Effect of knee stabilization training with and without blood flow restriction on patellofemoral pain in bodybuilding athletes: a randomized controlled trial

The application of blood flow restriction (BFR) during low-intensity exercise has been shown to acutely reduce pain. However, whether a similar phenomenon occurs following a training period with BFR is less studied, particularly in bodybuilding athletes. This study investigated the effects of knee stabilization training with and without BFR on patellofemoral pain, balance and proprioception in bodybuilding athletes. An 8-week, assessor-blinded, randomized controlled trial was conducted involving 60 elite male bodybuilders (age: 22.9 ± 3.1 years, height: 1.74 ± 0.04 m, body mass: 75.6 ± 5.6 kg) with patellofemoral pain. The primary outcome was pain intensity, assessed using the visual analog scale (VAS). Secondary outcomes included proprioception, and static and dynamic balance. Participants were randomly allocated into three groups: Group 1 (traditional exercise only), Group 2 (traditional exercise plus knee stabilization training), and Group 3 (traditional exercise plus knee stabilization training combined with blood flow restriction). All groups performed three 1-h resistance exercise (70–80% 1RM) sessions per week for 8 weeks. Additionally, Groups 2 and 3 performed knee stabilization exercises at 30% 1RM, without (2) or with (3) BFR. Data were analyzed using a linear mixed-effects model with Bonferroni adjustment for multiple comparisons. Main effects of time were observed for pain (MD = − 1.8 cm, 95% CI [− 2.5, − 1.1], P = 0.02), proprioception (MD = − 2.3°, 95% CI [− 3.0, − 1.6], P = 0.001), static balance (MD = 5.2 s, 95% CI [3.9, 6.5], P = 0.001), and dynamic balance (MD = 8.5 cm, 95% CI [6.8, 10.2], P = 0.001). Group by time interactions were found for pain (F = 4.43, P = 0.01), proprioception (F = 9.45, P = 0.001), and dynamic balance (F = 6.37, P = 0.004), but not for static balance (F = 6.36, P = 0.06). Posthoc analysis revealed that both intervention groups (Group 2 and Group 3) demonstrated improvements in all outcomes compared to the control group (Group 1) (all P < 0.05). Furthermore, Group 3 showed better outcomes than Group 2 for pain (MD = − 1.8 cm, 95% CI [− 2.5, − 1.1], P = 0.001), proprioception (MD = − 1.7°, 95% CI [− 2.4, -1.0], P = 0.004) and dynamic balance (MD = 8.5 cm, 95% CI [6.8, 10.2], P = 0.001). No significant difference was found between Group 3 and Group 2 in static balance (MD = 3.2 s, 95% CI [− 0.5, 6.9], P = 0.09). Traditional resistance training combined with knee stabilization exercises improved pain, proprioception, and balance in bodybuilding athletes with patellofemoral pain. Blood flow restriction may further enhance these improvements, particularly in pain reduction, proprioception, and dynamic balance.