Figure 2.

Pain intensity before (T0), during (T1), immediately after (T2), and 30 minutes after transcutaneous electrical nerve stimulation (TENS) application (T3) in young (A) and older (B) participants. When compared with baseline, there was a significant reduction in pain during and after high-frequency and low-frequency TENS in young (all P ≤ 0.01) but not in older individuals (all P ≥ 0.1). For the young group, a significant difference was observed at T1 between high-frequency and placebo TENS and between low-frequency and placebo TENS (all P ≤ 0.05). No significant difference was observed between the 3 TENS conditions in the older group (all P > 0.20).