David G Jenkins’s research while affiliated with University of the Sunshine Coast and other places

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Publications (179)


Responders And Non-responders To Hiit In Cancer Survivors; Implications For Body Composition And Systemic Inflammation?: 2958
  • Article

October 2024

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2 Reads

Medicine and Science in Sports and Exercise

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David G. Jenkins


High‐intensity exercise testing protocol
HIIE: high‐intensity interval exercise, HR: heart rate. [Colour figure can be viewed at wileyonlinelibrary.com]
Individual post‐training responses
2.1: pre‐training responses of (A) IL‐15, (B) IL‐6, (C) IL‐10 and (D) IL‐1ra to acute high‐intensity exercise; and 2.2: individual post‐training responses of (A) IL‐15, (B) IL‐6, (C) IL‐10 and (D) IL‐1ra to high‐intensity interval exercise after 7 months of high‐intensity interval training. Data are presented as median and interquartile range and analysed using a paired‐samples t test except where data were not normally distributed, and a Wilcoxon signed rank test was used. *P < 0.05; **P < 0.01. IL: interleukin, ra: receptor alpha.
Interleukin‐15 and high‐intensity exercise: relationship with inflammation, body composition and fitness in cancer survivors
  • Article
  • Full-text available

September 2024

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54 Reads

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1 Citation

Pre‐clinical murine and in vitro models have demonstrated that exercise suppresses tumour and cancer cell growth. These anti‐oncogenic effects of exercise were associated with the exercise‐mediated release of myokines such as interleukin (IL)‐15. However, no study has quantified the acute IL‐15 response in human cancer survivors, and whether physiological adaptations to exercise training (i.e. body composition and cardiorespiratory fitness) influence this response. In the present study breast, prostate and colorectal cancer survivors (n = 14) completed a single bout of high‐intensity interval exercise (HIIE) [4×4 min at 85–95% heart rate (HR) peak, 3 min at 50–70% HR peak] before and after 7 months of three times weekly high‐intensity interval training (HIIT) on a cycle ergometer. At each time point venous blood was sampled before and immediately after HIIE to assess the acute myokine (IL‐15, IL‐6, IL‐10, IL‐1ra) responses. Markers of inflammation, cardiorespiratory fitness and measures of body composition were obtained at baseline and 7 months. An acute bout of HIIE resulted in a significant increase in IL‐15 concentrations (pre‐intervention: 113%; P = 0.013, post‐intervention: 102%; P = 0.005). Post‐exercise IL‐15 concentrations were associated with all other post‐exercise myokine concentrations, lean mass (P = 0.031), visceral adipose tissue (P = 0.039) and absolute V̇O2V˙O2{{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}} peak (P = 0.032). There was no significant effect of 7 months of HIIT on pre‐ or post‐HIIE IL‐15 concentrations (P > 0.05). This study demonstrates HIIE is a sufficient stimulus to increase circulating IL‐15 and other myokines including IL‐6, IL‐10 and IL‐1ra which may be clinically relevant in the anti‐oncogenic effect of exercise and repetitive exposure to these effects may contribute to the positive relationship between exercise and cancer recurrence. image Key points Exercise has been demonstrated to reduce the risk of cancer recurrence. Pre‐clinical murine and in vitro models have demonstrated that exercise suppresses tumour and cancer cell growth, mediated by exercise‐induced myokines (IL‐6 and IL‐15). High‐intensity interval exercise significantly increased myokines associated with the anti‐oncogenic effect of exercise and the magnitude of response was associated with lean mass, but training did not appear to influence this response. Given IL‐15 has been implicated in the anti‐oncogenic effect of exercise and is being explored as an immunotherapy agent, high‐intensity interval exercise may improve outcomes for people living beyond cancer through IL‐15‐mediated pathways. Interventions that increase lean mass may also enhance this response.

