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Alex Stacoff, Xaver Kaelin, Edgar Stuessi and Bernhard Segesser

In the research of running shoes, excessive pronation is often related to various running injuries. Anatomically, pronation is a movement that occurs in more than one joint. Previous investigations that evaluated the pronation in running studied the movements of the lower leg and the rearfoot only. However, pronation could also be influenced by the movement of the forefoot and therefore depend on the torsional stiffness of the foot and of the shoe sole. This study investigated the relationship between the torsion and the pronation in running with a rearfoot touchdown and with a forefoot touchdown. The results show that, compared to running barefoot, running with a shoe decreases torsion and thereby increases pronation significantly (p < 0.01) for the forefoot and rearfoot touchdown conditions. Thus the reduction of torsional movement due to stiff shoe soles could well be a reason for running injuries caused by excessive pronation. It is concluded that modern running shoes could be designed to allow a certain torsional movement of the foot.

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Jeffery J. Summers, Victoria J. Machin and Gregory I. Sargent

This study was designed to examine some of the psychosocial factors underlying the recent marathon boom. A survey of 459 marathoners varying in age, sex, ability, and experience was conducted to assess their reasons for running a marathon, the outcomes derived, and their experiences during a marathon. Information was also sought regarding the psychological aspects of running in general, particularly the concept of addiction to running. Measures of addiction to running produced a consistent pattern of sex differences, with females evidencing higher levels of addiction than males. With respect to reasons for running a marathon and perceived outcomes, some interesting trends were evident as a function of age. It was suggested that the attraction of the marathon to people of all ages and abilities may lie partly in its unique ability to satisfy a wide range of needs, both extrinsic and intrinsic.

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Hugh Trenchard, Andrew Renfree and Derek M. Peters

Purpose:

Drafting in cycling influences collective behavior of pelotons. Although evidence for collective behavior in competitive running events exists, it is not clear if this results from energetic savings conferred by drafting. This study modeled the effects of drafting on behavior in elite 10,000-m runners.

Methods:

Using performance data from a men’s elite 10,000-m track running event, computer simulations were constructed using Netlogo 5.1 to test the effects of 3 different drafting quantities on collective behavior: no drafting, drafting to 3 m behind with up to ~8% energy savings (a realistic running draft), and drafting up to 3 m behind with up to 38% energy savings (a realistic cycling draft). Three measures of collective behavior were analyzed in each condition: mean speed, mean group stretch (distance between first- and last-placed runner), and runner-convergence ratio (RCR), which represents the degree of drafting benefit obtained by the follower in a pair of coupled runners.

Results:

Mean speeds were 6.32 ± 0.28, 5.57 ± 0.18, and 5.51 ± 0.13 m/s in the cycling-draft, runner-draft, and no-draft conditions, respectively (all P < .001). RCR was lower in the cycling-draft condition but did not differ between the other 2. Mean stretch did not differ between conditions.

Conclusions:

Collective behaviors observed in running events cannot be fully explained through energetic savings conferred by realistic drafting benefits. They may therefore result from other, possibly psychological, processes. The benefits or otherwise of engaging in such behavior are as yet unclear.

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Dietmar Wallner, Helmut Simi, Gerhard Tschakert and Peter Hofmann

Purpose:

To analyze the acute physiological response to aerobic short-interval training (AESIT) at various high-intensity running speeds. A minor anaerobic glycolytic energy supply was aimed to mimic the characteristics of slow continuous runs.

Methods:

Eight trained male runners (maximal oxygen uptake [VO2max] 55.5 ± 3.3 mL · kg−1 · min−1) performed an incremental treadmill exercise test (increments: 0.75 km · h−1 · min−1). Two lactate turn points (LTP1, LTP2) were determined. Subsequently, 3 randomly assigned AESIT sessions with high-intensity running-speed intervals were performed at speeds close to the speed (v) at VO2max (vVO2max) to create mean intensities of 50%, 55%, and 60% of vLTP1. AESIT sessions lasted 30 min and consisted of 10-s work phases, alternated by 20-s passive recovery phases.

