Verification of fingertip blood lactate measurement as an index of muscle fatigue recovery.

[Purpose] To evaluate the validity of measurement sites for assessing blood lactic acid levels following unilateral upper-limb exercises. [Participants and Methods] Blood lactic acid levels were measured at the fingertips of both hands in 40 healthy young men (mean age 20.9 ± 2.5 years). Measurements were taken before, immediately after, and at 90-s intervals following unilateral upper-limb exercises involving palmar flexion and dorsiflexion of the non-dominant hand. Exercise load was determined through maximum voluntary contraction testing. [Results] No significant differences were found in the average blood lactic acid levels between the fingers at any measurement time point. The peak blood lactic acid level occurred approximately 90 s earlier in the motor limb than in the non-motor limb. [Conclusion] This study found no significant difference in blood lactic acid levels between the motor and non-motor limbs when using fingertip measurements during unilateral upper-limb exercises. Therefore, either fingertip may be a suitable measurement site. However, because the peak lactic acid level in the non-motor limb was delayed by around 90 s, the timing of peak muscle fatigue evaluation in the non-motor limb should be considered.