The Effect of Exercise Order on Same Day Concurrent

The Effect of Exercise Order on Same Day Concurrent Training: Implications for the development of Maximal Strength, Power, Force and changes in Body Composition in Recreationally Trained Men Following 5 weeks of a Concurrent versus Resistance-only Training Program

James Ballantyne

This thesis is submitted in fulfilment of the requirements for the Bachelor of Applied Science (Honours) (Human Movement)

College of Sport and Exercise Science Victoria University Melbourne, Victoria

July 2017

Supervisor: Dr Jon Bartlett

HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

Table of Contents 1

Student Declaration .................................................................................................................5

2

Acknowledgements .................................................................................................................6

3

Abstract ..................................................................................................................................7

4

Chapter One - Introduction ......................................................................................................9 4.1

Adaptations to Resistance Training ......................................................................................................10

4.2

Adaptations to Endurance Training ......................................................................................................12

4.3

Concurrent Training and the “Interference Effect” ..............................................................................14

4.3.1 4.4

Role of Training Variables .............................................................................................................22

Influence of Same-Day Concurrent Training on Resistance Training Adaptations ...............................22

4.4.1

Same-Day Concurrent Training & Maximal Strength ....................................................................24

4.4.2

Same Day Concurrent Training and Muscular Force.....................................................................29

4.4.2.1

Peak Force and Same-Day CCT ..................................................................................................30

4.4.2.2

Rate of Force Development and Same-Day CCT .......................................................................31

4.4.3

Same Day Concurrent Training and Muscular Power ...................................................................32

4.5 Effect of Exercise Order with Varying periods of Recovery on Same Day Concurrent Training Adaptations .......................................................................................................................................................34 4.6

Conclusion .............................................................................................................................................36

4.7

Research Objectives ..............................................................................................................................37

4.7.1

5

Aims & Hypotheses .......................................................................................................................37

Chapter Two - Methods ......................................................................................................... 39 5.1

Overview of the project ........................................................................................................................39

5.2

Participants ...........................................................................................................................................39

5.2.1 5.3

Group Baseline Characteristic .......................................................................................................40

Procedure ..............................................................................................................................................41

5.3.1

Baseline Testing Outline ................................................................................................................41

5.3.2

Training Phase ...............................................................................................................................42

5.3.3

Post Testing ...................................................................................................................................42

5.3.4

Nutrition and Exercise Control ......................................................................................................42

5.4

Performance Tests ................................................................................................................................43

5.4.1

Counter Movement Jump .............................................................................................................43

5.4.2

Bilateral Isometric Squat ...............................................................................................................45

5.4.3

1-Reptition Maximum Leg Press (1-RM) .......................................................................................47

5.4.4

Graded Exercise Test (GXT) ...........................................................................................................49

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

5.4.5

Peak Oxygen Uptake (VO2peak) .......................................................................................................49

5.4.6

Body Composition .........................................................................................................................50

5.5

Training Intervention ............................................................................................................................51

5.5.1

Overall Training Program ..............................................................................................................51

5.5.2

Experimental Week .......................................................................................................................51

5.5.3

Weeks 1-5: 5-Week Training Program (Appendices D, E, G) ........................................................51

5.6

5.5.3.1

Resistance Training (RES) ..........................................................................................................52

5.5.3.2

Endurance Training (END) .........................................................................................................52

Statistical Analysis .................................................................................................................................53

5.6.1

6

Data Reporting ..............................................................................................................................53

Chapter Three - Results.......................................................................................................... 54 6.1

Training Sessions ...................................................................................................................................54

6.2

Performance Tests ................................................................................................................................54

6.2.1

One Repetition Maximum (1-RM) Leg Press .................................................................................54

6.2.2

Counter Movement Jump .............................................................................................................55

6.2.2.1

CMJ Peak Displacement ............................................................................................................55

6.2.2.2

CMJ Peak Force relative to FFMI (NPEAK/FFMI) ..........................................................................55

6.2.2.3

CMJ Peak Power ........................................................................................................................55

6.2.2.4

CMJ Mean Power ......................................................................................................................55

6.2.3 6.2.3.1

Peak Force Relative to FFMI ......................................................................................................57

