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  • Author: Enrico Rejc x
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Effects of an Uphill Marathon on Running Mechanics and Lower-Limb Muscle Fatigue

Nicola Giovanelli, Paolo Taboga, Enrico Rejc, Bostjan Simunic, Guglielmo Antonutto and Stefano Lazzer

Purpose:

To investigate the effects of an uphill marathon (43 km, 3063-m elevation gain) on running mechanics and neuromuscular fatigue in lower-limb muscles.

Methods:

Maximal mechanical power of lower limbs (MMP), temporal tensiomyographic (TMG) parameters, and muscle-belly displacement (D m) were determined in the vastus lateralis muscle before and after the competition in 18 runners (age 42.8 ± 9.9 y, body mass 70.1 ± 7.3 kg, maximal oxygen uptake 55.5 ± 7.5 mL · kg−1 · min−1). Contact (t c) and aerial (t a) times, step frequency (f), and running velocity (v) were measured at 3, 14, and 30 km and after the finish line (POST). Peak vertical ground-reaction force (Fmax), vertical displacement of the center of mass (Δz), leg-length change (ΔL), and vertical (k vert) and leg (k leg) stiffness were calculated.

Results:

MMP was inversely related with race time (r = –.56, P = .016), t c (r = –.61, P = .008), and Δz (r = –.57, P = .012) and directly related with Fmax (r = .59, P = .010), t a (r = .48, P = .040), and k vert (r = .51, P = .027). In the fastest subgroup (n = 9) the following parameters were lower in POST (P < .05) than at km 3: t a (–14.1% ± 17.8%), Fmax (–6.2% ± 6.4%), k vert (–17.5% ± 17.2%), and k leg (–11.4% ± 10.9%). The slowest subgroup (n = 9) showed changes (P < .05) at km 30 and POST in Fmax (–5.5% ± 4.9% and –5.3% ± 4.1%), t a (–20.5% ± 16.2% and –21.5% ± 14.4%), t c (5.5% ± 7.5% and 3.2% ± 5.2%), k vert (–14.0% ± 12.8% and –11.8% ± 10.0%), and k leg (–8.9% ± 11.5% and –11.9% ± 12%). TMG temporal parameters decreased in all runners (–27.35% ± 18.0%, P < .001), while D m increased (24.0% ± 35.0%, P = .005), showing lower-limb stiffness and higher muscle sensibility to the electrical stimulus.

Conclusions:

Greater MMP was related with smaller changes in running mechanics induced by fatigue. Thus, lower-limb power training could improve running performance in uphill marathons.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 11 (2016): Issue 4 (Jan 2016)

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Concurrent Validity of GPS for Deriving Mechanical Properties of Sprint Acceleration

Ryu Nagahara, Alberto Botter, Enrico Rejc, Masaaki Koido, Takeshi Shimizu, Pierre Samozino and Jean-Benoit Morin

Purpose:

To test the concurrent validity of data from 2 different global positioning system (GPS) units for obtaining mechanical properties during sprint acceleration using a field method recently validated by Samozino et al.

Methods:

Thirty-two athletes performed maximal straight-line sprints, and their running speed was simultaneously measured by GPS units (sampling rate: 20 or 5 Hz) and either a radar or laser device (devices taken as references). Lower-limb mechanical properties of sprint acceleration (theoretical maximal force, theoretical maximal speed, maximal power) were derived from a modeling of the speed–time curves using an exponential function in both measurements. Comparisons of mechanical properties from 20- and 5-Hz GPS units with those from reference devices were performed for 80 and 62 trials, respectively.

Results:

The percentage bias showed a wide range of overestimation or underestimation for both systems (-7.9% to 9.7% and -5.1% to 2.9% for 20- and 5-Hz GPS), while the ranges of its 90% confidence limits for 20-Hz GPS were markedly smaller than those for 5-Hz GPS. These results were supported by the correlation analyses.

