The effect of post-activation potentiation on performance according to circadian rhythm in young athletes

Canan Fikri Demirtaş1, Taner Akbulut2, Vedat Çinar3, Emsal Çağla Avcu4 , Gian Mario Migliaccio5,6, Gianfranco Beltrami5,7

1Firat Univ, Fac Sport Sci, Institute of Health Sciences, Elazig, Turkey; 2Firat Univ, Fac Sport Sci, Department of Coaching Education, Elazig, Turkey; 3Firat Univ, Fac Sport Sci, Department of Physical Education and Sport, Elazig, Turkey; 4Sivas Cumhuriyet Univ, Fac Sport Sci, Department of Coaching Education, Elazig, Turkey; 5Department of Human Sciences and Promotion of the Quality of Life, San Raffaele Rome Open University,Rome, Italy; 6Maxima Performa, Athlete Physiology, Psychology, and Nutrition Unit, Milan, Italy; 7Italian Federation of Sports Medicine (FMSI), Rome, Italy.

Summary. Background. The interaction between circadian rhythm and post-activation potentiation (PAP) - a phenomenon that causes temporary increases in muscle strength and performance following intense muscle contractions - is crucial for understanding daily variations in athletic performance. Methods. Fourteen male athletes voluntarily participated in a crossover design study. Athletes underwent both control and PAP interventions at different times of the day. Performance measurements included vertical jump, standing long jump, T-drill agility test, and 5-10 m sprint tests. Results. No significant differences were observed in standing long jump and vertical jump performances across different times of day or warm-up protocols (p>0.05). However, significant time-of-day dependent changes were found in both 5 and 10 m sprint performances between warm-up practices (p<0.05). Agility performance showed significant variations according to time of day (p<0.05). Conclusions. Athletic performance metrics may vary according to circadian rhythm, with PAP potentially contributing to these variations. The findings suggest that the effectiveness of PAP interventions might be influenced by the time of the day they performed.

Key words. Pap, circadian rhythm, warm-up, performance.

L’effetto della post-activation potentiation sulla prestazione in relazione al ritmo circadiano in giovani atleti

Riassunto. Background. L’interazione tra ritmo circadiano e post-activation potentiation (PAP) – un fenomeno che determina incrementi temporanei nella forza muscolare e nella performance in seguito a contrazioni muscolari intense – risulta fondamentale per comprendere le variazioni quotidiane della prestazione atletica. Metodi. Quattordici atleti di sesso maschile hanno partecipato volontariamente a uno studio con disegno crossover. Gli atleti sono stati sottoposti sia a interventi di controllo sia a protocolli PAP in diversi momenti della giornata. Le misurazioni delle prestazioni includevano il salto verticale, il salto in lungo da fermo, il test di agilità T-drill e sprint sui 5 e 10 metri. Risultati. Non sono emerse differenze significative nelle prestazioni del salto in lungo da fermo e del salto verticale tra i vari momenti della giornata né tra i differenti protocolli di riscaldamento (p>0,05). Tuttavia, sono state riscontrate variazioni significative, dipendenti dall’orario, nelle prestazioni degli sprint sui 5 e 10 metri tra le diverse modalità di riscaldamento (p<0,05). Anche la performance nei test di agilità ha mostrato variazioni significative in funzione del momento della giornata (p<0,05). Conclusioni. I parametri della prestazione atletica possono variare in relazione al ritmo circadiano, con un potenziale contributo della PAP a tali fluttuazioni. I risultati suggeriscono che l’efficacia degli interventi basati sulla PAP potrebbe essere influenzata dall’orario in cui vengono eseguiti.

Parole chiave. PAP, ritmo circadiano, riscaldamento, prestazione.

Introduction

Physical performance is a complex interaction of a number of multifaceted factors, including physiological parameters, energy metabolism, neuromuscular functions, and psychological elements required to perform motor tasks. These interactions include key components of performance such as power, endurance, and strength1. Each factor plays a decisive role in overall performance, influencing the dynamic and multidimensional nature of performance. As part of these complex interactions, the circadian system affects physiological, psychological and molecular mechanisms in the body, resulting in varying physical performance at different times of the day2. Circadian rhythms are changes in daily behavior and biological activities that occur through an organism’s ability to adapt to the 24-hour light and dark cycle of its environment.