6.2.3.2

Mean Force Relative to FFMI ....................................................................................................57

6.2.3.3

Max RFD Relative to FFMI .........................................................................................................57

6.2.4

6.3

Bilateral Isometric Squat ...............................................................................................................57

Graded Exercise Test .....................................................................................................................59

6.2.4.1

Vo2PEAK (ml.kg.min-1)..................................................................................................................59

6.2.4.2

Peak Aerobic Power (WPEAK) ......................................................................................................59

6.2.4.3

Wattage at Lactate Threshold (WLT) ..........................................................................................59

6.2.4.4

Graded Exercise Test – Time to Exhaustion (GXTTTE) ................................................................59

6.2.4.5

105% WPEAK Time to Exhaustion ................................................................................................59

Body Composition (DEXA Scan) ............................................................................................................61

6.3.1

Body Mass .....................................................................................................................................61

6.3.2

Fat Free Mass Index (lbm/m2) .......................................................................................................61

6.3.3

Upper Body LBM (UBLBM) ...............................................................................................................61

6.3.4

Lower Body Lean Mass ..................................................................................................................61

6.3.5

Body Fat Percentage .....................................................................................................................62

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

7

Chapter Four - Discussion ...................................................................................................... 64 7.1

Same Day Concurrent Training and Maximal Strength .........................................................................65

7.2

Same Day Concurrent Training and Muscular Power and Force ..........................................................66

7.3

Same Day Concurrent Training and Body Composition ........................................................................68

7.4

Limitations .............................................................................................................................................70

7.5

Implications ...........................................................................................................................................71

7.6

Practical Applications ............................................................................................................................72

8

Chapter Five - Conclusion....................................................................................................... 73

9

References ............................................................................................................................ 74

10 Appendices............................................................................................................................ 81

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

1 Student Declaration

Declaration by Student

I, James Ballantyne, declare that the Bachelor of Applied Science (Honours) in Human Movement thesis titled ‘The Effect of Exercise Order on Same Day Concurrent Training: Implications for the development of Maximal Strength, Power, Force and changes in Body Composition in Recreationally Trained Men Following 5 weeks of a Concurrent versus Resistance-only Training Program’ is no more than [28,000] words in length, exclusive of tables, figures, appendices, bibliography, and references. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or diploma. Except where otherwise indicated, this thesis is my own work.

Signature:

Date:

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

2 Acknowledgements I would like to start by sincerely thanking my supervisor Dr Jon Bartlett for your guidance, support, dedication and being a source of inspiration across the 15 months of my honours journey, both as a supervisor, researcher and your work as an applied sports scientist. The times that I needed your advice, feedback and support you were always available and provided valuable insight and knowledge into all elements of the research project. I really appreciate that although we were at some stages in different states of Australia and even sides of the world you were able to help me with bringing this project together. I thoroughly enjoyed the time we spent working together and hope future opportunities will present themselves to do so again. To Mr Matthew Lee, I appreciate you allowing me to work with you on your project. I’ve had a great experience working with you in the lab and during the training sessions, and appreciate the valuable insights you provided into the PhD process and the feedback on my project. I sincerely wish you the best with your current and future endeavours as a researcher.

To Professor Robert Hess and the Victoria University Honours Program, I appreciate the hard work you have put into cultivating and implementing an engaging and supportive course and environment to work within as a research student at Victoria University.

To all the participants who volunteered their own time to participate in this project, thanks very much and I wish you the best in your future personal endeavours.

To Mr Martyn Girvan thank you for first igniting my passion for applied sports science and the subsequent years of mentorship and friendship you have given me during my formative years in the strength and conditioning & sports science profession. Your insight, advice and dedication for your craft are highly appreciated and inspiring, and have had a profound effect on my career to date and future endeavours, thank you.

Lastly, a huge thanks to my mum, dad, brother and girlfriend Caitlin. You have all supported me with this endeavour over the last 15 months and words cannot describe how much I have appreciated everything you have all done for me to make my involvement and completion of this project possible, thank you all so much!

