Fig. 7From: Efficacy of silver needle therapy for the treatment of chronic nonspecific low back pain: a prospective, single-center, randomized, parallel-controlled clinical trialThe HRV results in the control group and silver needle group. This figure shows the comparison of InLF, InHF, and LF/HF of HRV within the same group according to the time. a The control group. b The silver needle group. *P < 0.05Back to article page