The purpose of this study was to determine the impact of localized cooling of the skeletal muscle during rest on mitochondrial related gene expression. Thermal wraps were applied to the vastus lateralis of each limb of 12 participants. One limb received a cold application (randomized) (COLD), while the other did not (RT). Wraps were removed at the 4 h time point and measurements of skin temperature, blood flow, and intramuscular temperature were taken prior to a muscle biopsy. RT-qPCR was used to measure expression of genes associated with mitochondrial development. Skin and muscle temperatures were lower in COLD than RT (p < 0.05). Femoral artery diameter was lower in COLD after 4 h (0.62 ± 0.05 cm, to 0.60 ± 0.05 cm, p = 0.018). Blood flow was not different in COLD compared to RT (259 ± 69 mL·min–1 vs. 275 ± 54 mL·min–1, p = 0.20). PGC-1α B and GABPA expression was higher in COLD relative to RT (1.57-fold, p = 0.037 and 1.34-fold, p = 0.006, respectively). There was no difference (p > 0.05) in the expression of PGC-1α, NT-PGC-1α, PGC-1α A, TFAM, ESRRα, NRF1, GABPA, VEGF, PINK1, PARK 2, or BNIP3-L. The impact of this small magnitude of difference in gene expression of PGC-1α B and GABPA without alterations in other genes are unknown. There appears to be only limited impact of local muscle cooling on the transcriptional response related to mitochondrial development.

No abstract

The purpose of the study is to determine the impact of local heating on skeletal muscle transcriptional response related to mitochondrial biogenesis and mitophagy. Twelve healthy subjects (height, 176.0 ± 11.9 cm; weight, 83.6 ± 18.3 kg; and body composition, 19.0 ± 7.7% body fat) rested in a semi-reclined position for 4 h with a heated thermal wrap (HOT) around one thigh and a wrap without temperature regulation (CON) around the other (randomized). Skin temperature, blood flow, intramuscular temperature, and a skeletal muscle biopsy from the vastus lateralis were obtained after the 4 h intervention. Skin temperature via infrared thermometer and thermal camera was higher after HOT (37.3 ± 0.7 and 36.7 ± 1.0 °C, respectively) than CON (34.8 ± 0.7, 35.2 ± 0.8 °C, respectively, p < 0.001). Intramuscular temperature was higher in HOT (36.3 ± 0.4 °C) than CON (35.2 ± 0.8 °C, p < 0.001). Femoral artery blood flow was higher in HOT (304.5 ± 12.5 mL‧min−1) than CON (272.3 ± 14.3 mL‧min−1, p = 0.003). Mean femoral shear rate was higher in HOT (455.8 ± 25.1 s−1) than CON (405.2 ± 15.8 s−1, p = 0.019). However, there were no differences in any of the investigated genes related to mitochondrial biogenesis (PGC-1α, NRF1, GAPBA, ERRα, TFAM, VEGF) or mitophagy (PINK-1, PARK-2, BNIP-3, BNIP-3L) in response to heat (p > 0.05). These data indicate that heat application alone does not impact the transcriptional response related to mitochondrial homeostasis, suggesting that other factors, in combination with skeletal muscle temperature, are involved with previous observations of altered exercise induced gene expression with heat.

The mechanisms for the age-related increase in fatigability of limb muscles during moderate-to high-velocity dynamic contractions are unresolved. PURPOSE: Determine whether the increased fatigability in older adults during dynamic exercise is associated with blunted blood flow and greater reductions in tissue oxygenation of the working muscles. METHODS: Fatigability, blood flow, and tissue oxygenation of the knee extensor muscles were measured in 10 young women (22.9 ± 3.8 yrs), 10 young men (22.3 ± 3.1 yrs), 9 old women (75.5 ± 4.2 yrs), and 11 old men (75.6 ± 4.7 yrs). Participants performed 80 maximal velocity contractions (1 every 3 s) with a load equivalent to 20% of their maximal voluntary isometric contraction. Blood flow through the superficial femoral artery was quantified before and immediately following the exercise via Doppler ultrasonography. Tissue oxygenation (StO 2 ) and deoxygenated hemoglobin (deoxy[heme]) of the rectus femoris were measured during exercise via near-infrared spectroscopy (NIRS). RESULTS: Fatigability (reduction in power) was less in young (22 ± 13 %) compared with older adults (38 ± 20 %, p=0.007) with no sex differences (p=0.432). Absolute blood flow after exercise was ~31% greater in young (1,140 ± 360 mLꞵmin -1 ) compared with older adults (869 ± 360 mLꞵmin -1 , p=0.009) and ~22% greater in men (1,100 ± 339 mLꞵmin -1 ) compared with women (899 ± 360 mLꞵmin -1 , p=0.043). However, blood flow normalized to the thigh lean tissue mass did not differ between young (185 ± 52 mLꞵmin -1 ꞵkg -1 ) and older adults (161 ± 49 mLꞵmin -1 ꞵkg -1 , p=0.154) or between men (163 ± 40 mLꞵmin -1 ꞵkg -1 ) and women (184 ± 61 mLꞵmin -1 ꞵkg -1 , p=0.223). There were also no associations between fatigability and absolute (p=0.865) or normalized end exercise blood flow (p=0.869). NIRS data could only be obtained from 16 of 20 young (10 men) and 12 of 20 older adults (9 men) due primarily to the amounts of subcutaneous adipose tissue. There were no age or sex differences in StO 2 or deoxy[heme] at the end of exercise for the remaining 28 participants (All p>0.05). CONCLUSION: These data suggest that the ability to deliver blood and oxygenate the working muscle are preserved in older adults during fatiguing knee extension exercise and that other factors must be responsible for the age-related increase in fatigability during dynamic exercise.

No abstract