Investigating the Relevance of Maximal Speed and Acceleration in Varsity-Level Female Ice Hockey Players

PURPOSE

To characterize and compare female ice hockey players' peak skating speed and acceleration ability during linear sprints and gameplay. We also sought to quantify the time spent at various speeds and the frequency of accelerations at different thresholds during games.

METHODS

Seventeen varsity-level female ice hockey players (20 [1.4] y, 68.9 [4.9] kg, 167.6 [4.7] cm) participated in an on-ice practice session (performing 3 × 40-m linear sprints) and 4 regular-season games while being monitored using a local positioning system. Speed and acceleration were recorded from the sprint and within-game monitoring. Time on ice spent in relative skating speed zones and the frequency of accelerations at different intensities were recorded.

RESULTS

Players' greatest peak speeds (29.5 [1.3] vs 28.3 [1.1] km/h) and accelerations (4.39 [0.48] vs 3.34 [0.36] m/s2) reached during gameplay were higher than those reached in linear sprinting (both P < .01). Peak in-game values were moderately predicted by linear sprint values for speed (r = .69, P < .01) but not for acceleration (r < .01, P = .95). Players spent little time at near-peak linear sprint speeds (≥80% [22.7 km/h], ∼3% time on ice; ≥90% [25.5 km/h], <1% of time on ice) during gameplay. However, 26% to 35% of accelerations recorded during the 4 games were ≥90% of linear sprint acceleration.

CONCLUSIONS

Although skating speed may be advantageous in specific game situations, our results suggest that players spend little time at near-maximal speeds while accelerating frequently during games. This warrants further investigation of direction changes, skating transitions, repeated sprints, and other determinant variables potentially related to on-ice success and the implementation of training strategies to improve repeated acceleration or qualities beyond maximal skating speed.

Food for thought: Physiological considerations for nutritional ergogenic efficacy

Top-class athletes have optimized their athletic performance largely through adequate training, nutrition, recovery, and sleep. A key component of sports nutrition is the utilization of nutritional ergogenic aids, which may provide a small but significant increase in athletic performance. Over the last decade, there has been an exponential increase in the consumption of nutritional ergogenic aids, where over 80% of young athletes report using at least one nutritional ergogenic aid for training and/or competition. Accordingly, due to their extensive use, there is a growing need for strong scientific investigations validating or invalidating the efficacy of novel nutritional ergogenic aids. Notably, an overview of the physiological considerations that play key roles in determining ergogenic efficacy is currently lacking. Therefore, in this brief review, we discuss important physiological considerations that contribute to ergogenic efficacy for nutritional ergogenic aids that are orally ingested including (1) the impact of first pass metabolism, (2) rises in systemic concentrations, and (3) interactions with the target tissue. In addition, we explore mouth rinsing as an alternate route of ergogenic efficacy that bypasses the physiological hurdles of first pass metabolism via direct stimulation of the central nervous system. Moreover, we provide real-world examples and discuss several practical factors that can alter the efficacy of nutritional ergogenic aids including human variability, dosing protocols, training status, sex differences, and the placebo effect. Taking these physiological considerations into account will strengthen the quality and impact of the literature regarding the efficacy of potential ergogenic aids for top-class athletes.

Reliability and validity of an indoor local positioning system for measuring external load in ice hockey players

This study determined the reliability and validity of a Kinexon local positioning system (LPS) for measuring external load in ice hockey players during an on-ice session. Fourteen ice hockey players (25.1 y, 78.6 kg, 176.9 cm) wore two LPS sensors to examine the inter-sensor reliability of the LPS during an on-ice session, and LPS speed and acceleration were measured during 40 m linear on-ice sprints and compared to a previously validated robotic sprint device to examine LPS accuracy. The coefficient of variation (CV), standard error of measurement (SEM), and intra-class correlation coefficient (ICC) were calculated for each LPS measure. Pearson's correlations, simple linear regressions, and Bland-Altman plots were used to test the agreement and relationship between the two systems. Statistical significance was determined at p < 0.05. The majority of LPS measures were reliable (CV < 10% and ICC > 0.9) when comparing the two sensors worn by each player. Peak speed, speed at 5 m, and 0-5 m acceleration were all comparable to those reported by the robotic sprint device, with nearly perfect (peak speed and 0-5 m acceleration) and very large (speed at 5 m) magnitudes of correlation and mean biases <0.5 km/hr for speed measures and <0.01 m/s² for acceleration. The present results demonstrate that the Kinexon LPS is reliable and accurate for investigating on-ice external load in ice hockey players when sensors are consistently secured on the back of the players' shoulder pads.