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The Acute and Chronic Effect of Endurance Versus Resistance Exercise on Circulating Irisin: A Systematic Review and Meta-Analysis

January 2024

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70 Reads

Journal of Clinical Exercise Physiology

Background Exercise-induced release of irisin is associated with various improved health outcomes. However, the most effective exercise mode(s) to stimulate irisin release remain unclear. In this systematic review, we separately examine potential differences in (i) resting irisin concentrations (chronic change) after resistance (RT) and endurance training (ET) and (ii) the concentrations of irisin after a single bout (acute change) of resistance (RE) and endurance exercise (EE). Methods Searching was completed February 2022 in PubMed, CINAHL, Web of Science, Cochrane Library, SCOPUS, and SportDiscus. Studies were included by consensus of 2 reviewers, if they were randomized controlled trials (RCTs) or comparison studies with adults over 18 years and compared chronic change after RT and ET for any intervention duration or acute change after RE and EE. Risk of bias and quality of findings were independently assessed using PEDRo and GRADE, respectively. Irisin post means and standard deviations were extracted to calculate standardized mean differences (SMDs) and 95% confidence intervals using a random effect model. Results Of 174 studies screened, 8 chronic and 4 acute studies were included in the analysis, comprising a total of 332 participants. No difference between RT or ET for chronic irisin response was found (P = 0.380, SMD = 0.17, n = 248); however, there tended to be greater acute increases in circulating irisin after RE than EE (P < 0.001, SMD = 0.93, n = 56). Conclusions A greater effect of RE on irisin concentrations than EE was found in acute studies. Future research requires larger sample sizes and matched intensities.


Figure 1. Timeline of study procedures involving repeated jump testing (5 minutes, 8 hours, 24 hours, 32 hours) following an initial morning baseline test and including an additional afternoon baseline test.
Figure 2. Squat jump and countermovement jump height: contraction time compared to AM baseline following the repeated jump protocol.
Figure 3. Bland-Altman plots showing PM baseline in squat jump and countermovement jump height between compared to AM baseline.
Figure 4. Bland-Altman plots showing PM baseline in squat jump and countermovement jump height: contraction time between compared to AM baseline.
Countermovement jump and squat jump height and height: contraction for male and female participants during repeated jump testing.*
Effects of Repeated Jump Testing and Diurnal Changes on Subsequent Countermovement Jump and Squat Jump Output and Force-Time Characteristics

January 2024

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245 Reads

The Journal of Strength and Conditioning Research

Harrison, PW, James, LP, Jenkins, DG, Holmberg, PM, and Kelly, VG. Effects of repeated jump testing and diurnal changes on subsequent countermovement jump and squat jump output and force-time characteristics. J Strength Cond Res 38(1): 174–179, 2024—The aim of this brief study was to investigate the effects of repeated jump testing on performance over 2 consecutive days while considering the possibility of diurnal changes. Fourteen male subjects and 14 recreationally active female subjects completed countermovement jump (CMJ) and squat jump (SJ) testing on 5 occasions (baseline [0,800], 5 minutes [0,820], 8 hours [1,600], 24 hours [0,800], and 32 hours [1,600]) over 32 hours. An additional rested baseline test was conducted on a separate day in the afternoon (1,600) to compare jump performance between morning and afternoon baseline values. Excluding small decreases in CMJ height at 24 hours ( p = 0.292, Cliff’s delta = −0.225) in male subjects and similar decreases in CMJ height at 5 minutes ( p = 0.034, Cliff’s delta = −0.245) in addition to SJ height:contraction time at 32 hours ( p = 0.126, Cliff’s delta = 0.153) in female subjects, findings generally showed no changes in jump performance over multiple assessments. Squat jump metrics may have showed small improvements between morning and afternoon baseline values in male subjects (SJ height:contraction time [ p = 0.030, Cliff’s delta = 0.225]) and female subjects (SJ height [ p = 0.013, Cliff’s delta = 0.173] and SJ height:contraction time [ p = 0.091, Cliff’s delta = 0.163)]. As jump performance was largely unaffected by repeated jump testing, the present findings support the use of monitoring practices and research designs that require multiple jump assessments within acute periods (∼32 hours).


Figure 2. Individual changes to countermovement jump height:contraction time following priming exercise compared to control. The ratio of positive:negative responders are as follows: ISO 3 hours (5:2), ISO 27 hours (6:2), LL 3 hours (8:3), and LL 27 hours (3:2). ISO 5 maximal isometric squat, LL 5 low-load squat jump performed with 20% 1-repetition-maximum loading.
Peak force output during the isometric mid-thigh pull following priming exercise compared to control.*
The Effects of Low-Load Squat Jump and Maximal Isometric Priming Exercise on Muscular Performance and Perceptual State

