The effect of resistance based post-activation performance enhancement interventions at different loads on maximal voluntary isometric contraction and muscle activation: Preliminary findings

Abstract

Background

The current literature lacks comprehensive information on how load and muscle activation affect performance in resistance exercise-based PAPE interventions. These effects remain unclear, and observations from studies focusing on both muscle activation and performance outcomes are needed to resolve this critical gap.

Objective

To examine the effects of PAPE interventions on maximum voluntary isometric contraction (MVIC) and muscle activation at different resistance loads via a coherence analysis approach.

Methods

The first experimental visit included anthropometric assessment, baseline MVIC and one repetition maximum (1RM) tests. In the next two visits, each subject completed a 5-m warm-up and performed the PAPE protocol (high Load or moderate Load) after a 5-m passive rest period. After 7-m of passive transition phase, subjects performed the MVIC and sEMG was recorded during each MVIC.

Results

We observed a significant load effect on peak force (p < 0.026). This difference was significant (p < 0.038) on the peak force output of the moderate load compared to the control condition, but not between the moderate and high load conditions (p < 1.000). We also observed that load had a significant effect on muscle activation (p < 0.001), and this effect was particularly significant in the high load condition (p < 0.001) compared to the control condition.

Conclusion

The preliminary findings of the study show that in resistance-based PAPE interventions applied at different loads, the moderate load condition positively affects the force output, while muscle activation increases more significantly, especially at high loads.

Keywords

Post-activation Performance Enhancement- Maximum Voluntary Isometric Contraction- Resistance Exercise- Muscle Synchronization

1. Introduction

In most sports, strength development is an important determinant of performance.¹ Therefore, it is critical to increase strength development with an optimal warm-up before performance.² When the literature is examined, post activation performance enhancement (PAPE), which provides this development, is a phenomenon that has received great interest by researchers and also plays an important role among performance enhancement strategies in the field.^3–5 PAPE describes the acute improvement in muscle strength and performance following maximal or near-maximal muscle contraction.⁶ The underlying physiological mechanisms of PAPE include complex processes such as increased motor unit synchronization, increased myosin light chain phosphorylation, increased activation of the central nervous system and improved neuromuscular efficiency.⁷

Table 1.
Descriptive Statistics

Age (years) Height (cm) Weight (kg) Training Age (years) 1RM

Mean 20.00 192 85.12 11.12 106.70

Std. Deviation 1.69 10 15.80 2.94 22.45

Minimum 18.00 180 63.00 5.00 85.97

Maximum 23.00 208 114.00 15.00 141.91

	Age (years)	Height (cm)	Weight (kg)	Training Age (years)	1RM
Mean	20.00	192	85.12	11.12	106.70
Std. Deviation	1.69	10	15.80	2.94	22.45
Minimum	18.00	180	63.00	5.00	85.97
Maximum	23.00	208	114.00	15.00	141.91

The use of the PAPE intervention with resistance exercise aims to improve performance by optimizing phenomenon-specific physiological processes.⁸ Resistance exercise is a forceful tool to help improve muscle size, force and many other positive physiological outcomes.⁹ In the literature, resistance back squat exercises with different loads are a widely used method to create the PAPE effect.^10–12 Research shows that different loads (1RM%) used in resistance exercises have different effects on acute physiological responses and performance improvement.¹³ As a result, heavy loads (> 80% of 1RM) activate fast contractile (type II) motor units with a high threshold according to the principle of size, producing the maximum activity.¹⁴ However, research has also shown that lower loads (30–60% of 1RM) can also lead to an increase in strength production without the motor units being fully activated.^15,16 Furthermore, previous studies have shown that peak and average speed decreases with increasing external load. A greater PAPE effect can be achieved by activating a greater number of motor units (especially type II fiber) and increasing the firing rate.

In relation to electrophysiological responses to resistance exercises with different applied loads, surface electromyography (sEMG) studies have shown that higher external loads lead to higher muscle activation compared with lower loads.¹⁷ In the literature, it was observed that the activation of the Vastus Lateralis (VL) muscle was not affected in 3 repetitions of squats performed with 1RM% 70, while the maximum power increased due to the external load.¹⁸ However, during squats performed at 90% and 100% 1RM loads compared to 80%, it was reported that general muscle activities increased with increasing loads, but significant increases were reported only for the Vastus Medialis (VM) and gluteus maximus (GM) muscles during 90% and 100% 1RM compared to 80%.¹⁹ Based on this information, electrophysiological factors affecting performance improvement, such as the load and number of repetitions used during warm-up and muscle activation, should be considered to obtain effective PAPE.¹⁷ Muscle-related electrophysiological analyses will allow more data to be collected on muscle behavior during performance in order to make the best decisions on whether the squat exercises used in PAPE interventions should be included in a subsequent training programme. Regardless of the task, muscles are known to spontaneously organize and respond to high physical demands through neuromuscular mechanisms.²⁰ However, there is insufficient information in the literature about the coherence of squat-based PAPE interventions during high physical demands.