Dietary Intake of Young Male Ice Hockey Players 10-13 Years of Age during a Week-Long Hockey Camp

This study recorded the dietary intakes of young male ice hockey players (10-13 year (yr)) for 3 consecutive days while participating in a 5-day summer hockey camp. Players were categorized as older children (OC, n = 10; 10.7 ± 0.2 yr; 37.1 ± 1.5 kg; 147.9 ± 2.1 cm) and young adolescents (YA, n = 10; 12.9 ± 0.1 yr; 45.2 ± 1.5 kg; 157.0 ± 2.4 cm). Players consumed their usual daily intakes. Parents recorded food intake in the mornings and evenings, while the researchers recorded food intake at camp. Energy intake was higher in both groups when compared to data for age-matched young Canadian (CDN) males (OC, 2967 ± 211 vs. 2000 kcal/day; YA, 2773 ± 91 vs. 2250 kcal/day). Carbohydrate (CHO) (OC, 11.2 ± 0.8 vs. YO, 8.9 ± 0.5 g/kg body mass/day) and protein (OC, 3.2 ± 0.3; YO, 2.4 ± 0.1 g/kg/day) intakes were higher than reported for young CDN males (CHO, 3.6 and protein, 1.0 g/kg/day) and were within the Acceptable Macronutrient Distribution Range (AMDR; CHO, 56 ± 2.3; 57.4 ± 0.8%; protein, 16.1 ± 1.0; 15.7 ± 0.7%). Fat intake was also within the AMDR in both groups (OC, 29.8 ± 1.6%; YA, 28.3 ± 1.0%). Micronutrient intake was adequate except for Vitamin D intakes that were below the recommended 15 ug/day at 6.3 ± 0.7 (OC) and 5.0 ± 1.5 ug/day (YA). In summary, energy and macronutrient intakes of the OC (10-11 yr) and YA (12-13 yr) players were high and well above the age matched CDN norms. The older children had higher energy intakes/kg body mass than the young adolescents. Higher energy intakes allowed for micronutrients intakes to be met in these young active males, except for vitamin D intake.

Dietary Intake over a 7-Day Training and Game Period in Female Varsity Rugby Union Players

This study estimated the daily energy intake (EI) and energy expenditure (TDEE) in female varsity rugby union players during a weekly training/game cycle. Fifteen (nine forwards, six backs) players (20.5 ± 0.4 y, 167.1 ± 1.8 cm, 74.9 ± 2.9 kg) were monitored for a 7-day period (one fitness, two heavy training, one light training, one game, and two recovery days) during their regular season. The average EI throughout the week for all 15 players was 2158 ± 87 kcal. There were no significant differences between days, but the lowest EI (1921 ± 227 kcal) occurred on the mid-week recovery day and the highest on game day (2336 ± 231 kcal). The average TDEE was 2286 ± 168 kcal (~6% > EI). The mean energy availability (EA) over the 7-day period was 31.1 ± 3.6 kcal/kg FFM/day for the group. Of the players, 14% were in the optimal EA range (>45 kcal/kg FFM/day); 34% were in the moderate range (≥30−45 kcal/kg FFM/day); and 52% had a poor EA of <30 kcal/kg FFM/day. Carbohydrate (3.38 ± 0.36 g/kg/day, 45% of EI); fat (1.27 ± 0.12 g/kg/day, 37% of EI); and protein (1.38 ± 0.12 g/kg/day, 18% of EI) consumption remained similar throughout the week (p > 0.05). The players consumed 6% less energy than they expended, providing poor to moderate EA; therefore, daily carbohydrate intake recommendations were not met.

Local Positioning System-Derived External Load of Female and Male Varsity Ice Hockey Players During Regular Season Games

Purpose

The purposes of this study were to quantify the external load for female and male varsity ice hockey players during regular season games using a local positioning system (LPS), compare LPS-derived external load between sexes and positions, and compare skating distances in absolute and relative speed zones.

