Is There an Optimal Pole Length for Double Poling in Cross Country Skiing?

The aim of this study was to determine the effects of pole length on energy cost and kinematics in cross country double poling. Seven sub-elite male athletes were tested using pole sets of different lengths (ranging between 77% and 98% of participants' body height). Tests were conducted on a treadmill, set to a 2% incline and an approximate racing speed. Poling forces, contact times, and oxygen uptake were measured throughout the testing. Pole length was positively correlated with ground contact time (r = .57, p < .001) and negatively correlated with poling frequency (r = -.48, p = .003). Pole length was also positively correlated with pole recovery time and propulsive impulse produced per poling cycle (r = .36, p = .031; r = .35, p = .042, respectively). Oxygen uptake and pole length were negatively correlated (r = -.51, p = .004). This acute study shows that increasing pole length for double poling in sub-elite cross country skiers under the given conditions seems to change the poling mechanics in distinct ways, resulting in a more efficient poling action by decreasing an athlete's metabolic cost.

Quadrupedal Locomotion-Respiration Entrainment and Metabolic Economy in Cross-Country Skiers.

A 1:1 locomotion-respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics.

We, ourselves and us: Tensions of identity, intersubjectivity and positionality stemming from the people and dancefloors project.

Grounded in intersubjective participatory action research, the people and dancefloors project has sought to produce a space for the co-creation of knowledge about dancefloors and drug taking, building a platform for developing insights from the positionality of current drug users. Through film, it provides hermeneutic insight while legitimising their voices. In this paper, we share some reflections as researchers/users/activists arising from our involvement in the project. To begin with, we reflect on the motivations for the project, and the epistemic suppositions that animated it. This is followed by conversational style interviews where we re-evaluate our position in light of the project, with a particular focus on the tensions that drug use introduces between professional, personal and political domains in our lives. These reflections are useful to people who use drugs and hold privilege by nature of their social and cultural position. While questioning the silencing of personal experiences in relation to drug use, we also react to some of the traditional tendencies of academia, including institutionalised individualism, which isolates researchers and discourages them from finding political collectivity, and the subjectivist/objectivist dichotomy, which supports a tendency to objectify research participants while removing the self from the equation. Despite the challenges that arise from disentangling our multiple experiences and identities, our intersubjective dialogue inspires deeper learning about ourselves and each other, encouraging us towards a more openly political stance.

Foot structure and knee joint kinetics during walking with and without wedged footwear insoles.

The relationship between static foot structure characteristics and knee joint biomechanics during walking, or the biomechanical response to wedged insoles are currently unknown. In this study, 3D foot scanning, dual X-ray absorptiometry and gait analysis methods were used to determine structural parameters of the foot and assess their relation to knee joint loading and biomechanical response to wedged insoles in 30 patients with knee osteoarthritis. In multiple linear regression models, foot fat content, height of the medial longitudinal arch and static hind foot angle were not associated with the magnitude of the knee adduction moment (R2 = 0.24, p = 0.060), knee adduction angular impulse (R2 = 0.21, p = 0.099) or 3D resultant knee moment (R2 = 0.23, p = 0.073) during gait. Furthermore, these foot structure parameters were not associated with the patients' biomechanical response to medial or lateral wedge footwear insoles (all p < 0.01). These findings suggest that static foot structure is not associated with gait mechanics at the knee, and that static foot structure alone cannot be utilized to predict an individual's biomechanical response to wedged footwear insoles in patients with knee osteoarthritis.