Abstract
Assessing current fatigue of athletes to fine-tune training prescriptions is a critical task in competitive sports. Blood-borne surrogate markers are widely used despite the scarcity of validation trials with representative subjects and interventions. Moreover, differences between training modes and disciplines (e.g. due to differences in eccentric force production or calorie turnover) have rarely been studied within a consistent design. Therefore, we investigated blood-borne fatigue markers during and after discipline-specific simulated training camps. A comprehensive panel of blood-born indicators was measured in 73 competitive athletes (28 cyclists, 22 team sports, 23 strength) at 3 time-points: after a run-in resting phase (d 1), after a 6-day induction of fatigue (d 8) and following a subsequent 2-day recovery period (d 11). Venous blood samples were collected between 8 and 10 a.m. Courses of blood-borne indicators are considered as fatigue dependent if a significant deviation from baseline is present at day 8 (Δfatigue) which significantly regresses towards baseline until day 11 (Δrecovery). With cycling, a fatigue dependent course was observed for creatine kinase (CK; Δfatigue 54±84 U/l; Δrecovery -60±83 U/l), urea (Δfatigue 11±9 mg/dl; Δrecovery -10±10 mg/dl), free testosterone (Δfatigue -1.3±2.1 pg/ml; Δrecovery 0.8±1.5 pg/ml) and insulin linke growth factor 1 (IGF-1; Δfatigue -56±28 ng/ml; Δrecovery 53±29 ng/ml). For urea and IGF-1 95% confidence intervals for days 1 and 11 did not overlap with day 8. With strength and high-intensity interval training, respectively, fatigue-dependent courses and separated 95% confidence intervals were present for CK (strength: Δfatigue 582±649 U/l; Δrecovery -618±419 U/l; HIIT: Δfatigue 863±952 U/l; Δrecovery -741±842 U/l) only. These results indicate that, within a comprehensive panel of blood-borne markers, changes in fatigue are most accurately reflected by urea and IGF-1 for cycling and by CK for strength training and team sport players.
Highlights
Training load and competition frequency of elite athletes are steadily increasing and performance differences between race winners and “-ran” are becoming more and more marginal
For all 3 exercise modes a significant decline in discipline specific performance over the simulated training camp could be confirmed
The restoration of performance over the recovery period was significant for cycling (p
Summary
Training load and competition frequency of elite athletes are steadily increasing and performance differences between race winners and “-ran” are becoming more and more marginal. Athletes and coaches face the difficult task of maximizing training load and adaptation whilst avoiding insufficient recovery, which would lead to maladaptation, loss of performance and possibly to non-functional overreaching or the overtraining syndrome. In this situation, assessing the current fatigue status of an individual athlete is a critical task in order to fine-tune training prescriptions. Requiring maximum effort, this parameter is not suitable for repeated routine assessment. Other indicators of fatigue and recovery have been investigated including a wide range of blood-borne parameters (biochemical [2,3,4], hormonal [2,4,5], immunological [6,7], psychological questionnaires [8] and the assessment of autonomous nervous system balance (heart rate and heart rate variability) [2,9,10]
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