1) High intensity interval training (HIIT) can overstimulate the sympathetic nervous system and delay recovery of the parasympathetic nervous system. 2) Repeated high intensity workouts without adequate rest in between can cause cumulative stress on the autonomic nervous system (ANS). 3) Most people should limit high intensity workouts to a maximum of 2-3 per week to allow for the 48-72 hours needed for full ANS recovery between sessions. Frequent deload weeks are also recommended.

1. Are Your Sprint Intervals
HIITing You in Your ANS?
Jamie ScottPGDipNutMed PGDipSportExMed BSc BPhEd
NEW ZEALAND
thatpaleoguy.com

2. New Zealand Ancestral Health
• Public health policy being driven by
evolutionary biology
• A strong and growing base of health
professionals and academics applying
evolutionary medicine
• Ancestral approaches to Maori health
• Synergy Health – a paleo corporate
health company ‘gamifying’ paleo
workplace challenges
• Whole9 South Pacific

3. Convergence

4. FREQUENCY
INTENSITY
TIME
TYPE
High-frequency
Moderate-to-high intensity
Long-duration
Highly-specific
Conventional Endurance Training
“Chronic Cardio”

5. FREQUENCY
INTENSITY
TIME
TYPE
Low-frequency
High-intensity
Short-duration
Multi-modal
High Intensity Training
- In Theory -

6. FREQUENCY
INTENSITY
TIME
TYPE
High-frequency
High-intensity
Short-to-moderate duration
Multi-modal
High Intensity Training
- In Practice -

7. Escape from Alcatraz
100 burpees over partner in plank
100 dumbbell snatches
100 barbell squats
100 box jumps
100 walking lunges
1000m farmers carry
100 sledge hammer strikes
50 partner push ups
1000m row

8. “I’m doing two WODs per day, 6 days per
week. I don’t sleep well and I am
frustrated I am not losing any weight…
…What is wrong with my diet?

9. Mon AM: WOD PM: WOD
Tue AM: WOD PM: Soccer
Wed Rest Day
Thu AM: WOD PM: WOD
Fri AM: WOD PM: WOD
Sat AM: WOD PM: Soccer
Sun AM: WOD

10. 45 minutes of box jumps,
air squats, and burpees.

11. High-frequency, high-intensity, longer-timed workouts
might not be classical marathon running or endurance
cycling but which are still in effect “chronic cardio”.

12. With ‘paleo chronic cardio’, we are seeing similar signs
and symptoms of over-training, driven not by
FREQUENCY + DURATION as in traditional endurance
sports, but through excessive FREQUENCY + INTENSITY.

14. Autonomic Nervous System (ANS)
Sympathetic Nervous System
Allows the body to function
under stress
– Fighting
– Fleeing
Parasympathetic Nervous System
Controls more vegetative
functions
– Feeding
– Breeding
– Flaking out

15. HIT

16. Following an acute bout of high-intensity activity
markers of sympathetic nervous system activity are
disturbed and remain disturbed for at least several
hours post-session.
Parasympathetic nervous system reactivation is delayed
following repeated high-intensity intervals.

17. The first signs of autonomic stress are seen once the
first ventilatory threshold (VT1) is exceeded, regardless
of how that threshold is exceeded…
Continuous Movement vs. Interval Training
Seiler S, Haugen O, Kuffel E. Autonomic recovery after exercise in trained athletes: intensity and duration effects.
Med Sci Sports Exerc. 2007 Aug;39(8):1366-73.

18. - exercise needs to
conclude due to
exhaustion.
ANS stress starts here.
High-intensity training zone

19. Whilst training above VT1 achieves a strong and positive
signalling effect in terms of adaptation, it also comes
with greater systemic stress requiring greater recovery.
Any prolonged efforts or repeated incursions above VT1
intensity delays ANS recovery.

20. The relatively lengthy ANS recovery time
also brings to consideration that appropriate
rest should be allowed between sessions or
between training and competition.
Studies examining long-term recovery have found that
autonomic indices […] remain depressed […] 48h after
the cessation of exercise.
Stuckey MI et al. Autonomic recovery following sprint interval exercise. Scand J Med Sci Sports. 2012 Dec;22(6):756-63.

21. This suggests that 2 days of recovery is
inadequate for complete autonomic
recovery...
Training every second day would not allow for
complete ANS recovery between sessions.
In such an instance, competition performance may be
hindered, or for certain populations, it may further
compromise their health.

24. Sympathetic Nervous System Over-stimulation
Digestion. Stress hormones slow the
release of stomach acid and interfere
with how well the stomach can
empty itself. This can cause
nausea, digestive
problems, diarrhoea…
Metabolic. Cortisol makes you crave
carbohydrates and fats, which can
cause you to gain weight. Cortisol
also makes you more likely to put on
weight in your abdominal area…
Immune system. The stress response
depresses your immune
system, slowing healing and making
you more likely to get
colds, infections, and other
inflammatory conditions…
Mental health. Being bombarded
with stress hormones creates a
constant state of
nervousness, tension and
anxiety, impatience, hyper-
vigilance, ruminations…

25. Adaptation?
Highly-trained athletes do seem to recover from such
ANS perturbations more rapidly.
But… We are currently unable to say whether this is an
actual adaptation to training or an inherent
characteristic of successful athletes.

26. - exercise needs to
conclude due to
exhaustion.
ANS stress starts here.
High-intensity training zone

27. Polarisation
Elite athletes tend to polarise their training;
• 75-90% of training volume covers low intensity training
(includes strength and movement work).
• 10-25% of training volume undertaken at intensities well above
VT1 (constant movement or interval-training).

28. High-frequency [daily] incursions into fight-or-flight
mode can make the stress-related side effects of high-
intensity training cumulative and can make such
training just as problematic as high-frequency, lower-
intensity, long-duration “chronic cardio” training.
Seiler S. et al. Autonomic recovery after exercise in trained athletes: intensity and duration effects. Med Sci Sports Exerc. 2007 Aug;39(8):1366-73.
Stuckey MI et al. Autonomic recovery following sprint interval exercise. Scand J Med Sci Sports. 2012 Dec;22(6):756-63.
West, DJ. et al. The neuromuscular function, hormonal, and mood responses to a professional rugby union match. J Strength Cond Res. 2013 Mar 27

29. Given the 48-72h required for full ANS recovery, the
prudent prescription for high-intensity training
sessions for most people would be a maximum of 2-3
high-intensity [fight or flight] sessions per week, with
relatively frequent deload weeks.
Seiler S. et al. Autonomic recovery after exercise in trained athletes: intensity and duration effects. Med Sci Sports Exerc. 2007 Aug;39(8):1366-73.
Stuckey MI et al. Autonomic recovery following sprint interval exercise. Scand J Med Sci Sports. 2012 Dec;22(6):756-63.
West, DJ. et al. The neuromuscular function, hormonal, and mood responses to a professional rugby union match. J Strength Cond Res. 2013 Mar 27

30. Are Your Sprint Intervals
HIITing You in Your ANS?
Jamie ScottPGDipNutMed PGDipSportExMed BSc BPhEd
NEW ZEALAND
thatpaleoguy.com