Effects of hybrid custom foot orthoses on running economy, running mechanics and comfort: A double-blinded randomized crossover study

Objective

This study examined the effects of orthotic materials on running economy, running mechanics, and footwear comfort.

Design

A double-blinded randomized crossover study design was used.

Method

Eighteen athletes ran on an instrumented treadmill for six minutes at speeds corresponding to 10 % below their first ventilatory threshold (average: 9.9 ± 1.3 km/h) in four footwear conditions [control (CON), Ethyl vinyl acetate (EVA), Thermoplastic Polyurethane (TPU), and a combination of EVA and TPU (HYB)].

Results

No differences were found in running economy between conditions (p = 0.099). All custom foot orthoses materials reduced peak heel impact force vs CON (p < 0.001). TPU reduced hysteresis at heel impact vs CON (-47.8 %, p = 0.016). Shorter flight time (-3.8 %, p = 0.016; −3.1 %, p = 0.021) and lower mean vertical loading rate (-4.0 %, p = 0.003; −7.1 %, p < 0.001) occurred for HYB vs TPU and CON, respectively. Higher peak vertical loading rates (+7.4 %, p = 0.002) and earlier impact peaks (-5.7 %, p < 0.001) were found for HYB vs TPU. HYB exhibited longer propulsive phase duration (+2.0 %, p = 0.003) but lower peak propulsive force (-3.3 %, p = 0.009) vs CON. Reduced ‘overall comfort’ (-26.4 %, p = 0.004), ‘comfort of heel cushioning’ (-43.3 %, p < 0.001), and ‘comfort of forefoot cushioning’ (-18.3 %, p = 0.048) was found for HYB vs TPU, but ‘comfort of forefoot cushioning’ (+48.0 %, p = 0.032) showed an increase vs EVA.

Conclusions

Combining materials could enhance comfort during running causing subtle changes in running mechanics. Overall, neither EVA, TPU nor their combination significantly improved running economy compared to CON.