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

3 Abstract Background: Concurrent training is the performance of both resistance and endurance training modalities within a single training program to simultaneously develop positive adaptations to resistance and endurance exercise, which may be beneficial for improving health outcomes and athletic performance. Previous research examining the effect of exercise ordering on, same-day concurrent training resistance training adaptations, have yielded conflicting results and few investigations have directly compared outcomes to resistance training in isolation. The aim of the study was to 1) assess the effect of concurrent training exercise sequencing on resistance training outcomes compared to resistance in isolation, and 2) assess the effect of exercise sequencing between concurrent training groups for adaptations to resistance exercise. Methods: 13 healthy recreationally active males were recruited to participate in this study. Prior to and after commencing the training program participants were required to perform performance tests: Counter Movement Jump, Bilateral Isometric Squat, 1-Repetition Maximum (1-RM) Leg Press, Graded Exercise Test on a cycle ergometer and a DEXA scan. Participants were matched into groups based on 1-RM maximal strength, 𝑉̇ O2peak and fat free mass index (FFMI). The participants then performed either concurrent training separated by 3-hours or resistance training only (END→RES, n =5) or (RES→END, n = 4) or (RES, n = 4), 3 days per week (training days separated by 48 hours) for 5 weeks. Data was analysed via a non-clinical magnitude based inference network to determine the effects of exercise sequencing on performance and body composition. The effect size (ES) statistic and 90% confidence intervals (90% CI) were calculated to determine the magnitude of effects by standardising the coefficients according to the appropriate betweensubject standard deviation, and assessed using the following criteria: < 0.5 = trivial, 0.50-1.25 = small effect, 1.25-1.90 = moderate effect, >2.0 = large effect. Results: All groups improved maximal 1-RM leg press strength relative to FFMI post training with a clear likely small improvement for END→RES (13.9 ± 7.8%, ES = 0.79 ±1.15), an unclear possible small effect improvement for RES (12.5 ± 5.3%, ES = 0.50 ±1.47) and an unclear possible small effect improvement for RES→END (12.7 ± 3.5%, ES = 0.63 ±1.43). No effects were observed between groups post-training. CMJ peak displacement was attenuated post-training with a clear likely small effect between RES vs END→RES (ES = -0.66 ±0.54) and RES vs RES→END (ES = -0.66 ±0.51). Post-training CMJ peak force (NPEAK/FFMI) observed a clear very likely small attenuation for END→RES vs RES (ES = -0.81 ±0.48), however this was not found for RES vs RES→END. CMJ peak power (WPEAK/FFMI) post-training showed a clear likely small attenuation between both concurrent training groups compared to resistance in isolation, RES vs END→RES (ES = -0.53 ±0.79) and RES vs RES→END (ES = -0.58 ±0.60). CMJ mean power (WMEAN/FFMI) posttraining showed a reduction in performance gains with a clear likely small effect for END→RES (-33.7 ± 36.2%, ES = -0.83 ±1.20). A clear very likely moderate effect for attenuation of CMJ mean power

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

(WMEAN/FFMI) was observed between RES and both concurrent training groups post-training; RES vs END→RES (ES = -1.78 ±1.15) and RES vs RES→END (ES = -1.91 ±1.15). The Bilateral Isometric Squat (BIS) showed unclear trivial-small changes for all groups across all measures post-training. Peak Force (N/PEAK/FFMI) showed there were clear likely trivial effects between groups post-training (RES vs END→RES; ES = -0.48 ±0.51, RES vs RES→END; ES = -0.03 ±0.23, END→RES vs RES→END; ES = 0.39 ± 0.45). There were unclear effects observed post-training for Max RFD for all groups and between groups. Body composition measured by dual x-ray absorptiometry (DEXA) reported unclear effects post training for all measures across all groups. Conclusion: The implementation of a same-day concurrent training intervention with different exercise ordering, implemented on 13 young males increased maximal leg press strength by a similar amount across all groups. In contrast CMJ peak displacement was shown to be attenuated by concurrent training compared to resistance training only. CMJ peak force showed a small effect for attenuation of performance between RES vs END→RES, but not for RES→END and both groups had moderate effect for attenuation of CMJ mean power compared to resistance only. The inclusion of same-day concurrent training in young males does not attenuate maximal strength adaptations, but may attenuate peak displacement, force and power during a CMJ when compared to resistance training in isolation. Despite the low sample size there does not appear to be an effect on maximal strength and body composition for exercise ordering within a same-day concurrent training program over 5 weeks in young recreationally trained males. The findings of this investigation may be of interest for recreationally active men undertaking a same-day concurrent training program to improve maximal strength and body composition, and may also guide practitioners working with young adult males looking to maximise specific training adaptations when performing multiple training sessions on the same-day.

