores endogenous production , for example, calcium may be extracted from bone when blood calcium levels are low.

Limb immobilization reduces resting muscle protein synthesis as well as induces an anabolic resistance to dietary protein Wall et al. This anabolic resistance can be attenuated although not prevented through increased dietary amino acid ingestion Glover et al.

It is beyond the scope of this manuscript to fully discuss what is appropriate protein intake for athletes and, for this, the reader is directed to several excellent reviews e. Contrary to popular belief, athletes engaged in whole-body resistance training are likely to benefit from more than the often cited 20 g of protein per meal, with recent research suggesting 40 g of protein may be a more optimum feeding strategy Macnaughton et al.

Protein intake should be equally distributed throughout the day, something that many elite athletes fail to achieve Gillen et al. In terms of an absolute amount of protein per day, increasing protein to 2. Taken together, despite the limitations of the current literature base, injured athletes may benefit from increasing their protein intake to overcome the immobilization-induced anabolic resistance as well as helping to attenuate the associated losses of lean muscle mass documented in injured athletes Milsom et al.

After a muscle injury, it is likely that athletic activities are reduced, if not stopped completely, to allow the muscle to recover, although some training in the noninjured limbs will likely continue. This reduction in activity results in reduced energy expenditure, which consequently requires a reduction in energy intake to prevent unwanted gains in body fat.

Given that many athletes periodize their carbohydrate intake, that is, increase their carbohydrate intake during hard training days while limiting them during light training or rest days, it seems appropriate that during inactivity, carbohydrate intake may need to be reduced Impey et al.

It should be stressed, however, that the magnitude of the reduction in energy intake may not be as drastic as expected given that the healing process has been shown to result in substantial increases in energy expenditure Frankenfield, , whereas the energetic cost of using crutches is much greater than that of walking Waters et al.

Moreover, it is common practice for athletes to perform some form of exercise in the noninjured limb s while injured to maintain strength and fitness.

It is, therefore, crucial that athletes do not reduce nutrition, that is, under fuel at the recovery stage through being too focused upon not gaining body fat; thus, careful planning is needed to manage the magnitude of energy restriction during this crucial recovery period. One thing that is generally accepted is that, when reducing energy intake, macronutrients should not be cut evenly as maintaining a high-protein intake will be essential to attenuate loss of lean muscle mass.

Poor attention has been paid to dietary lipids in the prevention of musculoskeletal injuries. In this context, mainly omega-3 polyunsaturated fatty acids n-3 PUFA have been studied because of their anti-inflammatory properties.

Many studies have investigated the effects of n-3 PUFA supplementation on the loss of muscle function and inflammation following exercise-induced muscle damage, with the balance of the literature suggesting some degree of benefit e.

This level of n-3 PUFA supplementation is far in excess of what would be consumed in a typical diet and much greater than most suggested supplement regimes.

Given that it is not possible to predict when an injury may occur, it could be suggested that athletes should take n-3 PUFA supplements on a regular basis; however, the long-term daily dose requires further investigation.

Again, however, relying on findings from the exercise-induced muscle damage model to rule on a benefit of n-3 PUFA in macroscopic muscle injury prevention or recovery is speculative at this stage.

Many of these nutrition strategies are claimed to work through either acting as an antioxidant or through a reduction in inflammation.

In reality, unless there is a dietary deficiency, the vast majority of nutritional interventions have limited research to support such claims. Some of the most frequently studied and supplemented micronutrients to help with skeletal muscle injury are summarized in Table 1.

Finally, consideration must be given to the balance between muscle recovery and muscle adaptation. There is growing evidence that nutritional strategies that may assist with muscle recovery, such as anti-inflammatory and antioxidant strategies, may attenuate skeletal muscle adaptions Owens et al.

It would, therefore, be prudent to differentiate between an injury that requires time lost from the sport and typical exercise-induced muscle soreness when it comes to implementing a nutritional recovery strategy.

Where adaptation comes before recovery, for example, in a preseason training phase, the best nutritional advice may simply to follow a regular diet and allow adaptations to occur naturally. Stress fractures are common bone injuries suffered by athletes that have a different etiology than contact fractures, which also have a frequent occurrence, particularly in contact sports.

