Muscle oxygenation after downhill walking‐induced muscle damage

Abstract

SummaryThe purpose of this study was to investigate changes in muscle oxygenation and blood flow within vastus lateralis after an exhaustive session of downhill walking (DW). Nine healthy males performed 40-min DW on a treadmill with a gradient of )25% and at walking velocity of 6AE4 km h )1 . To increase the likelihood that DW would induce muscle damage, subjects were loaded with 5% of their body weight carried in a back pack. Before and after DW exercise on day 1 and over the next 4 days, maximum voluntary contractions (MVCs), subjectsÕ perception of muscle soreness (SOR), plasma creatine kinase (CK) activity and myoglobin (Mb) concentrations, and muscle oxygenation (using near infrared spectroscopy; NIRS) within vastus lateralis were assessed. Repeated-measures ANOVA revealed that MVC decreased while SOR and Mb concentration increase significantly (P<0AE05) after DW, consistent with its effectiveness to evoke muscle damage. Resting tissue oxygen saturation increased immediately after DW, but recovered within 24 h. During isometric contractions at 30%, 50% and 80% of MVC, oxygen desaturation and re-saturation kinetics became significantly faster than pre-exercise values. The possible mechanism responsible for these changes might be increased resting muscle oxygen utilization after muscle damage because of an increased requirement for aerobic energy-demanding repair processes.

Efeitos da caminhada em declive na aptidão aeróbia e neuromuscular em adultos jovens

“…Thus, it was expected that the LWG group would not present any alterations in aerobic fitness. Based on evidences obtained in animal models 18,19 , we hypothesized that DW could represent an additional stress in relation to walking level, considering the oxidative adaptations provided by downhill walking and running 18,19 , to improve aerobic power. Hahn and colleagues 18 identified an increase in the total content of citrate synthase enzyme, a key regulatory enzyme in assessing oxidative capacity, after 6 weeks of downhill running training in mice.…”

“…Similarly, Gault & Willems 16 showed that IPT and torque steadiness were also improved after 12 weeks of DW training in older individuals. Interestingly, Hahn et al 18 found significant increases in the total content of citrate synthase enzyme after 6 weeks of downhill running training in mice, while Ahmadi et al 19 reported acute increases in vascularization and muscle oxygenation after a DW session in mice. These data, associated with the classical finding of Saltinet al 20 and Wagner 21 , which showed that peripheral adaptations play an important role in increasing aerobic power, indicate that DW training could improve aerobic fitness.…”

Eccentric contraction-induced muscle injury does not change walking economy in older adults

“…For example, 48 hours after downhill running, the MVIF of knee extensor muscles was decreased by 16% (Braun & Dutto, 2003;Chen et al, 2007Chen et al, , 2008Martin et al, 2005). A decrease in MVIF of 25% was shown for up to 3-days after a single downhill walk (Ahmadi et al, 2008).…”

“…This design ensured ecological validity as the participants determined their own self-selected walking speed rather than the same or standardized walking speed for all participants (Ahmadi et al, 2008). Maximal walking speed (MWS) was determined overground on a 10 metre hard non-slip walkway (Tiainen et al, 2007).…”

“…However, if unaccustomed intense exercise involves eccentric contractions, this will result in muscle injury. Muscle injury is characterized by a reduction in the ability to produce maximal voluntary isometric force (MVIF) (Ahmadi et al, 2008;Chen et al, 2007Chen et al, , 2008; Park et al, 2008;Warren et al, 1999) and can last for several days (Chen et al, 2008).…”