Methods

Data were collected for 21 female (7 defense, 14 forwards; 20.0 ± 1.4 yrs., 69.1 ± 6.7 kg, 167.1 ± 5.4 cm) and 25 male (8 defense, 17 forwards; 21.9 ± 1.1 yrs., 85.9 ± 5.4 kg, 181.1 ± 5.2 cm) varsity ice hockey players. Measures included skating distance (total, and in absolute and relative speed zones), peak skating speed, peak acceleration and deceleration, accumulative acceleration load, and number of accelerations, decelerations, turns, skating transitions, direction changes, and impacts.

Results

Female and male players had a high external load during games, with average peak skating speeds >28 km/h and average skating distances >4.4 km. Most LPS-derived measures showed greater external load in males than females (p < 0.05). Forwards skated further at higher speeds compared to defense in both sexes (p < 0.001). Skating distances were significantly different when comparing absolute and relative speed zones (p < 0.001), with absolute speed zones potentially overestimating skating at very slow, very fast, and sprint speeds and underestimating skating at slow and moderate speeds.

Conclusion

This was the first study to measure external load in female ice hockey players with a LPS. Both female and male varsity players had high external loads during games, with forwards having greater external load at higher intensities and defense having greater external load at lower intensities. Sex and positional differences outline the importance of individualized athlete monitoring.

Carbohydrate Mouth-Rinsing Improves Overtime Physical Performance in Male Ice Hockey Players During On-Ice Scrimmages

Purpose

This randomized, double-blind, crossover study examined the effects of mouth-rinsing (MR) with a carbohydrate (CHO) vs. a placebo (PLA) solution on external and internal loads in hydrated ice hockey players during regulation and overtime (OT) periods of an on-ice scrimmage.

Methods

Twelve skilled male hockey players (22.6 [3.4] years, 178.9 [4.7] cm, 84.0 [6.5] kg) played three 20-min regulation periods and one 12-min OT period of small-sided 3-on-3 scrimmage. Skaters repeated 2 min shift and rest intervals. Participants mouth rinsed with 25 mL of CHO or PLA solution approximately every 10 min for a total of 7 rinses. A local positioning system (LPS) tracked external load variables including speed, distance, acceleration, and deceleration. Internal load was monitored with heart rate (HR) sensors and a rating of perceived exertion (RPE).

Results

During regulation play, both the conditions developed similar fatigue, with significantly decreased high-intensity distance, average speed and decelerations, and increased RPE, from period 1 to 2 and 3. In OT, CHO MR increased the distance skated at high-intensity (224 [77], 185 [66] m, p = 0.042), peak speed (24.6 [1.6], 23.7 [1.3] km·h⁻¹, p = 0.016), number of sprints (1.9 [1.2], 1.2 [0.9], p = 0.011), and decreased distance skated at slow speed (300 [33], 336 [47], p = 0.034) vs. PLA MR. OT RPE was similar between the two conditions in spite of more work done in CHO MR.

Conclusions

CHO MR may be a valuable practice to protect against decrements in external load with increased playing time in ice hockey, and possibly allows athletes to perform more work relative to perceived levels of exertion.

Potential effect of beetroot juice supplementation on exercise economy in well-trained females

This study examined if acute dietary nitrate supplementation (140 mL beetroot juice, BRJ) would reduce oxygen consumption (V̇O2) during cycling at power outputs of 50 and 70% maximal oxygen consumption in 14 well-trained female Canadian University Ringette League athletes. BRJ had no effect on V̇O2 or heart rate but significantly reduced ratings of perceived exertion (RPE) at both intensities. Individually, 4 participants responded to BRJ supplementation with a ≥3% reduction in V̇O2 at the higher power output. Novelty: Acute BRJ supplementation did not improve exercise economy in well-trained females, but significantly reduced RPE. However, 4/14 subjects did respond with a ≥3% V̇O2 reduction.

Internal Load of Female Varsity Ice Hockey Players During Training and Games During a Season

This study quantified internal load, using sessional rating of perceived exertion (sRPE) and heart-rate derived training impulse (TRIMP), of female varsity ice hockey players throughout a season. Twenty-four female (19.8±1.4 yr, 68.0±6.9 kg) varsity ice hockey players participated in this prospective cohort study. Internal load was captured using sRPE and TRIMP for each on-ice session. Internal load was significantly higher (p<0.05) for games (sRPE: 324±202 AU, TRIMP: 95±60 AU) compared to training (sRPE: 248±120 AU, TRIMP: 68±32 AU). Overall, goalies had a higher internal load than forwards (sRPE and TRIMP) and defence (TRIMP), with no differences between forwards and defence. Micro-cycle periodization was present, with training sessions several days prior to game days having the highest internal load (sRPE and TRIMP) and tapering down as subsequent training sessions approached game day. For the meso-cycle assessment, for both training and competition combined, the post-season sRPE was greater than the pre-season (p=0.002) and regular season (p<0.001). Lastly, the association between sRPE and TRIMP, revealed a large, statistically significant relationship (r=0.592, p<0.001). Internal load was greater during competitions, training sessions and subsequent internal loads suggested prioritization around game days, the post-season phase demanded the highest internal load and there was a strong correlation between sRPE and TRIMP.

