Nonfunctional Overreaching Research Articles

Biomarkers Changes In Collegiate Female Power-Endurance Athletes

Non-functional overreaching (NFO) and overtraining Syndrome (OTS) result in impaired performance. Using biomarkers, it may be possible to detect early indications of these before deteriorations occur. PURPOSE: Evaluate changes in predictive biomarkers of NFO & OTS in female collegiate power-endurance athletes during the season and relate these changes to preseason fitness. METHODS: Division I female soccer & field hockey athletes (N=53, Mweight = 64.5 ± 6.9 kg; M%BF = 23.9 ± 5.7%; MVO2MAX = 47.6 ± 5.0 ml/kg/min; MVJ = 54.5 ± 7.4) participated in preseason fitness testing. Tests included body composition, vertical jump (VJ), VO2MAX & ventilatory threshold (VT). Blood was drawn at the start of preseason and 8 weeks later at midseason. The athletes arrived for blood draws in the morning in a euhydrated, fasted condition. Markers included insulin (IN), IL6, creatine kinase (CK), cortisol (CORT), prolactin (PRL), T3 & T4. RESULTS: IN (7.1 ± 2.9 vs 5.0 ± 4.6 uIU/ml) and T4 (1.2 ± .2 vs 1.1 ± .1 ng/dl) significantly decreased (P<.05), while IL6 (1.2 ± .6 vs 1.6 ± 1.3 pg/ml), CORT (25.2 ± 11.3 vs 30.4 ± 11.9 ug/dl), and PRL (14.1 ± 7.9 vs 18.5 ± 9.2 ng/ml) significantly increased (P<.05). Additionally, there were trends for increased CK (116 ± 106 vs 152 ± 110 U/L, P = .061) and T3 (108 ± 23.9 vs 113 ± 24.2 ng/dl, P = .072). Correlations for fitness measures and changes in biomarkers revealed significant associations between VT and T4, r = .506, P<.05, and LBM and CORT, r = .454, P<.05. Regression analyses revealed VT, VJ, and VO2MAX predicted 14.3% of variability in CORT (P<.05), with the largest predictive ability attributed to VO2MAX alone (R2 = .14, P<.05). Fitness also accounted for a considerable (R2 = .29, P<.05) amount of the variability in PRL while %BF also predicted changes in PRL (R2 = .18, P<.05). In all cases, higher fitness was associated with greater changes in biomarkers. CONCLUSION: Intense training without adequate rest leads to increased muscle breakdown, inflammation and stress as the body enters a more catabolic state. This is met with elevated metabolism to expedite recovery. Fitter athletes likely play more and receive less rest, so early detection of NFO symptoms through biomarkers may be a particularly useful monitoring strategy. Sponsored by Quest Diagnostics

Overtraining and Overreaching Syndrome in Athletes

Training for sports is a difficult balance between overload and recovery. If physical stress placed on the athlete is greater than what they can handle, imbalances can occur, leading to nonfunctional overreaching, defined as excessive training without adequate recovery, leading to a decrease in performance. It is a multisystem disorder that causes a variety of symptoms such as fatigue, anxiety, reduced motivation and concentration, and variation of mood. Nurse practitioner awareness of the causes, signs, and symptoms, as well as prevention, is essential for providers who care for this population in their practices.

Perceptions of well-being and physical performance in English elite youth footballers across a season

The 2011 English Elite Player Performance Plan (EPPP) stipulates training volumes that could put elite youth players at high risk of non-functional overreaching. The aim of the study was to assess player perceptions of well-being and physical performance to these high training loads. Fourteen academy football players (mean ± SD: age 17 ± 1 years; stature 179 ± 6 cm; body mass 70.8 ± 8.6 kg, at pre-season) completed a perception of well-being questionnaire 1–4 times per week throughout each training block (pre-season, in-season 1, 2, 3). Physical performance tests were carried out at the end of each training block. Increases in training exposure (P < 0.05; = 0.52) and moderate to large deteriorations in perceptions of well-being (motivation, sleep quality, recovery, appetite, fatigue, stress, muscle soreness P < 0.05; = 0.30–0.53) were evident as the season progressed. A moderate decrease in 30 m sprint performance (P < 0.05; = 0.48), a large improvement in Yo-Yo intermittent recovery test performance (P < 0.05; = 0.93) and small decreases in countermovement jump (P > 0.05; = 0.18) and arrowhead agility (P < 0.05; = 0.24) performance were evident as the season progressed. The present findings show an imbalance between stress and recovery in English elite youth players even when players experience lower training exposure than stipulated by the EPPP.

