A Simple Model for Diagnosis of Maladaptations to Exercise Training

Abstract

Background: The concept of overreaching and super compensation is widely in use by athletes and coaches seeking to maximize performance and adaptations to exercise training. The physiological aspects of acute fatigue, overreaching and non-functional overreaching are, however, not well understood, and well-defined negative physiological outcomes are missing. Instead, the concept relies heavily on performance outcomes for differentiating between the states. Recent advancements in the field of integrated exercise physiology have associated maladaptations in muscular oxidative function to high loads of exercise training.

Method: Eleven female and male subjects that exercised regularly but did not engage in high-intensity interval training (HIIT) were recruited to a 4-week long training intervention where the responses to different training loads were studied. Highly monitored HIIT sessions were performed on a cycle ergometer in a progressive fashion with the intent to accomplish a training overload. Throughout the intervention, physiological and psychological responses to HIIT were assessed, and the results were used to construct a diagnostic model that could indicate maladaptations during excessive training loads.

Results: We here use mitochondrial function as an early marker of excessive training loads and show the dynamic responses of several physiological and psychological measurements during different training loads. During HIIT, a loss of mitochondrial function was associated with reduced glycolytic, glucoregulatory and heart rate responses and increased ratings of perceived exertion in relation to several physiological measurements. The profile of mood states was highly affected after excessive training loads, whereas performance staled rather than decreased. By implementing five of the most affected and relevant measured parameters in a diagnostic model, we could successfully, and in all the subjects, identify the training loads that lead to maladaptations.

Conclusions: As mitochondrial parameters cannot be assessed without donating a muscle biopsy, this test can be used by coaches and exercise physiologists to monitor adaptation to exercise training for improving performance and optimizing the health benefits of exercise. Clinical trial registry number NCT04753021 . Retrospectively registered 2021-02-12.

Keywords: Exercise; Maladaptations; Mitochondria; Overreaching; Performance; Physiology; Testing.

Conflict of interest statement

Filip J. Larsen is co-founder of Silicon Valley Exercise Analytics, a company using data science to improve athletic performance. The company had no role in funding, data collection and analysis, or preparation of the manuscript. Mikael Flockhart, Lina Nilsson and Björn Ekblom declare no conflict of interest.

© 2022. The Author(s).

Figures

Fig. 1

a The difference in coupled intrinsic mitochondrial respiration using pyruvate, glutamate, malate, succinate and ADP activating complex I + II in each phase compared to normal respiration (the mean of BL, LT, MT1 and RE measurements), i.e., unaffected by excessive training load. Significant main effect RM one-way ANOVA p < 0.05 is marked with #. All values are means ± SD, (n = 11). b Study design, c a representative HIIT session by a subject showing the acute physiological responses during submaximal warm up at 100 W and at free pacing during HIIT. BL = baseline, LT = light training load, MT1 and MT2 = moderate training load, MAL = maladaptive training load, RE = recovery

Fig. 2

a Power output during HIIT, b VO2 at submaximal work rate, c VO2 during HIIT, d cycling economy at submaximal work rate, e VO2 per W during HIIT, f gross efficiency at submaximal work rate, g HR at submaximal work rate, h mean HR during HIIT, i max HR during HIIT, j power output per HR during HIIT, k mean HRR after submaximal work rate and l mean HRR after HIIT. HRRs with a significant main effect is highlighted in separate graphs. Significant main effect RM one-way ANOVA p < 0.05 is marked with #. All values are means ± SD, (n = 11). Figure g has previously been published [7]. BL = baseline, LT = light training load, MT1 and MT2 = moderate training load, MAL = maladaptive training load, RE = recovery

Fig. 3

a Lactate at rest, b lactate after submaximal work rate, c mean lactate during HIIT, d lactate at end of HIIT, e glucose at rest, f glucose after submaximal work rate, g mean glucose during HIIT, h glucose at end of HIIT sessions, (i) glucoregulatory response during intervals, j power output per lactate during HIIT. Significant main effect RM one-way ANOVA p < 0.05 is marked with #. All values are means ± SD with exception of (i), (n = 11). Figures d, f and h have previously been published [7]. BL = baseline, LT = light training load, MT1 and MT2 = moderate training load, MAL = maladaptive training load, RE = recovery

Fig. 4

a POMS scores during the whole intervention, b total mood disturbance, c the energy index (vigor–fatigue), d RPEs at submaximal work rate, e RPEs during HIIT, f power output per RPE during HIIT, g HR per RPE during submaximal work rate, h HR per RPE during HIIT, i lactate per RPE during submaximal work rate, j lactate per RPE during HIIT and k maximal hand grip strength. Significant main effect RM one-way ANOVA p < 0.05 is marked with #. All values are means ± SD, (n = 11). l The number of scores achieved in each phase using our diagnostic test and the difference in intrinsic mitochondrial respiration activating complex I + II in each phase compared to normal respiration (the mean of BL, LT, MT1 and RE measurements). Each subject and situation is represented by a dot. BL = baseline, LT = light training load, MT1 and MT2 = moderate training load, MAL = maladaptive training load, RE = recovery. 5 × 8, 3 × 8 and 3 × 4 = HIIT training sessions