Hematopoietic stem and progenitor cells (HSPC) are responsible for the reconstitution of blood cells and thought to contribute to peripheral tissue repair. Following acute exercise in young adults, HSPC are mobilized from their niche in bone marrow into circulation, however the kinetics of mobilization following exercise is not well understood in older adults. In the present study, we aimed to investigate how exercise intensity influences mobilization of specific subpopulations of HSPC, and how mobilization is affected by aging.
Healthy older men (OM; 69.9 ± 2.0 years) and young men (YM; 21.5 ± 0.8 years) performed three separate bouts of exercise on a cycle ergometer: 70% of their peak work rate (WRpeak) until volitional fatigue, 30% of their WRpeak work matched to the 70% WRpeak trial, and a high intensity interval training (HIIT) trial. Blood samples were collected before, immediately post, and 10, 30, and 60 min post-exercise. Total blood cells, hematocrit, and mononuclear cells isolated by density gradient centrifugation were quantified using flow cytometry.
Mononuclear cells, CD34+, CD34+/CD38+, CD34+/CD110+, CD3+/CD(16 + 56)+, CD11c+/CD123−, and CD11c−/CD123+ cells per millilitre of blood increased immediately post-exercise, but predominately in the 70% WRpeak trial in both OM and YM.
Taken together, our evidence suggests that higher intensity exercise but also volume is necessary for the mobilization of HSPC. Furthermore, the pattern of mobilization was nearly identical in OM as compared to YM though to a lesser extent than their younger counterparts.
Landing is considered a “high-risk” movement for anterior cruciate ligament (ACL) injuries. Foot progression angle (FPA) during landing has been shown to influence hip, knee, and ankle mechanics. The purpose of this study was to compare five FPA conditions during drop landings between males and females.
Twenty males and females were tested using five FPA conditions: self-selected, toe-in 15°, toe-in 30°, toe-out 15°, and toe-out 30°. Right hip, knee, and ankle joint kinematics and kinetics were collected using a 12-camera motion capture system and two force plates. Five successful trials were collected and compared between FPA conditions.
The main effect for FPA condition was statistically different for initial contact hip flexion, hip abduction, hip internal rotation, knee flexion, knee abduction, knee external rotation, and ankle inversion angles compared to self-selected FPA at P < 0.05. Peak hip extension, hip abduction, knee adduction, knee internal rotation, ankle plantar flexion, and ankle inversion moments were also found to be statistically significant (P < 0.05). Overall, females experienced greater initial knee abduction angle (P = 0.028), hip abduction moment (P = 0.006), knee extension moment (P = 0.033), and knee internal rotation moment (P = 0.044), regardless of FPA condition. Males experienced greater initial contact hip abduction angle (P = 0.0017), regardless of FPA condition.
The results suggest that landing with large toe-in FPA will increase the magnitude of ACL injury risk variables, and females demonstrated a greater magnitude in these variables compared to males. Injury prevention programs may seek to target FPA as part of training activities to avoid large FPA toe-in landings.