Internal Physiological Load Measured Using Training Impulse in Varsity Men's and Women's Ice Hockey Players Between Game Periods

ABSTRACT

Bigg, JL, Gamble, ASD, and Spriet, LL. Internal physiological load measured using training impulse in varsity men's and women's ice hockey players between game periods. J Strength Cond Res 35(10): 2824-2832, 2021-This study quantified internal load in male and female ice hockey players throughout a season, with comparisons between game periods and match outcome. Twenty-seven male and 24 female varsity ice hockey players participated in this longitudinal prospective cohort study monitoring internal load, using Banister's training impulse (TRIMP). Data were assessed according to game periods, match outcome (win or loss), and games played in noncongested (1 game/wk) or congested (2 + games/wk) weeks. Statistical significance was considered at p < 0.05. The TRIMP for period 1 for both male (25 ± 16 arbitrary units [AU]) and female (23 ± 19 AU) players was significantly lower than period 3 (males: 30 ± 21 AU; p = 0.001; females: 29 ± 21 AU; p = 0.003) but not period 2 (males: 27 ± 17 AU; p = 0.183; females: 27 ± 19 AU; p = 0.681). There were no differences in TRIMP within any period between games resulting in a win compared with a loss. Overall, there were no differences in TRIMP between male and female players. However, when stratified by position, male forwards experienced greater TRIMP than female forwards (p < 0.001 for all periods), whereas female defense had greater TRIMP than male defense (p ≤ 0.032 for all periods). There were no differences between noncongested and congested week games and no differences in TRIMP between nonback-to-back and back-to-back games, or the first and second games played of a back-to-back series. This study measured physiological demand throughout the periods of ice hockey games in men and women and concluded that internal load was highest in the third period. Understanding the demands throughout a game can provide information to coaches and players that would be useful in managing fatigue and optimizing physical performance.

Sex differences in the physiological responses to exercise-induced dehydration: consequences and mechanisms

Physiological strain during exercise is increased by mild dehydration (∼1%-3% body mass loss). This response may be sex-dependent, but there are no direct comparative data in this regard. This review aimed to develop a framework for future research by exploring the potential impact of sex on thermoregulatory and cardiac strain associated with exercise-induced dehydration. Sex-based comparisons were achieved by comparing trends from studies that implemented similar experimental protocols but recruited males and females separately. This revealed a higher core temperature (T_c) in response to exercise-induced dehydration in both sexes; however, it seemingly occurred at a lower percent body mass loss in females. Although less clear, similar trends existed for cardiac strain. The average female may have a lower body water volume per body mass compared with males, and therefore the same percent body mass loss between the sexes may represent a larger portion of total body water in females potentially posing a greater physiological strain. In addition, the rate at which T_c increases at exercise onset might be faster in females and induce a greater thermoregulatory challenge earlier into exercise. The T_c response at exercise onset is associated with lower sweating rates in females, which is commonly attributed to sex differences in metabolic heat production. However, a reduced sweat gland sensitivity to stimuli, lower fluid output per sweat gland, and sex hormones promoting fluid retention in females may also contribute. In conclusion, the limited evidence suggests that sex-based differences exist in thermoregulatory and cardiac strain associated with exercise-induced dehydration, and this warrants future investigations.