The aim of the study was to investigate the effects of resistance-based PAPE interventions applied at high and moderate loads on muscle activation and maximum voluntary isometric contraction (MVIC) output. The main hypotheses of the study were i) resistance-based High load PAPE will increase the coherence coefficient of the VL and VM muscles during the MIVC task, ii) High load and Moderate load PAPE will improve the peak force output in MVIC tasks compared to the control condition.

2. Methods

2.1. Subjects

We used version 3.1.9.7 of the G*Power program to determine the number of participants required in this study. We measured the effect size as 0.7 from the variance. The alpha error was determined as 0.05. Regarding these values, the minimum number of subjects was calculated as 7.²¹ However, 8 male athletes were included in our study (Table 1). The criteria for inclusion in the study were the absence of any injury or illness, a regular training activity with at least 3 training sessions per week, and regular participation in competitions. Before starting the tests of the study, the athletes were prohibited from intense physical activities for 3-d before the study and caffeine consumption for 24-h before the study. Data were obtained at specific time intervals of the day (10.00–12.00 a.m.) for each subjects. Before all tests, the researchers obtained an informed consent form from the participants, which included information about potential risks related to the study and experimental designs. The Ethics Committee of Dokuz Eylül University approved all procedures and the experimental design (GOA 2022/39-08). The study protocol was carried out at Manisa Celal Bayar University, Faculty of Sports Sciences, Performance Laboratory. The study protocol is in accordance with the latest version of the Declaration of Helsinki.

2.2. Experimental design

Subjects performed three experimental runs in the laboratory at least one week apart. The first experimental visit included anthropometric assessment, baseline (control) MVIC and one repetition maximum (1RM) tests. On the next two visits, each subject completed a standardized warm-up on a bicycle ergometer at a cadence of 30 watts/60 cadence for 5-m and performed the resistance-based back squat PAPE protocol [Low Repetition-High Load (90% of 1RMx3 repetitions)] or [Moderate Repetition-Moderate Load (60% of 1RMx6 repetitions)] after a 5-m passive rest period. After 7-m of passive transition phase, subjects performed the MVIC and sEMG recording was obtained during each MVIC (Figure 1).

Figure 1.

Experimental Design MVIC: Maximum Voluntary Isometric Contraction, 1RM: One Repetition Maximum PAPE: Post-activation Performance Enhancement, sEMG: Surface Electromyography.

2.3. Procedures

2.3.1. Anthropometric Data Collection

The height measurements of the participants were obtained with a manual stadiometer. Measurements of the participant: The distance between the top of the head and the sole of the foot was determined in an upright position with the back turned and recorded in centimeters (cm). Body weights were measured using an electronic scale. The data obtained were recorded in kilograms (kg).

2.3.2. One Repetition Maximum Test

The initial load for a 1RM test is determined by the weight that subjects estimate they can lift during the back squat, taking into account their prior experience, with a minimum of 4 reps. During the initial load determination phase, if the subjects were able to lift less than 4 reps, they were given a 5-m break, and the experiment was repeated with a less load. Alternatively, if the participant achieved to complete more than 12 reps successfully, they were granted a 5-m period of rest, and the weight was augmented for the subsequent round of lift.²² Concerning the lifting method, the initial position involved having the bar positioned at shoulder level, with the feet placed apart at shoulder width, and the knees and hips completely extended. Each repetition consisted of a 1-s eccentric action followed by a 1-s concentric action, with a 1-s rest between each repetition, all while maintaining a 90° knee angle.

The Epley formula (1RM = [weight lifted × number of reps × 0.0333] + weight lifted) was used to calculate the estimated 1RM of the participants.²³

2.3.3. Post-activation Performance Enhancement Protocol

For the PAPE protocol, participants performed back squats at Low Repetition-High Load (90% of 1RMx3 reps) or Moderate Repetition-Moderate Load (60% of 1RMx6 reps). All routines are performed at normal speed (2-s eccentric and 2-s concentric actions with a 1-s rest between each repetition). Google metronome (60 bpm) was used to control the speed of the movement. A height-adjustable seat was placed behind the participant to standardize the back squat depth during the repetition of the movement.

