Skip to main content
2024 NSCA National Conference Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Resistance Training/Periodization

(07) THE EFFECTS OF REPETITION CADENCE ON NEUROMUSCULAR RESPONSES DURING FATIGUING EXERCISE

Friday, July 12, 2024
10:00 AM – 10:15 AM East Coast USA Time
Location: Room 337-338
Abstract Details: During resistance exercise, the neuromuscular responses to dynamic contractions reflect the external demand placed on working muscles. This demand may be influenced by the relative amount of time spent performing concentric (CON) or eccentric (ECC) contractions in a repetition. Additionally, CON contractions require greater internal work than ECC contractions to meet the same external demand. Neuromuscular responses may provide insight on the differences in internal demand between CON and ECC contractions at different repetition cadences during constant-load resistance exercise.

Purpose: To examine the effect of repetition cadence on neuromuscular responses during fatiguing dynamic single-limb leg extension exercise.

Methods: 5 men and 10 women (age:23±7 yr, height:171±6.6 cm, body mass:75.9±24.6 kg) performed leg extensions to failure at 40% one-repetition maximum (1RM) at 2 cadences: 3 sec CON, 1 sec ECC (3C:1E) and 1 sec CON, 3 sec ECC (1C:3E). Surface electromyography (EMG) and mechanomyography (MMG) amplitude (AMP) and mean power frequency (MPF) were measured from the vastus lateralis of the dominant limb during the fatiguing task. Separate 3-way ANOVAs (cadence [3C:1E, 1C:3E] x contraction [CON, ECC] x time [first 10% reps, last 10% reps]) were run for each neuromuscular response, with appropriate follow-up pairwise comparisons (p < 0.05).

Results: There was no 3-way interaction for any signal (p=0.341-0.814). For EMG AMP, there were cadence x contraction (F=12.682, p=0.003, η2p=0.475) and contraction x time (F=40.231, p< 0.001, η2p=0.742) interactions. Pairwise comparisons indicated EMG AMP was greater during CON than ECC for 1) the first (CON: 55.8% ± 15.13%, ECC: 34.4% ± 10.6%) and last repetitions (CON: 95.9% ± 28.9%, ECC: 47.2% ± 20.1%, p < 0.001) and 2) during both cadences (3C:1E CON: 68.6% ± 18.9%, ECC: 44.2% ± 18.7%, 1C:3E CON: 83.2% ± 25.7%, ECC: 37.4% ± 11.2%, p < 0.001). For EMG MPF, there was a main effect of time (F=72.637, p< 0.001, η2p=0.838) that indicated a decrease from the first (90.2% ± 17.3%) to the last rep (72.6% ± 15.4%, p< 0.001). For MMG AMP, there were cadence x contraction (F=11.989, p=0.004, η2p=0.461) and contraction x time (F=7.416, p=0.016, η2p=0.346) interactions. MMG AMP for CON was greater than ECC for the 1C:3E cadence (CON: 115.5% ± 60.4%, ECC: 68.2% ± 30.5%, p< 0.001), but not during 3C:1E cadence (CON: 89.3% ± 46.8%, ECC: 121.6% ± 71.7%, p=0.013). MMG AMP decreased from the first (117.8% ± 70.3%) to the last rep (72.0% ± 32.6%, p=0.003) for ECC but not CON (p=0.128). For MMG MPF, there were cadence x time (F=11.186, p=0.005, η2p=0.444) and contraction x time (F=5.914, p=0.029, η2p=0.297) interactions. MMG MPF decreased over time for the 1C:3E cadence (first: 139.9% ± 61.8%, last: 107.8% ± 71.6%, p< 0.001) and for the CON contraction (first: 142.6% ± 51.2%, last: 108.2% ± 47.8%).

Conclusion: The differences in neuromuscular responses between CON and ECC contractions suggest altered neuromuscular excitation dependent on cadence. The greatest internal demand was placed on the muscle during shorter CON contractions and the least during longer ECC contractions. PRACTICAL APPLICATIONS: Manipulating excitation via contraction cadences may be a useful tool for coaches and practitioners in prescribing resistance exercise to individuals who have a limited capacity to produce internal work. Particularly for individuals who cannot adjust external demands, such as novice athletes or during rehabilitation.

Acknowledgements: None