ABSTRACT
Running economy (RE) is defined as the oxygen consumption (VO2) or caloric unit cost required to move at a specific velocity and is an important performance marker. Ground contact time (GCT) has been associated with RE; however, it has not been established how GCT imbalances between feet impact RE. PURPOSE: Determine the relationship between cadence, GCT, and GCT imbalances and RE. METHODS: 11 NCAA Division I distance runners (7 male) completed a graded exercise test on a treadmill to determine lactate threshold (LT) and VO2max. Body composition was also assessed via DEXA. Subjects ran with a heart rate monitor capable of measuring cadence, GCT, and GCT balance between feet. VO2 and respiratory exchange ratio were recorded over the last minute of the 5-minute stages. RE expressed as caloric unit cost (kcal·kg-1·km-1) was calculated for the stage determined to be just below the LT (prior to > 4mmol/L) and was correlated with cadence, GCT, and GCT imbalance by Pearson correlations. RESULTS: Pearson correlations between RE and the running dynamics measures were as follows: cadence (r = -.444, p = .171), GCT (r = .492, p = .125), GCT Imbalance (r = .808, p < .005). An independent t-test revealed greater (p = .023) leg lean mass imbalances in runners with larger GCT imbalances compared to runners with smaller GCT imbalances. CONCLUSION: GCT imbalances are strongly related to impaired RE. Future research should determine how to improve GCT imbalances and if doing so improves RE.
ABSTRACT
The click-evoked auditory brainstem response (ABR) is widely used in clinical settings, partly due to its predictability and high test-retest consistency. More recently, the speech-evoked ABR has been used to evaluate subcortical processing of complex signals, allowing for the objective assessment of biological processes underlying auditory function and auditory processing deficits not revealed by responses to clicks. Test-retest reliability of some components of speech-evoked ABRs has been shown for adults and children over the course of months. However, a systematic study of the consistency of the speech-evoked brainstem response in school-age children has not been conducted. In the present study, speech-evoked ABRs were collected from 26 typically-developing children (ages 8-13) at two time points separated by one year. ABRs were collected for /da/ presented in quiet and in a 6-talker babble background noise. Test-retest consistency of response timing, spectral encoding, and signal-to-noise ratio was assessed. Response timing and spectral encoding were highly replicable over the course of one year. The consistency of response timing and spectral encoding found for the speech-evoked ABRs of typically-developing children suggests that the speech-evoked ABR may be a unique tool for research and clinical assessment of auditory function, particularly with respect to auditory-based communication skills.