Figure 2.

Electromyography (EMG) electrode placements of the Vastus Lateralis and Vastus Medialis muscles. VL vastus lateralis; VM vastus medialis; REF; reference electrode; Gnd; Ground electrode.

2.3.4. Maximum Voluntary Isometric Contraction Measurement

The VL and VM muscles’ isometric contraction was measured using a chair on a platform and a force transducer. The subjects position was determined according to Konrad.²⁴ As a result, after leaning back and sitting on the chair, the subject's upper leg was 90° away from the pelvis and the knee was 90° away from the upper leg. After checking the angles, the subjects were fixed to the chair from the waist with a belt. The ankle of the dominant leg is fixed to the force transducer with the apparatus, and the force transducer is fixed to the chair with a chain. The subjects were asked to do a knee extension after the command; maximum voluntary isometric contraction (N) output (10-s) was obtained from the force transducer by doing the extension.

2.3.5. Electromyography Data Collection

sEMG data were acquired using a Synergy EMG system (Medelec Synergy, Oxford Instruments, UK) at a sampling frequency of 50000. The skin areas where the electrodes were to be implanted were pre-shaven and cleaned with an abrasive gel (Nuprep, Weaver and Company, CO, USA) and then wiped with 70% ethyl alcohol. Single gold disc electrodes (natus, Genuine Grass, Gold Disc Electrodes) were placed in the direction of the muscle fiber using electrolyte gel (Ten20, Neurodiagnostic Electrode Paste) according to Stegeman and Hermens²⁵; active electrodes were placed in the middle of the VL and VM muscles (13–15 cm between electrodes); reference electrodes were placed on the right and left tibial tuberosities for VL and VM muscles; and the ground electrode was placed on the mastoid muscle (Figure 2). During the test, the electrodes were fixed with elastic bandages and checked throughout the test to prevent the electrodes from slipping and the wires from moving and creating noise.²⁶ Before the maximum voluntary contraction (MVC) test, the initial noise level was visually checked while the muscle of interest was relaxed. The obtained sEMG data were uploaded to MATLAB (2024a) software program and analysed by applying a 20–500 Hz filter.

2.3.6. Statistical Analyses

We used JASP 0.16.2 (JASP Team, 2018; https://jasp-stats.org/, accessed November 1, 2023) for statistical analysis and rain cloud graphics. We checked the normal distribution of the obtained data using the Shapiro-Wilk test. To determine the effect of PAPE (control condition, moderate load, high load) on MVIC (force) and muscle activation (VL, VM), we used a parametric test separately (one-way repeated measures ANOVA for within-group comparisons). For all statistical tests, the significance level was set for all statistical tests at α < 0.05 were reported. Post hoc comparisons were performed with the Bonferroni test. The effect sizes were calculated using Partial Eta squared ( $η$ p²) on JASP. The Partial Eta squared are rated as follows: 0.01: small effect; 0.06: moderate effect; 0.14: large effect.²⁷

Figure 3.

Peak force output during MVIC *denotes within group control, moderate and high load comparisons with a p < 0.05.

3. Results

Table 1. Descriptive Statistics.

One-way repeated measures ANOVA was used to examine the effect of control condition, moderate load and high load on force. The main effects of loads on force were significant (F (2, 14) = 4.78, p < .026, ηp² = 0.406). Bonferroni post hoc test revealed that load (moderate load) had an effect on force. This is because the moderate load force output (p < 0.038) was higher compared to the control and high condition. The mean values obtained from control, moderate load and high load conditions were 366, 508 and 488 (N), respectively (Figure 3).

The raw EMG data obtained are presented in separate tables (A-B) for both muscles (VL and VM) in Figure 4.

Figure 4.

Raw sEMG data of one subject. A : Vastus Lateralis B : Vastus Medialis.

Figure 5.

Power Spectrum of EMG signals (V²/Hz) from vastus lateralis and vastus medialis under conditions control, moderate, and high load.

In the present EMG signal processing operation, the power spectrum of the signals taken from different locations and under various conditions are analyzed to understand the underlying electrophysiological mechanisms Figure 5 illustrates a portion of the amplitude of the power spectrum obtained from the electrical activity of the vastus lateralis and vastus medialis muscles within a certain frequency band, where the spectral behavior is more apparent. It is clearly seen that there is a notable identical spectral behavior under certain frequency bands in case of control a high load. Although, it should be noted that the similar behavior between amplitude spectrums shown in Figure 5 does not directly ensure the existence of a synchronization since the phase information is not taken into account, this appearance is remarkable to investigate the existence of the synchronization between different signals in frequency domain using metrics involving both phase and amplitude and phase variations together.

