The trace element iron plays a number of crucial physiological roles within the body. Despite its importance, iron deficiency remains a common problem among athletes. As an individual’s iron stores become depleted, it can affect their well-being and athletic capacity. Recently, altered iron metabolism in athletes has been attributed to postexercise increases in the iron regulatory hormone hepcidin, which has been reported to be upregulated by exercise-induced increases in the inflammatory cytokine interleukin-6. As such, when hepcidin levels are elevated, iron absorption and recycling may be compromised. To date, however, most studies have explored the acute postexercise hepcidin response, with limited research seeking to minimize/attenuate these increases. This review summarizes the current knowledge regarding the postexercise hepcidin response under a variety of exercise scenarios and highlights potential areas for future research—such as: a) the use of hormones though the female oral contraceptive pill to manipulate the postexercise hepcidin response, b) comparing the use of different exercise modes (e.g., cycling vs. running) on hepcidin regulation.
Marc Sim, Brian Dawson, Grant Landers, Debbie Trinder and Peter Peeling
Patrick Gray, Andrew Chappell, Alison McE Jenkinson, Frank Thies and Stuart R. Gray
Due to the potential anti-inflammatory properties of fish-derived long chain n-3 fatty acids, it has been suggested that athletes should regularly consume fish oils—although evidence in support of this recommendation is not clear. While fish oils can positively modulate immune function, it remains possible that, due to their high number of double bonds, there may be concurrent increases in lipid peroxidation. The current study aims to investigate the effect of fish oil supplementation on exercise-induced markers of oxidative stress and muscle damage. Twenty males underwent a 6-week double-blind randomized placebo-controlled supplementation trial involving two groups (fish oil or placebo). After supplementation, participants undertook 200 repetitions of eccentric knee contractions. Blood samples were taken presupplementation, postsupplementation, immediately, 24, 48, and 72 hr postexercise and muscle soreness/maximal voluntary contraction (MVC) assessed. There were no differences in creatine kinase, protein carbonyls, endogenous DNA damage, muscle soreness or MVC between groups. Plasma thiobarbituric acid reactive substances (TBARS) were lower (p < .05) at 48 and 72 hr post exercise and H2O2 stimulated DNA damage was lower (p < .05) immediately postexercise in the fish oil, compared with the control group. The current study demonstrates that fish oil supplementation reduces selected markers of oxidative stress after a single bout of eccentric exercise.
Paraskevi Detopoulou and Vasilios Papamikos
Omega-3 fatty acids exert a plethora of physiological actions including triglycerides lowering, reduction of inflammatory indices, immunomodulation, anti- thrombotic effects and possibly promotion of exercise performance. Their use is widespread and for commonly ingested doses their side- effects are minimal. We report a case of a 60y amateur athlete who consumed about 20 g omega-3 fatty acids daily from supplements and natural sources for a year. After the intake of cortisone and antibiotics he presented duodenum ulcer and bleeding although he had no previous history of gastrointestinal problems. Although several animal data support gastro-protective effects of omega-3 fatty acids in the present case they were not able to prevent ulcer generation. The present observation may be explained by (i) the high dose of omega-3 fatty acids and their effect on bleeding, (ii) the fact that cortisone increases their oxidation and may render them proinflammatory, (iii) other antithrombotic microconstituents included in the consumed cod-oil and/or the diet of the subject and (iv) the differences in the coagulation and fibrinolytic systems of well- trained subjects. Further studies are needed to substantiate any possible interaction of cortisone and omega-3 fatty acids in wide ranges of intake.