These rhythms come from the biological clock inside the body, which regulates many physiological elements in humans, such as the sleep cycle, daily changes in blood pressure, and body temperature3. A recent systematic review highlighted that most studies examining the impact of circadian processes on athletic performance found greater athletic performance in the evening than in the morning4. Mirizio et al. stated that performances in short-term maximal exercises peak at approximately 16:00-20:00 in the afternoon. It has been shown that this situation fluctuates depending on the time of day, and these fluctuations reach up to 29.4% between morning and evening hours5. Another systematic review reported that anaerobic performance (short-term, maximum power output), such as anaerobic power in activities lasting less than 6 seconds, peaked between 17:00 and 19:005.

These findings indicate that performance may vary depending on the time of day and that evening hours may be more suitable for anaerobic power and performance. Post activation potentiation (PAP) stands out as an important strategy in improving anaerobic power and performance. PAP is the idea that exercises performed following a maximal or near-maximal muscle contraction (i.e., a conditioning activity) can provide a temporary increase in strength and power production7. PAP depends on the athletes’ training level, muscle fiber type, muscle contraction type and duration, and stimulation volume and intensity8.

Although research has extensively examined the effects of circadian rhythms and PAP on performance, their combined effect is not yet well researched. The potential of PAP to improve performance by activating muscles with a high-intensity preload may vary depending on different times of day. PAP protocols implemented under the influence of circadian rhythms can be used as a strategy to maximize the anaerobic performance of athletes. For this reason, it was hypothesized in the study that PAP may affect performance according to circadian rhythm in young athletes. Based on this hypothesis, the research aimed to investigate the effects of PAP on jumping, sprint and agility performances depending on the time of day.

Materials and methods

In this study designed with a cross-over design, power analysis was performed to determine the number of participants. According to the analysis, the amount of Type I error (alpha) was 0.05, the power of the test (1-beta) was 0.8, the effect size was 1.39, and the alternative hypothesis (H1) was two-sided. The minimum sample size required to find a significant difference using this test was calculated as 7. However, in order to obtain a stronger result and strong statistical evaluations, the number of groups was determined as 14. For this reason, 14 volunteer male athletes (age 14.57±0.92 years) were included in the study. Inclusion criteria: Not having had any injury in the last six months, not having any disease, not being a smoker and being a licensed athlete for at least 2 years. Athletes who abandoned performance tests and did not comply with warm-up protocols were excluded from the study. All athletes and their family members were informed in advance about the study aims and experimental procedures prior to assessments and intervention sessions. Parents of all participants gave their written informed consent to be included in this study. The current study was conducted in accordance with the Declaration of Ethical Principles of Helsinki. In addition, ethics committee approval was received for the research from Fırat University Non-invasive Research Ethics Committee with session number 2022/15-44.

Research design

The research lasted 2 weeks, and during this period, the participants visited the study hall 7 times. At the first visit, the athletes’ height and weight were measured and 1 RM values were calculated. In the other 6 visits, the participants were randomly divided into two on each visit day and administered the interventions. For control intervention; the athletes performed a 10-minute warm-up jogging at only 9 km/h in different time periods (morning, noon, evening) in accordance with the Cross-over design, and after this application, performance tests were carried out with a 4-minute rest period. A 30-second rest was given between test protocols (measurements). Participants avoided anaerobic exercise for at least 48 hours before all visits and abstained from caffeine and food consumption for at least 2 hours before each testing session.




Vertical Jump (VJ). The vertical jumping performance of the participants was determined according to the Squat Jump (SJ) test procedure, one of the VJ tests. Participants were instructed to jump up with maximum effort using only their legs and to land on the ground with both feet. In the starting position of the test, participants stood in an upright standing position with their hands on their hips to minimize the effect of upper extremity sway on the test results. When they were ready, they maintained a static position with a 90° knee flexion angle for 1 second before jumping and jumped directly upwards from this position9.

Standing Long Jump (SLJ). Participants were instructed to jump with maximum effort and land on both feet. In the starting position of the test, participants stood naturally behind the starting line with their feet shoulder-width apart and their arms at the sides of their bodies. When they were ready, they performed a single jump in a horizontal direction for maximum horizontal distance. The best jumping distance was measured from the starting line to the point where the heel landed closest to the starting line and recorded in cm10.

Agility (T Drill Test). The T-drill test is an assessment tool used to evaluate the agility of athletes. For this, four cones are placed in a “T” shape. With a sound signal, the athlete started running in a straight line towards cone A and then touched the top of the cone with his right hand and ran at maximum speed to cone B (A – B: 5m). Then turned left and side-stepped as fast as he could until he touched the top of cone C (B – C: 5m). Then, they changed direction and moved away using the side steps, reaching cone D (C – D: 10m) and touching the top of the cone. Finally, he stepped back laterally to touch cone B (D–B: 5m) and finally ran back to cone A (B–A: 5m). The time was recorded in seconds with the photocell system11.