Specifically, the existence of correlation and synchronization in a particular frequency range between the muscles vastus lateralis and vastus medialis respectively obtained from the time domain signals x(t) and y(t) can be conveniently analyzed by coherence²⁸ and phase lock value (PLV),²⁹ lying within interval [0 1] representing uncorrelated behavior for “0” and perfect correlation for “1”, respectively.

The coherence function C, statistically obtained from K different and independent observations, determines the possible existence of intrinsic information about neural activity and muscle coordination which is analytically formulated as below

\begin{aligned} C = \frac{{| \sum_{k = 1}^{K} \bar{X_{k} (f)} Y_{k} (f) |}^{2}}{\sum_{k = 1}^{K} {| X_{k} (f) |}^{2} \cdot \sum_{k = 1}^{K} {| Y_{k} (f) |}^{2}} \end{aligned}

where the term

\bar{(\cdot)}

denotes the complex conjugate and

X_{k} (f) = F x_{k} (t)

and

Y_{k} (f) = F y_{k} (t)

are Fourier transforms of

k^{t h}

time domain observations of

x_{k} (t)

and

y_{k} (t)

respectively. The detailed derivation related to coherence function is given in appendix section.³⁰ Since these metrics are extracted from spectral analysis, it gives information about whether two muscles or regions are working together at specific frequencies. High coherence at a certain frequency band can indicate that the signals are spectrally related with each other and may be driven by common neural inputs or synchronized motor unit firing.

According to the coherence function given in Figure 6 that increasing coherence in the specific frequency range yields a possible clue reflecting both muscles are controlled by a common neural input.

Figure 6.

Coherence function obtained in different states.

It should be noted that in addition to coherence measure concentrating on frequency-domain relationships including both of amplitude and phase information, the spectral synchronization is characterized by a similar measure called as phase lock value obtained directly from the phase difference between different signals. Unlike the conventional $P L V$ determined from time domain observations, it is analytically formulated in this study in frequency domain to reveal spectral synchronization as shown below

\begin{aligned} P L V (f) = | \frac{1}{K} \sum_{k = 1}^{K} e^{Δ φ_{k} (f)} | \end{aligned}

where

\begin{aligned} Δ φ_{k} (f) = \arg (\frac{X_{k} (f) Y_{k}^{*} (f)}{| X_{k} (f) | | Y_{k} (f) |}) \end{aligned}

According to the PLV results shown in Figure 7, it is apparent that the coherence and

P L V

results are consistently similar to each other in frequency domain and reveals the frequency bands reflecting the spectral synchronization between the electrical activity of the given muscles

Figure 7.

Phase Lock Value (PLV) function obtained in different states.

One-way repeated measures ANOVA was used to examine the effect of control condition, moderate load and high load on muscle activation (Coherence). The main effects of loads on muscle activation were significant (F (2, 19) = 28.63, p < .001, ηp² = 0.22). Bonferroni post hoc test revealed that load (high load) had an effect on muscle activation. In addition, the mean values of coherence in the frequency band 20–50 Hz showed that the high load (0.353) had a larger mean effect than the control (0.193) and moderate load (0.200) condition (Figure 8).

Figure 8.

Muscle activation (Coherence) during MVIC *denotes within group control, moderate and high load comparisons with a p < 0.05.

4. Discussion

The aim of this study was to investigate the acute effect of resistance-based PAPE intervention with two different loads on the force output produced during MVIC as well as on the activation of the quadriceps muscle (VL, VM). To the authors’ knowledge, this is the first study to examine the coherence of the VL and VM muscles during force production after two different resistance-induced PAPE interventions. The findings revealed that the resistance applied with a moderate load had a significant effect on force compared to the control condition, but the muscles exhibited more coherent behavior in the high load condition than in the control and moderate load conditions.

As a result of the study, it was observed that during 10-s MVIC, moderate load affected the performance output more positively than high load (Figure 3). In the literature, it is noticeable that the loads applied to resistance-based PAPE interventions in exercises involving dynamic contractions show different results. Accordingly, some studies reported that performance improvement was higher as a result of PAPE intervention in high-load conditions.^31–34 These studies are particularly in the range of 80–100% of 1RM. On the other hand, when looking at research showing that low and moderate loads are better, researchers focus on 40–70% of 1RM loads.^32,35 In these studies, variables such as force training history, muscle architectural structure, and specificity due to the nature of the exercise applied after PAPE may be effective. Since our study findings focused on the change during a 10-s maximum voluntary isometric contraction, the nature and the duration of the isometric contraction affected muscular endurance rather than force, suggesting that moderate load had a more positive effect.

