Overreaching Attenuates Training-induced Improvements in Muscle Oxidative Capacity

Abstract

Introduction The aim of this study was to determine whether muscle oxidative capacity is influenced by alterations in training volume in middle-distance runners. Methods Twenty-four highly trained middle-distance runners (n = 16 males; V˙O2peak = 73.3(4.3) mL·kg−1·min−1; n = 8 females, V˙O2peak = 63.2(3.4) mL·kg−1·min−1) completed 3 wk of normal training (NormTr), 3 wk of high-volume training (HVTr; a 10%, 20%, and 30% increase in training volume during each successive week from NormTr), and a 1-wk taper (TapTr; 55% exponential reduction in training volume from HVTr week 3). Before and immediately after each training period, the rate of recovery of muscle oxygen consumption (mV˙O2) of the gastrocnemius medialis was measured using near-infrared spectroscopy, with the rate constant indicating muscle oxidative capacity. Time to exhaustion (TTE) and V˙O2peak were determined during a maximal incremental treadmill test. Results Twelve subjects were classified as being functionally overreached (FOR) after HVTr (decreased running TTE and high perceived fatigue), whereas the other 12 subjects were classified as acutely fatigued (AF; no decrease in running TTE). The AF group demonstrated a significant increase in muscle oxidative capacity after HVTr (rate constant: 15.1% ± 9.7% min−1; P = 0.009), with no further improvement after TapTr, whereas there was no change in muscle oxidative capacity for FOR at any time point (P > 0.05). Compared with the FOR group, the AF group had substantially larger improvements in TTE from pre-HVTr to post-TapTr (FOR, 8.8% ± 3.7%; AF, 3.2% ± 3.0%; P = 0.04). Conclusion The present study was able to demonstrate that muscle oxidative capacity was increased in response to a period of HVTr, but only in runners who did not develop FOR. Furthermore, runners who did not develop FOR had substantially larger performance improvements after a taper period.

Functional Overreaching in Endurance Athletes: A Necessity or Cause for Concern?

“…Exercise performance in a sport-specific task (i.e., time trial) or incremental exercise test and physiological and psychological variables are compared from before and after an overload training period, and also after a recovery period in most cases, within the same athlete or, between athletes who have a decrement in performance (i.e., overreached) and those that show no decrease in performance. In reference to the latter, athletes who complete the overload training period and maintain or increase their exercise performance despite having high perceived fatigue, have been termed acutely fatigued (AF) in some studies [12,3,11,5,10,37,17,16]. A number of well-designed studies [10,5,[11][12][13]4] have also included a control group who continue their normal training as well as undertake a taper period alongside the experimental group who are exposed to the overload training period (Figure 1).…”

“…On the basis of this analysis, a decrement in maximal exercise performance greater than the test-retest magnitude is used as the criteria to discriminate the overreached subjects in the overload training group. An alternative design that is also effective, includes exercise performance assessments before and after a control period that all subjects complete prior to the overload training intervention [3].…”

“…Indeed, the impairment in exercise performance, disturbed sleep [11,44,14,45], increased muscle soreness [41] and higher incidence of illness [11,43] in FOR endurance athletes could all contribute to impaired training intensity and lead to suboptimal training adaptations [12,3].…”

“…Short-term periods of increased training intensity [1,2], training volume [3][4][5], or a combination of both [6,7] have been shown to improve performance in trained endurance athletes. However, these increases in training load may result in variable responses [3, 8-10, 5, 11, 7, 12-14, 4, 15-21], whereby some athletes improve without deleterious effects on performance, while others show diminished exercise performance.…”

“…Despite the supposition that deliberately inducing FOR in athletes may be necessary in order to achieve performance super-compensation [22,23,14,24], recent research suggests that FOR has been associated with various negative cardiovascular [5,29], hormonal [30,5] and metabolic consequences [8,9,13] which may be associated with maladaptation to training. Indeed, in two recent studies, endurance athletes who were classified as being FOR had smaller performance improvements and dampened training adaptations compared to nonoverreached athletes who completed the same relative increase in training load [12,3]. Furthermore, Hausswirth et al [11] demonstrated that FOR athletes experienced disturbed sleep and had a higher incidence of illness compared with athletes who completed the same training but were only acutely fatigued (maintenance of performance but increased subjective fatigue).…”