Results:

To produce mean velocities of 50%, 55%, and 60% of vLTP1, running speeds were calculated as 18.6 ± 0.7 km/h (93.4% vVO2max), 20.2 ± 0.6 km/h (101.9% vVO2max), and 22.3 ± 0.7 km/h (111.0% vVO2max), which gave a mean blood lactate concentration (La) of 1.09 ± 0.31 mmol/L, 1.57 ± 0.52 mmol/L, and 2.09 ± 0.99 mmol/L, respectively. La at 50% of vLTP1 was not significantly different from La at vLTP1 (P = .8894). Mean VO2 was found at 54.0%, 58.5%, and 64.0% of VO2max, while at the end of the sessions VO2 rose to 71.1%, 80.4%, and 85.6% of VO2max, respectively.

Conclusion:

The results showed that AESIT with 10-s work phases alternating with 20 s of passive rest and a running speed close to vVO2max gave a systemic aerobic metabolic profile similar to slow continuous runs.

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Marc Sim, Brian Dawson, Grant Landers, Dorine W. Swinkels, Harold Tjalsma, Debbie Trinder and Peter Peeling

The effect of exercise modality and intensity on Interleukin-6 (IL-6), iron status, and hepcidin levels was investigated. Ten trained male triathletes performed 4 exercise trials including low-intensity continuous running (L-R), low-intensity continuous cycling (L-C), high-intensity interval running (H-R), and high-intensity interval cycling (H-C). Both L-R and L-C consisted of 40 min continuous exercise performed at 65% of peak running velocity (vVO2peak) and cycling power output (pVO2peak), while H-R and H-C consisted of 8 × 3-min intervals performed at 85% vVO2peak and pVO2peak. Venous blood samples were drawn pre-, post-, and 3 hr postexercise. Significant increases in postexercise IL-6 were seen within each trial (p < .05) and were significantly greater in H-R than L-R (p < .05). Hepcidin levels were significantly elevated at 3 hr postexercise within each trial (p < .05). Serum iron levels were significantly elevated (p < .05) immediately postexercise in all trials except L-C. These results suggest that, regardless of exercise mode or intensity, postexercise increases in IL-6 may be expected, likely influencing a subsequent elevation in hepcidin. Regardless, the lack of change in postexercise serum iron levels in L-C may indicate that reduced hemolysis occurs during weight-supported, low-intensity activity.

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Matthew F. Moran, Brendan J. Rickert and Beau K. Greer

Context:

Treadmills that unload runners via a differential air-pressure (DAP) bladder (eg, AlterG Anti-Gravity Treadmill) are commonly used to reduce effective body weight (BW) in a clinical setting. However, the relationship between the level of unloading and tibial stress is currently unknown.

Objective:

To determine the relationship between tibial impact acceleration and level of BW unloading during running.

Design:

Cross-sectional.

Setting:

University motion-analysis laboratory.

Participants:

15 distance runners (9 male, 6 female; 20.4 ± 2.4 y, 60.1 ± 12.6 kg).

Main Outcome Measures:

Peak tibial acceleration and peak-to-peak tibial acceleration were measured via a uniaxial accelerometer attached to the tibia during a 37-min continuous treadmill run that simulated reduced-BW conditions via a DAP bladder. The trial began with a 10-min run at 100% BW followed by nine 3-min stages where BW was systematically reduced from 95% to 60% in 5% increments.

Results:

There was no significant relationship between level of BW and either peak tibial acceleration or peak-to-peak tibial acceleration (P > .05). Both heart rate and step rate were significantly reduced with each 5% reduction in BW level (P < .01).

Conclusions:

Although ground-reaction forces are reduced when running in reduced-BW conditions on a DAP treadmill, tibial shock magnitudes are unchanged as an alteration in spatiotemporal running mechanics (eg, reduced step rate) and may nullify the unloading effect.

