Exercise-Induced Oxidative Stress in Overload Training and Tapering

Reactive Oxygen Species: Beyond Their Reactive Behavior

Cellular homeostasis plays a critical role in how an organism will develop and age. Disruption of this fragile equilibrium is often associated with health degradation and ultimately, death. Reactive oxygen species (ROS) have been closely associated with health decline and neurological disorders, such as Alzheimer's disease or Parkinson's disease. ROS were first identified as by-products of the cellular activity, mainly mitochondrial respiration, and their high reactivity is linked to a disruption of macromolecules such as proteins, lipids and DNA. More recent research suggests more complex function of ROS, reaching far beyond the cellular dysfunction. ROS are active actors in most of the signaling cascades involved in cell development, proliferation and survival, constituting important second messengers. In the brain, their impact on neurons and astrocytes has been associated with synaptic plasticity and neuron survival. This review provides an overview of ROS function in cell signaling in the context of aging and degeneration in the brain and guarding the fragile balance between health and disease.

Tapering strategies applied to plyometric jump training: a systematic review with meta-analysis of randomized-controlled trials

INTRODUCTION

The purpose of this systematic review was to analyze the effect of plyometric jump training (PJT) applied in conjunction with tapering strategies on the jump performance of team-sport athletes.

EVIDENCE ACQUISITION

The meta-analysis included: 1) randomized-controlled studies that incorporated a PJT program; 2) cohorts of team-sport athletes; 3) jump performance assessments; and 4) studies that incorporated a programmed taper. A systematic search was conducted in distinct electronic databases for relevant studies. Aside from jump performance, the extracted data included characteristics of the participants, PJT, and tapering. Means and standard deviations were used to calculate the effect sizes (ES). To assess the effects of moderator variables, subgroup analyses were performed. The statistical significance level was set as P<0.05.

EVIDENCE SYNTHESIS

From 7020 records initially identified, 14 studies were eligible for meta-analysis. Across all included studies, there was a moderate, significant improvement in jump performance (ES=0.73; P<0.001). Additionally, the subgroup analysis demonstrated that the duration and intensity of the taper and the volume of the PJT induced similar improvements in jump performance (P<0.01).

CONCLUSIONS

In summary, PJT interventions that included a programmed taper induced significant improvements in jump performance in team-sport athletes. These effects were observed after different tapering strategies in terms of volume, taper duration, and the type of PJT prescribed.

Short-term intense exercise training reduces stress markers and alters the transcriptional response to exercise in skeletal muscle

The purpose of this investigation was to examine the influence of short-term intense endurance training on cycling performance, along with the acute and chronic signaling responses of skeletal muscle stress and stability markers. Ten recreationally active subjects (25 ± 2 yr, 79 ± 3 kg, 47 ± 2 ml·kg^-1·min^-1) were studied before and after a 12-day cycling protocol to examine the effects of short-term intense (70-100% V̇o_2max) exercise training on resting and exercise-induced regulation of molecular factors related to skeletal muscle cellular stress and protein stability. Skeletal muscle biopsies were taken at rest and 3 h following a 20-km cycle time trial on days 1 and 12 to measure mRNA expression and protein content. Training improved (P < 0.05) cycling performance by 5 ± 1%. Protein oxidation was unaltered on day 12, while resting SAPK/JNK phosphorylation was reduced (P < 0.05), suggesting a reduction in cellular stress. The maintenance in the myocellular environment may be due to synthesis of cytoprotective markers, along with enhanced degradation of damage proteins, as training tended (P < 0.10) to increase resting protein content of manganese superoxide dismutase and heat shock protein 70 (HSP70), while mRNA expression of MuRF-1 was elevated (P < 0.05). Following training (day 12), the acute exercise-induced transcriptional response of TNF-α, NF-κB, MuRF-1, and PGC1α was attenuated (P < 0.05) compared with day 1 Collectively, these data suggest that short-term intense training enhances protein stability, creating a cellular environment capable of resistance to exercise-induced stress, which may be favorable for adaptation.

Going retro: Oxidative stress biomarkers in modern redox biology

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Acute Oxidative Effect and Muscle Damage after a Maximum 4 Min Test in High Performance Athletes

The purpose of this investigation was to determine lipid peroxidation markers, physiological stress and muscle damage in elite kayakers in response to a maximum 4-min kayak ergometer test (KE test), and possible correlations with individual 1000m kayaking performances. The sample consisted of twenty-three adult male and nine adult female elite kayakers, with more than three years’ experience in international events, who voluntarily took part in this study. The subjects performed a 10-min warm-up, followed by a 2-min passive interval, before starting the test itself, which consisted of a maximum 4-min work paddling on an ergometer; right after the end of the test, an 8 ml blood sample was collected for analysis. 72 hours after the test, all athletes took part in an official race, when then it was possible to check their performance in the on site K1 1000m test (P1000m). The results showed that all lipoproteins and hematological parameters tested presented a significant difference (p≤0.05) after exercise for both genders. In addition, parameters related to muscle damage such as lactate dehydrogenase (LDH) and creatine kinase (CK) presented significant differences after stress. Uric acid presented an inverse correlation with the performance (r = -0.76), while CK presented a positive correlation (r = 0.46) with it. Based on these results, it was possible to verify muscle damage and the level of oxidative stress caused by indoor training with specific ergometers for speed kayaking, highlighting the importance of analyzing and getting to know the physiological responses to this type of training, in order to provide information to coaches and optimize athletic performance.