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

4 Chapter One - Introduction The systematic integration of endurance (END) and resistance (RES) training within a single program has been termed concurrent training [1]. The primary aim of a concurrent training program is to simultaneously enhance both endurance and resistance training adaptations relative to training goals. This training approach is utilized across general and athletic populations, as a means of improving general health and wellbeing, athletic performance and body composition [1-5]. Long term physical adaptations to training are driven by the accumulation of specific physiological responses to acute bouts of stress placed on the body during exercise, over a prolonged period of time [6].

Resistance and endurance training represent two distinct ends of the physiological adaptations to training spectrum [7]. Therefore, the very nature of simultaneously integrating both endurance and resistance training into a single program presents a dilemma for the trainee or practitioner, as combining both training modalities creates a physiological environment for divergent adaptations [8, 9]. When both training modalities are combined in a single program, improvements in resistance adaptations, (maximal muscular strength, muscle cross sectional area, rate of force development, peak force and power) may be attenuated in comparison to performing resistance training in isolation [9-11]. Furthermore, evidence suggests that a bout of resistance training prior to maximal endurance effort may result in decreased time to exhaustion [12, 13]. The attenuation of resistance and endurance training performance when undertaken simultaneously has been termed the “interference effect” [14].

Same day exercise order within a concurrent training program has received increased attention over the last 45 years, as researchers seek to uncover if there is an optimal order for performing concurrent resistance and endurance training on the same day to optimise long term adaptations to resistance training [9, 12, 13, 1524] (refer to Table 2, pg 17-21 for a full description of studies). The ordering of resistance and endurance exercise on the same day may impact on neuromuscular and peripheral muscle tissue adaptations, which may have long term implications for resistance training adaptations. Therefore, it is of interest to elucidate if adaptations to resistance exercise are attenuated by concurrently training compared to resistance training in isolation, and if a particular exercise ordering has a greater effect than the other, when the goal of the program is to improve maximal muscular strength, increase muscle cross sectional area, and develop maximal power and force.

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

4.1 Adaptations to Resistance Training Resistance training involves the use of bodyweight or external loading on the body to create sufficient stress on the neuromuscular system, muscle tissue, tendons and joints to elicit a favourable muscular, hormonal, neural and metabolic response which will facilitate increased muscular power, strength and size and subsequently improve musculoskeletal performance over time [25]. Resistance training has been shown to significantly benefit all age groups from young children to elderly adults [26-29] and is recommended by a range of health organisations for its significant benefits on physical fitness relating to health and performance outcomes [30]. The American College of Sports Medicine recommends resistance training should be performed 2-3 days per week for each major muscle group in healthy adult populations, however for unhealthy or clinical populations, training interventions should be determined on a condition specific basis [2]. Muscular strength for general health and wellbeing has been associated with lowering risk of all-cause mortality, fewer cardiovascular events, lower risk of developing functional limitations and non-fatal disease [2]. Furthermore, regular participation in resistance training improves a number of markers for health including, blood glucose levels [31], insulin sensitivity [32] and blood pressure [33]. Thus, the inclusion of resistance training into fitness programs should be a priority for healthy general and athletic populations looking to enhance health, wellbeing and performance.

