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. 2017 May 29;8:331.
doi: 10.3389/fphys.2017.00331. eCollection 2017.

Greater Neural Adaptations Following High- Vs. Low-Load Resistance Training

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Free PMC article

Greater Neural Adaptations Following High- Vs. Low-Load Resistance Training

Nathaniel D M Jenkins et al. Front Physiol. .
Free PMC article

Abstract

We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 1RM; n = 13) resistance training group and completed leg extension resistance training to failure 3 times per week for 6 weeks. Testing was completed at baseline, 3, and 6 weeks of training. During each testing session, ultrasound muscle thickness and echo intensity, 1RM strength, maximal voluntary isometric contraction (MVIC) strength, and contractile properties of the quadriceps femoris were measured. Percent voluntary activation (VA) and electromyographic (EMG) amplitude were measured during MVIC, and during randomly ordered isometric step muscle actions at 10-100% of baseline MVIC. There were similar increases in muscle thickness from Baseline to Week 3 and 6 in the 80 and 30% 1RM groups. However, both 1RM and MVIC strength increased from Baseline to Week 3 and 6 to a greater degree in the 80% than 30% 1RM group. VA during MVIC was also greater in the 80 vs. 30% 1RM group at Week 6, and only training at 80% 1RM elicited a significant increase in EMG amplitude during MVIC. The peak twitch torque to MVIC ratio was also significantly reduced in the 80%, but not 30% 1RM group, at Week 3 and 6. Finally, VA and EMG amplitude were reduced during submaximal torque production as a result of training at 80% 1RM, but not 30% 1RM. Despite eliciting similar hypertrophy, 80% 1RM improved muscle strength more than 30% 1RM, and was accompanied by increases in VA and EMG amplitude during maximal force production. Furthermore, training at 80% 1RM resulted in a decreased neural cost to produce the same relative submaximal torques after training, whereas training at 30% 1RM did not. Therefore, our data suggest that high-load training results in greater neural adaptations that may explain the disparate increases in muscle strength despite similar hypertrophy following high- and low-load training programs.

Keywords: morphological adaptations; muscle activation; neural adaptations; training load.

Figures

Figure 1
Figure 1
(A) Muscle thickness in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for muscle thickness in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant increase from Baseline.
Figure 2
Figure 2
(A) Echo intensity in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for echo intensity in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant decrease from Baseline. Indicates a significant decrease from Week 3.
Figure 3
Figure 3
(A) One repetition maximum strength in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for one repetition maximum strength in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant increase from Baseline. Indicates a significant increase from Week 3. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM > 30% 1RM.
Figure 4
Figure 4
(A) Maximum voluntary isometric strength in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for maximal voluntary isometric strength in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant increase from Baseline. Indicates a significant increase from Week 3. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM > 30% 1RM.
Figure 5
Figure 5
(A) Voluntary activation in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for voluntary activation in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant increase from Baseline. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM > 30% 1RM.
Figure 6
Figure 6
Actual MVIC torque (Solid Black Bars) and extrapolated MVIC torque (Solid + White Bars) in the 80% 1RM (A,C) and 30% 1RM (B,D) groups at Baseline, Week 3, and Week 6. Extrapolated torque represents the theoretical maximal torque generating capacity of the leg extensors. Note that in (A,B), the y-axis is torque in Nm. In (C,D), torque has been normalized such that the extrapolated torque is equivalent to 100% (thus the units are %MVIC). As can clearly be shown in (C,D), qualitatively, the relative contribution of actual MVIC torque to maximal torque generating capacity increased to a greater degree in the 80% than 30% 1RM groups.
Figure 7
Figure 7
(A) Normalized electromyographic amplitude in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for electromyographic amplitude in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant increase from Baseline.
Figure 8
Figure 8
(A) Peak twitch torque in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for peak twitch torque in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM > 30% 1RM.
Figure 9
Figure 9
(A) The peak twitch torque to maximal voluntary contraction ratio (PTT:MVIC) in the 80 and 30% 1RM groups at Baseline, Week 3, and Week 6; and (B) adjusted means for PTT:MVIC in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant decrease from Baseline.
Figure 10
Figure 10
Voluntary activation from 0 to 100% of the Baseline MVIC at Baseline, Week 3, and Week 6 in the (A) 80% 1RM and (B) 30% 1RM groups; (C) voluntary activation (collapsed across torque) in the 80 and 30% 1RM groups; and (D) the adjusted means for voluntary activation in the 80 and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant decrease from Baseline to Week 6. **Indicates a significant decrease from Week 3 to Week 6. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM < 30% 1RM.
Figure 11
Figure 11
Normalized electromyographic amplitude (EMGQAMP) from 0 to 100% of the Baseline MVIC at Baseline, Week 3, and Week 6 in the (A) 80% 1RM and (B) 30% 1RM groups; (C) EMGQAMP (collapsed across torque) in the 80 and 30% 1RM groups; and (D) the adjusted means for EMGQAMP in the 80% and 30% 1RM groups at Week 3 and Week 6. Error bars are standard errors. *Indicates a significant decrease from Baseline to Week 6. Indicates a significant difference between the 80 and 30% 1RM groups. 80% 1RM < 30% 1RM.

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References

    1. Aagaard P., Andersen J. L., Dyhre-Poulsen P., Leffers A. M., Wagner A., Magnusson S. P., et al. . (2001). A mechanism for increased contractile strength of human pennate muscle in response to strength training: changes in muscle architecture. J. Physiol. 534(Pt 2), 613–623. 10.1111/j.1469-7793.2001.t01-1-00613.x - DOI - PMC - PubMed
    1. Aagaard P., Simonsen E. B., Andersen J. L., Magnusson P., Dyhre-Poulsen P. (2002). Neural adaptation to resistance training: changes in evoked V-wave and H-reflex responses. J. Appl. Physiol. 92, 2309–2318. 10.1152/japplphysiol.01185.2001 - DOI - PubMed
    1. Ahtiainen J. P., Hoffren M., Hulmi J. J., Pietikainen M., Mero A. A., Avela J., et al. . (2010). Panoramic ultrasonography is a valid method to measure changes in skeletal muscle cross-sectional area. Eur. J. Appl. Physiol. 108, 273–279. 10.1007/s00421-009-1211-6 - DOI - PubMed
    1. Allen G. M., Gandevia S. C., McKenzie D. K. (1995). Reliability of measurements of muscle strength and voluntary activation using twitch interpolation. Muscle Nerve 18, 593–600. 10.1002/mus.880180605 - DOI - PubMed
    1. Arabadzhiev T. I., Dimitrov V. G., Dimitrov G. V. (2014). The increase in surface EMG could be a misleading measure of neural adaptation during the early gains in strength. Eur. J. Appl. Physiol. 114, 1645–1655. 10.1007/s00421-014-2893-y - DOI - PubMed
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