Monitoring rowers to determine under-performance

Over the past few years, training load and performance in competition has continuously increased and is fraught with risk to result in the accumulation of fatiguing conditions. The coach determines training success by controlling boat speed, performance, power and soft parameters like stability of rowing technique, capacity to teamwork, and mood state. However, in team sports like rowing, monitoring of individual rowers fatigue to optimize regeneration is difficult. While training should voluntarily cause acute fatigue, the accumulation of training leads to more severe fatigue, which is called “overreaching”. When fatigue is more prolonged and recovery is impaired, the condition is defined as “non-functional overreaching” ending in a primarily unexplained, long-term, and unplanned decreasing performance, a condition defined as “Unexplained Underperformance Syndrome” (UUPS) or “overtraining syndrome” (OTS). Good standards and appropriate markers for diagnosis and treatment are currently lacking.

Understanding the Fatigue-Recovery Cycle in Team Sport Athletes

Identifying and understanding the fatigue response of athletes following intensive training and competition is necessary to avoid injury, performance decrements and overtraining. There is an abundance of tests and monitoring tools that have been used to describe the fatigue response of both individualand team-sport athletes. These tests typically include measures of neuromuscular function, subjective questionnaires, blood and salivary markers, or physical performance tests. Importantly though, the tests employed must be valid, reliable and practically convenient in applied settings. Investigators have commonly assessed fatigue measures during tournament competition [1-3] or over subsequent days following competitive matches [4-6] in an attempt to identify the time course of the fatigue-recovery cycle. This provides an understanding of how an athlete recovers from competition and guides training loads and recovery practices when athletes may be most vulnerable to nonfunctional overreaching and injury.

An 8-year longitudinal study of overreaching in 114 elite female Chinese wrestlers.

Successful training involves structured overload but must avoid the combination of excessive overload and inadequate recovery. The aim of this study was to determine the incidence of functional overreaching (FOR), nonfunctional overreaching (NFOR), and overtraining syndrome in elite female wrestlers during their normal training and competition schedules and to explore the utility of blood markers for the early detection of overreaching. Classification of FOR, NFOR, and overtraining syndrome was based on the European Congress of Sports Medicine position statement. Case series. China Institute of Sport Science. Over an 8-year period, 114 wrestlers from the women's Asian wrestling team were monitored to help identify if and when they experienced FOR, NFOR, or overtraining syndrome. Creatine kinase, hemoglobin, testosterone, and cortisol were measured throughout the period to identify whether wrestlers were outside the reference intervals (constructed from normal recovery data) during periods of overreaching and not overreaching. Among the 114 athletes, there were 13 (3.6%) instances of FOR, 23 (6.4%) instances of NFOR, and 2 (0.6%) instances of overtraining syndrome. The diagnostic sensitivity for FOR was 38%, 15%, 45%, and 18% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. The diagnostic sensitivity for NFOR was 29%, 33%, 26%, and 35% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. Specificity was 79%, 88%, 90%, and 82% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. Post hoc analysis showed no mean differences in creatine kinase (F = 0.5, P = .47), hemoglobin (F = 3.8, P = .052), testosterone (F = 0.2, P = .62), or cortisol (F = 0.04, P = .85) between monitoring periods when wrestlers were and were not diagnosed with FOR and NFOR. Coaches and sports scientists should not use single blood variables as markers of overreaching in elite female wrestlers.

Alterations in redox homeostasis in the elite endurance athlete.

