Influence of interval duration on immunological responses to 4-weeks’ high-intensity interval training

• High-intensity interval training (HIT) encompasses a wide range of training prescriptions where up to nine variables can be manipulated (Buchheit and Laursen, 2013, Sports Medicine, 43(5), 313–338). Four weeks of HIT with longer intervals and accumulated work durations (AWD) has been shown to elicit greater improvements in peak oxygen consumption (V O 2peak ) despite more modest physiological, hormonal and perceptual responses (Sylta et al., 2017, Medicine & Science in Sports & Exercise, 49(6), 1137–1146). However, immunological responses to different HIT pre- scriptions have rarely been investigated. The purpose of this study was to compare the cumulative effects of a four-week HIT intervention, performed either as short or long intervals with the same AWD, on V O 2peak , the immunological biomarker salivary secretory IgA (s-IgA) and upper respiratory illness (URI) incidence. In addition, we explored the influence of HIT on serum cortisol, testosterone, 25(OH)D and ferritin as biomarkers related to immune competence. Following local ethics committee approval, twenty-five well-trained male cyclists and triath- letes provided written consent to take part and were randomised to one of three HIT groups (Long Intervals [LI]: 4 × 8min; Short Intervals 1 [SI1]: 4×[12 × 40/20s]; Short Intervals 2 [SI2]: 4×[8 ×40/20s]). Participants per- formed three cycling HIT sessions per week for four weeks at maximal session effort (“isoeffort”) intensity, supplemented with ad libitumlow-intensity training. Participants recorded upper respiratory symptoms (URS) daily using the Jackson Common Cold Scale; episodes of URI were identified retrospectively. V O 2peak as well as rested saliva and blood biomarkers were analysed before and after the training period. Fourteen of twenty-five participants reported an episode of URI (LI: 4/8, SI1: 4/8, SI2: 6/9) but there were no differences in URI incidence, severity or duration between groups. Following the train- ing intervention, we observed a moderate increase in V O 2peak across the cohort (mean± SD: 4.75 ± 0.42 to 4.86 ± 0.43 L· min−1 ,Cohen’s d= 0.65, 90% confidence intervals: [0.16, 1.13]) but the change in V O 2peak was not different between groups. Serum cortisol displayed a moderate increase (367 ± 98 to 415 ± 108 nmol· L −1 ,d=0.60 [0.12, 1.08]) and 25(OH)D a large decrease (79.2 ± 17.1 to 70.4 ± 17.6 nmol· L −1 ,d= -0.87 [−1.36,−0.37]) from pre- to post-training, but there were no differences in the magnitude of the responses between groups. Four weeks’HIT did not influence s-IgA secretion rate, serum testosterone or ferritin. We conclude that four weeks’ AWD-matched HIT performed as short- or long-intervals at isoeffort intensity does not differentially influence ill- ness incidence, immunological responses to training nor other immune-related biomarkers. This observation can be viewed as a positive finding for training planning, since it could allow coaches some flexibility in constructing AWD-matched isoeffort HIT sessions to achieve performance goals, without concern about detrimental effects on athletes’ immune status.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Idrottsvetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Sport and Fitness Sciences (hsv//eng)

Publication and Content Type

ref (subject category)

kon (subject category)