Dietary Macronutrient and Micronutrient Intake over a 7-Day Period in Female Varsity Ice Hockey Players

This study examined the energy, macronutrient, and micronutrient intakes of female ice hockey players over a 7-d period including game, practice, and rest days. Twenty-three female varsity players (19.0 ± 1.1 yr, 167.1 ± 6.5 cm, 67.0 ± 8.0 kg) volunteered for the study. Average total daily energy expenditure (TDEE) was estimated over the 7-day period. Average 7-day energy intake (EI) and TDEE were 2354 ± 353 and 2304 ± 204 kcal. The majority (n = 19) of athletes had an EI ≥ 90% of their estimated TDEE. Macronutrient intake was 52% carbohydrate (CHO), 32% fat, and 16% protein of total EI, although CHO intake was slightly below recommendations (5 g/kg BM/d) on game and practice (4.8 ± 1.4 and 4.5 g/kg BM/d) days. Game day EI was greater than practice and rest days. Recommended micronutrient intakes were not met by most athletes for iron, calcium, vitamin D, and potassium, and intakes were similar between game, practice, and rest days. In summary, the average EI for female varsity ice hockey players appeared adequate to meet their energy needs over a weekly cycle of game, practice, and rest days. However, these female athletes would benefit from increasing CHO intake on game and practice days and selecting foods that are rich in vitamins and minerals.

External Training Demands in Women's Varsity Rugby Union Players Quantified by Wearable Microtechnology With Individualized Speed Thresholds

ABSTRACT

Nyman, DLE and Spriet, LL. External training demands in women's varsity rugby union players quantified by wearable microtechnology with individualized speed thresholds. J Strength Cond Res XX(X): 000-000, 2021-This study used wearable Global Positioning System (GPS) microtechnology with individualized speed thresholds to examine external training demands in 29 female varsity rugby union athletes during competitive season practices. Players were categorized as forwards or backs and observed during fitness, game-based, or skill training days (FT/GT/ST). Global Positioning System-derived variables included distances, high-intensity running (HIR), work-to-rest ratio, power plays, and PlayerLoad. Five speed zones categorized athlete movements and were customized according to each individual's overall maximum velocity (V[Combining Dot Above]max). Compared with backs, forwards had lower overall V[Combining Dot Above]max (6.62 ± 0.66 m·s-1; 7.38 ± 0.61 m·s-1, p = 0.003) and HIR thresholds (3.97 ± 0.40 m·s-1; 4.43 ± 0.37 m·s-1, p = 0.003). There were no interaction effects between position and training day for any GPS-derived variables. However, there were several effects of position (p ≤ 0.05), with forwards being lower than backs in mean V[Combining Dot Above]max, zone 1 distance, and power plays, and greater than backs in zone 3, zone 4, and HIR distances. Effects of the training day (p ≤ 0.05) were also observed in zone 1 distance, with FT being lower than GT and ST, and in power plays, with FT being greater than ST. In female varsity rugby union athletes, there were significant positional differences in individualized speed thresholds and external training demands. However, there were few marked differences between fitness, game-based, and skill training days.

Moderate Load Resisted Sprints Do Not Improve Subsequent Sprint Performance in Varsity-Level Sprinters

ABSTRACT

Thompson, K, Whinton, AK, Ferth, S, Spriet, LL, and Burr, JF. Moderate load resisted sprints do not improve subsequent sprint performance in varsity-level sprinters. J Strength Cond Res 35(1): 72-77, 2021-Resisted sprint training (RST) is commonly used for performance enhancement in athletics and team sports to develop acceleration ability. Evidence suggests that RST may be effective as a short-term intervention to improve successive sprints. Although these improvements have been measured in team sport athletes, limited research has considered the acute effects of RST training in sprint-trained athletes. Therefore, the aim of the current study was to determine whether performing RST with varsity-level sprinters using sled-equivalent resistive loads of ∼45% body mass results in a potentiation effect, leading to improvements in subsequent maximal sprint performance over 0-5 m and 0-20 m. Competitive sprinters (n = 20) were randomly assigned to perform a pre/post maximal 20-m sprint separated by either 3 resisted (RST group) or unresisted (URS group) sprints. The RST or URS protocol was performed on 4 occasions separated by at least 7 days. No significant differences were observed between the RST and URS groups comparing changes in sprint times over 0-5 m (URS Δ <0.01 ± 0.03 seconds, RST Δ <0.01 ± 0.03 seconds) and 0-20 m (URS Δ 0.013 ± 0.04 seconds, RST Δ <0.01 ± 0.04 seconds). We conclude that resisted sprints using sled-equivalent loads of 45% body mass are ineffective at inducing a potentiating effect on subsequent sprint performance in varsity-level sprinters. In this population of trained athletes, greater loads may be necessary to induce a potentiating effect.