January 2024

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433 Reads

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3 Citations

The Journal of Strength and Conditioning Research

Harrison, PW, James, LP, Jenkins, DG, McGuigan, MR, Holmberg, PM, and Kelly, VG. The effects of low-load squat jump and maximal isometric priming exercise on muscular performance and perceptual state. J Strength Cond Res 38(1): 1–9, 2024—The aim of this study was to examine responses at 3 and 27 hours after low-load jump squat (LL) and maximal isometric half-squat (ISO) priming stimuli. Fifteen resistance-trained males performed LL (4 × 3 at 20% 1 repetition maximum [1RM]), ISO (4 × 3 seconds), and control (CON) activities (standardized warm-up) in a randomized and counterbalanced order. Countermovement jump (CMJ) and isometric midthigh pull tests were conducted to assess performance changes after priming and CON activities. No clear changes in CMJ measures were found after priming activities compared with CON. However, small effect size improvements were found after priming stimuli completed on the same day. A 2.9% decrease in concentric phase duration (CI = 0.3–5.9, p = 0.333, Cliff's delta = −0.156) and a 9.1% increase in RSImod (CI = 0.2–12.3, p = 0.151, Cliff's delta = −0.218) occurred at 3 hours after LL compared with CON. Braking phase duration (CI = 0.8–10.6, p = 0.333, Cliff's delta = −0.213) was 2.9% shorter at 3 hours after ISO compared with CON. No clear changes in isometric peak force occurred after priming activities compared with CON. Additionally, questionnaires were completed to assess perceptual state and perceived effectiveness of the priming stimulus to influence performance. An increase in the “effect of activity” was perceived at 3 hours after LL and ISO ( p = 0.013–0.044, Cliff's delta = 0.578–0.6) and at 27 hours after ISO ( p = 0.99, Cliff's delta = 0.173) compared with CON. An increase in “muscular heaviness” was also reported at 3 hours after ISO compared with CON ( p = 0.199, Cliff's delta = 0.320). The collective findings suggest limited benefits over the day after LL and ISO priming stimuli. However, as there was substantial variation in individual responses, the relative nature of priming responses should be considered when prescribing similar strategies in practical environments.


Changes in peak velocity of the maximal bench throw and bench pull tests after priming and compared with control.*
Does Moderate-Load Priming Activity Influence Maximal Upper-Body Performance and Perceptual State?

November 2023

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172 Reads

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2 Citations

The Journal of Strength and Conditioning Research

Harrison, PW, Kelly, VG, Jenkins, DG, McGuigan, MR, Holmberg, PM, and James, LP. Does moderate-load priming activity influence maximal upper-body performance and perceptual state?. J Strength Cond Res 37(11): e581–e587, 2023—The results of previous research indicate that resistance exercise “priming” may improve strength-power measures within 48 hours after their completion. Although researchers have primarily examined performance responses after lower-body priming stimuli, investigations examining the effects of upper-body resistance priming exercises are presently limited. Therefore, the aim of this study was to examine upper-body pushing and pulling performance in addition to perceptual responses 3 and 27 hours after moderate-load (ML) upper-body resistance priming exercise. Fourteen resistance-trained men were assigned to complete ML priming (4 × 3 bench press and bench pull at 65% 1RM [repetition maximum]) and control (rest) protocols in a randomized and counterbalanced order. Peak velocity during the bench throw and bench pull tests involving different loads (25, 50, and 75% 1RM) showed no practical change at 3 and 27 hours after the priming session ( p = 0.216–0.99, Cliff's d = −0.041 to 0.225). Small effect size increases in perceptual measures (“physical feeling,” “physical performance,” “aggression” [ p = 0.400–0.553, Cliff's d = 0.183–0.201], and “muscular heaviness” [ p = 0.178, Cliff's d = 0.231]) were found at 3 hours postpriming. A moderate practical increase was observed in perceived “physical feeling” compared with control ( p = 0.385, Cliff's d = 0.349) in addition to small effect size increases in perceived “physical performance” and “aggression” (Cliff's d = 0.243–0.290) at 27 hours after priming activities. These results indicate that upper-body strength-power changes within 27 hours after ML upper-body resistance exercise priming are not practically meaningful.