Alterations in redox homeostasis in the elite endurance athlete

BACKGROUND

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.

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Functional cobalamin (vitamin B12) deficiency: role of advanced age and disorders associated with increased oxidative stress

BACKGROUND/OBJECTIVE

Functional cobalamin (Cbl; vitamin B12) deficiency (that is, high levels of the Cbl-dependent metabolites, methylmalonic acid (MMA) and homocysteine (HCys), despite normal serum Cbl values) is common in the elderly and is associated with neurocognitive abnormalities, but its cause is unknown. As only reduced Cbls are metabolically active, the possibility that functional Cbl deficiency is associated with disorders having biomarkers indicative of increased oxidative stress (oxidant risks) was considered.

SUBJECTS/METHODS

A retrospective record review of community-dwelling adults evaluated over a 12-year period for Cbl deficiency in a primary care setting who had serum Cbl values ⩾400 pg/ml (n=170).

RESULTS

When no oxidant risks were present, older subjects (⩾70 years) had higher metabolite values than younger individuals (<70 years). MMA values were even higher in the elderly when one oxidant risk was present and in younger subjects when two or more oxidant risks were present. Even at Cbl levels ⩾800 pg/ml, MMA values were increased in 73% of elderly subjects with at least one oxidant risk. HCys values were also higher in both age groups when at least two oxidant risks were present. Cyanocobalamin therapy decreased MMA and HCys values in 86 and 76% of subjects, respectively, with nonresponders more likely to have two or more oxidant risks.

CONCLUSION

Functional Cbl deficiency is associated with disorders marked by increased oxidative stress particularly in the elderly; it occurs even when Cbl levels are high and is not consistently corrected with high-dose cyanocobalamin therapy. Thus, current approaches to recognizing and managing this disorder may be inadequate.

Guidelines to Classify Subject Groups in Sport-Science Research

Purpose:

The aim of this systematic literature review was to outline the various preexperimental maximal cycle-test protocols, terminology, and performance indicators currently used to classify subject groups in sportscience research and to construct a classification system for cycling-related research.

Methods:

A database of 130 subject-group descriptions contains information on preexperimental maximal cycle-protocol designs, terminology of the subject groups, biometrical and physiological data, cycling experience, and parameters. Kolmogorov-Smirnov test, 1-way ANOVA, post hoc Bonferroni (P < .05), and trend lines were calculated on height, body mass, relative and absolute maximal oxygen consumption (VO2max), and peak power output (PPO).

Results:

During preexperimental testing, an initial workload of 100 W and a workload increase of 25 W are most frequently used. Three-minute stages provide the most reliable and valid measures of endurance performance. After obtaining data on a subject group, researchers apply various terms to define the group. To solve this complexity, the authors introduced the neutral term performance levels 1 to 5, representing untrained, recreationally trained, trained, well-trained, and professional subject groups, respectively. The most cited parameter in literature to define subject groups is relative VO2max, and therefore no overlap between different performance levels may occur for this principal parameter. Another significant cycling parameter is the absolute PPO. The description of additional physiological information and current and past cycling data is advised.

Conclusion:

This review clearly shows the need to standardize the procedure for classifying subject groups. Recommendations are formulated concerning preexperimental testing, terminology, and performance indicators.

Altered oxidative stress in overtrained athletes

The purpose of the present study was to examine the relationship between oxidative stress and overtraining syndrome. Indicators of oxidative stress (plasma protein carbonyls, nitrotyrosine, and malondialdehyde) and antioxidant status (oxygen radical absorbance capacity) were measured in severely overtrained (two women, five men) and control athletes (five women, five men). Samples were collected from both groups at baseline (i.e. in the overtraining state of overtrained athletes) and after 6 months of recovery, both at rest and immediately after an exercise test to volitional exhaustion. At baseline, overtrained athletes had higher plasma protein carbonyls at rest than controls (mean difference 0.03 nmol . mg(-1), 95% CI = 0.01-0.05 nmol . mg(-1), P = 0.003, effect size = 0.40). Both at baseline and after recovery, exercise to exhaustion led to an increase in oxygen radical absorbance capacity and malondialdehyde (P = 0.001-0.006) in the controls but not in the overtrained athletes. Furthermore, at baseline, only overtrained athletes showed negative correlations between oxygen radical absorbance capacity at rest and protein carbonyls after exhaustive exercise (r = -0.98, P = 0.0001). These results suggest that increased oxidative stress has a role in the pathophysiology of overtraining syndrome. The attenuated responses of oxidative stress and antioxidant capacity to exercise in the overtrained state could be related to an inability to perform exercise effectively and impaired adaptation to exercise.

