Running demands and activity profile of men's rugby sevens: a tournament scenario.

This study profiled the changes in running performances and collisions within a Rugby sevens tournament. Sixteen male players were equipped with global positioning system units while competing at the 2015 and 2016 Asia Rugby Sevens series held in Colombo and Hong Kong, respectively. Both tournaments consisted of 4 matches each, and were played over 2 days (i.e., 2 matches/day). Total distance (TD) covered increased in match 3 compared with matches 1 (19 ± 19%; p < 0.001) and 2 (16 ± 11%; p = 0.001), whilst a decrease in TD in match 4 compared with match 3 (8 ± 9%; p = 0.019) was observed. Distances covered within 6.1-12 km·h-1 and 12.1-14 km·h-1 speed bands were generally higher in matches 3 and/or 4 when compared with match 1 and/or 2 (p < 0.05). Frequency of entries into 14.1-18 km·h-1 speed zone was decreased in match 4 compared with match 3 (45 ± 41%; p = 0.009), whilst incidences of heavy, very heavy and severe collisions were generally higher in matches 3 or 4 compared with matches 1 or 2 (p < 0.05). In conclusion, while some decrements in the final match were evident, running performance were generally maintained throughout despite the competitive and congested nature of Rugby Sevens tournaments.

Effects of mild heat exposure on fatigue responses during two sets of repeated sprints matched for initial mechanical output.

OBJECTIVES: We examined whether mild heat exposure alters performance, perceptual responses and neural drive to the quadriceps during two sets of repeated sprints matched for initial mechanical output. DESIGN: Repeated measures. METHODS: Twelve males performed 10 × 6-s sprints (recovery = 30 s), followed 6 min later by 5 × 6-s sprints (recovery = 30 s) in either COOL (24 °C/30% rH) or HOT (35 °C/40% rH) conditions. Subsequently, two sets of five consecutive sprints matched for initial mechanical output were compared. RESULTS: On the basis of peak power, performance in sprint 2 was not significantly different to sprint 11 in both conditions (p ≥ 0.32). Average peak power across the five sprints compared (i.e., sprints 2-6 and 11-15, respectively) was 2.6 ±â€¯3.4% higher in HOT compared to COOL (p = 0.025). Electromyographic activity (root mean square value) of the vastus lateralis muscle remained unchanged. Core (sprints 2-6: 37.85 ±â€¯0.21 vs. 37.53 ±â€¯0.19 °C, sprints 11-15: 38.26 ±â€¯0.33 vs. 37.89 ±â€¯0.24 °C; p < 0.001) and skin (sprints 2-6: 36.21 ±â€¯0.29 vs. 30.72 ±â€¯0.52 °C, sprints 11-15: 36.37 ±â€¯0.28 vs. 30.99 ±â€¯0.55 °C; p < 0.001) temperatures were overall higher in HOT compared to COOL. Heart rate, thermal sensation and comfort were significantly elevated in HOT compared to COOL (p ≤ 0.02), irrespective of sprint number. CONCLUSIONS: When two sets of repeated sprints were matched for initial mechanical output, performance was enhanced with mild heat exposure. This occurred despite higher thermal, cardiovascular, and perceptual strain, and without alterations in quadriceps neural drive.

Performance, Metabolic, and Neuromuscular Consequences of Repeated Wingates in Hypoxia and Normoxia: A Pilot Study.