Christopher D. Black and Patrick J. O’Connor
Ginger has known hypoalgesic and anti-inflammatory properties. The effects of an oral dose of ginger on quadriceps muscle pain, rating of perceived exertion (RPE), and recovery of oxygen consumption were examined during and after moderateintensity cycling exercise. Twenty-five college-age participants ingested a 2-g dose of ginger or placebo in a double-blind, crossover design and 30 min later completed 30 min of cycling at 60% of VO2peak. Quadriceps muscle pain, RPE, work rate, heart rate (HR), and oxygen uptake (VO2) were recorded every 5 min during exercise, and HR and VO2 were recorded for 20 min after exercise. Compared with placebo, ginger had no clinically meaningful or statistically significant effect on perceptions of muscle pain, RPE, work rate, HR, or VO2 during exercise. Recovery of VO2 and HR after the 30-min exercise bout followed a similar time course in the ginger and placebo conditions. The results were consistent with related findings showing that ingesting a large dose of aspirin does not acutely alter quadriceps muscle pain during cycling, and this suggests that prostaglandins do not play a large role in this type of exercise-induced skeletal-muscle pain. Ginger consumption has also been shown to improve VO2 recovery in an equine exercise model, but these results show that this is not the case in humans.
Alison C. Jozsi, Esther E. Dupont-Versteegden, Jane M. Taylor-Jones, William J. Evans, Todd A. Trappe, Wayne W. Campbell and Charlotte A. Peterson
Studies have been performed in humans to identify changes in gene expression that may account for the relatively weak and variable response of aged muscle to resistance exercise. The gene expression profile of skeletal muscle from elderly (62–75 years old) compared to younger (20–30 years old) men demonstrated elevated expression of genes typical of a stress or damage response. The expression of the majority of these genes was unaffected by a single bout of high-intensity resistance exercise in elderly subjects but was altered acutely by exercise in younger subjects so as to approach the pre-exercise levels observed in older subjects. The inability of muscle from elderly subjects to respond to resistance exercise was also apparent in the expression of inflammatory response genes, which increased within 24 hours of the exercise bout only in younger subjects. Other genes with potentially important roles in the adaptation of muscle to exercise, showed a similar or even more robust response in older compared to younger subjects. Taken together, these results may help to explain the variable hypertrophic response of muscle from older individuals to resistance training.
Pedro Tauler, Sonia Martinez, Pau Martinez, Leticia Lozano, Carlos Moreno and Antoni Aguiló
This study compared the response of interleukin (IL)-10, and also of IL-6 and IL-12 p40, to exercise and caffeine supplementation between plasma and blood mononuclear cells (BMNCs). Participants in the study (n = 28) were randomly allocated in a double-blind fashion to either caffeine (n = 14) or placebo (n = 14) treatments. One hour before completing a 15-km run competition, athletes took 6 mg/kg body mass of caffeine or a placebo. Plasma and BMNCs were purified from blood samples taken before and after competition. Concentrations of interleukins (IL-10, IL-6, and IL-12 p40), cyclic adenosine monophosphate (cAMP), caffeine, adrenaline, and cortisol were measured in plasma. IL-10, IL-6, and IL-12 p40 and cAMP levels were also determined in BMNCs. Exercise induced significant increases in IL-6 and IL-10 plasma levels, with higher increases in the caffeine-supplemented group. After 2-hr recovery, these levels returned to almost preexercise values. However, no effect of caffeine on BMNC cytokines was observed. IL-10, IL-6, and IL-12 p40 levels in BMNCs increased mainly at 2 hr postexercise. cAMP levels increased postexercise in plasma and after recovery in BMNCs, but no effects of caffeine were observed. In conclusion, caffeine did not modify cytokine levels in BMNCs in response to exercise. However, higher increases of IL-10 were observed in plasma after exercise in the supplemented participants, which could suppose an enhancement of the anti-inflammatory properties of exercise.
Martin D. Hoffman, Kristin J. Stuempfle, Ian R. Rogers, Louise B. Weschler and Tamara Hew-Butler
To determine the incidence of exercise-associated hyponatremia (EAH), the associated biochemical measurements and risk factors for EAH, and whether there is an association between postrace blood sodium concentration ([Na+]) and changes in body mass among participants in the 2009 Western States Endurance Run, a 161-km mountain trail run.
Change in body mass, postrace [Na+], and blood creatine phosphokinase (CPK) concentration, and selected runner characteristics were evaluated among consenting competitors.
