Optimising functional neuromuscular recovery with carbohydrate and protein supplementation in athletes

Introduction: Neuromuscular (NM) fatigue is the inevitable loss of force production capability stemming from participation in physical exercise. As the effects of NM fatigue can last several days after exercise, performance in subsequent exercise can be negatively impacted by residual fatigue, a common occurrence for athletes during congested periods of training or competition. Implementing recovery interventions that accelerate the natural time-course of recovery from fatigue is, therefore, an approach with the potential to optimise sporting performance and impact competition outcomes. Supplemental intake of nutrients represents a relatively simple and non-invasive recovery intervention; therefore, the aim of this thesis was to investigate the effect of combined carbohydrate and protein (CHO+PRO) ingestion on functional NM recovery. Study 1: Based on previous research, it was determined that performance changes in the countermovement jump (CMJ) would be a useful NM fatigue marker to assess the efficacy of CHO+PRO on the enhancement of functional NM recovery. Specifically, the CMJ is a sport-specific task sensitive to NM fatigue and has been linked with changes to physical performance in Australian rules football (ARF) that were perceived negatively by coaches for match performance. Identifying the optimal protocol for quantifying CMJs in field settings would enhance the utility of the CMJ as a marker of NM function. Therefore, the aim of this study was to examine the validity and reliability of the CMJ when measured using the portable GymAware (GA; Kinetic Performance Technologies, ACT, Australia) linear position transducer in four different set-up protocols. On two occasions, 14 professional cricketers performed one set of five CMJs in two different set-up protocols. All CMJs were simultaneously assessed using a force plate as the criterion measure, and with two GA units. In the dowel set-up, one GA unit was attached to the side of the dowel and positioned beneath this point, whilst the other GA was attached near the midpoint of the dowel and suspended overhead. In the waist set-up, both GA units were attached to a waist belt and positioned at different distances in front of the jumper. There were significant differences (p < 0.05) in all CMJ variables as measured by the GA compared to force plates, which were accompanied with substantial systematic biases and random errors. The coefficient of variation and intraclass correlation coefficients were ‚Äöv¢¬ß 10% and ‚Äöv¢‚Ä¢ 0.75, respectively, for most CMJ variables as measured by the force plate or the GA. It was concluded that in all four set-up protocols, the GA could reliably measure most CMJ variables and, therefore, be used effectively to assess changes in CMJ performances over time despite not being a valid measurement. Study 2: Most research exploring the recovery effect of supplemental CHO+PRO coingestion have induced fatigue using a single bout of endurance cycling and examined the potential recovery effects within a 24 h period. Therefore, findings from such studies have limited applicability to field-based team sport athletes wanting to restore baseline levels of performance during periods of congested training schedules or competition fixtures. As ARF is a physically demanding sport that induces significant levels of fatigue, the aim of this study was to investigate whether CHO+PRO ingestion during ARF matches and training sessions across a tournament in sub-elite junior athletes would improve recovery or cause gastrointestinal (GI) discomfort, compared to CHO alone. In this double-blinded nine-day long study, ARF players competing in a national youth tournament were randomised into either the CHO (n = 10) or CHO+PRO group (n = 11). Experimental supplements were provided during matches (day 2, day 5 and day 8) and training sessions (day 4 and day 7). CMJs, ratings of muscle soreness, autonomic function, and GI discomfort were assessed throughout the tournament. In the CHO+PRO group, median ranks of CMJ peak velocity and jump height increased from day 3 to day 8 and day 2 to day 5, respectively, but were unchanged throughout the tournament in the CHO group. In both groups, muscle soreness increased from day 1 and day 2 to day 3 but did not remain elevated. R-R intervals (time elapsed between successive peaks in QRS complexes) increased in both groups from day 2 to day 8. Post-match GI discomfort was not different between groups. It was concluded that ingestion of CHO+PRO during matches and training sessions across a tournament did not improve, nor impair recovery from fatigue, and did not cause GI discomfort, compared to CHO. It was theorised that participants‚ÄövÑv¥ daily diet was sufficiently high in PRO and this may have negated the potential recovery benefits from CHO+PRO. Conclusion: This thesis incorporates the first study to investigate how CHO+PRO ingestion during a field-based team sport impacts functional NM recovery and extends the limited CHO+PRO research conducted throughout multi-day events. Results indicated that CHO+PRO was neither beneficial nor detrimental to recovery, compared to CHO. Because GI comfort was not impaired by CHO+PRO, this recovery intervention may still have merit in certain situations, although further research is needed. This thesis also provides evidence to demonstrate that in four different set-up protocols, the GA can reliably measure a range of CMJ variables but does not provide valid measures.