Stress fractures are overuse injuries of the bone that are caused by the rhythmic and repeated application of mechanical loading in a subthreshold manner McBryde, Given this, athletes involved in high-volume, high-intensity training, where the individual is body weight loaded, are particularly susceptible to developing a stress fracture Fredericson et al.

The pathophysiology of stress fracture injuries is complex and not completely understood Bennell et al. That said, there is little direct information relating to the role of diet and nutrition in either the prevention or recovery from bone injuries, such as stress fractures.

As such, the completion of this article requires some extrapolation from the information relating to the effects of diet and nutrition on bone health in general.

Palacios provides a brief summary of some of the key nutrients for bone health, which include an adequate supply of calcium, protein, magnesium, phosphorus, vitamin D, potassium, and fluoride to directly support bone formation.

Other nutrients important to support bone tissue include manganese, copper, boron, iron, zinc, vitamin A, vitamin K, vitamin C, and the B vitamins. Silicon might also be added to this list of key nutrients for bone health.

Given this, the consumption of dairy, fruits, and vegetables particularly of the green leafy kind are likely to be useful sources of the main nutrients that support bone health. Of the more specific issues for the athlete, undoubtedly the biggest factor is the avoidance of low energy availability, which is essential to avoid negative consequences for bone Papageorgiou et al.

In athletes, this poses the question of whether the effect of low energy availability on bone is a result of dietary restriction or high exercise energy expenditures. Low EA achieved through inadequate dietary energy intake resulted in decreased bone formation but no change in bone resorption, whereas low EA achieved through exercise did not significantly influence bone metabolism, highlighting the importance of adequate dietary intakes for the athlete.

Evidence of the impact of low energy availability on bone health, particularly in female athletes, comes from the many studies relating to both the Female Athlete Triad Nattiv et al.

A thorough review of these syndromes is beyond the scope of the current article; however, those interested are advised to make use of the existing literature base on this topic.

That said, this is likely to be an unrealistic target for many athlete groups, particularly the endurance athlete e. This target may also be difficult to achieve in youth athletes who have limited time to fuel given the combined demands of school and training.

In addition, a calorie deficit is often considered to drive the endurance phenotype in these athletes, meaning that work is needed to identify the threshold of energy availability above which there are little or no negative implications for the bone.

However, a recent case study on an elite female endurance athlete over a 9-year period demonstrated that it is possible to train slightly over optimal race weight and maintain sufficient energy availability for most of the year, and then reduce calorie intake to achieve race weight at specific times in the year Stellingwerff, This may be the ideal strategy to allow athletes to race at their ideal weight, train at times with low energy availability to drive the endurance phenotype, but not be in a dangerously low energy availability all year round.

Moran et al. The development of stress fractures was associated with preexisting dietary deficiencies, not only in vitamin D and calcium, but also in carbohydrate intake. Although a small-scale association study, these data provide some indication of potential dietary risk factors for stress fracture injury.

Miller et al. Similarly, other groups have shown a link between calcium intake and both bone mineral density Myburgh et al. Despite these initially encouraging findings, there remain relatively few prospective studies evaluating the optimal calcium and vitamin D intake in athletes relating to either a stress fracture prevention or b bone healing.

For a more comprehensive review of this area, readers are directed toward a recent review by Fischer et al. One further consideration that might need to be made with regard to the calcium intake of endurance athletes and possibly weight classification athletes practicing dehydration strategies to make weight is the amount of dermal calcium loss over time.

Although the amount of dermal calcium lost with short-term exercise is unlikely to be that important in some endurance athletes performing prolonged exercise bouts or multiple sessions per day e.

Athletes are generally advised to consume more protein than the recommended daily allowance of 0. More recently, however, several reviews Rizzoli et al. Conversely, inadequacies in dietary intake have a negative effect on physical performance, which might, in turn, contribute to an increased risk of injury.

This is as likely to be the case for the bone as it is for other tissues of importance to the athlete, like muscles, tendons, and ligaments.

Despite this, there is a relative dearth of information relating to the effects of dietary intake on bone health in athletes and, particularly, around the optimal diet to support recovery from bone injury.

In the main, however, it is likely that the nutritional needs for bone health in the athlete are not likely to be substantially different from those of the general population, albeit with an additional need to minimize low energy availability states and consider the potentially elevated calcium, vitamin D, and protein requirements of many athletes.