Directions for future research
Summarised are some directions for future research that will address current gaps in the literature and test whether exercise snacks should be recommended for those who have been diagnosed and treated for cancer. (Created with BioRender.com).
Benefits beyond cardiometabolic health: the potential of frequent high intensity ‘exercise snacks’ to improve outcomes for those living with and beyond cancer

September 2023

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196 Reads

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7 Citations

High intensity interval training (HIIT) has been shown to consistently elicit rapid and significant adaptations in a number of physiological systems, across many different healthy and clinical populations. In addition, there is increasing interest in how some acute, yet transient responses to high intensity exercise potentially reduce the risks of particular diseases. Recent work has shown that discrete, brief bouts of high intensity exercise (termed ‘exercise snacks’) can improve glucose control and vascular health and thus counter the negative cardiometabolic consequences of prolonged, uninterrupted periods of inactivity. In this brief review, we advance the case, using evidence available from pre‐clinical studies in the exercise oncology literature, that brief, frequently completed bouts of high intensity exercise embedded within an individual's overall daily and weekly physical activity schedule, may transiently impact the tumour microenvironment and improve the health outcomes for those who have been diagnosed and treated for cancer. image



Thinking About Elite Performance: The Experience and Impact of Mental Fatigue in Elite Sport Coaching

June 2023

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370 Reads

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4 Citations

International Journal of Sports Physiology and Performance

Purpose: Mental fatigue causes decreases in aspects of athletes' performance. Elite coaches commonly undertake cognitively demanding tasks and are seemingly at similar risk of subsequent performance impairment. However, elite sport coaches' experiences of mental fatigue, alongside other markers of psychobiological stress, have yet to be quantified. Methods: Three elite coaching and performance staff (2 women and 1 man) provided 100-mm visual analog scale ratings of mental fatigue, physical fatigue, readiness to perform, and salivary samples for later cortisol (sCort) and alpha-amylase (sAA) analysis. Data were obtained on the same morning each week across a 16-week preseason. Data were subset by individual coach for descriptive and repeated-measures correlational analyses. Results: Fluctuating mental fatigue was observed over the 16 weeks (min-max; coach 1 = 25-86 AU; coach 2 = 0-51 AU; and coach 3 = 15 - 76 AU). Elevated levels of mental fatigue were reported at multiple time points, with individual variability observed. sCort (in nanomoles per liter), sAA (in micromoles per liter), and sAA:sCort indicated that coaches experienced psychophysiological stress (min-max; coach 1 sCort = 8.42-17.31, sAA = 52.40-113.06, sAA:sCort = 3.20-12.80; coach 2 sCort = 4.20-9.70, sAA = 158.80-307.20, sAA:sCort = 21.10-61.70; and coach 3 sCort = 6.81-19.66, sAA = 86.55-495.85, sAA:sCort = 4.90-35.50). A significant inverse relationship between mental fatigue and readiness to perform (r = -.44 [-.64 to -.17], P = .002) was identified. Conclusions: Elite sport coaches report elevated instances of mental fatigue during a preseason training period. Those involved in elite sports should act to understand the presence and potential subsequent impacts of staff mental fatigue and consider management or mitigation strategies. Optimization of the cognitive performance of coaches and performance staff presents as a potential source of competitive advantage.


Citations (83)


... Thus, the effect of exercise on circulating and chronic IL-15 concentrations in patients with cancer remains to be elucidated. To this end, Farley et al. (2024) address both short-term and long-term IL-15 dynamics in a population of cancer survivors. As such, they extend on previous studies which have addressed only the acute IL-15 response following a single bout of aerobic exercise (Kim et al., 2023). ...

Reference:

Cycling away from cancer: can aerobic training enhance interleukin‐15 response to acute exercise?
Interleukin‐15 and high‐intensity exercise: relationship with inflammation, body composition and fitness in cancer survivors

... Based on the known data, the unknown variables of the relevant equation system are eliminated, and the data of students with the same characteristics are then connected for solving. Finally, the relationship between the natural walking speed and the weight carried [21][22][23][24] by each group of students in a short period of time is obtained. At the same time, through the literature review, it is known that there is a correlation between the speed of natural walking and the travel time during long-term travel, which can be used to obtain the changes in the speed of the second and third round trips with equal load. ...

The Effects of Low-Load Squat Jump and Maximal Isometric Priming Exercise on Muscular Performance and Perceptual State

The Journal of Strength and Conditioning Research

... Nevertheless, no changes occurred in any of the countermovement jump (CMJ) measures, suggesting that, at least for the variables and protocols evaluated in this study, the priming effects were not evident for lower-body power or force expression. Likewise, Harrison et al. [19] did not observe any significant increases in upper-body strength-power qualities (i.e., bar-peak velocities assessed in maximal bench throw and bench pull tests at 25%, 50%, and 75% 1RM) in resistance-trained subjects 3-and 27-h after completing a priming stimulus involving 4 sets of 3 reps of bench press and bench pull exercises executed at 65% 1RM. These initial findings indicate that, regardless of the time course or exercise stimuli, positive changes in physical performance are difficult to achieve through the use of typical or even atypical (i.e., variable resistance training) priming strategies [18]. ...

