The Time-Course of Changes in Muscle Mass, Architecture and Power During 6 Weeks of Plyometric Training

Abstract

To investigate the time-course of changes in knee-extensors muscle mass, architecture and function in response to plyometric training (PLT) performed on a novel training device, the Tramp-Trainer. This machine consists in a trampoline connected to an inclined sledge which allows the performance of repeated jumps while the subject is sitting on a chair. Methods: Eight healthy males (173.6 ± 4.7 cm, 69.7 ± 13.5 kg, 25.3 ± 4.6 years) underwent 6 weeks of bilateral PLT on the tramp-trainer machine. Training was performed three times per week (between 120 and 150 bounces per session). Kneeextensor maximum voluntary torque (MVT) and power, quadriceps femoris (QF) volume (VOL), cross-sectional area from the 20% to the 60% of femur length and CSA mean , together with vastus lateralis (VL) architecture (fascicle length, Lf, and pennation angle, PA) were assessed after 2, 4, and 6 weeks of PLT. Results: All results are presented as changes versus baseline values. MVT increased by 17.8% (week 2, p < 0.001) and 22.2% (week 4, p < 0.01), respectively, and declined to 13.3% (p < 0.05) at week 6 of PLT. Power increased by 18.2% (week 4, p < 0.05) and 19.7% (week 6, p < 0.05). QF VOL increased by 4.7% (week 4, p < 0.05) and 5.8% (week 6, p < 0.01); VL VOL increased by 5.2%, (p < 0.05), 8.2%, (p < 0.01), and 9.6% (p < 0.05) at weeks 2, 4, and 6, respectively. An increase in Lf was detected already at wk 2 (2.2%, p < 0.05), with further increase at 4 and 6 weeks of PLT (4 and 4.4%, respectively, p < 0.01). PA increased by 5.8% (p < 0.05) at week 6. Significant positive correlations were found between CSA mean and Power (R 2 = 0.46, p < 0.001) and between QF VOL and Power (R 2 = 0.44, p < 0.024). Conclusions: PLT induced rapid increases in muscle volume, fascicle length, pennation angle, torque and power in healthy younger adults. Notably, changes in VL VOL and Lf were detectable already after 2 weeks, followed by increases in knee extensors

Training-Induced Muscle Adaptations During Competitive Preparation in Elite Female Rowers

“…However, in this study, PCSA did not change with concurrent training focused on APL (ES = −0.07), illustrating that radial muscle hypertrophy was negligible in elite athletes. Similarly, it was previously observed that pennation angle increased in untrained individuals with plyometric [+6%; (Monti et al, 2020)] and eccentric training +5-21%; (Blazevich et al, 2007;Franchi et al, 2014)], however, pennation angle decreased in the rowers in our study after concurrent training with APL (−2 • , −9 ± 15%, ES = −0.71), similar to observations in elite athletes after sprint and jump training [−3 • ; (Blazevich et al, 2003)]. Therefore, adaptations in muscle morphology are likely different in elite athletes compared to untrained individuals.…”

Short-Term, Equipment-Free High Intensity Interval Training Elicits Significant Improvements in Cardiorespiratory Fitness Irrespective of Supervision in Early Adulthood

“…In this study, although we were not able to assess whole-body muscle mass as reported in a number of HIIT studies (Boereboom et al, 2016;Brown et al, 2018;Marcos-Pardo et al, 2019;Scott et al, 2019), we saw no change in VL MT, reported to be representative of muscle mass (Franchi et al, 2018) or VL FL (Randhawa and Wakeling, 2015) in any of the groups. We did however observe an increase in PA in both HIIT groups which is thought to represent an increase in cross sectional area and associated force and contractile capability (Lee et al, 2015;Monti et al, 2020). Whilst improvements in muscle PA have been shown following training modalities commonly associated with hypertrophy and strength gains, e.g., resistance and plyometric exercise training (Monti et al, 2020), the impact of HIIT on PA has been less well-studied.…”

“…We did however observe an increase in PA in both HIIT groups which is thought to represent an increase in cross sectional area and associated force and contractile capability (Lee et al, 2015;Monti et al, 2020). Whilst improvements in muscle PA have been shown following training modalities commonly associated with hypertrophy and strength gains, e.g., resistance and plyometric exercise training (Monti et al, 2020), the impact of HIIT on PA has been less well-studied.…”

ACSAuto-semi-automatic assessment of human vastus lateralis and rectus femoris cross-sectional area in ultrasound images

“…We acquired pictures at rest while the participants laid in a supine position on their back. A guide was mounted to the leg in order to keep the same transversal path 19 . We took pictures of both muscles at 33 and 50% of the distance between the trochanter major and the lateral femur condyle.…”