Power loss is attenuated following a second bout of high-intensity eccentric contractions due to the repeated bout effect's protection of rate of torque and velocity development

High-intensity unaccustomed eccentric contractions result in weakness and power loss because of fatigue and muscle damage. Through the repeated bout effect (RBE), adaptations occur, then damage and weakness are attenuated following a subsequent bout. However, it is unclear whether the RBE protects peak power output. We investigated the influence of the RBE on power production and estimated fatigue- and damage-induced neuromuscular impairments following repeated high-intensity eccentric contractions. Twelve healthy adult males performed 5 sets of 30 maximal eccentric elbow flexions and repeated an identical bout 4 weeks later. Recovery was tracked over 7 days following both bouts. Reduced maximum voluntary isometric contraction torque, and increased serum creatine kinase and self-reported soreness indirectly inferred muscle damage. Peak isotonic power, time-dependent measures - rate of velocity development (RVD) and rate of torque development (RTD) - and several electrophysiological indices of neuromuscular function were assessed. The RBE protected peak power, with a protective index of 66% 24 h after the second eccentric exercise bout. The protection of power also related to preserved RVD (R² = 0.61, P < 0.01) and RTD (R² = 0.39, P < 0.01). Furthermore, the RBE's protection against muscle damage permitted the estimation of fatigue-associated neuromuscular performance decrements following eccentric exercise. Novelty: The repeated bout effect protects peak isotonic power. Protection of peak power relates to preserved rates of torque and velocity development, but more so rate of velocity development. The repeated bout effect has little influence on indices of neuromuscular fatigue.

Chronic pantothenic acid supplementation does not affect muscle coenzyme A content or cycling performance

This study determined if supplementation with pantothenic acid (PA) for 16 weeks could increase skeletal muscle coenzyme A (CoASH) content and exercise performance. Trained male cyclists (n = 14) were matched into control or PA (6 g·day^-1) groups. At 0, 4, 8, and 16 weeks, subjects performed an incremental time to exhaustion cycle with muscle biopsies taken prior to and following exercise. Prolonged PA supplementation did not change skeletal muscle CoASH and acetyl-CoA contents or exercise performance. Novelty: Supplementation with pantothenic acid for 16 weeks had no effect on skeletal muscle CoASH and acetyl-CoA content or exercise performance in trained male cyclists.

Author Correction: Skeletal muscle energy metabolism during exercise

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Skeletal muscle energy metabolism during exercise

The continual supply of ATP to the fundamental cellular processes that underpin skeletal muscle contraction during exercise is essential for sports performance in events lasting seconds to several hours. Because the muscle stores of ATP are small, metabolic pathways must be activated to maintain the required rates of ATP resynthesis. These pathways include phosphocreatine and muscle glycogen breakdown, thus enabling substrate-level phosphorylation ('anaerobic') and oxidative phosphorylation by using reducing equivalents from carbohydrate and fat metabolism ('aerobic'). The relative contribution of these metabolic pathways is primarily determined by the intensity and duration of exercise. For most events at the Olympics, carbohydrate is the primary fuel for anaerobic and aerobic metabolism. Here, we provide an overview of exercise metabolism and the key regulatory mechanisms ensuring that ATP resynthesis is closely matched to the ATP demand of exercise. We also summarize various interventions that target muscle metabolism for ergogenic benefit in athletic events.

Dietary Supplement Use among Non-athlete Students at a Canadian University: A Pilot-Survey

Despite the emerging evidence of adverse consequences and interaction with doping substances, dietary supplements (DS) are commonly used by many Canadians. The purpose of this study was to evaluate the patterns and determinants of current DS use among non-athlete students at a Canadian university using a cross-sectional approach. Of the 475 participants who completed the online survey, 43.4% declared using DS in the past six months. Participants who were male, aged ≥20 years old, and had a parent/guardian with a bachelor’s degree were significantly more likely to use DS. The types of DS used and the sources of information regarding DS were significantly influenced by age and gender. The most commonly used DS were vitamin and mineral and protein supplements. Most participants referred to healthcare professionals for information on DS, but many continued to depend on unreliable sources including family and friends. Of DS users, 10.1% reported experiencing adverse events from using DS. Findings from this study indicate that supplementation is very common among Canadian non-athlete students and highlight the urgent need for the development of educational programs surrounding DS use.

Impairment of Thermoregulation and Performance via Mild Dehydration in Ice Hockey Goaltenders

During play, ice hockey goaltenders routinely dehydrate through sweating and lose ≥2% body mass, which may impair thermoregulation and performance.

PURPOSE

This randomized, crossover study examined the effects of mild dehydration on goaltender on-ice thermoregulation, heart rate, fatigue, and performance.

