Influence of running shoes on muscle activity

A methodological proof-of-concept of the teeter-totter effect

The Nike Vaporfly 4% (VP4) shoe is popular due to its unique design and reported performance benefits. However, the underlying mechanisms responsible for the improvements remain unclear. One proposed mechanism is the teeter-totter effect. This study aimed to 1) experimentally test the teeter-totter theory by estimating the teeter-totter moment (MTT) in the VP4 compared to a flat shoe (CONTROL) and 2) quantify the change in the anterior-posterior position of the centre of pressure (Δxa-p) in the VP4 compared to the CONTROL. Plantar pressures and high-speed video were recorded from 15 runners in two shoe conditions. The VP4 generated a larger propulsion moment, MP, (∫ M P dt  = 90.46 ± 38.87 Nms; p < 0.001, d = 1.95), suggesting the presence of an MTT in the VP4 (∫ M TT dt  = 57.16 ± 24.35 Nms) when compared to the CONTROL (∫ M P dt  = 33.30 ± 14.52 Nms). Δxa-p was greater in the VP4 (Δxa-p = 9.48 ± 6.08 mm; p < 0.001, d = 2.07) compared to the CONTROL (Δxa-p = 0.54 ± 0.67 mm). This study provides a methodological proof-of-concept for the teeter-totter theory. The findings highlight the possibility of a teeter-totter effect resulting in greater heel propulsion while running in an AFT shoe construction, assuming a constant muscle moment and pivot point.

A four-week minimalist shoe walking intervention influences foot posture and balance in young adults-a randomized controlled trial

INTRODUCTION

Minimalist shoes (MS) are beneficial for foot health. The foot is a part of the posterior chain. It is suggested that interventions on the plantar foot sole also affect the upper segments of the body. This study aimed to investigate the local and remote effects along the posterior chain of four weeks of MS walking in recreationally active young adults.

METHODS

28 healthy participants (15 female, 13 male; 25.3 ± 5.3 years; 70.2 ± 11.9 kg; 175.0 ± 7.8 cm) were randomly assigned to a control- or intervention group. The intervention group undertook a four-week incremental MS walking program, which included 3,000 steps/day in the first week, increasing to 5,000 steps/day for the remaining three weeks. The control group walked in their preferred shoe (no MS). We assessed the following parameters in a laboratory at baseline [M1], after the four-week intervention [M2], and after a four-week wash-out period [M3]: Foot parameters (i.e., Foot Posture Index-6, Arch Rigidity Index), static single-leg stance balance, foot-, ankle-, and posterior chain range of motion, and muscle strength of the posterior chain. We fitted multiple hierarchically built mixed models to the data.

RESULTS

In the MS group, the Foot Posture Index (b = -3.72, t(51) = -6.05, p < .001, [-4.94, 2.51]) and balance (b = -17.96, t(49) = -2.56, p = .01, [-31.54, 4.37]) significantly improved from M1 to M2, but not all other parameters (all p >.05). The improvements remained at M3 (Foot Posture Index: b = -1.71, t(51) = -2.73, p = .009, [-4,94,0.48]; balance: b = -15.97, t(49) = -2.25, p = .03, [-29.72, 2.21]).

DISCUSSION

Walking in MS for four weeks might be advantageous for foot health of recreationally active young adults but no chronic remote effects should be expected.

The influence of running shoes on familiarization time for treadmill running biomechanics evaluation

This study investigated treadmill familiarisation time in different shoe conditions by comparing lower limb consecutive kinematics waveforms using a trend symmetry method to calculate trend symmetry index, range amplitude ratio and range offset. Eighteen young adults (26.6 ± 3.3 years, 7 females) completed three 10-minute running trials at their preferred running speed (2.30 ± 0.17 m/s) on a treadmill with three shoe conditions (i.e., usual, minimalist and maximalist shoes) in a random order. Sagittal lower limb kinematic data were recorded using inertial measurement units. The results showed that sagittal-plane kinematic waveforms in the hip, knee and ankle remained consistent (trend symmetry > 0.95) without extreme excursions (range amplitude ratio ≈ 1) over 10 minutes within each testing shoe condition. Significant time × shoe interaction effect was observed in range offset (i.e., absolute differences in the average degree of kinematic waveforms between consecutive minutes) at ankle (p = 0.029, ŋ_p² = 0.096) and knee (p = 0.002, ŋ_p² = 0.126). Post-hoc analysis suggested that running with novel shoes required a shorter time to achieve stable lower limb kinematics (2 to 3 minutes) compared with usual shoes (7 minutes). In conclusion, young healthy adults need up to 3 and 7 minutes to familiarise to the treadmill when running at their preferred speed with their novel and usual running shoes.