The production of reactive oxygen (ROS) and nitrogen species (RNS) is a fundamental feature of mammalian physiology, cellular respiration and cell signalling, and essential for muscle function and training adaptation. Aerobic and anaerobic exercise results in alterations in redox homeostasis (ARH) in untrained, trained and well trained athletes. Low to moderate doses of ROS and RNS play a role in muscle adaptation to endurance training, but an overwhelming increase in RNS and ROS may lead to increased cell apoptosis and immunosuppression, fatigued states and underperformance. The objectives of this systematic review are: (a) to test the hypotheses that ARH occur in elite endurance athletes; following an acute exercise bout, in an endurance race or competition; across a micro-, meso- or macro-training cycle; following a training taper; before, during and after altitude training; in females with amenorrhoea versus eumenorrhoea; and in non-functional over-reaching (NFOR) and overtraining states (OTS); (b) to report any relationship between ARH and training load and ARH and performance; and (c) to apply critical difference values for measures of oxidative stress/ARH to address whether there is any evidence of ARH being of physiological significance (not just statistical) and thus relevant to health and performance in the elite athlete. Electronic databases, Embase, MEDLINE, and SPORTDiscus were searched for relevant articles. Only studies that were observational articles of cross-sectional or longitudinal design, and included elite athletes competing at national or international level in endurance sports were included. Studies had to include biomarkers of ARH; oxidative damage, antioxidant enzymes, antioxidant capacity, and antioxidant vitamins and nutrients in urine, serum, plasma, whole blood, red blood cells (RBCs) and white blood cells (WBCs). A total of 3,057 articles were identified from the electronic searches. Twenty-eight articles met the inclusion criteria and were included in the review. ARH occurs in elite endurance athletes, after acute exercise, a competition or race, across training phases, and with natural or simulated altitude. A reduction in ARH occurs across the season in elite athletes, with marked variation around intensified training phases, between individuals, and the greatest disturbances (of physiological significance) occurring with live-high-train-low techniques, and in athletes competing. A relationship with ARH and performance and illness exists in elite athletes. There was considerable heterogeneity across the studies for the biomarkers and assays used; the sport; the blood sampling time points; and the phase in the annual training cycle and thus baseline athlete fitness. In addition, there was a consistent lack of reporting of the analytical variability of the assays used to assess ARH. The reported biochemical changes around ARH in elite athletes suggest that it may be of value to monitor biomarkers of ARH at rest, pre- and post-simulated performance tests, and before and after training micro- and meso-cycles, and altitude camps, to identify individual tolerance to training loads, potentially allowing the prevention of non-functionally over-reached states and optimisation of the individual training taper and training programme.

Monitoring training load to understand fatigue in athletes.

Many athletes, coaches, and support staff are taking an increasingly scientific approach to both designing and monitoring training programs. Appropriate load monitoring can aid in determining whether an athlete is adapting to a training program and in minimizing the risk of developing non-functional overreaching, illness, and/or injury. In order to gain an understanding of the training load and its effect on the athlete, a number of potential markers are available for use. However, very few of these markers have strong scientific evidence supporting their use, and there is yet to be a single, definitive marker described in the literature. Research has investigated a number of external load quantifying and monitoring tools, such as power output measuring devices, time-motion analysis, as well as internal load unit measures, including perception of effort, heart rate, blood lactate, and training impulse. Dissociation between external and internal load units may reveal the state of fatigue of an athlete. Other monitoring tools used by high-performance programs include heart rate recovery, neuromuscular function, biochemical/hormonal/immunological assessments, questionnaires and diaries, psychomotor speed, and sleep quality and quantity. The monitoring approach taken with athletes may depend on whether the athlete is engaging in individual or team sport activity; however, the importance of individualization of load monitoring cannot be over emphasized. Detecting meaningful changes with scientific and statistical approaches can provide confidence and certainty when implementing change. Appropriate monitoring of training load can provide important information to athletes and coaches; however, monitoring systems should be intuitive, provide efficient data analysis and interpretation, and enable efficient reporting of simple, yet scientifically valid, feedback.

