Muscle use during double poling evaluated by positron emission tomography

Area of Science:

• Sports Medicine
• Exercise Physiology
• Medical Imaging

Background:

• Cross-country skiing (XCS) muscle activation is complex and not fully understood.
• Surface electromyography (SEMG) has limitations in assessing muscle use during dynamic movements.
• Advancements in 3D imaging, like positron emission tomography (PET), offer new insights into muscle activation.

Purpose of the Study:

• To investigate muscle activation patterns during double poling (DP) in XCS using PET.
• To compare muscle glucose uptake at two different exercise intensities (53% and 74% of peak oxygen uptake).

Main Methods:

• Eight male subjects performed two 20-minute DP bouts at distinct intensities.
• [(18)F]fluorodeoxyglucose ([(18)F]FDG) was administered, followed by a full-body PET scan.
• Glucose uptake index (GUI) was calculated for 15 key muscles to quantify activation.

Main Results:

• Shoulder, elbow, abdominal, and hip flexor muscles showed the highest glucose uptake during DP.
• Increased intensity led to significant glucose uptake increases in knee flexors (27%), knee extensors (16%), and abdominal muscles (21%).
• Upper body muscles remained primary movers, but lower limb and core muscles contributed more at higher intensities.

Conclusions:

• PET imaging confirms the dominant role of upper limb muscles in XCS double poling.
• Higher exercise intensities necessitate greater recruitment of muscles around the lumbar spine, hip, and knee.
• PET is a viable and promising method for assessing muscle activation in complex human movements, complementing existing techniques.