The purpose of this study was to examine the association between nine measures of limb and trunk flexibility and running economy. Within a week prior to running economy assessment, and after 10 min of jogging at 3.13 m.s-1, 19 well-trained male sub-elite distance runners underwent two complete sets of lower limb and trunk flexibility assessments. Runners then completed two 10-min running economy assessment sessions on consecutive days at 4.13 m.s-1 following two 30-min sessions of treadmill accommodation at 4.13 m.s-1. Intraclass correlation coefficients indicated that the repeated flexibility measurements were highly reliable (X R = 0.92 +/- 0.09), as were the two running economy appraisals (R = 0.99). Correlational analyses revealed that dorsiflexion (r = 0.65) and standing hip rotation (r = 0.53) were significantly (P< or = 0.05) associated with the mean aerobic demand of running, such that runners who were less flexible on these measures were more economical. Although speculative, these results suggest that inflexibility in certain areas of the musculoskeletal system may enhance running economy in sub-elite male runners by increasing storage and return of elastic energy and minimizing the need for muscle-stabilizing activity.

No abstract

To assess whether distance runners displaying uneconomical freely chosen step lengths (FCSL) could be trained to shift FCSL toward a more optimal setting, six males and three females who exhibited uneconomical FCSL [mean optimal step length (OSL) = -9.81% of leg length from FCSL; mean change in oxygen uptake (VO2) (FCSL - OSL) = 1.46 ml.kg-1.min-1] comprised an experimental group that completed 15 treadmill sessions (30 min/day, 5 days/wk, 3 wk) of OSL training at individually determined running velocities (2.87-3.74 m/s). Training sessions featured alternating 5-min periods of combined audio and visual feedback matching OSL and no feedback. A control group of three subjects with uneconomical FCSL (2 males, 1 female) performed 3 wk of treadmill running without feedback. The extent of step length optimization was evaluated by comparing pre- and posttraining differences between FCSL and OSL and between pre- and posttraining VO2. Compared with the control group, the experimental group demonstrated a significantly (P < or = 0.05) greater relative shift in FCSL toward OSL and a marked reduction in FCSL VO2. Taken together, these results suggest that short-term audiovisual feedback training can be effective in optimizing step length and producing a decrease in aerobic demand among distance runners exhibiting uneconomical FCSL.

Relationships between running economy (RE; submaximal VO(2) for a given running speed) and the temporal EMG characteristics of bi-articular leg muscles were quantified in a group of well-trained runners. Nine subjects completed three test sessions: a determination of maximal aerobic demand (VO(2)max); an accommodation session at the experimental speed of 4.13 m.s(-1) and a session during which EMG and RE data were collected simultaneously at the experimental speed of 4.13 m.s(-1) Measures of muscle onset, on-time durations, and on-time coactivation durations were calculated from the following muscles: rectus femoris, medial hamstrings, lateral hamstrings, and gastrocnemius. Nonparametric correlations between RE and EMG characteristics displayed both positive and negative relationships and exhibited a wide range of values. Two EMG measures were significantly correlated (r > 0.67) with RE. Earlier onset of rectus femoris during swing phase and a shorter duration of hamstring - gastrocnemius coactivation during swing were associated with more economical runners. Although not statistically significant, correlation coefficients calculated for measures of coactivation during stance and RE ranged from -0.42 to -0.65. This trend indicates that individuals who exhibited a greater amount of coactivation between bi-articular muscles during the stance phase of the running cycle tended to be more economical. These relationships suggest different activation patterns in bi-articular muscles between economical and uneconomical runners.

No abstract

Although running economy (RE) is an important physiological characteristic associated with superior distance running performance, little is known about the potential psychological correlates of RE. Therefore, the current study examined the relationship of anxiety and self-attention to RE. Anxiety was measured with the Sport Competition Anxiety Test (SCAT; Martens, 1977) and the Trait Anxiety Inventory (TAI; Spielberger et al., 1970). Self-attention was assessed with the Private Self-Consciousness (PSC) subscale of the Self-Consciousness Scale Revised (SCSR; Scheier and Carver, 1985). Running economy was determined by the oxygen cost of running at a submaximal velocity of 4.13 m s-1 (< 80% of maximal aerobic capacity). The subjects were 18 competitive male distance runners (mean 10-km race time 34.17 min). No relationship was found between anxiety (SCAT: r = -0.18, N.S.; TAI: r = -0.17, N.S.) and RE. However, PSC and RE were related (r = 0.50, P < 0.05), suggesting that runners who habitually directed attention inwards were also the most economical. Runners high in PSC may have been more economical because they were sensitive to muscle tension interfering with performance and subsequently employed relaxation techniques to reduce tension. Additionally, they may have employed cognitive techniques aimed at increasing RE such as positive self-talk and associative strategies. Despite the tenability of these explanations, the association between PSC and RE should be interpreted cautiously due to the small sample size.

The purpose of this study was to quantify daily intra-individual variability in mean step length, a basic descriptor for the running pattern. Following 60 minutes of treadmill accommodation, nine trained male subjects (X age = 34.2 yrs +/- 7.2, X VO2max = 57.0 +/- 4.8 ml.kg-1.min-1) performed daily (Mon-Fri) 6-minute treadmill runs at three submaximal speeds (2.68, 3.13 and 3.58 m.s-1) over a 4-week period. To minimize extraneous influences, subjects refrained from road racing and completed the 20 running sessions (5 d.wk-1.4 weeks for each speed) at the same time of day and in the same footwear. Treadmill velocity was calibrated for each 6-minute running bout and step length was determined during the last 2 minutes of each run. Results indicated that mean step length and coefficient of variation values were 0.984 m and 2.50% at 2.68 m.s-1, 1.124 m and 2.22% at 3.13 m.s-1, and 1.254 m and 2.26% at 3.58 m.s-1. Reliability analyses indicated that the percentage of variation accounted for in step length across all speeds was high and improved very little as test number increased (range = 96% for two days vs 99% for five days). Taken together, these findings suggest that when testing conditions are controlled, within-subject variability in step length measures obtained at multiple submaximal running speeds is small in trained subjects and that criterion step length values can be obtained by averaging duplicate measurements.

Following treadmill accommodation and a 3-day period of tapered running, ten well-trained male distance runners [x maximum oxygen uptake (VO2max) = 71.3 ml.kg-1.min-1] performed two 10-min level treadmill runs designed to assess running economy at 90% VO2max. Video recordings were obtained during the last minute of each run to quantify selected gait descriptors. Two to 3 days following the second economy run, each subject completed 30 min of high-intensity (HI) running at 90% VO2max. One 2, and 4 days after the HI run, subjects repeated the 10-min economy runs. Compared to pre HI-run values, no significant change (P > 0.05) in running economy was observed during the post-HI runs. Biomechanical analyses also revealed that running style remained unaltered after the HI run. These results support earlier findings obtained on moderately trained subjects featuring measurement of running economy and gait mechanics at less-demanding intensities and suggest that among well-trained athletes, 30 min of HI running does not elicit an increase in VO2 or disrupt gait mechanics over the short term in subsequent distance runs performed at near-maximal speeds.