Conclusions:

Overall, the concurrent validity for all variables derived from 20-Hz GPS measurements was better than that obtained from the 5-Hz GPS units. However, in the current state of GPS devices’ accuracy for speed–time measurements over a maximal sprint acceleration, it is recommended that radar, laser devices, and timing gates remain the reference methods for implementing the computations of Samozino et al.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 12 (2017): Issue 1 (Jan 2017)

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Short-Term Effects of Rolling Massage on Energy Cost of Running and Power of the Lower Limbs

Nicola Giovanelli, Filippo Vaccari, Mirco Floreani, Enrico Rejc, Jasmine Copetti, Marco Garra, Lea Biasutti and Stefano Lazzer

Purpose: Self-myofascial release (SMFR) is a type of self-massage that is becoming popular among athletes. However, SMFR’s effects on running performance have not yet been investigated. The aim of this study was to evaluate the effects of SMFR on the cost of running (Cr). In addition, the authors evaluated the effects of SMFR on lower-limb muscle power. Methods: Cr and lower-limb muscle power during squat jump (SJ) and countermovement jump (CMJ) were measured before (PRE), immediately after (POST), and 3 h after (POST 3h) an SMFR protocol (experimental condition). In the control-condition testing session, the same measurements were performed without undergoing the SMFR protocol. Experimental and control conditions were tested in a randomized order. Results: Cr at POST trended to increase compared with PRE (+6.2% [8.3%], P = .052), whereas at POST 3h, Cr was restored to PRE values (+0.28% [9.5%], P = .950). In the experimental condition, no significant effect of time was observed for maximal power exerted during SJ. By contrast, maximal power exerted during CMJ at POST and at POST 3h was significantly higher than that observed at PRE (+7.9% [6.3%], P = .002 and +10.0% [8.7%], P = .004, respectively). The rate of force development measured during CMJ also increased after SMFR, reaching statistical significance at 200 ms from force onset at POST 3h (+38.9%, P = .024). Conclusions: An acute use of foam rollers for SMFR performed immediately prior to running may negatively affect endurance running performance, but its use should be added before explosive motor performances that include stretch-shortening cycles.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 13 (2018): Issue 10 (Nov 2018)

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Effects of the Etna Uphill Ultramarathon on Energy Cost and Mechanics of Running

Stefano Lazzer, Desy Salvadego, Paolo Taboga, Enrico Rejc, Nicola Giovanelli and Pietro E. di Prampero

Purpose:

To investigate the effects of an extreme uphill marathon on the mechanical parameters that are likely to affect the energy cost of running (Cr).

Methods:

Eleven runners (27–59 y) participated in the Etna SuperMarathon (43 km, 0–3063 m above sea level). Anthropometric characteristics, maximal explosive power of the lower limb (P max), and maximal oxygen uptake were determined before the competition. In addition, before and immediately after the race, Cr, contact (t c) and aerial (t a) times, step frequency (f), and running velocity were measured at constant self-selected speed. Then, peak vertical ground-reaction force (F max), vertical downward displacement of the center of mass (Δz), leg-length change (ΔL), and vertical (k vert) and leg (k leg) stiffness were calculated.

Results:

A direct relationship between Cr, measured before the race, and race time was shown (r = .61, P < .001). Cr increased significantly at the end of the race by 8.7%. Immediately after the race, the subjects showed significantly lower t a (–58.6%), f (–11.3%), F max (–17.6%), k vert (–45.6%), and k leg (–42.3%) and higher t c (+28.6%), Δz (+52.9%), and ΔL (+44.5%) than before the race. The increase of Cr was associated with a decrement in F max (r = –.45), k vert (r = –.44), and k leg (r = –.51). Finally, an inverse relationship between P max measured before the race and ΔCr during race was found (r = –.52).

Conclusions:

Lower Cr was related with better performance, and athletes characterized by the greater P max showed lower increases in Cr during the race. This suggests that specific power training of the lower limbs may lead to better performance in ultraendurance running competition.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 10 (2015): Issue 2 (Jan 2015)