The current study involved the completion of two distinct experiments. Experiment 1 compared fibre specific and whole muscle responses to acute bouts of either low-volume high-intensity interval training (LV-HIT) or moderate-intensity continuous endurance exercise (END) in a randomized crossover design. Experiment 2 examined the impact of a six-week training intervention (END or LV-HIT; 4 days/week), on whole body and skeletal muscle fibre specific markers of aerobic and anaerobic capacity. Six recreationally active men (Age: 20.7±3.8 yrs; VO2peak: 51.9±5.1 mL/kg/min) reported to the lab on two separate occasions for experiment 1. Following a muscle biopsy taken in a fasted state, participants completed an acute bout of each exercise protocol (LV-HIT: 8, 20-second intervals at ∼170% of VO2peak separated by 10 seconds of rest; END: 30 minutes at ∼65% of VO2peak), immediately followed by a muscle biopsy. Glycogen content of type I and IIA fibres was significantly (p<0.05) reduced, while p-ACC was significantly increased (p<0.05) following both protocols. Nineteen recreationally active males (n = 16) and females (n = 3) were VO2peak-matched and assigned to either the LV-HIT (n = 10; 21±2 yrs) or END (n = 9; 20.7±3.8 yrs) group for experiment 2. After 6 weeks, both training protocols induced comparable increases in aerobic capacity (END: Pre: 48.3±6.0, Mid: 51.8±6.0, Post: 55.0±6.3 mL/kg/min LV-HIT: Pre: 47.9±8.1, Mid: 50.4±7.4, Post: 54.7±7.6 mL/kg/min), fibre-type specific oxidative and glycolytic capacity, glycogen and IMTG stores, and whole-muscle capillary density. Interestingly, only LV-HIT induced greater improvements in anaerobic performance and estimated whole-muscle glycolytic capacity. These results suggest that 30 minutes of END exercise at ∼65% VO2peak or 4 minutes of LV-HIT at ∼170% VO2peak induce comparable changes in the intra-myocellular environment (glycogen content and signaling activation); correspondingly, training-induced adaptations resulting for these protocols, and other HIT and END protocols are strikingly similar.

The present study examined the effect of concurrent exercise training and daily resveratrol (RSV) supplementation (150 mg) on training-induced adaptations following low-dose high-intensity interval training (HIIT). Sixteen recreationally active (∼22 years, ∼51 mL·kg(-1)·min(-1)) men were randomly assigned in a double-blind fashion to either the RSV or placebo group with both groups performing 4 weeks of HIIT 3 days per week. Before and after training, participants had a resting muscle biopsy taken, completed a peak oxygen uptake test, a Wingate test, and a submaximal exercise test. A main effect of training (p < 0.05) and interaction effect (p < 0.05) on peak aerobic power was observed; post hoc pairwise comparisons revealed that a significant (p < 0.05) increase occurred in the placebo group only. Main effects of training (p < 0.05) were observed for both peak oxygen uptake (placebo - pretraining: 51.3 ± 1.8, post-training: 54.5 ± 1.5 mL·kg(-1)·min(-1), effect size (ES) = 0.93; RSV - pretraining: 49.6 ± 2.2, post-training: 52.3 ± 2.5 mL·kg(-1)·min(-1), ES = 0.50) and Wingate peak power (placebo: pretraining: 747 ± 39, post-training: 809 ± 31 W, ES = 0.84; RSV - pretraining: 679 ± 39, post-training: 691 ± 43 W, ES = 0.12). Fibre-type distribution was unchanged, while a main effect of training (p < 0.05) was observed for succinate dehydrogenase activity and glycogen content, but not α-glycerophosphate dehydrogenase activity or intramuscular lipids in type I and IIA fibres. The fold change in PGC-1α, SIRT1, and SOD2 gene expression following training was significantly (p < 0.05) lower in the RSV group than placebo. These results suggest that concurrent exercise training and RSV supplementation may alter the normal training response induced by low-volume HIIT.

Objective: To identify key characteristics and habits of recreational opioid users.Design: The data were compiled from volunteers who participated in clinical studies at a contract research organization in Toronto, Ontario, Canada.Interventions: Data were collected from 5,018 male and female recreational opioid users via telephone and face-to-face screening interviews. Five recreational opioid users participated in a live interview broadcast on the internet.Main outcome measures: Demographic data, recreational drug use history, routes of recreational drug administration, alcohol use, and smoking status. A subset of the demographic information and recreational drug use history was summarized separately using data collected between 2013 and 2016 from 114 recreational opioid users who were not dependent on opioids. Interview excerpts were included from five recreational opioid users who described their real-world experiences with drug abuse, including the impact of abuse-deterrent opioid formulations on their drug abuse behavior.Results: The preferred route of administration of opioids was oral (52 percent), followed by intranasal (36 percent), intravenous (10 percent), and buccal (chewing on a patch; 2 percent). Other substances used included nicotine, alcohol, and non-opioid psychoactive drugs (primarily cannabis). Oxycodone was the most frequently reported opioid of abuse.Conclusions: Recreational opioid users have distinct drug-related behaviors and preferences. Monitoring current trends and examining these behaviors is an important component to understand the potential safety risks associated with recreational opioid use.

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Muscle activation following a bout of high‐intensity interval training (HIT) and endurance exercise (END) was examined in recreationally active men (n=6; age, 19.3±1.4 yrs; VO2peak, 51.9±5.1 ml/min/kg; WRpeak, 264.1±41.6 W). Muscle biopsies were obtained at rest and immediately following a bout of HIT (8 20s intervals, separated by 10s rest, at 170% WRpeak; 481.4±60.1 W) and END (30min of steady state cycling at 65% of WRpeak; 173.7±29.8 W). Bouts were performed a minimum of 1 week apart in random order. MHC expression was identified via immunofluorescent staining while glycogen content was determined via PAS staining. Changes in phosphorylated AMPK (p‐AMPK) and mTOR (p‐mTOR) were determined in whole muscle homogenates via western blotting. Changes in glycogen content were only examined in type I and IIA fibers as only 8 and 16 of 24 samples contained IIX and IIAX fibers, respectively. Significant (p<0.05) glycogen depletion was observed in both type I (HIT −55% END −42%) and IIA (HIT −49%; END −72%) fibers following both protocols but was greater (p<0.05) in type IIA fibers following END than HIT. Interestingly, whole muscle markers of activation, p‐AMPK and p‐mTOR were only elevated (p<0.01) following END (HIT: p‐AMPK, p=0.34; p‐mTOR, p=0.50). These data suggest that use of p‐AMPK and p‐mTOR as markers of whole muscle activation may not be appropriate following HIT. This research was supported by NSERC.