Sex-Specific Responses to Self-Paced, High-Intensity Interval Training With Variable Recovery Periods

This study examined sex-specific responses during self-paced, high-intensity interval training (HIIT). Sixteen (8 men and 8 women) individuals completed a peak oxygen uptake test and 3 treadmill HIIT sessions on separate days. The HIIT sessions consisted of six 4-minute intervals performed at the highest self-selected intensity individuals felt they could maintain. Recovery between intervals was counterbalanced and consisted of 1-, 2-, or 4-minute recovery during each trial. Relative measures of intensity, including percentage of velocity at VO2peak (vVO2peak), %VO2peak, %HRmax, and blood lactate concentration ([La]), were observed during the trials. Perceived readiness was recorded immediately before and ratings of perceived exertion (RPE) were recorded at the end of each interval with session RPE recorded after each trial. Results revealed a significant effect of sex on %vVO2peak (p < 0.01) and %HRmax (p < 0.01). Data show that across trials, men self-select higher %vVO2peak (84.5 vs. 80.7%), whereas women produce higher %HRmax (96.9 vs. 92.1%) and %VO2peak (89.6 vs. 86.1%) with no difference in [La] or perceptual responses. These findings support the notion that women may demonstrate improved recovery during high-intensity exercise, as they will self-select intensities resulting in greater cardiovascular strain. Moreover, results confirm previous findings suggesting that a 2:1 work-to-rest ratio is optimal during HIIT for both men and women.

Improving Training Condition Assessment in Endurance Cyclists: Effects of Ganoderma lucidum and Ophiocordyceps sinensis Dietary Supplementation.

The main reasons for taking daily dietary supplements are to maintain good health, to improve homeostasis, and to create conditions for reducing the risk of disease. Due to growing market demand, the search for effective, nontoxic, natural compounds with antioxidant and ergogenic properties has increasingly become a matter of interest. This paper describes how a specific combination of fungal supplements can help improve the performance of endurance athletes. We report the effects of a brief 3-month trial of two fungal supplements, Ganoderma lucidum and Cordyceps sinensis (3 capsules of O. sinensis and 2 capsules of G. lucidum per day), in 7 healthy male volunteers, aged between 30 and 40 years, who are all amateur cyclists that participate in “Gran Fondo” cycling races. This trial investigated the effects of fungal supplements on the level of physical fitness of the athletes by monitoring and comparing the following biomarkers just before and after physical exertion: the testosterone/cortisol ratio in the saliva and oxidative stress (DPPH free radical scavenging activity). A decrease of more than 30% in the testosterone/cortisol ratio after race compared to before race was considered as a risk factor for nonfunctional overreaching (NFO) or the overtraining syndrome (OTS). The results show that, after 3 months of supplementation, the testosterone/cortisol ratio changed in a statistically significant manner, thereby protecting the athletes from NFO and OTS. Antioxidant activity was measured by quantifying the scavenging ability of the human serum on the synthetic free radical DPPH. After 3 months of fungal supplementation, the data demonstrate an increased scavenger capacity of free radicals in the athletes' serum after the race, thereby protecting the athletes from oxidative stress.

Nonfunctional Overreaching Leads to Inflammation and Myostatin Upregulation in Swiss Mice

The aims of the this study were a) to verify whether the performance decrease induced by nonfunctional overreaching (NFOR) is linked to high concentrations of cytokines in serum, skeletal muscles and liver; b) to verify muscle myostatin adaptation to NFOR; c) to verify the effects of chronic glucose supplementation on the parameters mentioned above. Mice were divided into control (C), trained (TR), overtrained (OTR) and supplemented overtrained (OTR + S). The incremental load test (ILT) and exhaustive test (ET) were used to measure performances before and after exercise protocols. 24 h after ET, muscles and liver were removed and stored at -80°C for subsequent measurements. Total blood was collected from decapitation for subsequent determination of cytokine concentrations. Generally, OTR and OTR + S presented higher contents of IL-6, TNF-alpha, GLUT-4 and myostatin in muscle samples compared to C and TR. Glucose supplementation attenuated the high contents of IL-6, TNF-alpha and IL-15 in liver, and of IL-6 in serum. In summary, NFOR led to low-grade chronic inflammation and myostatin upregulation.