Performing regular high resistance strength training has been shown to result in significant positive alterations in neurological and morphological adaptations, which may drive improvements in health, wellbeing and physical performance. Several key factors influence the specific neurological and morphological adaptations to resistance training. These include muscle action velocity, mechanical tension, muscle damage and metabolic stress [34]. The manipulation of these variables within a resistance training program underpin specific adaptations within human skeletal muscle. Neurological adaptations to resistance training are relative to the specificity of the motor task performed, the specific tension, velocity and joint angle of loading. These variables result in neurological adaptations to resistance training essentially being driving by improvements in coordination which facilitates improved recruitment and activation of muscles involved in the specific task [35]. Neuromuscular adaptations can occur independently of increases in muscle cross sectional area and may be the primary driver of resistance training adaptations within the early stages of resistance training [36]. Furthermore, resistance training may improve muscle activation, increases in the firing frequency of motor units (rate coding) and motor unit synchronization [37]. Together, these adaptations may result in increases in maximal strength, rate of force development and power output.

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

Morphological changes may occur due to moderate-high intensity (65-95% 1RM) resistance strength training with these changes localized to the muscle tissue. The primary morphological adaptation to resistance training is an increase in muscle cross sectional area (mCSA) of the whole muscle and individual muscle fibres, due to increases in myofibrillar size and number. Further changes occur in muscle architecture, myofilament density, increases in muscle fibre pennation angle and alterations in connective tissue structure and stiffness [35]. Furthermore, chronic moderate-high intensity resistance training produces alterations in phenotypic adaptations at the muscle fibre level. This is seen with a preferential shift in the activation and hypertrophy of fast twitch glycolytic type II muscle fibres, and in particular a transition from Type IIx & Type IIb to Type IIa fibres [38] (a smaller effect occurs in slow twitch oxidative Type I fibres following resistance training [39]). The transition of Type IIb fibres to Type IIa fibres may occur in as little as 4 weeks for men and 2 weeks for women who undertake a progressively overloaded resistance training program [40] suggesting morphological adaptations to resistance training may also occur in the early phases of training.

Due to the high force and velocity nature of many sports, resistance training adaptations may also be of value to athletic populations. Increases in muscular strength and power are implicated in improving physical characteristics associated with athletic performance in young and adult athletes, across a range of athletic disciplines [41, 42]. Furthermore, strong evidence has emerged that the addition of resistance training to training programs for both recreational and elite runners and cyclists enhances endurance based performances in these activities. This is achieved primarily through improvements in movement economy and force generating capabilities [43-45].

The simultaneous integration of both endurance and resistance training for healthy youth/adult populations and recreational and/or high level endurance athletes may confer significant additional benefits compared to endurance training in isolation. As such regular resistance training and the physiological adaptions to it, are of significant interest for a range of populations and practitioners, who may seek to enhance health and performance.

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

4.2 Adaptations to Endurance Training Endurance training is primarily utilised to develop cardiovascular and cardiorespiratory function, and improve metabolic pathways responsible for enhancing energy substrate usage during continuous and intermittent endurance exercise [46, 47]. Particularly, the preferential usage of free fatty acids at lower to moderate intensities and the increased efficiency of muscle glycogen usage at higher training intensities are enhanced through chronic endurance training [48, 49]. Endurance training increases maximal oxygen uptake, cardiac output, and improves oxidative metabolism [50], muscular capillarisation and mitochondrial biogenesis [46]. These adaptations to endurance training have also been implicated in conferring significant general health benefits [2]. Improved levels of aerobic fitness are associated with a decreased risk of allcause and cardiovascular mortality and morbidity, with significant benefits also found for decreasing cardiometabolic risk factors, bodyweight regulation and psychological health [2]. It is currently recommended for healthy non-athlete adult populations to engage in endurance based training daily for at least 30 minutes, five times a week, at a moderate intensity to deliver the aforementioned benefits and training adaptations [2].

Endurance training adaptations are typically developed with low-moderate intensity steady state continuous or high-intensity intermittent physical activity such as walking, cycling, rowing or running. Traditional endurance training has focused on continuous steady state activity at a low to moderate intensity (60-80% Maximal Heart Rate [MHR]) as the preferred method of enhancing endurance specific adaptations. However, it should be noted that exercise intensity rather than total duration is a key consideration when undertaking endurance training to improve cardiovascular fitness [51]. Evidence suggests that relatively short-duration high-intensity efforts of endurance training may have similar health and lead to potentially greater physiological improvements in maximal oxygen uptake and key metabolic and cellular markers of endurance training adaptations, in both male and female populations [47, 51-55]. Furthermore, high-intensity intermittent training (HIIT) may be more enjoyable [56] and time efficient [57] for cardiovascular and respiratory adaptations compared to continuous steady state endurance training. As such, high-intensity intermittent activity is a viable alternative for both practitioners and trainees looking for a more enjoyable and time efficient method to improve cardiovascular and cardiorespiratory function [51].

