Evaluating Stretch-Shortening Cycle Function in Athletes After ACL Reconstruction Using a Repeat Hop Test

The purpose of this thesis was to evaluate the influence of external task constraints on repeat hop testing (RHT) performance, neuromuscular control, and interlimb force-time asymmetry in athletes following anterior cruciate ligament reconstruction (ACLR). The first study compared three methods for estimating landing velocity during RHT kinetic analysis against traditional temporal methods such as flight time. The results demonstrated that kinetic outcomes were highly sensitive to the method used, with methods based on flight time and spring mechanics demonstrating practical utility. The second study investigated the influence of two separate verbal cues: “hop fast” (FAST) and “hop high and fast” (HIGH) on unilateral RHT kinetics, kinematics, and muscle activity in ACLR and healthy athletes. ACLR limbs exhibited reduced hop heights and reactive strength index (jump height/ground contact time) during the HIGH condition relative to non-injured contralateral and healthy control limbs, but not during the FAST condition. It was also observed that isometric knee extensor strength, but not quadriceps muscle activity, demonstrated a strong positive relationship with RSI during the HIGH condition. The third study examined eccentric and concentric impulse asymmetries during unilateral and bilateral variations of RHT and the countermovement jump (CMJ). ACLR athletes demonstrated greater concentric impulse asymmetry across all conditions, with strong inter-task correlations only the ACLR group. In contrast, elevated eccentric impulse asymmetry was observed during all tasks except the bilateral CMJ, but with moderate inter-task correlations only in the ACLR group. In summary, these findings provide evidence that RHT is sensitive to ACLR-related neuromuscular deficits and may be an appropriate addition to comprehensive testing batteries used to inform return to sport decisions in ACLR athletes.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Kinesiology

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2025

Author dc:creator

• Boon-van Mossel, Nathan

Advisors dc:contributor.advisor

• Jordan, Matthew
• Herzog, Walter

Committee members dc:contributor.committeemember

• Martin, Ryan
• Bertram, John

• ACL
• hopping

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/50347

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/122754