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11/25/18 Physiology of Interval Exercise Training: Mechanistic Basis for Adaptation Martin Gibala, PhD McMaster University Hamilton, Canada @ gibalam @ gibalam gibalam@ mcmaster.ca gibalam@ mcmaster.ca www.martingibala.com

  1. 11/25/18 Physiology of Interval Exercise Training: Mechanistic Basis for Adaptation Martin Gibala, PhD McMaster University Hamilton, Canada @ gibalam @ gibalam gibalam@ mcmaster.ca gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com Overall Message “Fast and short repetitions with suitable recoveries... are superior to even Interval training is an infinitely variable form of exercise speed running around the track for the development of endurance.” that elicits physiological adaptations linked to improved health and performance in a time-efficient manner. — Lauri Pihkala, 1916 @ gibalam @ gibalam gibalam@ mcmaster.ca gibalam@ mcmaster.ca https://upload.wikimedia.org/wikipedia/commons/9/99/J_O_Stockholm_1912_Bouin_et_Koleheimen.jpg www.martingibala.com www.martingibala.com Interval Training Terminology Alternating periods of more intense effort and recovery in a single session Aerobic Interval Training Resistance Interval Training (e.g., “cardio”-style exercise) (e.g., bodyweight exercise) Sprint interval training (SIT) Maximal efforts to failure ‘near max’ / ‘all out’ / ‘supra-max’ High-intensity interval training (HIIT) Vigorous but not all out ≥80% of HRmax Light-moderate intermittent exercise Light-moderate effort e.g., interval walking @ gibalam gibalam@ mcmaster.ca www.martingibala.com 1

  2. 11/25/18 Interval vs Traditional Endurance Training Interval vs Traditional Endurance Training HIIT can elicit SIT can elicit adaptations adaptations superior to MICT similar to MICT when total work despite less is matched (and total work (and time commitment often in much is similar). less time) @ gibalam @ gibalam gibalam@ mcmaster.ca MacInnis & Gibala, J Physiol 595: 2915-2930, 2017. MacInnis & Gibala, J Physiol 595: 2915-2930, 2017. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com Soldiers assigned to 1 of 3 of exercise groups or control (n=20 each) Soldiers assigned to 1 of 3 of exercise groups or control (n=20 each) � Interval training is equally effective or even more effective in improving the maximum working performance.” @ gibalam @ gibalam gibalam@ mcmaster.ca gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com Physiological Determinants of Performance 337 untrained or recreationally active subjects � Interval training produces improvements in VO 2max slightly (120 women) aged 18-45 y who performed ≥10 greater (than) continuous training even though many of the min of interval exercise per session for 6-13 wk studies were of short duration with limited sessions per week.” VO 2 max @ gibalam @ gibalam gibalam@ mcmaster.ca Joyner & Coyle. J Physiol 586: 35-44, 2008. Bacon et al., PLoS One 8: e73182, 2013. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 2

  3. 11/25/18 318 participants from 16 RCTs Inactive men performed 1x4-min or 4x4-min bouts of cycling at 90% HRmax who were assigned to 30-s “maximal” or “all out” interval exercise training or control � a single bout of AIT performed � SIT improves aerobic capacity three times per week may be a in healthy young people. time-efficient strategy to improve VO 2 max (and reduce blood Relative to continuous endurance training of moderate pressure and fasting glucose) in inactive but otherwise healthy intensity, SIT presents an equally effective alternative with middle-aged individuals.” a reduced volume of activity.” @ gibalam @ gibalam gibalam@ mcmaster.ca Bacon et al., PLoS One 8: e73182, 2013. Gist et al. Sports Med. 44:269-279, 2014. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 723 untrained or recreationally active subjects aged 18-45 y who performed 3-24 wk of CRF é 19% (~ 2 METs) interval or continuous training SIT MICT 10 � In healthy, young to middle- Protocol 3 x 20-s sprints 50 min Δ VO 2 peak (ml/kg/min) 8 (3x/wk) within 10 min continuous aged adults, high intensity 6 Workload ~ 500 W (50 W) ~ 110 W interval training improves 4 maximal oxygen uptake to a RPE 16 (hard) 13 (somewhat hard) 2 greater extent than traditional Mean HR ~83% ~73% 0 endurance training.” Work/session ~60 kJ ~300 kJ -2 MICT SIT CTL @ gibalam @ gibalam PLoS One 11: e0154075, 2016. gibalam@ mcmaster.ca gibalam@ mcmaster.ca Milanovic et al. Sports Med 45: 1469-1481, 2015. www.martingibala.com www.martingibala.com Physiological Determinants of Performance VO 2 max Central vs peripheral factors? @ gibalam @ gibalam gibalam@ mcmaster.ca Joyner & Coyle. J Physiol 586: 35-44, 2008. Lundby et al. Acta Physiol 2017, 220, 218-228. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 3