A escolha do calçado por corredores amadores: caracterização e associação com o histórico de lesão auto reportada

RESUMO O calçado é um elemento importante para a prática de corrida. As evidências sobre os impactos das características do calçado e de sua prescrição nas lesões de corredores são restritas. Dessa forma, os objetivos deste estudo foram investigar o processo de escolha do calçado por corredores e verificar se variáveis relacionadas ao calçado e seu processo de escolha estavam associadas à presença e recorrência de lesão no último ano. Foi realizado um estudo observacional com 254 corredores que responderam um questionário autoadministrado sobre características demográficas, a prática esportiva, o calçado e o processo de sua escolha, e lesões ocorridas nos últimos 12 meses. O teste qui-quadrado foi empregado para verificar se havia diferença na distribuição das respostas de cada questão, enquanto o teste de regressão logística para verificar se as variáveis relacionadas ao calçado e ao processo de escolha predizem a presença e recorrência de lesão no último ano. Os resultados indicaram que a maioria dos corredores possui tênis específico para a prática esportiva e considera algumas características ao adquiri-lo, como o amortecimento intermediário e a diferença na altura do solado entre a parte posterior e a anterior de aproximadamente 10mm. A maioria indica conhecer seu tipo de pisada, mas não a considera na escolha do calçado. Além disso, a maioria não usa palmilha e não recebeu orientação para a escolha do calçado. O modelo obtido com a regressão não foi significativo. Assim, apesar de os corredores considerarem as características do calçado ao adquiri-lo, essas características e o processo de escolha não foram associados à presença e recorrência de lesão nos últimos 12 meses.

Selection of running shoes by amateur runners: characterization and association with the self-reported history of injury

ABSTRACT Running shoes are an essential element for sports practice. Evidence on the effect of the shoe characteristics and prescription in running injuries are scarce. Thus, this study aimed to investigate runners's process of choosing running shoes and to verify whether the variables related to running shoes and their selection process are associated with the presence and recurrence of injuries in the previous year. An observational study was conducted with 254 runners who answered a self-reported questionnaire about demographics, sports practice, shoe characteristics and selection criteria, and injuries in the last 12 months. The chi-square test evaluated whether there was a difference in the distribution of answers to each question. The logistic regression evaluated whether the variables related to shoes and selection criteria predicted injury’s presence and recurrence in the previous year. The results showed that most runners had specific shoes for sports practice and considered some characteristics of the shoes to choose them, including intermediate cushioning and a difference in the heel-to-toe drop of approximately 10mm. Most respondents indicated knowing their foot type but not considering it when choosing shoes. Besides, most individuals did not use foot orthotics and did not receive guidance to select their shoes. The model obtained with the regression was not significant. Therefore, despite considering shoe characteristics when choosing it, these features and the selection criteria were not associated with the presence and recurrence of injuries in the previous 12 months.

Systematic reduction of leg muscle activity throughout a standard assessment of running footwear

PURPOSE

This study aimed to investigate whether there is a systematic change of leg muscle activity, as quantified by surface electromyography (EMG), throughout a standard running footwear assessment protocol at a predetermined running speed.

METHODS

Thirty-one physically active adults (15 females and 16 males) completed 5 testing rounds consisting of overground running trials at a speed of 3.5 m/s. The level of muscle activity from 6 major leg muscles was recorded using surface EMG. The variables assessed were the EMG total intensity as a function of time and the cumulative EMG overall intensity. Systematic effects of the chronological testing round (independent variable) on the normalized EMG overall intensity (dependent variable) were examined using Friedman analysis of variates and post hoc pairwise Wilcoxon signed-rank tests (α = 0.05).

RESULTS

There was a systematic reduction in overall EMG intensity for all 6 muscles over the time course of the running protocol (p < 0.001) until the fourth testing round when EMG intensities reached a steady state. The one exception was the biceps femoris muscle, which showed a significant reduction of EMG intensity during the stance phase (p < 0.001) but not the swing phase (p = 0.16).

CONCLUSION

While running at a predetermined speed, the neuromuscular system undergoes an adaptation process characterized by a progressive reduction in the activity level of major leg muscles. This process may represent an optimization strategy of the neuromuscular system towards a more energetically efficient running style. Future running protocols should include a familiarization period of at least 7 min or 600 strides of running at the predetermined speed.

Comparison of Joint Kinematics in Transition Running and Isolated Running in Elite Triathletes in Overground Conditions

Triathletes often experience incoordination at the start of a transition run (TR); this is possibly reflected by altered joint kinematics. In this study, the first 20 steps of a run after a warm-up run (WR) and TR (following a 90 min cycling session) of 16 elite, male, long-distance triathletes (31.3 ± 5.4 years old) were compared. Measurements were executed on the competition course of the Ironman Frankfurt in Germany. Pacing and slipstream were provided by a cyclist in front of the runner. Kinematic data of the trunk and leg joints, step length, and step rate were obtained using the MVN Link inertial motion capture system by Xsens. Statistical parametric mapping was used to compare the active leg (AL) and passive leg (PL) phases of the WR and TR. In the TR, more spinal extension (~0.5–1°; p = 0.001) and rotation (~0.2–0.5°; p = 0.001–0.004), increases in hip flexion (~3°; ~65% AL−~55% PL; p = 0.001–0.004), internal hip rotation (~2.5°; AL + ~0–30% PL; p = 0.001–0.024), more knee adduction (~1°; ~80–95% AL; p = 0.001), and complex altered knee flexion patterns (~2–4°; AL + PL; p = 0.001–0.01) occurred. Complex kinematic differences between a WR and a TR were detected. This contributes to a better understanding of the incoordination in transition running.