Differing hypertrophy patterns from open and closed kinetic chain training affect quadriceps femoris center of mass and moment of inertia.

Purpose: To determine whether kinetic chain pattern during knee extensor strength training influences quadriceps femoris center of mass and moment of inertia about the hip in a predictable manner as such changes can affect running economy. Methods: Twelve participants completed 8 weeks of both unilateral open (OKC) and closed (CKC) kinetic chain resistance training on opposing legs. Changes in quadriceps femoris muscle volume (VOL _QF ), center of mass location (CoM _QF ), and moment of inertia ( I _QF ) about the hip were determined from magnetic resonance images scans. Regional hemodynamics of the vastus lateralis taken at 30% and 70% of muscle length during OKC and CKC bouts early in the training program were measured using near-infrared spectroscopy (NIRS) and used post hoc to predict changes in CoM _QF . Results: While increases in VOL _QF were similar between OKC (Δ79.5 ± 87.9 cm ³ ) and CKC (Δ60.2 ± 110.5 cm ³ , p = 0.29), the patterns of hypertrophy differed; a distal shift in CoM _QF (Δ2.4 ± 0.4 cm, p < 0.001) and increase in I _QF (Δ0.017 ± 0.014 kg m ² , p < 0.001) occurred in OKC but not in CKC (CoM _QF : Δ-2.2 ± 2.0 cm, I _QF : Δ-0.022 ± 0.020 kg m ² , p > 0.05). Regional hemodynamics assessed by NIRS during a single training session displayed similar exercise and regional differences and predicted 39.6% of observed changes in CoM _QF . Conclusions: Exercise selection influences muscle shape sufficiently to affect CoM _QF and I _QF , and these changes may be predicted in part from NIRS measurements during a single workout. Given I _QF is inversely related to running economy and since CKC exercise provides a more proximal pattern of hypertrophy than OKC, it may be more preferential for running. The results from the present study also highlight the potential of NIRS as a tool for predicting patterns of hypertrophy between different exercises and exercise conditions.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Earp, Angelino, Hatfield, Colantuono, Jackson, Morgan, Adami, Melanson and Blazevich.)