Of the 47 study participants, 14 (30%) had EAH as defined by a postrace [Na+] <135 mmol/L. Postrace [Na+] and percent change in body mass were directly related (r = .30, P = .044), and 50% of those with EAH had body mass losses of 3–6%. EAH was unrelated to age, sex, finish time, or use of nonsteroidal anti-inflammatory drugs during the run, but those with EAH had completed a smaller (P = .03) number of 161-km ultramarathons. The relationship of CPK levels to postrace [Na+] did not reach statistical significance (r = –.25, P = .097).
EAH was common (30%) among finishers of this 161-km ultramarathon and it was not unusual for those with EAH to be dehydrated. As such, changes in body mass should not be relied upon in the assessment for EAH during 161-km ultramarathons.
Margareta I. Hellgren, Charlotte A. Larsson, Bledar Daka, Max Petzold, Per-Anders Jansson and Ulf Lindblad
We aimed to explore the association between self-reported leisure time physical activity (LTPA) and C-reactive protein (CRP) concentrations in men and women with and without impaired glucose tolerance (IGT).
In a cross-sectional study, a random sample (n = 2,816) was examined with an oral glucose tolerance test, CRP and information about LTPA. Those with IGT or normal glucose tolerance (NGT) and CRP value ≤10 mg/L were selected (n = 2,367) for the study.
An inverse association between LTPA and CRP concentrations was observed in the population (P < .001), though, only in men with IGT (P = .023) and in women with NGT. Men with IGT, reporting slight physical activity up to 4 hours a week presented significantly higher CRP concentrations than normoglycemic men (∆0.6 mg/L, P = .004). However, this difference could not be found in men with IGT reporting more intense physical activity (∆0.01 mg/L, P = .944).
Physical inactivity seems to have greater inflammatory consequences for men (vs. women) with IGT. More importantly, although 4 hours of physical activity per week is more than the usual minimum recommendation, an even greater intensity of LTPA appears to be required to limit subclinical inflammation in men with IGT.
Esther Suter, Walter Herzog, Kelly De Souza and Robert Bray
The present study was aimed at determining muscle inhibition (MI) and knee extensor moments in 42 subjects with unilateral anterior knee pain syndrome. The results were compared to a normal, healthy population with no history of knee injury. Also, the effects of 1 week of a nonsteroidal anti-inflammatory drug (NSAID) on MI and knee extensor moments were tested in a randomized controlled trial. At baseline, the involved leg showed significantly higher MI than the noninvolved leg. In both legs, MI was significantly higher and knee extensor moments lower than the corresponding values of the nonimpaired subjects. There was a direct relationship between knee pain during testing and the extent of MI. Higher MI, in turn, was associated with lower knee extensor moments. The study demonstrated significant MI in the quadriceps muscles of the involved and noninvolved legs of subjects with unilateral anterior knee pain syndrome. The results indicate that the noninvolved leg cannot be considered a normal control for a contralateral injury. NSAIDs did not affect MI or knee extensor moments, despite significantly reducing pain. This finding suggests that factors other than pain are responsible for the MI observed in this specific subject population, or that after removal of pain, more time is required to fully restore muscle function.
Michelle L. Weber, Kelsey J. Picha and Tamara C. Valovich McLeod
Calcaneal apophysitis, or Sever's disease, is common among physically active youth between the ages of 8-15. This condition is related to skeletal growth during maturation and relief often comes once growth is complete. However, it is not feasible to limit participation in physical activity until growth ceases; therefore, it is important to determine effective interventions to regulate pain while continuing participation. A search of the literature yielded nine studies that met the inclusion criteria and were included for data analysis. Within these publications, many treatment methods were suggested, including nonsteroidal anti-inflammatory drugs (NSAIDs), taping, orthoses, heel lifts, stretching, activity modification, and ice. However, few of the treatment options were compared with a control group. Analysis revealed that clinicians should provide treatments with caution when treating patients suffering from Sever's disease, understanding that strong evidence is not supportive of one treatment option alone. Data are limited for individual treatments related to calcaneal apophysitis and more research in this area is warranted. Clinicians should work with patients on an individual basis to determine if one form of treatment provides a reduction of pain and allows that patient to continue with activity.