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The "bilateral deficit" during explosive efforts of the lower limbs. On its causes and on its changes by bed rest
No full textEffects of Bilateral or Unilateral Plyometric Training of Lower Limbs on the Bilateral Deficit During Explosive Efforts
No full textObjectives: Bilateral Deficit (BLD) occurs when the force generated by both limbs together is smaller than the sum of the forces developed separately by the two limbs. BLD may be modulated by physical training. Here, were investigated the effects of unilateral or bilateral plyometric training on BLD and neuromuscular activation during lower limb explosive extensions. Methods: Fourteen young males were randomized into the unilateral (UL_) or bilateral (BL_) training group. Plyometric training (20 sessions, 2 days/week) was performed on a sled ergometer, and consisted of UL or BL consecutive, plyometric lower limb extensions (3-to-5 sets; 8-to-10 repetitions). Before and after training, maximal explosive efforts with both lower limbs or with each limb separately were assessed. Electromyography of representative lower limb muscles was measured. Results: BL_training significantly and largely decreased BLD (p=0.003, effect size=1.63). This was accompanied by the reversion from deficit to facilitation of the electromyography amplitude of knee extensors during bilateral efforts (p=0.007). Conversely, UL_training had negligible effects on BLD (p=0.781). Also, both groups showed similar improvements in their maximal explosive power generated after training. Conclusions: Bilateral plyometric training can mitigate BLD, and should be considered for training protocols focused on improving bilateral lower limb motor performance
Effects of Bilateral or Unilateral Plyometric Training of Lower Limbs on the Bilateral Deficit During Explosive Efforts
Full text linkObjectives: Bilateral Deficit (BLD) occurs when the force generated by both limbs together is smaller than the sum of the forces developed separately by the two limbs. BLD may be modulated by physical training. Here, were investigated the effects of unilateral or bilateral plyometric training on BLD and neuromuscular activation during lower limb explosive extensions. Methods: Fourteen young males were randomized into the unilateral (UL_) or bilateral (BL_) training group. Plyometric training (20 sessions, 2 days/week) was performed on a sled ergometer, and consisted of UL or BL consecutive, plyometric lower limb extensions (3-to-5 sets; 8-to-10 repetitions). Before and after training, maximal explosive efforts with both lower limbs or with each limb separately were assessed. Electromyography of representative lower limb muscles was measured. Results: BL_training significantly and largely decreased BLD (p=0.003, effect size=1.63). This was accompanied by the reversion from deficit to facilitation of the electromyography amplitude of knee extensors during bilateral efforts (p=0.007). Conversely, UL_training had negligible effects on BLD (p=0.781). Also, both groups showed similar improvements in their maximal explosive power generated after training. Conclusions: Bilateral plyometric training can mitigate BLD, and should be considered for training protocols focused on improving bilateral lower limb motor performance
Effects of Bilateral or Unilateral Plyometric Training of Lower Limbs on the Bilateral Deficit During Explosive Efforts
No full textObjectives: Bilateral Deficit (BLD) occurs when the force generated by both limbs together is smaller than the sum of the forces developed separately by the two limbs. BLD may be modulated by physical training. Here, were investigated the effects of unilateral or bilateral plyometric training on BLD and neuromuscular activation during lower limb explosive extensions. Methods: Fourteen young males were randomized into the unilateral (UL_) or bilateral (BL_) training group. Plyometric training (20 sessions, 2 days/week) was performed on a sled ergometer, and consisted of UL or BL consecutive, plyometric lower limb extensions (3-to-5 sets; 8-to-10 repetitions). Before and after training, maximal explosive efforts with both lower limbs or with each limb separately were assessed. Electromyography of representative lower limb muscles was measured. Results: BL_training significantly and largely decreased BLD (p=0.003, effect size=1.63). This was accompanied by the reversion from deficit to facilitation of the electromyography amplitude of knee extensors during bilateral efforts (p=0.007). Conversely, UL_training had negligible effects on BLD (p=0.781). Also, both groups showed similar improvements in their maximal explosive power generated after training. Conclusions: Bilateral plyometric training can mitigate BLD, and should be considered for training protocols focused on improving bilateral lower limb motor performance
Effects of strength, explosive and plyometric training on energy cost of running in ultra-endurance athletes
No full textSpinal Cord Epidural Stimulation Improves Lower Spine Sitting Posture Following Severe Cervical Spinal Cord Injury
Full text linkEffects of the Etna Uphill Ultra-Marathon on Energy Cost and Mechanics of Running.