Cell-free plasma DNA and purine nucleotide degradation markers following weightlifting exercise

The present study aimed to investigate the acute effects of a single bout of high-intensive strength training on the production of cell-free plasma DNA (cf-DNA), as well as on the degradation of purine nucleotides as assessed by the concentration of xanthine (XA) and hypoxanthine (HX) in urine and serum. Twelve trained weightlifters performed six sets of six lifting exercises with 90-95% of the one repetition maximum. Blood samples and urine were obtained 1 h before training, immediately after finishing the exercise session and following 2 h of recovery. Cf-DNA, HX, and XA (in serum) significantly increased (P < 0.05-P < 0.001) immediately after heavy lifting exercise when compared with baseline levels, and significantly decreased (P < 0.05-P < 0.001) after 2 h of recovery. These results indicate that, cf-DNA and oxypurines might be relevant biomarkers for cellular damage, mechanical, energetic, and/or ischemic stress in context with exercise.

Evolução de biomarcadores de estresse oxidativo e relação com a performance competitiva em dois momentos da temporada de treinamento de natação

Estudos têm demonstrado aumento na formação de espécies reativas de oxigênio após o esforço físico intenso. Esses eventos podem aumentar a suscetibilidade das células musculares a danos oxidativos como a peroxidação lipídica. Assim, variações na intensidade e no volume de treinamento durante a temporada podem modular o metabolismo oxidativo e influenciar a performance dos atletas. OBJETIVO: Estudar a evolução de biomarcadores de peroxidação lipídica em dois momentos de um ciclo periodizado de treinamento e relacionar com a performance competitiva de natação. MÉTODOS: Participaram do presente estudo 16 nadadores (nove do gênero masculino e sete do feminino). Amostras de sangue foram coletadas em dois períodos do ciclo de treinamento: período preparatório específico e período de polimento. Espécies reativas ao ácido tiobarbitúrico (TBARS) e peróxidos totais foram determinados como biomarcadores de peroxidação lípidica. Creatina quinase foi determinada como parâmetro de dano celular muscular. O índice técnico alcançado no estilo de especialidade de cada atleta foi utilizado como parâmetro de performance competitiva. O índice técnico foi determinado na competição preparatória Troféu Electro Bonini realizada no período preparatório específico, e no Campeonato Paulista realizado no final do período de polimento. RESULTADOS: Foi encontrado aumento significativo (p < 0,05) no índice técnico no Campeonato Paulista (769,6 ± 51,1 pontos) em relação ao Troféu Electro Bonini (751,1 ± 55,7 pontos). Significativas reduções na concentração de TBARS (5,7 ± 2,9 vs 3,3 ± 2,2µmol/L) e peróxidos totais (45,1 ± 20,6 vs 29,6 ± 13,0, µmol H2O2/L) foram encontrados no período de polimento com relação ao período preparatório específico. O mesmo não foi encontrado para creatina quinase (123,6 ± 60,1 vs 137,4 ± 74,9U/L). CONCLUSÃO: A significativa diminuição nos biomarcadores de peroxidação lipídica decorrente do decréscimo no volume e intensidade do treinamento após o período de polimento demonstra a influência das variações do treinamento sobre o estresse oxidativo e sua possível relação com a performance.

Overreaching-induced oxidative stress, enhanced HSP72 expression, antioxidant and oxidative enzymes downregulation

Overreaching (OVR) is defined as the initial phase of overtraining syndrome and is known as a metabolic imbalance leading to short-term fatigue. Exercise increases reactive oxygen species production, which can oxidize intracellular structures impairing cell function and thus leads to OVR process. The aim of this work is to study the behavior of oxidative stress markers in subjects submitted to an OVR protocol. Thirty rats were divided in exercise and control group, and submitted to an 8-week-endurance training (ET) and a 3-week-OVR protocol. Thiobarbituric acid reactive substances (TBARs), reactive carbonylated derivatives (RCD), glutathione reductase (GR), catalase (CAT) and citrate synthase (CS) activities and stress protein HSP72 were measured in soleus (SO), extensor digital longus (EDL) and semitendinuous (ST) muscles. ET induced significant enhancement (P<0.05) in CS, GR, CAT, TBARs, RCD and HSP72 in SO, EDL and ST. OVR induced higher levels (P<0.05) of TBARs, RCD and HSP72 compared with ET only in SO, while in EDL and ST all measured parameters ranged at same levels reached during ET. We concluded that stress-induced OVR protocol is fiber type dependent, the SO muscle fiber type I being the most affected by this treatment.