5-10 m Sprint Tests. Photocells are placed at the beginning and end of the track for distances of 5 m and 10 m. Participants were told to stand just behind the starting line, exit and run with maximum effort to the finish line. Time was recorded in seconds12.

Statistical Analysis. Data were analyzed using SPSS 22.0. The demo of the GraphPad program was used to prepare the figures. According to the histogram graph, kurtosis and skewness values and the Shapiro-Wilk test, it was determined that the data showed normal dis-tribution. Two-way repeated measures ANOVA was used to compare performances between control and PAP interventions and between each time (2 interventions x 3 times). Statistical significance level was accepted as p<0.05. Partial eta squared (ηρ2) was used to evaluate effect sizes. Effect sizes were categorized as small if <0.4, medium if 0.41-0.70, and large if >0.7013.ηρ2

Results

As reported in figure 1, standing long jump and vertical jump performances did not differ according to time (morning, noon and evening) (respectively; F=0,440, p>0.05, F=1,935, p>0.05).




It was determined that the interaction between interventions (Control and PAP) and measurement times was not statistically significant (respectively; F=1.151, p>0.05, F=0,416, p>0.05). Additionally, it was determined that there was no statistically significant difference between the interventions (Control and PAP) (respectively; F=0,365, p>0.05, (F=0,011, p>0.05). When standing long jump and vertical jump performances were evaluated in terms of effect size, it was seen that they had small effect sizes according to time (respectively; ηρ2=.017, ηρ2=,069), time and intervention interaction (respectively; ηρ2=.042, ηρ2=,016), and interventions (ηρ2=.014, ηρ2=,000).

As reported in figure 2, 5m and 10m Sprint variable does not differ according to time (morning, noon and evening) (respectively; F=0,218, p>0.05, F=2,136, p>0.05). It was determined that the interaction between interventions (Control and PAP) and measurement times was statistically significant (respectively; F=3,720, p<0.05, F=5,336, p<0.01).




Additionally, it was determined that there was no statistically significant difference between the interventions (Control and PAP) (respectively; F=0,031, p>0.05, F=0,298, p>0.05). When 5m and 10m Sprint performance is evaluated in terms of impact size; It was observed that they had small effect sizes according to time (respectively; ηρ2=.008, ηρ2=,076), time and intervention interaction (respectively; ηρ2=.128, ηρ2=,170) and interventions (respectively; ηρ2=.001, ηρ2=,011).

As shown in figure 3, there is a significant difference in agility performance according to time (morning, noon and evening) (F=7,147, p<0.01). It was determined that the interaction between interventions (Control and PAP) and measurement times was not statistically significant (F=1,244, p>0.05).




Additionally, it was determined that there was no statistically significant difference between the interventions (Control and PAP) (F=0,155, p>0.05). When performance in agility is evaluated in terms of effect size; It was observed that they had small effect sizes according to time (ηρ2=.216), time and application interaction (ηρ2=.046), and application (ηρ2=.006).

Discussion

The aim of this study was to investigate the acute effect of Post Activation Potentiation (PAP) on physical performance according to the circadian rhythm in young athletes. The findings showed that physical performance can vary depending on the time of day and the PAP intervention. One of the main findings of the study is that PAP does not have a significant effect on vertical jump and standing long jump performance based on the time of day. Another important result is that both the time of day and its interaction with PAP significantly affect 5 m and 10 m sprint performance. Although the PAP protocol did not influence agility performance, a significant difference in agility performance was observed depending on the time of day.

The fact that different times of the day and PAP interaction have a significant effect on 5 m and 10 m sprint performances shows that PAP can optimize sprint performance under the influence of circadian rhythm. In the current study, it was found that a single set of 5 repetitions of half squat used as PAP was not effective in improving sprint performance. Squat variations have been widely used in research to reveal the PAP effect. Although many studies report no change in performance after different squat protocols14,15, there are also studies reporting improvements in performance16,17. Additionally, in the current study, it was observed that sprint performance did not change according to different time of the day. Chtourou et al. have reported that repeated sprint performance in the morning and afternoon did not differ significantly in elite judoka18. Egesoy et al. have reported that 20 m sprint performance did not show a significant difference in amateur football players (age: 12.33±0.69 years) at different times of the day19. Falgairette et al. showed that the time of day (09.00, 14.00 and 18.00) did not have a significant effect on sprint performance20. Dinç and Hayta reported that the time of the day of performance (09.00, 12.00 and 15:00) did not show a significant difference on the 40-meter sprint performance of faculty of sports sciences students (21.5±1.60 years)21.

