This study investigated three ways of performing "intervals with (1) fast start followed by decreasing speed (DEC), (2) systematic variation in exercise intensity (VAR), and (3) constant speed (CON)". The insight here could be the optimal way to perform VO2 Max intervals. The results showed that:
DEC and VAR led to longer time ≥90% VO2peak and higher mean %VO2peak compared with CON, with no differences between DEC and VAR.
VAR, DEC, and CON led to similar time ≥90% of peak heart rate (HRpeak), mean HR, mean breathing frequency, mean ventilation, and mean blood lactate concentration ([La−]). Furthermore, no differences between sessions were observed for perceptual responses, such as mean rate of perceived exertion, session rate of perceived exertion or pain score.
This led the authors to conclude that:
These intervals (DEC) can be a good alternative for accumulating more time at a high percentage of VO2peak and at the same time mimicking the pronounced variation in exercise intensities experienced during XC-skiing competitions.
PRACTICAL TAKEAWAY - fast-start intervals may be the optimal way to perform shorter, intense intervals.
In this study the authors "compared physiological and perceptual responses elicited by work intervals matched for duration and mean power output but differing in power-output distribution". The cyclists completed either varied intensity or constant intensity intervals. The results were that:
Cyclists spent more time at >90% VO2 max during HIIT with varied-intensity work intervals, but there were no differences between sessions in heart-rate- or perceptual-based training-load metrics.
When considering individual work intervals, minute ventilation was higher in the varied-intensity mode, but not respiratory frequency, tidal volume, blood lactate concentration [La], ratings of perceived exertion, or cadence.
Well-trained cyclists sustain higher fractions of VO2 max when work intervals involved power-output variations.
PRACTICAL TAKEAWAY - varied interval intensities appear superior to constant interval intensities for eliciting a VO2 Max response.
Looking further into interval training, this study set out to compare "two interval trainings (long intervals HIIT3m: 3 min work, 3 min active rest vs. short intervals HIIT30s: 30 s work, 30 s active rest) at the same overall work rate and training duration". The authors found that:
Although times above gas exchange threshold were shorter in HIIT3m, both protocols evoked similar average fractional utilization of VO2peak. However, HIIT3m resulted in higher cardiovascular responses during the loaded phases.
Average physiological responses were not different in both protocols owning to incomplete rests in HIIT30s and large response amplitudes in HIIT3m.
The authors conclude:
Differences between the protocols were detected regarding loaded and unloaded phases in central hemodynamic parameters and oxygen uptake, where the long-interval training regimen results in stronger cardiovascular and metabolic responses.
PRACTICAL TAKEAWAY - 3' intervals may be optimal for cardiovascular load, however, shorter intervals can have a place where less cardiac stress is needed.
PSYCHOLOGY: The mechanisms underpinning the effects of self-control exertion on subsequent physical performance
A need for prior self-control has been shown to decrease subsequent performance. This review is a meta analysis "examining the effects of self-control exertion on subsequent physical performance, as well as the mechanisms underpinning the effect". For self-control manipulations lasting 30' or less, the authors found that:
Prior exertion of self-control resulted in a statistically significant medium sized negative effect of prior self-control exertion on subsequent physical performance.
Further analysis revealed a small increase in initial perceptions of pain and a medium sized reduction in self-efficacy, while motivation and RPE were unaffected following the exertion of self-control.
Explanatory mechanisms that underpin the effect were also established, whereby self-efficacy was lower and initial perceptions of pain were higher, following the prior exertion of self-control.
PRACTICAL TAKEAWAY - avoid having to exert self-control prior to key performances to reduce any negative impact on those performances.
FATIGUE: Is there Evidence for the Suggestion that Fatigue Accumulates Following Resistance Exercise?
This "paper explores the time course of the changes in various fatigue-related measures in order to understand how they may accumulate or lessen over time following an exercise bout or in the context of an exercise program". This is useful for coaches and athletes considering how to distribute training loads. The authors found that:
Overall, evidence for the presence of fatigue accumulation with resistance training is equivocal, making it difficult to draw the conclusion that fatigue accumulates.
A potential candidate that may be interpreted as accumulated fatigue is muscle damage, which shares similar characteristics (i.e., prolonged strength loss). Due to the delayed appearance of muscle damage, it may be interpreted as accumulated fatigue.
PRACTICAL TAKEAWAY - it does not appear that fatigue accumulates, although it may be useful to consider the impacts of muscle damage when scheduling training.