Tendinopathy is one of the most common musculoskeletal issues in high-jerk sports. Jerk, the rate of change of acceleration, is the physical property that coaches and athletes think of as plyometric load. Given that the volume of high-jerk movements increases in elite athletes, interventions to prevent or treat tendinopathies would have a significant impact on elite performance.

The goal of any intervention to treat tendinopathy is to increase the content of directionally oriented collagen and the density of cross-links within the protein to increase the tensile strength of the tendon. The most common intervention to treat tendinopathy is loading.

The realization that tendons are dynamic tissues that respond to load began when the Kjaer laboratory demonstrated an increase in tendon collagen synthesis, in the form of increased collagen propeptides in the peritendinous space 72 hr after exercise Langberg et al.

They followed this up using stable isotope infusion to show that tendon collagen synthesis doubled within the first 24 hr after exercise Miller et al. Therefore, loading can increase collagen synthesis, and this may contribute to the beneficial effects of loading on tendinopathy.

Recently, combining loading with nutritional interventions has been proposed to further improve collagen synthesis Shaw et al.

Nutrition has been recognized as being essential for collagen synthesis and tendon health for over years. The two sailors given the oranges and lemon recovered within 6 days; however, the relationship between the citrus fruit and scurvy continued to be debated for over years.

In , Jerome Gross showed that guinea pigs on a vitamin C deficient diet did not synthesize collagen at a detectable level Gross, , making the molecular connection between vitamin C and scurvy. The requirement for vitamin C in the synthesis of collagen comes from its role in the regulation of prolyl hydroxylase activity Mussini et al.

As vitamin C is consumed in the hydroxylation reaction, and humans lack the l -gulono-γ-lactone oxidase enzyme required for the last step in the synthesis of vitamin C Drouin et al. Even though a basal level of vitamin C is required for collagen synthesis, whether exceeding this value results in a concomitant increase in collagen synthesis has yet to be determined.

Therefore, currently, there is no evidence that increasing vitamin C intake will increase collagen synthesis and prevent tendon injuries. Like vitamin C, copper deficiency leads to impaired mechanical function of collagen-containing tissues, such as bone Jonas et al.

However, the beneficial effects of copper are only seen in the transition from deficiency to sufficiency Opsahl et al. There is no further increase in collagen function with increasing doses of copper. This sequence allows collagen to form the tight triple helix that gives the protein its mechanical strength.

Because of the importance of glycine, some researchers have hypothesized that increasing dietary glycine would have a beneficial effect on tendon healing.

Vieira et al. The authors repeated the results in a follow-up study Vieira et al. Another potential source of the amino acids found in collagen is gelatin or hydrolyzed collagen. Gelatin is created by boiling the skin, bones, tendons, and ligaments of cattle, pigs, and fish.

Further chemical or enzymatic hydrolysis of gelatin breaks the protein into smaller peptides that are soluble in water and no longer form a gel.

Because both gelatin and hydrolyzed collagen are derived from collagen, they are rich in glycine, proline, hydroxylysine, and hydroxyproline Shaw et al. As would be expected from a dietary intervention that increases collagen synthesis, consumption of 10 g of hydrolyzed collagen in a randomized, double-blinded, placebo-controlled study in athletes decreased knee pain from standing and walking Clark et al.

The decrease in knee pain could be the result of an improvement in collagen synthesis of the cartilage within the knee since cartilage thickness, measured using gadolinium labeled magnetic resonance imaging, increases with long-term consumption of 10 g of hydrolyzed collagen McAlindon et al.

The role of gelatin consumption in collagen synthesis was directly tested by Shaw et al. In this randomized, double-blinded, placebo-controlled, crossover-designed study, subjects who consumed 15 g of gelatin showed twice the collagen synthesis, measured through serum propeptide levels, as either a placebo or a 5-g group.

Furthermore, when serum from subjects fed either gelatin or collagen is added to engineered ligaments, the engineered ligaments demonstrate more than twofold greater mechanics and collagen content Avey and Baar unpublished; Figure 1. Even though bathing the engineered ligaments in serum rich in procollagen amino acids provides a beneficial effect, this is a far cry from what would be seen in people.

