Acute responses of bone specific and related markers to maximal eccentric exercise of the knee extensors and flexors in young men

OBJECTIVES

The present study determined time-course changes in plasma bone-specific and -related markers following a bout of maximal eccentric contractions (MaxEC) of bilateral knee extensors (KE) and flexors (KF).

METHODS

Sedentary young men (n=30) performed a bout of 10 sets of 10 MaxEC (30°/s) of KE and KF with each leg, respectively. Maximal voluntary isometric contraction (MVC) torque, muscle soreness (SOR), plasma creatine kinase (CK) activity, insulin, leptin, tumor necrosis factor-α (TNF-α), undercarboxylated-osteocalcin (ucOCN), carboxy-terminal crosslinking telopeptide of type I collagen (CTX-1) and procollagen type I N-terminal propeptide (P1NP) concentrations were measured from before to 7 days after MaxEC.

RESULTS

Significant changes in MVC (KE: -28%, KF: -38%), SOR and plasma CK activity (peak: 39,163 IU/L) following MaxEC were evident (P<0.05) compared to baseline. Plasma leptin (17%) concentrations decreased at 1 day after MaxEC. In bone related markers, plasma ucOCN concentrations (20%) increased at 7 days after MaxEC, and plasma CTX-1 concentrations decreased at 2, 4 and 7 days after MaxEC (6~7%; P<0.05).

CONCLUSION

These results demonstrate that a lean effect of bone generation and an enhanced energy anabolism can be induced by a single bout of MaxEC.

Extensive Functional Evaluations to Monitor Aerobic Training in Becker Muscular Dystrophy: A Case Report

Low-intensity aerobic training seems to have positive effects on muscle strength, endurance and fatigue in Becker Muscular Dystrophy (BMD) patients. We describe the case of a 33-year old BMD man, who performed a four-week aerobic training. Extensive functional evaluations were executed to monitor the efficacy of the rehabilitative treatment. Results evidenced an increased force exertion and an improvement in muscle contraction during sustained exercise. An improvement of walk velocity, together with agility, endurance capacity and oxygen consumption during exercise was observed. Moreover, an enhanced metabolic efficiency was evidenced, as shown by reduced lactate blood levels after training. Interestingly, CK showed higher levels after the training protocol, revealing possible muscle damage. In conclusion, aerobic training may represent an effective method improving exercise performance, functional status and metabolic efficiency. Anyway, a careful functional assessment should be taken into account as a useful approach in the management of the disease’s rehabilitative treatment.

Effect of Maximal Versus Supra-Maximal Exhausting Race on Lipid Peroxidation, Antioxidant Activity and Muscle-Damage Biomarkers in Long-Distance and Middle-Distance Runners

Background

Exhausting physical exercise increases lipid peroxidation and causes important muscle damages. The human body tries to mitigate these adverse effects by mobilizing its antioxidant defenses.

Objectives

This study aims to investigate the effect of a maximal versus supra-maximal race sustained until exhaustion on lipid peroxidation, antioxidant activity and muscle-damage biomarkers in trained (i.e. long-distance and middle-distance runners) and sedentary subjects.

Materials and Methods

The study has been carried out on 8 middle-distance runners (MDR), 9 long-distance runners (LDR), and 8 sedentary subjects (SS). Each subject has undergone two exhaustive running tests, the first one is an incremental event (VAMEVAL test), the second one is a constant supra-maximal intensity test (limited-time test). Blood samples were collected at rest and immediately after each test.

Results

A significant increase in malondialdehyde (MDA) concentrations was observed in SS and MDR after the VAMEVAL test and in LDR after the Limited-Time test. A significant difference was also observed between LDR and the other two groups after the VAMEVAL test, and between LDR and MDR after the Limited-Time test. Significant modifications, notably, in myoglobin, CK, LDH, IL-6, TNF-α, and TAS were likewise noted but depending on the race-type and the sportive specialty.

Conclusions

Maximal and supra-maximal races induce a significant increase in lipid peroxidation and cause non-negligible inflammation and muscle damage. These effects were relatively related to the physical exercise type and the sportive specialty.