ABSTRACT
PURPOSE/BACKGROUND: Muscle fatigue is related to a decline in force output and proprioception. These can ultimately have an adverse effect on neuromuscular control and functional performance. Local muscle fatigue has been shown to have adverse consequences on dynamic standing balance; however, much less is known regarding the relationship between distant fatigue and dynamic standing. The purpose of this study was to investigate the effects of upper body fatigue on dynamic standing balance. It was hypothesized that distant fatigue in upper body musculature would show a significant decrease in dynamic standing balance as assessed by the Lower Quarter Y-Balance Test (YBT-LQ). METHODS: TWENTY HEALTHY INDIVIDUALS (AGE: 25.0 ± 3.42 years, height: 172.72 ± 13.11 cm, mass: 71.36 ± 13.50 kg) participated in this study. A kayak ergometer was used to implement a fatigue protocol for the upper body. The protocol consisted of a graded intensity session ranging from 50% to 90% of maximum effort lasting ten minutes in duration (2 minutes each at 50% 60%, 70%, 80%, and 90%). The anterior (ANT), posteromedial (PM), and posterolateral (PL) reach directions were normalized to leg length and measured on the YBT-LQ before and after the fatigue protocol for each participant. A fourth value termed overall balance was calculated as the sum of the furthest reach distance of the three directions. Blood lactate analysis taken before and immediately after the fatigue protocol was used to quantify fatigue. Multiple paired t-tests were performed for pre-fatigue and post-fatigue balance assessment. A Bonferroni correction was applied to set the significance value ≤0.0125 a priori. Effect size was calculated using the effect size index. RESULTS: Blood lactate values immediately following the fatigue protocol had an average concentration of 6.15 millimoles (pre: 2.3, post: 8.4). The ANT reach direction (ρ = 0.004) and the calculated overall balance (ρ = 0.011) significantly decreased post-fatigue in the dominant lower extremity. No significant differences were found for the PM (ρ = 0.017) or PL (ρ = 0.021) directions. The ANT reach direction (0.64) and overall balance (0.44) also showed a moderate effect size based on the effect size index. CONCLUSIONS: ANT and overall dynamic standing balance were negatively affected after completing the upper body fatigue protocol. The findings of this research demonstrate that upper body fatigue has adverse effects on dynamic standing balance, as measured by performance on the YBT-LQ. Significant and clinically relevant differences were noted in ANT and overall dynamic standing balance. CLINICAL RELEVANCE: Physical therapists should be aware of the adverse influence distant fatigue may exhibit on neuromuscular control in muscles not actively involved in the fatiguing exercise. The balance deficits noted may indicate an increased risk of injury with muscle fatigue in muscles not directly contributing to standing balance. LEVEL OF EVIDENCE: 3b, Case-control study.
ABSTRACT
BACKGROUND: Since anthropometric variables are critical to the creation of pulmonary nomograms for FVC, FEV1, and other volumes and capacities, it is logical that anthropometric variables also influence the values of the maximal respiratory pressures (MRPs). Since nomograms are race-specific, it is important that tribe-specific tables of normal maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) be developed. To date normal tables for MRPs do not exist for Navajo children. OBJECTIVE: Therefore the purpose of this study was to derive MRP normative reference values for Navajo children in the age range of 6-14 years. METHODS-PARTICIPANTS AND MEASUREMENTS: A cross-sectional study was undertaken with a representative sample of 534 healthy children, ages 6-14 years, attending Navajo Nation elementary schools in Arizona. MIP and MEP were measured. RESULTS: Test results from 275 girls and 259 boys met American Thoracic Society quality control standards and showed that MRPs all increased with height. Mean MIP in cm H2 O was 77 for boys and 67 for girls with lower limits of 44 and 40, respectively. Mean MEP in cm H2 O was 75 for boys and 66 for girls with the lower limits of 42 and 38, respectively. CONCLUSION: Since the data were collected from the population of interest, the resulting MIP and MEP reference equations should be used when testing Navajo children ages 6-14 years.