BACKGROUND: Compared with normoxia, repeated short (5-10 s) sprints (>10 efforts) with incomplete recovery (≤30 s) in hypoxia likely cause substantial performance reduction accompanied by larger metabolic disturbances and magnitude of neuromuscular fatigue. However, the effects of hypoxia on performance of repeated long (30 s) "all-out" efforts with near complete recovery (4.5 min) and resulting metabolic and neuromuscular adjustments remain unclear. PURPOSE: The intention was to compare acute performance, metabolic, and neuromuscular responses across repeated Wingates between hypoxia and normoxia. METHODS: On separate visits, 6 male participants performed 4 × 30-second Wingate efforts with 4.5-minute recovery in either hypoxia (fraction of inspired oxygen: 0.145) or normoxia. Responses to exercise (muscle and arterial oxygenation trends, heart rate, and blood lactate concentration) and the integrity of neuromuscular function in the knee extensors were assessed for each exercise bout. RESULTS: Mean (P = .80) and peak (P = .92) power outputs, muscle oxygenation (P = .88), blood lactate concentration (P = .72), and perceptual responses (all Ps > .05) were not different between conditions. Arterial oxygen saturation was significantly lower, and heart rate higher, in hypoxia versus normoxia (P < .001). Maximal voluntary contraction force and peripheral fatigue indices (peak twitch force and doublets at low and high frequencies) decreased across efforts (all Ps < .001) irrespective of conditions (all Ps > .05). CONCLUSION: Despite heightened arterial hypoxemia and cardiovascular solicitation, hypoxic exposure during 4 repeated 30-second Wingate efforts had no effect on performance and accompanying metabolic and neuromuscular adjustments.

Neuromuscular and perceptual responses during repeated cycling sprints-usefulness of a "hypoxic to normoxic" recovery approach.

PURPOSE: We investigated the consequence of varying hypoxia severity during an initial set of repeated cycling sprints on performance, neuromuscular fatigability, and exercise-related sensations during a subsequent set of repeated sprints in normoxia. METHODS: Nine active males performed ten 4-s sprints (recovery = 30 s) at sea level (SL; FiO2 ~ 0.21), moderate (MH; FiO2 ~ 0.17) or severe normobaric hypoxia (SH; FiO2 ~ 0.13). This was followed, after 8 min of passive recovery, by five 4-s sprints (recovery = 30 s) in normoxia. RESULTS: Mean power decrement during Sprint 10 was exacerbated in SH compared to SL and MH (- 34 ± 12%, - 22 ± 13%, - 25 ± 14%, respectively, p < 0.05). Sprint performance during Sprint 11 recovered to that of Sprint 1 in all conditions (p = 0.267). All exercise-related sensations at Sprint 11 recovered significantly compared to Sprint 1, with no difference for Set 2 (p > 0.05). Ratings of overall perceived discomfort, difficulty breathing, and limb discomfort were exacerbated during Set 1 in SH versus SL (p < 0.05). Compared to SL, the averaged MPO value for Set 2 was 5.5 ± 3.0% (p = 0.003) lower in SH. Maximal voluntary force and twitch torque decreased similarly in all conditions immediately after Set 1 (p < 0.05), without further alterations after Set 2. Peripheral and cortical voluntary activation values did not change (p > 0.05). CONCLUSION: Exercise-related sensations, rather than neuromuscular function integrity, may play a pivotal role in influencing performance of repeated sprints and its recovery.

The effects of lower body passive heating combined with mixed-method cooling during half-time on second-half intermittent sprint performance in the heat.

PURPOSE: This study examined the effects of combined cooling and lower body heat maintenance during half-time on second-half intermittent sprint performances. METHODS: In a repeated measures design, nine males completed four intermittent cycling trials (32.1 ± 0.3 °C and 55.3 ± 3.7% relative humidity), with either one of the following half-time recovery interventions; mixed-method cooling (ice vest, ice slushy and hand cooling; COOL), lower body passive heating (HEAT), combined HEAT and COOL (COMB) and control (CON). Peak and mean power output (PPO and MPO), rectal (Tre), estimated muscle (Tes-Mus) and skin (TSK) temperatures were monitored throughout exercise. RESULTS: During half-time, the decrease in Tre was substantially greater in COOL and COMB compared with CON and HEAT, whereas declines in Tes-Mus within HEAT and COMB were substantially attenuated compared with CON and COOL. The decrease in TSK was most pronounced in COOL compared with CON, HEAT and COMB. During second-half, COMB and HEAT resulted in a larger decrease in PPO and MPO during the initial stages of the second-half when compared to CON. In addition, COOL resulted in an attenuated decrease in PPO and MPO compared to COMB in the latter stages of second-half. CONCLUSION: The maintenance of Tes-Mus following half-time was detrimental to prolonged intermittent sprint performance in the heat, even when used together with cooling.