In the literature, it is observed that the data related to sEMG outputs obtained as a result of PAPE intervention are generally evaluated on the amplitude and frequency.^36–39 Research results show that more significant results are obtained in sEMG amplitude and frequency in PAPE interventions applied at high or near high load conditions. For example, when we look at the sEMG amplitude-based findings of PAPE and two different intervention results, it was reported that the sEMG findings obtained from the quadriceps muscles in the PAPE intervention performed with 70% of Pmax and 130% of Pmax were higher at both loads compared to the control condition.⁴⁰ In another study, significant increases in mean concentric sEMG activity (VL) were detected in PAPE intervention using 85% of 1RMx3, especially after resistance banded intervention.¹⁸ In a different study, the sEMG activity of the Pectoralis major muscle was found to be significantly higher than the baseline value as a result of PAPE intervention when the effect of bench press pushing speed on muscle activation was examined using a similar load (80% of 1RM).³⁸ In the study in which different PAPE warm-up interventions (traditional, dynamic and static) were applied and 90% of 1RM resistance was used, a significant difference was observed between the three warm-up methods in median frequency means.⁴¹ The general belief is that as the load increases, more high threshold motor units are activated and this contributes to higher sEMG amplitudes.⁴² In our study, unlike the existing literature, sEMG findings were evaluated over the mean frequency with coherence analysis (Figure 6). According to the findings obtained from the study, especially in the frequency bands of 20–50 Hz, it is seen that VL and VM show more compatible behaviour in the high load condition compared to the moderate load condition (Figure 8). The 20–50 Hz frequency range is considered to be the range in which especially type II fiber types are activated.⁴³ In the analysis results, it was observed that the high load condition provided higher type II muscle activation than the other conditions and the muscles showed concerted behaviour. The synchronized behaviour of the muscles is considered to be related to the increased rate of force development during rapid contractions.⁴⁴ During a 10-s MVIC, it was shown that there was higher and more synchron type II muscle recruitment at high load. Due to the nature of the 10-s MVIC task (only the contraction phase), the results were not naturally reflected in force output. However, these findings showed that type II fibril activation and synchronization in isometric contraction tasks were positively affected in a force output-independent manner.

5. Conclusion

The results of the study showed that resistance-based PAPE interventions applied at moderate and high loads positively affected muscle activation and synchronization during 10-s MVIC, and the effect was more significant at high loads. Resistance-based PAPE interventions provide a positive effect on contraction tasks requiring type II muscle activation and synchronization. The results suggest that this effect may be more significant at high loads in terms of activation and synchronization. In addition, the coherence analysis method applied in the study is considered to be a valuable method in terms of revealing the synchronization of different parts within a muscle group.

On the other hand, due to the nature of isometric contraction, it was observed that moderate-load PAPE made a more positive contribution to force output. It is thought that moderate-load PAPE interventions in exercises involving isometric contraction tasks may make a more positive contribution to performance output. In future studies, there is a need for studies with large subject groups and a focus on different genders in which different types of tasks will be investigated with a coherence approach.

6. Limitations

There are some limitations that need to be addressed. The number of participants was limited due to the small number of teams in the province where the study was conducted and the intense training and match schedule of the athletes. Therefore, further studies with a larger sample size (if possible) should be conducted to confirm, refute and/or extend our findings.

7. Practical Applications

Considering individual differences, the authors suggest that the PAPE resistance loads that athletes perform optimally in training sessions should be studied in advance to determine the best strategy for the competition.

Footnotes

Acknowledgement

We would like to thank all the participants in the study.

Ethical consideration

The Ethics Committee of Dokuz Eylül University approved all procedures and the experimental design (GOA 2022/39-08). All participants were informed about the aims and risks of the study and provided written informed consent to participated.

Author contributions

Conception: S.G, M.E.Ç, Ç.G, E.G.

Performance of Work: S.G, E.M, E.G.

Interpretation or Analysis of Data: S.G, Ç.G, M.E.Ç.

Preparation of The Manuscript: S.G, M.E.Ç, Ç.G, E.M, E.G.

Revision for Important Intellectual Content: Ç.G, E.G.