However, these data suggest that consuming gelatin or hydrolyzed collagen may increase collagen synthesis and potentially decrease injury rate in athletes. Citation: International Journal of Sport Nutrition and Exercise Metabolism 29, 2; These and other nutraceuticals have recently been reviewed by Fusini et al.

Interestingly, many of these nutrients are thought to decrease inflammation, and the role of inflammation in tendinopathy in elite athletes remains controversial Peeling et al. Therefore, future work is needed to validate these purported nutraceuticals in the prevention or treatment of tendon or ligament injuries.

Although injuries are going to happen in athletes, there are several nutrition solutions that can be implemented to reduce the risk and decrease recovery time. To reduce the risk of injury, it is crucial that athletes do not have chronic low energy availability, as this is a major risk factor for bone injuries.

Cycling energy intake throughout the year to allow race weight to be achieved, while achieving adequate energy availability away from competitions, may be the most effective strategy.

It is also crucial for bone, muscle, tendon, and ligament health to ensure that there are no dietary deficiencies, especially low protein intake or inadequate vitamin C, D, copper, n-3 PUFA, or calcium.

This highlights the importance of athletes having access to qualified nutrition support to help them achieve their goals without compromising health.

If an injury does occur, one of the key considerations during the injury is to ensure excessive lean muscle mass is not lost and that sufficient energy is consumed to allow repair, without significantly increasing body fat. It is crucial to understand the change in energy demands and, at the same time, ensure sufficient protein is consumed for repair, especially since the muscle could become anabolic resistant.

In terms of tendon health, there is a growing interest in the role of gelatin to increase collagen synthesis. Studies are now showing that gelatin supplementation can improve cartilage thickness and decrease knee pain, and may reduce the risk of injury or accelerate return to play, providing both a prophylactic and therapeutic treatment for tendon, ligament, and, potentially, bone health.

Where supplementation is deemed necessary e. Last but not least, more human-based research is needed, ideally in elite athlete populations, on the possible benefits of some macro- and micronutrients in the prevention or boosted recovery of injured athletes.

Given that placebo-controlled, randomized control trials are exceptionally difficult to perform in elite athletes no athlete would want to be in a placebo group if there is a potential of benefit of an intervention, combined with the fact that the time course and pathology of the same injuries are often very different , it is important that high-quality case studies are now published in elite athletes to help to develop an evidence base for interventions.

All authors contributed equally to the manuscript, with each author writing specific sections and all authors editing the final manuscript prior to final submission. They also declare no conflicts of interest related to this manuscript. Baar , K. Stress relaxation and targeted nutrition to treat patellar tendinopathy.

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Nutrition may not be able to prevent injuries related to overuse or improper training; however, nutrition can play a role in how fast a student-athlete recovers. Exercise related fatigue, which is characterized by an inability to continue exercise at the desired pace or intensity, is just one example.

Nutritional causes of fatigue in athletes include inadequate total energy intake, glycogen depletion, dehydration and poor iron status. For nutrition to aid in injury prevention, the body must meet its daily energy needs. Insufficient daily overall calories will limit storage of carbohydrate as muscle or liver glycogen.

Poor food choices day after day can lead to the deficiencies resulting in chronic conditions, such as iron deficiency or low bone mineral density. Whether the focus is injury prevention or rehabilitation, getting adequate calories, carbohydrates, protein, fluids, vitamins and minerals are all important.

Prevention of dehydration and muscle glycogen depletion necessitates maximizing muscle glycogen stores prior to and during exercise, as well as beginning activity in a euhydrated state. Following a proper hydration schedule will help athletes maintain their hydration status. Iron deficiency can occur in both male and female athletes; however, it has been estimated that approximately 60 percent of female college athletes are affected by iron deficiency.

For female athletes there is yet more to consider. Research shows a positive relationship among injury, disordered eating, menstrual dysfunction and low bone mineral density. Many student-athletes faced with an injury are quick to worry about their body composition.

Fears such as gaining weight or muscle turning to fat are common. To reduce the risk of unwanted weight fat gain and to help the athlete minimize loss of lean mass, special nutritional considerations must be paid to the injured athlete.

Energy intake and distribution will need to be reevaluated to match a decreased volume and intensity or to aid in rehabilitation and recovery. There are a wide range of athletic injuries that can take student-athletes out of the game and the nutritional concerns can vary greatly for each.