Does Moderate-Load Priming Activity Influence Maximal Upper-Body Performance and Perceptual State?

The Journal of Strength and Conditioning Research

... Epidemiological studies focusing on the UK Biobank accelerometer cohort have demonstrated that VILPA, in the form of exercise snacks, reduces mortality 7 , incidence of cardiovascular diseases 8 , and cancer 9 . These associations may be attributed to the transient, repeated bouts of high-intensity exercise embedded in daily activities, impacting the accrual of bene ts 23 . The distinction between snack exercise and VILPA lies in its primarily planned or organized nature as part of daily activities (rather than being occasional or inherent in life). ...

Benefits beyond cardiometabolic health: the potential of frequent high intensity ‘exercise snacks’ to improve outcomes for those living with and beyond cancer

... Finally, there was a negative and significant influence of the passing of the season on perceived mental fatigue, meaning that perceived mental fatigue declines as the season progresses. Previous research in different sports 30,38,39 found that the perceived mental fatigue significantly fluctuated across a season, although it does not necessarily decrease over the course of the season. 30 Some of the reasons for these fluctuations suggested by Russell et al. 40 may be pressure to achieve expected targets, media commitments, changes in training volumes or environmental instability (i.e., play-off phases, long travels, …). ...

Thinking About Elite Performance: The Experience and Impact of Mental Fatigue in Elite Sport Coaching
  • Citing Article
  • June 2023

International Journal of Sports Physiology and Performance

... A longitudinal analysis of these populations can uncover novel connections between the microbiome and host phenotypes (both beneficial and detrimental). For example, the gut microbiome adapts to exercise, and the composition of the microbiome changes when one changes from a more sedentary to a more active lifestyle [6][7][8][9][10][11]. Correlating these changes to host outcomes over time can improve our understanding of the bacterial strains promoting health. ...

The Effect of Exercise Prescription on the Human Gut Microbiota and Comparison between Clinical and Apparently Healthy Populations: A Systematic Review

... One key area of interest is the microbiome's role in modulating chemotherapy efficacy. Studies have shown that certain bacterial species, particularly F. nucleatum, can metabolize chemotherapeutic agents, reducing their effectiveness [18]. This interaction enables cancer cells to evade the cytotoxic effects of chemotherapy, ultimately promoting resistance. ...

Exercise‐induced changes to the human gut microbiota and implications for colorectal cancer: a narrative review

... Studies have shown that IL-15 is highly expressed in skeletal muscles, can be secreted by skeletal muscle, and can mediate the physiological activity of the bones. 26 The skeletal muscle and bone are important components of the locomotor system, suggesting a significant link between IL-15 and the locomotor system. Recent studies have shown that IL-15 is closely associated with metabolic processes in the bone and skeletal muscle. ...

Immunomodulatory Function of Interleukin-15 and Its Role in Exercise, Immunotherapy, and Cancer Outcomes
  • Citing Article
  • November 2022

Medicine and Science in Sports and Exercise

... Various indicators have been employed to assess internal load (IL) in basketball. These indicators encompass the analysis of HR dynamics 7,8 , Rating Perceived Exertion (RPE) 9,10 , as well as their interrelationship 11 . Furthermore, the hormonal profile, specifically the testosterone-cortisol ratio 12,13 , and the concentration of metabolites such as lactate or ammonium 14,15 , have also been examined. ...

Relationship Between Training Workloads, Match Workloads, and Match Performance in Elite Netball
  • Citing Article
  • September 2022

International Journal of Sports Physiology and Performance

... Given that athletes' power output and vertical jump performance are significantly higher on competition days, particularly after the end of games, than on training days, a well-founded training program should be developed. As most official ice hockey games are scheduled in the evening, a plyometric training session in the morning can serve as a priming method [44]. According to the review made by Holmberg and colleagues, 3 sets of 5 optimally loaded CMJ with 1 min rest between sets is an effective performance-enhancing strategy [44]. ...

Factors Modulating the Priming Response to Resistance and Stretch-Shortening Cycle Exercise Stimuli

Strength & Conditioning Journal