Aging alters gastrocnemius muscle hemoglobin oxygen saturation (StO2) characteristics in healthy individuals

Purpose Functional limitations during exercise from alterations in the balance of oxygen supply and demand-as reported by lower tissue oxygen saturation and longer recovery time-are well documented in clinical populations. We aimed to assess changes in skeletal muscle hemoglobin oxygen saturation (StO(2)) characteristics during exercise as a result of aging in otherwise healthy individuals. Methods We recruited healthy male and female participants (n = 101) from three age ranges-young (18-39 years), middle age (40-65 years), and older (> 65 years)-to complete exercise tests commonly used in clinical populations. Using near-infrared spectroscopy (NIRS) we assessed StO(2) in the medial gastrocnemius during the Gardner Treadmill Protocol and 6 min walk test (6MWT). Results Minimum StO(2) (%) during the treadmill test was significantly lower for both middle-age (36.1 +/- 20.6) and older (27.3 +/- 19.4) participants compared to young (46.8 +/- 14.8) (p < 0.05 and p < 0.01 respectively), and recovery time (minutes) was significantly prolonged (young = 0.22 +/- 0.34; middle age = 0.66 +/- 0.52; older = 1.04 +/- 1.00) (p < 0.001 for both middle age and older compared to young). Similar results were shown during the 6MWT, as minimum StO(2) (%) was lower in middle-age (41.7 +/- 17.2) and older (40.0 +/- 25.9) participants compared to young (53.6 +/- 14.5) (p < 0.05), and recovery times (minutes) were prolonged (young: 0.11 +/- 0.17; middle age: 0.46 +/- 0.42; older: 0.93 +/- 0.43) (p < 0.001 for both middle age and older compared to young). Simple linear regression analyses demonstrated that age predicted treadmill recovery and 6MWT recovery. Conclusion Our study provides evidence that aging, even in otherwise healthy individuals, negatively impacts muscle StO(2) characteristics. In older individuals, working muscle tissue may reach lower oxygen saturation during exercise and take longer to return to baseline oxygen saturation post-exercise.

Automated summary

The study aimed to assess the impact of aging on exercise performance in otherwise healthy individuals. Using near-infrared spectroscopy, the researchers measured skeletal muscle hemoglobin oxygen saturation (StO(2)) during exercise and found that middle-aged and older participants had lower levels of StO(2) compared to younger participants, and longer recovery times. This suggests that aging negatively affects muscle oxygen saturation characteristics.