External load variables such as peak tibial acceleration (PTA), peak vertical ground reaction forces (GRF) and its instantaneous vertical loading rate (IVLR) may contribute to running injuries ...although evidence is conflicting given the influence of training load and tissue health on injuries. These variables are influenced by footwear, speed, surface and foot strike pattern during running. The purpose of this study was to assess the influence of four surfaces and two running speeds on external load variables in rearfoot strike (RFS) runners. Twelve RFS runners (confirmed with sagittal foot contact angle) completed a 2-min running bout on a treadmill and 50-m running bouts over the three surfaces (pavement, rubber track and grass) in standardised shoes at their preferred speed and 20% faster. PTA and vertical GRFs were collected using inertial measurement units and in-shoe force insoles. No interaction or surface effects were observed (p > 0.017). The faster speed produced greater axial PTA (+19.2%; p < 0.001), resultant PTA (+20.7%; p < 0.001), peak vertical GRF (+6.6%; p = 0.002) and IVLR (+16.5%; p < 0.001). These findings suggest that surface type does not influence PTA, peak vertical GRF and IVLR but that running faster increases the magnitude of these external loads regardless of surface type in RFS runners.
Carbohydrate (CHO) ingestion is an established nutritional strategy to improve endurance performance, yet currently available products may contribute to gastrointestinal (GI) distress. Potatoes have ...a high-glycemic index, indicating that their CHO content is readily available. We aimed to compare the effects of ingesting potato purée (POT), commercial CHO gel (GEL), or a control (water, CTL) during cycling on GI Symptoms and affective indices in trained athletes.
In a randomized crossover study, twelve trained cyclists (9 M and 3F; 30.5 ± 8.7y; 70.6 ± 7.6 kg; 1.70 ± 7 cm; 60.7 ± 8.9 mL/kg/min) completed a 2 h cycling challenge (60–85%VO2max) followed by a 6 kJ/kg time trial. Cyclists were randomly assigned to consume POT, GEL, or CTL during the challenge. Rating of perceived exertion (RPE), GI symptoms, and affective responses (Feeling Scale −5/+5) were collected throughout the challenge via visual analog scales. Differences between treatments were assessed by mixed model analysis of variance using time and condition as a fixed factor and subject as a random factor. All data represent mean ± standard deviation.
RPE was not different between POT, GEL, or CTL condition at the end of the cycling challenge (POT: 17 ± 1; GEL: 17 ± 1, CTL: 18 ± 1, P > 0.05). Higher GI symptoms (P < 0.01) were observed at the end of the challenge during POT condition (15 ± 3%) when compared to GEL (8 ± 3%) and CTL (7 ± 3%), with no significant difference in these symptoms prior to this time. FS response significantly increased (P = 0.04) during POT trial (2 ± 2) compared to GEL (0 ± 0.2) and CTL (0 ± 2) conditions at end of the challenge.
While POT ingestion resulted in greater GI distressed compared to CHO gel, cyclists perceived the exertion to be similar and even reported feeling more pleasant after POT ingestion in endurance exercise.
Alliance for Potato Research and Education.
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