Heart Rate Variability Threshold Values for Early-Warning Nonfunctional Overreaching in Elite Female Wrestlers

Functional overreaching (FOR) represents intense training followed by a brief reduction in performance and then a rapid recovery (<2 weeks) and performance supercompensation. Nonfunctional overreaching (NFOR) occurs when the reduced performance continues ≥3 weeks. Heart rate variability (HRV) is a promising tool for detecting NFOR. In this study, the authors examined HRV thresholds in 34 elite female wrestlers (mean ± SD: age 23 ± 3 years; height 165.6 ± 6 cm, weight 63 ± 8 kg) for FOR/NFOR during training before 11 major competitions. Supine HRV was analyzed weekly at the same time of day using time and frequency domain methods. The authors observed that the time domain index, square root of the mean of the sum of the squares of differences between adjacent R-to-R intervals (rMSSD, milliseconds), denoting parasympathetic tone, showed those responding normally to training (82.76 ms, 95% confidence interval 77.75-87.78) to be significantly different to those showing a decrease (45.97 ms, 95% confidence interval, 30.79-61.14) or hyper-responsiveness (160.44 ms, 95% confidence interval, 142.02-178.85; all, p < 0.001). Similar results were observed for mixed sympathetic and parasympathetic signal standard deviation of the NN intervals (ms): normal (65.39; 95% confidence interval, 62.49-68.29), decrease (40.07; 95% confidence interval, 29-51.14), and hyperresponse (115.00; 95% confidence interval, 105.46-124.54; all, p < 0.001) and synonymous frequency domain components. An examination of the 95% confidence interval shows a narrow band surrounding a normal response compared with broader bands accompanying adverse responses. Thus, severe perturbations both above and below normal responses lasting >2 weeks indicated an athlete's transition to NFOR and, hence, are useful for assessing possible overreaching/training.

Adrenal Cortical Responses to High-Intensity, Short Rest, Resistance Exercise in Men and Women

Commercial high-intensity, short rest (HI/SR) protocols have been anecdotally postured to be extremely demanding. However, limited prior studies have demonstrated HI/SR protocols to produce hyperreactions in metabolic and adrenal function; thus, the purpose of this study was to evaluate the physiological effects of an acute, high-intensity (75% 1-repetition maximum), short rest resistance exercise protocol. Nine trained men (age: 23.5 ± 3.5 years, height: 172.4 ± 4.0 cm, weight: 77.8 ± 8.8 kg) and 9 trained women (age: 22.9 ± 2.0 years, height: 168.4 ± 9.4 cm, weight: 68.5 ± 10.4 kg) participated in the HI/SR protocol, which consisted of a descending pyramid scheme of back squat, bench press, and deadlift, beginning with 10 repetitions of each, then 9, then 8, and so on until 1 repetition on the final set. Significant time effects were observed in lactate (immediate post [IP], +15, +60) and cortisol (IP, +15, +60) response. Significant sex effects were observed in lactate response (IP, +15) but not in cortisol response. Total work was higher in men and influenced magnitude of increase in lactate but not cortisol. No significant sex differences were noted in time to completion, average relative intensity, heart rate response or rating of perceived exertion scores. Highest lactate (IP men: 17.3 mmol·L(-1); IP women: 13.8 mmol·L(-1)) and cortisol (+15 men: 1,860.2 nmol·L(-1); +15 women: 1,831.7 nmol·L(-1)) values were considerably greater than those produced in typical resistance exercise programs, confirming that relative intensity and rest period length are important factors determining magnitude of metabolic and adrenal stress. Practical applications for the coach include cautious implementation of HI/SR protocols, as long-term sequential use may promote overtraining. A gradual reduction in rest interval length with concurrent gradual increase in intensity should be used to minimize potential negative effects such as nonfunctional overreaching.

Prevention, Diagnosis, and Treatment of the Overtraining Syndrome

Successful training not only must involve overload but also must avoid the combination of excessive overload plus inadequate recovery. Athletes can experience short-term performance decrement without severe psychological or lasting other negative symptoms. This functional overreaching will eventually lead to an improvement in performance after recovery. When athletes do not sufficiently respect the balance between training and recovery, nonfunctional overreaching (NFOR) can occur. The distinction between NFOR and overtraining syndrome (OTS) is very difficult and will depend on the clinical outcome and exclusion diagnosis. The athlete will often show the same clinical, hormonal, and other signs and symptoms. A keyword in the recognition of OTS might be "prolonged maladaptation" not only of the athlete but also of several biological, neurochemical, and hormonal regulation mechanisms. It is generally thought that symptoms of OTS, such as fatigue, performance decline, and mood disturbances, are more severe than those of NFOR. However, there is no scientific evidence to either confirm or refute this suggestion. One approach to understanding the etiology of OTS involves the exclusion of organic diseases or infections and factors such as dietary caloric restriction (negative energy balance) and insufficient carbohydrate and/or protein intake, iron deficiency, magnesium deficiency, allergies, and others together with identification of initiating events or triggers. In this article, we provide the recent status of possible markers for the detection of OTS. Currently, several markers (hormones, performance tests, psychological tests, and biochemical and immune markers) are used, but none of them meet all the criteria to make their use generally accepted.