Athletic populations also benefit from improving maximal oxygen uptake, aerobic power and energy substrate utilization, which may have important performance implications for competition, recovery and injury prevention [58, 59]. Improvements in cardiovascular function have been associated with a number of important parameters implicated in athletic performance, including increased time-to-exhaustion, increased lactate threshold [60], and increased high velocity movements during intermittent team sports [61].

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

Furthermore, cardiovascular fitness has been shown to be a discriminator of selection in semi-professional rugby league [62] and level of competition in junior soccer players [63]. The undertaking of endurance based training to elicit favourable cardiorespiratory and cardiovascular adaptations should be a priority for healthy youth and adult general and athletic populations looking to improve heath, wellbeing and performance.

Performing resistance training and endurance training in isolation can infer significant benefits to a range of populations. Although the two exercise modes represent opposite ends of the exercise adaptations continuum (Figure 1), the development of both adaptations may be desirable. It is possible to train both simultaneously and significantly improve both endurance and resistance training adaptation outcomes [23, 64].

Figure 1 – The strength-endurance continuum (SEC) is depicted in the context of sports performance and its relation to exercise duration and energy metabolism. Reproduced from Nader. Concurrent Strength and Endurance Training: From Molecules to Man. Med Sci Sports Exerc, 38(11), 1965–1970, 2006

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

4.3 Concurrent Training and the “Interference Effect” Interest in researching concurrent training began over 45 years ago in 1970 when Robert Hickson [14] first investigated the effects of a 10 week concurrent training program in formally untrained males and females. Over the course of the 10-week program participants were required to complete same day resistance and endurance (cycling or running) training. Hickson found, the concurrent training group exhibited similar increases in VO2max, on both a bicycle (25%) and treadmill (20%) graded exercise test protocol (GXT) when compared to the endurance only group. However, maximal strength adaptations for the concurrent training group only improved until week 7 (34% increase from baseline) prior to a significant decline at week 10, finishing with an overall improvement of 25% from baseline compared to the resistance only groups 44% increase from baseline (Figure 2). Identifying the attenuation in maximal muscular strength in the concurrent training group compared to the resistance only group, Hickson termed this observation the “Interference Effect” [14]. This research was the first to directly suggest the implementation of same-day resistance and endurance training may result in the impaired development of maximal strength, compared to resistance training performed in isolation over the course of a 10-week training program.

Figure 2 – The interference of strength development, following simultaneous training for strength and endurance on the same-day, compared to strength development in isolation. Hickson 1980, adapted from Perez-Schindler et al. Eur J Sport Sci, 15(1): 41-52, 2014.

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HHHM Bachelor of Applied Science (Honors) (Human Movement) – Thesis

Following Hickson’s seminal work, subsequent research has sought to elucidate the underpinnings of the interference effect. Several investigations have found an attenuation for the development of maximal strength, power and force when resistance training is combined with endurance training on the same day compared to resistance training in isolation [14, 65-68]. However, endurance training adaptations are largely unaffected by resistance training. The addition of resistance exercise may in fact augment adaptations to endurance training [12, 44, 45].

Currently, the same-day concurrent training literature has investigated the effect of exercise ordering on young men and women [69], recreationally trained [64] and untrained women [21], untrained/recreationally trained [17, 19, 65, 70], athletically trained young men [71, 72] and elderly male [16] and female populations [20] (for a complete list of studies refer to Table 2, pg 17-21). This makes it difficult to extrapolate results from specific populations and provide generalised recommendations regarding exercise ordering for sameday concurrent training. Alongside the diversity of investigated populations, a wide variety of training protocols have been utilised across studies. With some investigations employing higher frequency (>4 days per week) [21] moderate frequency (3 days per week) [64, 69, 72] and low frequency (