The Effects of DOMS Caused by Eccentric Exercise on Microvascular Function, Measured by Near-Infrared Spectroscopy
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Delayed Onset Muscle Soreness (DOMS) is the sore and tender feeling that appears after severe or unaccustomed exercise, especially eccentric exercise (EE), which causes structural damage to the muscle fiber. Some of these structural damages are related to microvascular function and therefore there is suggested an effect on the microvascular function in the damaged muscle due to mechanisms such as alteration in activation patterns, myoglobin leakage and increased capillary luminal area. Near Infrared Spectroscopy (NIRS) is a noninvasive measuring tool, based on optical light, measuring oxygen saturation in tissue continuously that enables measurement of microvascular function. The aim of this study was to investigate the effect of DOMS caused by EE to the microvascular function, using NIRS as measuring tool. Fourteen (8 female, 6 male) subjects participated in the study. The study consisted of pretest, EE and posttest. Pretest measured indirect DOMS markers by registration of perceived pain ranged on a visual analog scale (VAS), a maximum voluntary contraction test (MVC), a pain pressure threshold test (PPT). Microvascular function was investigated with NIRS, measuring oxygen saturation in vastus lateralis (VL) and rectus femoris (RF) at both legs during a 10 min occlusion and a 5 min cycling period. The EE consisted of 6x10 repetitions of front lunges, with an external loading of 40% of body weight for women and 50% for men, performed with the dominant leg only, to induce one DOMS leg and one control leg. Posttest was identical to the pretest and was performed 48h after EE. VAS increased significantly (P<0.01) with 2.7 cm from pre to post in DOMS leg, while no significant change in control leg with an increase of 0.7 cm. PPT showed no significant differences. MVC during extension decreased in DOMS leg (P=0.01), while not in control leg. MVC during flexion increased in DOMS leg (P=0.02) while not in control leg. NIRS results showed significant difference (P=0.04) in recovery rate (tauSmO2%) in RF DOMS leg compared to control leg at post test, with 5.4 (±5.2) s faster recovery in DOMS leg after cycling. There were significant differences in VL control leg from pre to post (P=0.01) after cycling, with 3.6 (±2.7) s slower recovery rate at posttest. There were no significant differences in either desaturation, oxyhaemoglobin or total haemoglobin from either pre to post EE or DOMS to control in either occlusion or cycling test. Due to the lack of clear results for the DOMS markers the results of microvascular function is affected, and one has to evaluate the results with a limitation. However the minor significant results that were found in 2 changes in microvascular functions indicates that there might be changes in microvascular function. The study do not provide support to the findings of any of the earlier studies in the field. As there are suggested microvascular changes following muscle damage as a result of EE, the subject is interesting for further research to confirm or disprove these theories.