It is seen in the current research that PAP intervention does not affect vertical jump and standing long jump performance. Previous studies on acute performance in the lower extremity are consistent with our findings, which did not report positive improvements after preloading strategies. Scott et al. who applied a similar PAP protocol to our research, reported that preload was increased by vertical jump and horizontal jump with 1 set of 5-repetition back squats in resistance-trained men (age = 25.0±4.8 years). showed no significant difference in performance between average or maximum values22. Pearson and Hussain have reported that different squat preloads did not show a significant increase in jump height and jump power23. Bauer et al. reported a nonsignificant effect of the preload protocol on countermovement jump performance in resistance-trained men (age, 23.3 ± 3.3 years)24. Additionally, according to our data, different times of the day do not change vertical jump and standing long jump performance, which is consistent with previous research. Chtourou et al. reported that repeated vertical jump heights in the morning and afternoon did not differ significantly in elite judokas18. Martín-Lopez et al. did not report any difference in vertical jump performance in semi-professional volleyball players according to morning (9:00) and evening (19:00) time25.

In the current research, it appears that PAP is not effective in agility performance. Kalinowski et al. showed that preload did not affect agility performance in semi-professional volleyball players (age: 25±4 years)26. McErlain-Naylor et al. reported that no post-activation performance increase was observed in direction change performance after flywheel squat in amateur male athletes (age: 22±2 years)27. At the same time, according to our findings, it has been determined that there are differences in agility performance depending on the time of day and the best performance is in the morning time. López-Samanes et al. have reported that circadian rhythm affects performance in male tennis players, and agility performance varies depending on the time of day in the morning (09:00) and afternoon (16:30), and agility performance is lower in the morning time28. Öken et al. reported that there was a significant difference in agility performance in kickboxing athletes at different times of the day (09.00; 13.00; 17.00) and the best values were in the evening (17:00)29,30. Although these studies are similar to our findings showing that agility performance varies according to circadian rhythm, the most important difference, according to our research, is that the best value of agility performance is in the morning.

Limitations

As with every research, there are some limitations in this research. Only male and alpine ski athletes aged 14-16 were included in the research and it was conducted under certain temperature conditions in the same season. In addition, only jumping, sprint and agility performances were evaluated in the study. Finally, only the half squat PAP intervention was preferred in the study. These factors limit the generalizability of the present research.

Conclusions

As a result, it was found that agility performance changed according to different times of the day, but vertical jump, standing long jump and sprint performance did not change. In addition, although PAP application does not have a significant effect on vertical jump, standing long jump, sprint and agility performance, the interaction of circadian rhythm and PAP interventions to affect 5 m and 10 m sprint performance. Considering that circadian rhythm and PAP interactions may affect performance, it is recommended that athletes’ training and competition programs be optimized according to their personal circadian rhythms and appropriate PAP protocols. In future studies, it may be recommended to design research by taking into account diversification of the sample group (different age group, gender and sports branch), performance criteria (endurance, strength, flexibility, etc.) and environmental conditions (different altitude, temperature and season conditions).

Conflicts of interest. The authors declare that there is no conflict of interest.

Funding. This research received no external funding.

Authors’ contributions: Conceptualization, CFD and TA; methodology, CFD and TA; validation, CFD, TA, VÇ; formal analysis, CFD, TA and VÇ; investigation, CFD and TA; data curation, CFD, TA and VC; writing - original draft preparation, CFD, TA, VÇ and EÇA; CFD, TA, VÇ, EÇA, GF and GMM; visualization, TA; supervision, TA, VÇ, EÇA, GMM, GB. All authors have read and agreed to the published version of the manuscript.

Acknowledgements. We would like to thank all participants and their families who volunteered to participate in this study. This study was also derived from the first author’s master’s thesis.

Institutional review board statement. The study was conducted in accordance with the Declaration of Helsinki, and Ethics committee approval was received for the research from Fırat University Non-invasive Research Ethics Committee with session number 2022/15-44.

Informed consent statement. Informed consent was obtained from all subjects involved in the study.

Data availability statement. The data presented in this study are available on request from the corresponding authors.

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