Resistance exercise is defined as any activity that causes the skeletal muscles to contract, such as weightlifting, push-ups and squats. Endurance exercise, or aerobic exercise, is any activity that maintains an increase in heart rate and breathing, such as walking, cycling and swimming.
Both forms of exercise have a different impact on the body. While resistance exercise can improve strength of skeletal muscles, endurance exercise can improve overall functional capacity.
Because the effects of resistance and endurance exercise are so diverse, researchers speculate that there are numerous different processes involved in how the body responds to each form of physical activity.
"Yet," Kainulainen and colleagues note, "there have been attempts to identify single signaling cascades or molecules that could work as a master regulator for controlling exercise-specific adaptations."
Previous research has indicated that a gene called peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) may be involved in how the body responds to certain forms of exercise. The team set out to investigate the role of this gene further in this latest study.
PGC-1α isoform production differs by type of exercise
The researchers enrolled 19 physically active men to their study and divided them into two groups. One group performed 50 minutes of endurance exercise in the form of walking on a treadmill, while the other group performed 50 minutes of leg press exercises, representing resistance activity.
Biopsies were taken from the thigh muscles of the men just before exercise, as well as 30 and 180 minutes after, which the researchers analyzed in order to assess PGC-1α activity.
The team found that both endurance and resistance exercise stimulated the PGC-1α gene, causing it to produce isoforms known as PGC-1α exon 1b, PGC-1α exon 1b' and truncated PGC-1α. Isoforms are different types of a protein that are produced from the same gene or produced from different genes if only a part of a gene's code is identified.
However, the researchers noticed that only endurance exercise triggered the production of an isoform called PGC-1α exon 1a.
What is more, the team found that endurance exercise activated genes that encouraged new blood vessel growth and increased stamina. While resistance exercise also stimulated a gene that boosted blood vess
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