Comparison of Physiological Variables Between the Elliptical Bicycle and Run Training in Experienced Runners

Influence of Body Mass on Running-Induced Changes in Mechanical Properties of Plantar Fascia

ABSTRACT

Shiotani, H, Mizokuchi, T, Yamashita, R, Naito, M, and Kawakami, Y. Influence of body mass on running-induced changes in mechanical properties of plantar fascia. J Strength Cond Res 37(11): e588-e592, 2023-Body mass is a major risk factor for plantar fasciopathy; however, evidence explaining the process between risk factors and injury development is limited. Long-distance running induces transient and site-specific reduction in plantar fascia (PF) stiffness, reflecting mechanical fatigue and microscopic damage within the tissue. As greater mechanical loads can induce greater reduction in tissue stiffness, we hypothesized that the degree of running-induced change in PF stiffness is associated with body mass. Ten long-distance male runners (age: 21 - 23 years, body mass: 55.5 ± 4.2 kg; mean ± SD ) and 10 untrained men (age: 20 - 24 years, body mass: 58.4 ± 5.6 kg) ran for 10 km. Before and immediately after running, the shear wave velocity (SWV) of PF at the proximal site, which is an index of tissue stiffness, was measured using ultrasound shear wave elastography. Although the PF SWV significantly decreased after running in runners (-4.0%, p = 0.010) and untrained men (-21.9%, p < 0.001), runners exhibited smaller changes ( p < 0.001). The relative changes in SWV significantly correlated with body mass in both runners ( r = -0.691, p = 0.027) and untrained individuals ( r = -0.723, p = 0.018). These results indicate that a larger body mass is associated with a greater reduction in PF stiffness. Our findings provide in vivo evidence of the biomechanical basis for body mass as a risk factor for plantar fasciopathy. Furthermore, group differences suggest possible factors that reduce the fatigue responses, such as adaptation enhancing the resilience of PF and running mechanics.

Applicability of Dmax Method on Heart Rate Variability to Estimate the Lactate Thresholds in Male Runners

Introduction

The purpose of this study was to evaluate the application of the Dmax method on heart rate variability (HRV) to estimate the lactate thresholds (LT), during a maximal incremental running test (MIRT).

Methods

Nineteen male runners performed two MIRTs, with the initial speed at 8 km·h^-1 and increments of 1 km·h^-1 every 3 minutes, until exhaustion. Measures of HRV and blood lactate concentrations were obtained, and lactate (LT₁ and LT₂) and HRV (HRVT_DMAX1 and HRVT_DMAX2) thresholds were identified. ANOVA with Scheffe's post hoc test, effect sizes (d), the bias ± 95% limits of agreement (LoA), standard error of the estimate (SEE), Pearson's (r), and intraclass correlation coefficient (ICC) were calculated to assess validity.

Results

No significant differences were observed between HRVT_DMAX1 and LT₁ when expressed for speed (12.1 ± 1.4 km·h^-1 and 11.2 ± 2.1 km·h^-1; p=0.55; d = 0.45; r = 0.46; bias ± LoA = 0.8 ± 3.7 km·h^-1; SEE = 1.2 km·h^-1 (95% CI, 0.9-1.9)). Significant differences were observed between HRVT_DMAX2 and LT₂ when expressed for speed (12.0 ± 1.2 km·h^-1 and 14.1 ± 2.5 km·h^-1; p=0.00; d = 1.21; r = 0.48; bias ± LoA = -1.0 ± 1.8 km·h^-1; SEE = 1.1 km·h^-1 (95% CI, 0.8-1.6)), respectively. Reproducibility values were found for the LT₁ (ICC = 0.90; bias ± LoA = -0.7 ± 2.0 km·h^-1), LT₂ (ICC = 0.97; bias ± LoA = -0.1 ± 1.1 km·h^-1), HRVT_DMAX1 (ICC = 0.48; bias ± LoA = -0.2 ± 3.4 km·h^-1), and HRVT_DMAX2 (ICC = 0.30; bias ± LoA = 0.3 ± 3.5 km·h^-1).

Conclusions

The Dmax method applied over a HRV dataset allowed the identification of LT₁ that is close to aerobic threshold, during a MIRT.

Gait biomechanics of skipping are substantially different than those of running

The inherit injury risk associated with high-impact exercises calls for alternative ways to achieve the benefits of aerobic exercise while minimizing excessive stresses to body tissues. Skipping presents such an alternative, incorporating double support, flight, and single support phases. We used ground reaction forces (GRFs), lower extremity joint torques and powers to compare skipping and running in 20 healthy adults. The two consecutive skipping steps on each limb differed significantly from each other, and from running. Running had the longest step length, the highest peak vertical GRF, peak knee extensor torque, and peak knee negative and positive power and negative and positive work. Skipping had the greater cadence, peak horizontal GRF, peak hip and ankle extensor torques, peak ankle negative power and work, and peak ankle positive power. The second vs first skipping step had the shorter step length, higher cadence, peak horizontal GRF, peak ankle extensor torque, and peak ankle negative power, negative work, and positive power and positive work. The first skipping step utilized predominately net negative joint work (eccentric muscle action) while the second utilized predominately net positive joint work (concentric muscle action). The skipping data further highlight the persistence of net negative work performed at the knee and net positive work performed at the ankle across locomotion gaits. Evidence of step segregation was seen in distribution of the braking and propelling impulses and net work produced across the hip, knee, and ankle joints.

CONCLUSIONS

Skipping was substantially different than running and was temporally and spatially asymmetrical with successive foot falls partitioned into a dominant function, either braking or propelling whereas running had a single, repeated step in which both braking and propelling actions were performed equally.

Metabolic and Mechanical Effects of Laddermill Graded Exercise Testing

Allerton, TD, Earnest, CP, and Johannsen, NM. Metabolic and mechanical effects of laddermill graded exercise testing. J Strength Cond Res 32(1): 195-200, 2018-The purpose of this study was to compare the metabolic responses and mechanical impact forces during a maximal graded exercise test (GXT) on a laddermill (LM) vs. a standard treadmill (TM). Twenty college-aged men (n = 10) and women completed a GXT on the TM and LM in random order. During the GXT, expired gases (V[Combining Dot Above]O2 and V[Combining Dot Above]CO2), heart rate, accelerometer data, blood lactate (BLa), and rating of perceived exertion (RPE) were collected in the last minute of each stage. Data were analyzed by paired t-tests and presented herein as mean ± SD. Treadmill exercise resulted in a higher V[Combining Dot Above]O2peak than LM exercise (45.6 ± 7.5 vs. 41.2 ± 5.6 ml·kg·min, p < 0.001). Blood lactate threshold was similar (p = 0.2) between LM (62 ± 17% V[Combining Dot Above]O2peak) and TM (68 ± 1% V[Combining Dot Above]O2peak). The average activity level experienced during LM (0.14 ± 0.04 vector magnitude unit [VMU]) exercise was lower (p < 0.0001) vs. TM (0.67 ± 0.01 VMU). Additionally, impact forces were reduced (p < 0.005) from the vertical plane during LM (-0.46 ± 0.12g) compared with TM (-0.81 ± 0.06g) exercise. Our results suggest that the nature of LM exercise does not elicit the same V[Combining Dot Above]O2peak response observed during TM exercise. However, impact forces were reduced and energy expenditure remained higher during LM testing, whereas RPE was similar between modalities. LM exercise may provide an alternative to individuals seeking to incur a negative energy balance, but to whom higher impact forces are detrimental.