Evaluation of muscle activity just after straight leg raising exercise by using ¹⁸FDG-PET

Exercise therapy is one of the recognized treatment methods for knee osteoarthritis (KOA). One such exercise technique, straight leg raising (SLR), is widely known as a home exercise method for strengthening the quadriceps femoris muscle. However, whether this exercise truly strengthens the quadriceps is not known. The objective of the present study was to investigate which lower limb muscle is stimulated and shows increased activity with SLR.

A total of 14 lower limbs in seven healthy adult male volunteers (mean age: 31.3 ± 2.2 years) were investigated. Participants were asked to perform SLR and subsequently underwent FDG-PET/CT examination for evaluation of the muscles of the entire lower limb. The maximum standardized uptake value (SUVmax) of each muscle (iliacus, psoas major, gluteus maximus, gluteus medius, gluteus minimus, vastus medialis, vastus intermedius, vastus lateralis, rectus femoris, biceps femoris, semimembranosus, semitendinosus, adductor, sartorius, gracilis, tibialis anterior, tibialis posterior, soleus, medial head of gastrocnemius, and lateral head of gastrocnemius) was measured in four cross-sections: at the trunk, pelvis, thigh, and lower leg.

SUVmax was significantly greater in: iliacus and adductor compared to vastus medialis, vastus lateralis, biceps, semitendinosus, gracilis, tibialis anterior, and gastrocnemius; psoas major compared to all muscles except for gluteus minimus and adductor; gluteus minimus compared to all muscles except for iliacus, psoas major, gluteus medius, and adductor; and gluteus medius compared to semitendinosus and gracilis.

After SLR, SUVmax was significantly greater in iliacus, psoas major, gluteus minimus, gluteus medius, and adductor compared to some of the other muscles. Performing SLR increased glucose metabolism of the above muscles in particular, and this may have increased their activity levels.