No full textPURPOSE: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 years) participated in the "Etna SuperMarathon" (43 km, 0-3063 m a.s.l.). Anthropometric characteristics, maximal explosive power of the lower limb (Pmax) and VO2max were determined before the competition. In addition, before and immediately after the race, Cr, contact (tc) and aerial (ta) times, step frequency (f) and running velocity (v) were measured at constant self-selected speed. Then, peak vertical ground reaction force (Fmax), vertical downward displacement of the centre of mass (Δz), leg length change (ΔL), vertical (kvert) and leg (kleg) stiffness were calculated.
RESULTS:Direct relationship between Cr, measured before de race, and race time was shown (r= 0.61; p<0.001). Cr increased significantly at the end of the race by 8.7%. Immediately after the race, the subjects showed significantly lower ta (-58.6%), f (-11.3%), Fmax (-17.6%), kvert (-45.6%) and kleg (-42.3%) and higher tc (+28.6%), Δz (+52.9%) and ΔL (+44.5%) than before the race. The increase of Cr was associated with a decrement in Fmax (r=-0.45), kvert (r=-0.44) and kleg (r=-0.51). Finally, an inverse relationship between Pmax measured before the race and ΔCr during race was found (r=-0.52).
CONCLUSIONS:Lower Cr was related with better performance, and athletes characterized by the greater Pmax showed lower increases in Cr during the race. This suggests that specific power training of the lower limbs may lead to better performance in ultra-endurance running competitio
Effects of an uphill marathon on running mechanics and lower-limb muscle fatigue
No full textPurpose: 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 (Dm ) 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 (tc ) and aerial (ta ) 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 (kvert ) and leg (kleg ) stiffness were calculated. Results: MMP was inversely related with race time (r = -.56, P = .016), tc (r = -.61, P = .008), and Δz (r = -.57, P = .012) and directly related with Fmax (r = .59, P = .010), ta (r = .48, P = .040), and kvert (r = .51, P = .027). In the fastest subgroup (n = 9) the following parameters were lower in POST (P < .05) than at km 3: ta (-14.1% ± 17.8%), Fmax (-6.2% ± 6.4%), kvert (-17.5% ± 17.2%), and kleg (-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%), ta (-20.5% ± 16.2% and -21.5% ± 14.4%), tc (5.5% ± 7.5% and 3.2% ± 5.2%), kvert (-14.0% ± 12.8% and -11.8% ± 10.0%), and kleg (-8.9% ± 11.5% and -11.9% ± 12%). TMG temporal parameters decreased in all runners (-27.35% ± 18.0%, P < .001), while Dm 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
The energetics of ultra-endurance running
No full textOur objective was to determine the effects of long-lasting endurance events on the energy cost of running (C(r)), and the role of maximal oxygen uptake (VO(2max)), its fractional utilisation (F) and C(r) in determining the performance. Ten healthy runners (age range 26-59 years) participated in an ultra-endurance competition consisting of three running laps of 22, 48 and 20 km on three consecutive days in the North-East of Italy. Anthropometric characteristics and VO(2max) by a graded exercise test on a treadmill were determined 5 days before and 5 days after the competition. In addition, C(r) was determined on a treadmill before and after each running lap. Heart rate (HR) was recorded throughout the three laps. Results revealed that mean C(r) of the individual laps did not increase significantly with lap number (P = 0.200), thus ruling out any chronic lap effect. Even so, however, at the end of lap 3, C(r) was 18.0% (P < 0.001) greater than before lap 1. In addition, a statistically significant acute lap effect on C(r) was observed at the end of the second and third laps (by 11.4 and 7.2%, respectively). The main factors determining performance were VO(2max), F, as estimated from the average HR, and the average C(r-mean) throughout the three laps; the grand average speed over the three laps being described by v (end-mean) = F × VO(2max) × C(r-mean)(-1). We concluded that (1) the substantial increase of C(r-mean) during the competition yields to marked worsening of the performance, and (2) the three variables F, VO(2max) and C(r-mean) combined as described above explaining 87% of the total competition time varianc
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