Heart rate modulations in overtraining syndrome

Every sports training program includes a component of repetitive overloading, but with an inadequate recovery time, such overloading may produce undesired effects, such as chronic fatigue and a lack of performance improvement. The state of underperformance known as the overtraining syndrome (OTS) is characterized by a number of physiological and psychological symptoms of maladaptation. It may take weeks, months or years to restore proper sports form after the development of OTS. Although overtraining has been studied for decades, the mechanism of overtraining and the tools for the early detection of overtraining are still not defined. In addition to other physiological, biochemical, immunological, psychological and performance markers, heart rate (HR) and its modulations are intensively investigated as a practical and reliable sign of overtraining. In general, resting bradycardia, a decrease in HR during submaximal exercise, an increase in speed of heart rate recovery and increased vagal-related heart rate variability indices are all well accepted markers of improved aerobic fitness. In contrast, changes of these HR measures in the opposite direction are commonly interpreted as indicators of detraining, chronic fatigue, non-functional overreaching or overtraining. However, based on the limited and diverse literature available, these parameters may be used for monitoring training status, optimising training programs and following the accumulation of fatigue, but their role in overtraining detection and assessment has yet to be elucidated. There is a need for well-controlled prospective studies where a longitudinal follow-up of athletes is performed. Because it is unethical to excessively train an athlete to produce OTS, an animal experimental model of OTS may advance our understanding of the 'unexplained underperformance syndrome.'.

Prevention, diagnosis and treatment of the overtraining syndrome: Joint consensus statement of the European College of Sport Science (ECSS) and the American College of Sports Medicine (ACSM)

Successful training must involve overload, but also must avoid the combination of excessive overload plus inadequate recovery. Athletes can experience short-term performance decrement, without severe psychological, or lasting other negative symptoms. This Functional Overreaching (FOR) will eventually lead to an improvement in performance after recovery. When athletes do not sufficiently respect the balance between training and recovery, Non-Functional Overreaching (NFOR) can occur. The distinction between NFOR and the Overtraining Syndrome (OTS) is very difficult and will depend on the clinical outcome and exclusion diagnosis. The athlete will often show the same clinical, hormonal and other signs and symptoms. A keyword in the recognition of OTS might be ‘prolonged maladaptation’ not only of the athlete, but also of several biological, neurochemical, and hormonal regulation mechanisms. It is generally thought that symptoms of OTS, such as fatigue, performance decline and mood disturbances, are more severe than those of NFOR. However, there is no scientific evidence to either confirmor refute this suggestion. One approach to understanding the aetiology of OTS involves the exclusion of organic diseases or infections and factors such as dietary caloric restriction (negative energy balance) and insufficient carbohydrate and/or protein intake, iron deficiency, magnesium deficiency, allergies, etc., together with identification of initiating events or triggers. In this paper, we provide the recent status of possible markers for the detection of OTS. Currently several markers (hormones, performance tests, psychological tests, biochemical and immune markers) are used, but none of them meets all criteria to make its use generally accepted.

A new overtraining protocol for mice based on downhill running sessions

1. The purpose of the present study was to verify whether a downhill running protocol was able to induce non-functional overreaching in > 75% of mice. 2. Mice were divided into control (C), trained (TR) and overtrained (OTR) groups. Bodyweight and food intake were recorded weekly. The incremental load test (ILT) and the exhaustive test (ET) were used to measure performance before and after aerobic training and overtraining protocols. 3. Although the bodyweight of the OTR group was lower than that of the C group at the end of Week 7, the food intake of the OTR group was higher than that of the C and TR groups at the end of Week 8. Evaluation of results from the ILT and ET revealed significant intra- and inter-group differences: whereas the parameters measured by both tests increased significantly in the TR group, they were significantly decreased in the OTR group. 4. In conclusion, this new overtraining protocol based on downhill running sessions induced non-functional overreaching in 100% of mice.