  4. 11/25/18 40 trained men assigned to 1 of 4 groups matched for total work (3x/wk for 8 wk) 40 trained men assigned to 1 of 4 groups matched for total work (3x/wk for 8 wk) LSD (~70% HR max ) LT ~85% HR max � When total work and training frequency are matched, higher aerobic intensity leads to larger improvements in VO 2max (which) seem to be a function of increased SV resulting in increased Q.” 15/15 (~90-95% HR max ) 4 x 4-min (~90-95% HR max ) @ gibalam @ gibalam gibalam@ mcmaster.ca Helgerud et al., Med Sci Sports Exerc. 39: 665-671, 2007. Helgerud et al., Med Sci Sports Exerc. 39: 665-671, 2007. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 8-12 x 60-s intervals at ~100% PPO with 75-s recovery (6 sessions over 2 wk) � The improvements in exercise performance occurred independent from any alterations in maximal cardiac capacity or blood characteristics (and) suggest that increases in mitochondrial content may facilitate improvements in respiratory capacity and oxygen extraction.” � Further research, directly comparing different training intensities and volumes within the same study is required.” @ gibalam @ gibalam Jacobs et al. J Appl Physiol 115: 785-793, 2013. gibalam@ mcmaster.ca gibalam@ mcmaster.ca Biochim Biophys Acta 1840: 1266-1275, 2014. www.martingibala.com www.martingibala.com 6 sessions per leg over 2 wk SPT = 48 x 10 sec sprints Greater mitochondrial � We did not expect to (99 m/min) with 40 sec recov adaptations after interval find an increase in vs continuous cycling 8 min total work (800 m) muscles of sprint-trained despite same total work animals because END = 50 min continuous Exercise intensity aerobic metabolism running (36 m/min) and/or contraction contributes very little pattern is important of the energy . � 50 min total work (1800 m) @ gibalam @ gibalam gibalam@ mcmaster.ca MacInnis et al., J Physiol 595: 2955-2968, 2017. Hickson RC et al. J Appl Physiol. 40: 868-872, 1976. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 4

  5. 11/25/18 Sprinting is Highly Dependent on Aerobic Metabolism! Sprinting is Highly Dependent on Aerobic Metabolism! 3 x 30-s ‘all out’ sprints with 4 min recovery periods 3 x 30-s ‘all out’ sprints with 4 min recovery periods (Bout 1) (Bout 3) (Bout 1) (Bout 3) Energy Anaerobic Anaerobic Aerobic Aerobic Time @ gibalam @ gibalam gibalam@ mcmaster.ca Parolin et al. Am J Physiol 277: E890-E900, 1999. Parolin et al. Am J Physiol 277: E890-E900, 1999. gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com Group (n = 10 each) Sprint Endurance Similar increases in mitochondrial enzymes Training Intensity � All out � effort 65% VO 2 peak (~500 W) (~150 W) Exercise Protocol (6 wk) 30 sec x 4-6, 4 min 40-60 min recov 3x / wk 5x / wk Weekly Exercise Time ~10 min ~4.5 h Weekly Training Time ~1.5 h ~4.5 h (including recovery) ~225 kJ ~2250 kJ Weekly Training Volume 90% lower in Sprint group Citrate Synthase ß-HAD @ gibalam @ gibalam Burgomaster et al. J Physiol. 151-160, 2008. gibalam@ mcmaster.ca gibalam@ mcmaster.ca Burgomaster et al. J Physiol. 151-160, 2008. www.martingibala.com www.martingibala.com How Do Sprints Elicit Endurance Adaptations? Similar changes in fuel utilization (1 h at 65% VO 2 peak) PRE PRE POST * POST * 600 600 500 500 � Low-volume SIT is a time-efficient strategy to induce changes in selected 400 400 markers of whole-body and skeletal muscle metabolism during exercise that are 300 300 comparable to changes induced by traditional high-volume (endurance training)”. 200 200 100 100 0 0 Rest 60 min Rest 60 min Sprint Group Endurance Group @ gibalam @ gibalam gibalam@ mcmaster.ca Burgomaster et al. J Physiol. 151-160, 2008. Hawley et al. Cell 159: 738-749, 2014 (left); Egan & Zierath, Cell Metab 17: 162-184, 2013 (right). gibalam@ mcmaster.ca www.martingibala.com www.martingibala.com 5

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