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Ben J. Lee and Charles Douglas Thake

mechanical strain and subjective pain imposed by ground reaction forces when walking or running without BWS are reduced. 4 , 5 In athletic groups, LBPP permits the use of natural gait patterns during rehabilitation and can also be used for overspeed running training. 6 By contrast, in aging, obese, and

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Michael S. Cherry, Sridhar Kota, Aaron Young and Daniel P. Ferris

Although there have been many lower limb robotic exoskeletons that have been tested for human walking, few devices have been tested for assisting running. It is possible that a pseudo-passive elastic exoskeleton could benefit human running without the addition of electrical motors due to the spring-like behavior of the human leg. We developed an elastic lower limb exoskeleton that added stiffness in parallel with the entire lower limb. Six healthy, young subjects ran on a treadmill at 2.3 m/s with and without the exoskeleton. Although the exoskeleton was designed to provide ~50% of normal leg stiffness during running, it only provided 24% of leg stiffness during testing. The difference in added leg stiffness was primarily due to soft tissue compression and harness compliance decreasing exoskeleton displacement during stance. As a result, the exoskeleton only supported about 7% of the peak vertical ground reaction force. There was a significant increase in metabolic cost when running with the exoskeleton compared with running without the exoskeleton (ANOVA, P < .01). We conclude that 2 major roadblocks to designing successful lower limb robotic exoskeletons for human running are human-machine interface compliance and the extra lower limb inertia from the exoskeleton.

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Konstantinos Tsintzas, Raymond Liu, Clyde Williams, Ian Campbell and George Gaitanos

Seven experienced endurance runners completed a 30-km road race on two occasions separated by 10 days. On each occasion the subjects consumed 250 ml of either a 5% carbohydrate (CHO) solution or nonflavored tap water (W) immediately prior to the start of the race, and 150 ml of the assigned fluid every 5 km thereafter. Performance time for the CHO trial was faster compared with the time recorded for the W trial (128.3 ± 19.9 min vs. 131.2 ± 18.7 min [p<0.01] respectively). Running speed was maintained throughout the race in the CHO trial, whereas a decrease in the running speed occurred after 25 km (p<0.05) in the W trial. No difference was found between the two trials in blood glucose concentration, plasma electrolyte concentrations, body weight loss, change in plasma volume, and rating of perceived exertion. Blood lactate concentration was higher at 25 km during the CHO trial compared with the W trial (p<0.01), but plasma FFA and glycerol concentrations were lower at 30 km during the CHO trial than during the W trial (p<0.05). In conclusion, this study shows that performance time for a 30-km road race is improved after ingesting a 5% CHO solution.

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Joanne L. Fallowfield, Clyde Williams and Rabindar Singh

Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. The present study examined the influence of ingesting a carbohydrate-electrolyte (CE) solution following prolonged running, on exercise capacity 4 hr later. Twelve men and 4 women were divided into two matched groups, which were randomly assigned to either a control (P) or a carbohydrate (CHO) condition. Both groups ran at 70% of maximal oxygen uptake (VO2max) on a level treadmill for 90 min or until volitional fatigue (R,), and they ran at the same %VO2max to exhaustion 4 hr later to assess endurance capacity (R2). The CHO group ingested a 6.9% CE solution providing 1.0 g CHO · kg body weight−1 immediately post-R, and again 2 hr later. The P group ingested equal volumes of a placebo solution. Run times (mean ± SEM) for Rj did not differ between the groups (P 86.3 ± 3.8 min; CHO 87.5 ± 2.5 min). The CHO group ran 22.2 (±3.5) min longer than the P group during R2 (P 39.8 ± 6.1 min; CHO 62.0 ± 6.2 min) (p < .05). Thus, ingesting a 6.9% carbohydrate-electrolyte beverage following prolonged, constant-pace running improves endurance capacity 4 hr later.