Supervision: S.G, E.G.

Funding

This study was carried out within the TUBITAK project and supported by the approval number 222S720 (TUBITAK 1002-A).

Conflict of interest

The authors have no conflicts of interest to report

Appendix

Principally, coherence function, defining a correlation between two random signals $x (t)$ and $y (t)$ in frequency domain, can be expressed as in A.1 A.1

γ_{x y} (f) = \frac{{| S_{x y} (f) |}^{2}}{S_{x x} (f) S_{x x} (f)}

where the cross power spectral density

S_{x y} (f)

, auto power spectral densities

S_{x x} (f)

and

S_{y y} (f)

are obtained from their crosscorrelation and autocorrelation functions

R_{x y} (τ)

R_{x x} (τ)

and

R_{y y} (τ)

, respectively given in A.2 – A.4

A.2

\begin{aligned} S_{x y} (f) = F R_{x y} (τ) \end{aligned}

A.3

\begin{aligned} S_{x x} (f) = F R_{x x} (τ) \end{aligned}

A.4

\begin{aligned} S_{y y} (f) = F R_{y y} (τ) \end{aligned}

Note that the term

F \cdot

denotes Fourier transformation and the functions

R_{x y} (τ),

R_{x x} (τ)

and

R_{y y} (τ)

are respectively determined as in A.5 – A.7

A.5

\begin{aligned} R_{x y} (τ) = E [x (t) y (t + τ)] \end{aligned}

A.6

\begin{aligned} R_{x x} (τ) = E [x (t) x (t + τ)] \end{aligned}

A.7

\begin{aligned} R_{y y} (τ) = E [y (t) y (t + τ)] \end{aligned}

where

E [\cdot]

is the expectation operator. However, almost all biomedical signals exhibit nonstationary behaviour and vary rapidly. Therefore, calculating spectral densities over limited observation interval may not yield accurate results. In such cases, the coherence function can be alternatively approximated by Fourier transforms of the signals

X (f) = F x (t)

and

Y (f) = F y (t)

, themselves as given in A.8 – A.10.

A.8

\begin{aligned} S_{x y} (f) = E \bar{X} (f) Y (f) \end{aligned}

A.9

\begin{aligned} S_{x x} (f) = E {| X (f) |}^{2} \end{aligned}

A.10

\begin{aligned} S_{y y} (f) = E {| Y (f) |}^{2} \end{aligned}

where the overline symbol

\bar{(\cdot)}

denotes complex conjugate operation. The coherence function can be expressed as in A.11 A.11

γ_{x y} (f) = \frac{| E X (f) Y^{*} (f) |}{E {| X (f) |}^{2} E {| X (f) |}^{2}}

In case of K observation exists, the expectation operator corresponds to ensemble averaging and the coherence function in A.11 can be rewritten as A.12

γ_{x y} (f) = \frac{{| \sum_{k = 1}^{K} \bar{X_{k} (f)} Y_{k} (f) |}^{2}}{\sum_{k = 1}^{K} {| X_{k} (f) |}^{2} \cdot \sum_{k = 1}^{K} {| Y_{k} (f) |}^{2}}

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The effect of resistance based post-activation performance enhancement interventions at different loads on maximal voluntary isometric contraction and muscle activation: Preliminary findings

Abstract

Background

Objective

Methods

Results

Conclusion

Keywords

1. Introduction

Table 1. Descriptive Statistics Age (years) Height (cm) Weight (kg) Training Age (years) 1RM Mean 20.00 192 85.12 11.12 106.70 Std. Deviation 1.69 10 15.80 2.94 22.45 Minimum 18.00 180 63.00 5.00 85.97 Maximum 23.00 208 114.00 15.00 141.91

2.1. Subjects

2.2. Experimental design

2.3.1. Anthropometric Data Collection

2.3.2. One Repetition Maximum Test

2.3.3. Post-activation Performance Enhancement Protocol

2.3.5. Electromyography Data Collection

2.3.6. Statistical Analyses

5. Conclusion

6. Limitations

7. Practical Applications

Footnotes

Acknowledgement

Ethical consideration

Author contributions

Funding

Conflict of interest

Appendix

References

Table 1.
Descriptive Statistics

Age (years) Height (cm) Weight (kg) Training Age (years) 1RM

Mean 20.00 192 85.12 11.12 106.70

Std. Deviation 1.69 10 15.80 2.94 22.45

Minimum 18.00 180 63.00 5.00 85.97

Maximum 23.00 208 114.00 15.00 141.91