Quadriceps and Hamstrings Activation Peaks Earlier as Athletes Repeatedly Hop, but There are Differences Depending on ACL Reconstruction Technique.
Einar Einarsson, Olivia Barbosa, Magnus Kjartan Gislason and 3 others
PMID 38576837WHAT IT FOUND
During 30-second maximal single-leg hopping, quadriceps and hamstring activation peaks moved earlier in the hop cycle as athletes repeated hops.
Injured legs after ACL reconstruction also showed lower peak quadriceps activation, with both graft types.
Key findings
01Peak quadriceps activation shifted earlier in the hop cycle from the first to the third hop phase in controls, in both bone-patellar tendon-bone legs, and in healthy hamstring-graft legs; lateral hamstring showed this shift in all groups except the bone-patellar tendon-bone-injured leg, and medial hamstring only in controls.
02Injured ACL reconstruction legs had lower peak vastus lateralis and vastus medialis activation than healthy legs.
03Both bone-patellar tendon-bone and hamstring graft groups had lower lateral hamstring peak activation than controls, and medial hamstring peak activation was lower from the first to the third phase in all groups.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The paper states 44 male participants were included, then separately reports 24 hamstring graft patients, 20 bone-patellar tendon-bone graft patients, and 31 controls, so the total analysed count is unclear. Only male athletes who had already met return-to-training criteria were studied, so it may not apply to female athletes or less recovered athletes. The study did not measure kinematics, kinetics, or jump height, so it cannot link EMG changes to movement mechanics. Time since surgery varied from 5 to 12 months, and the study was not powered to examine that effect. Only hamstring and bone-patellar tendon-bone grafts were included, so other graft types were not examined. Controls were footballers, while the ACL reconstruction group included athletes from football, futsal, rugby, handball, and volleyball.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that these EMG timing changes explain reinjury risk or that repeated hopping is a validated return-to-sport test. The study did not measure kinematics, kinetics, jump height, clinical outcomes, or injury risk.