Proteomic profiling of skeletal muscle in an animal model of overtraining

Excessive training (i.e. overtraining, OT) may result in underperformance, which can be characterized by the time needed to re-establish performance (i.e. functional overreaching (FOR), nonfunctional overreaching, OT syndrome). The present study is an initial screening for proteins presenting altered abundance in the red (RG) and white (WG) portions of the gastrocnemius muscle from rats submitted to an OT protocol that induced FOR. In the RG, compared to the nontrained control, FOR demonstrated an increased abundance of proteins normally related to adaptation to endurance training (e.g. proteins of oxidative phosphorylation complexes, proteins related to lipid metabolism, antioxidants, and chaperones). In the WG, spots identified as mitochondrial aconitase and a component of the succinate dehydrogenase complex were downregulated in FOR, as were proteins related to myofibril stabilization; these latter were upregulated in the RG. This initial study shows that skeletal muscles with different fiber-type compositions respond differently to an OT period. Also, it is likely that actin-interacting proteins have an important role in muscle adaptation to endurance exercise.

Heart rate variability in elite triathletes, is variation in variability the key to effective training? A case comparison

Measures of an athlete's heart rate variability (HRV) have shown potential to be of use in the prescription of training. However, little data exists on elite athletes who are regularly exposed to high training loads. This case study monitored daily HRV in two elite triathletes (one male: 22 year, VO2max 72.5 ml kg min(-1); one female: 20 year, VO2max 68.2 ml kg min(-1)) training 23 ± 2 h per week, over a 77-day period. During this period, one athlete performed poorly in a key triathlon event, was diagnosed as non-functionally over-reached (NFOR) and subsequently reactivated the dormant virus herpes zoster (shingles). The 7-day rolling average of the log-transformed square root of the mean sum of the squared differences between R-R intervals (Ln rMSSD), declined towards the day of triathlon event (slope = -0.17 ms/week; r2 = -0.88) in the NFOR athlete, remaining stable in the control (slope = 0.01 ms/week; r2 = 0.12). Furthermore, in the NFOR athlete, coefficient of variation of HRV (CV of Ln rMSSD 7-day rolling average) revealed large linear reductions towards NFOR (i.e., linear regression of HRV variables versus day number towards NFOR: -0.65%/week and r2 = -0.48), while these variables remained stable for the control athlete (slope = 0.04%/week). These data suggest that trends in both absolute HRV values and day-to-day variations may be useful measurements indicative of the progression towards mal-adaptation or non-functional over-reaching.

Interaction between overtraining and the interindividual variability may (not) trigger muscle oxidative stress and cardiomyocyte apoptosis in rats.

Severe endurance training (overtraining) may cause underperformance related to muscle oxidative stress and cardiomyocyte alterations. Currently, such relationship has not been empirically established. In this study, Wistar rats (n = 19) underwent eight weeks of daily exercise sessions followed by three overtraining weeks in which the daily frequency of exercise sessions increased. After the 11th training week, eight rats exhibited a reduction of 38% in performance (nonfunctional overreaching group (NFOR)), whereas eleven rats exhibited an increase of 18% in performance (functional overreaching group (FOR)). The red gastrocnemius of NFOR presented significantly lower citrate synthase activity compared to FOR, but similar to that of the control. The activity of mitochondrial complex IV in NFOR was lower than that of the control and FOR. This impaired mitochondrial adaptation in NFOR was associated with increased antioxidant enzyme activities and increased lipid peroxidation (in muscle and plasma) relative to FOR and control. Cardiomyocyte apoptosis was higher in NFOR. Plasma creatine kinase levels were unchanged. We observed that some rats that presented evidence of muscle oxidative stress are also subject to cardiomyocyte apoptosis under endurance overtraining. Blood lipid peroxides may be a suitable biomarker for muscle oxidative stress that is unrelated to severe muscle damage.