METHODS

Eleven goaltenders played a 70-minute scrimmage followed by a shootout and drills to analyze reaction time and movements. On ice, they either consumed no fluid (NF) and lost 2.4% (0.3%) body mass or maintained body mass with water (WAT) or a carbohydrate-electrolyte solution (CES). Save percentage, rating of perceived exertion, heart rate, and core temperature were recorded throughout, and a postskate questionnaire assessed perceived fatigue.

RESULTS

Relative to NF, intake of both fluids decreased heart rate (interaction: P = .03), core temperature (peak NF = 39.0°C [0.1°C], WAT = 38.6°C [0.1°C], and CES = 38.5°C [0.1°C]; P = .005), and rating of perceived exertion in the scrimmage (post hoc: P < .04), as well as increasing save percentage in the final 10 minutes of scrimmage (NF = 75.8% [1.9%], WAT = 81.7% [2.3%], and CES = 81.3% [2.3%], post hoc: P < .04). In drills, movement speed (post hoc: P < .05) and reaction time (post hoc: P < .04) were slower in the NF versus both fluid conditions. Intake of either fluid similarly reduced postskate questionnaire scores (condition: P < .0001). Only CES significantly reduced rating of perceived exertion in drills (post hoc: P < .05) and increased peak movement power versus NF (post hoc: P = .02). Shootout save percentage was similar between conditions (P = .37).

CONCLUSIONS

Mild dehydration increased physiological strain and fatigue and decreased ice hockey goaltender performance versus maintaining hydration. Also, maintaining hydration with a CES versus WAT may further reduce perceived fatigue and positively affect movements.

Assessment of Na+/K+ ATPase Activity in Small Rodent and Human Skeletal Muscle Samples

INTRODUCTION

In skeletal muscle, the Na/K ATPase (NKA) plays essential roles in processes linked to muscle contraction, fatigue, and energy metabolism; however, very little information exists regarding the regulation of NKA activity. The scarcity of information regarding NKA function in skeletal muscle likely stems from methodological constraints, as NKA contributes minimally to total cellular ATP utilization, and therefore contamination from other ATPases prevents the assessment of NKA activity in muscle homogenates. Here we introduce a method that improves accuracy and feasibility for the determination of NKA activity in small rodent muscle samples (5-10 mg) and in human skeletal muscle.

METHODS

Skeletal muscle homogenates from mice (n = 6) and humans (n = 3) were used to measure NKA and sarcoplasmic reticulum Ca ATPase (SERCA) activities with the addition of specific ATPase inhibitors to minimize "background noise."

RESULTS

We observed that myosin ATPase activity was the major interfering factor for estimation of NKA activity in skeletal muscle homogenates, as the addition of 25 μM of blebbistatin, a specific myosin ATPase inhibitor, considerably minimized "background noise" (threefold) and enabled the determination of NKA maximal activity with values three times higher than previously reported. The specificity of the assay was demonstrated after the addition of 2 mM ouabain, which completely inhibited NKA. On the other hand, the addition of blebbistatin did not affect the ability to measure SERCA function. The coefficient of variation for NKA and SERCA assays were 6.2% and 4.4%, respectively.

CONCLUSION

The present study has improved the methodology to determine NKA activity. We further show the feasibility of measuring NKA and SERCA activities from a common muscle homogenate. This methodology is expected to aid in our long-term understanding of how NKA affects skeletal muscle metabolic homeostasis and contractile function in diverse situations.

Mild dehydration impaired intermittent sprint performance and thermoregulation in females

The effects of mild dehydration during ice hockey are well-studied in males but not females. In a randomized, crossover design, 11 female varsity hockey players drank no fluid (1.7% ± 0.3% body mass loss) or water to maintain hydration during simulated-hockey exercise. Core temperature (P < 0.01) and perceived fatigue (P = 0.02) were higher and sprint power lower (P < 0.01) when mildly dehydrated. Thus, mild dehydration may impair hockey performance and thermoregulation while increasing perceived fatigue in females. Novelty Female stop-and-go sport athletes may benefit their in-game sprint performance and thermoregulation by following personalized in-game hydration to prevent becoming mildly dehydrated.

Resting metabolic rate and skeletal muscle SERCA and Na+ /K+ ATPase activities are not affected by fish oil supplementation in healthy older adults

Omega-3 polyunsaturated fatty acids (PUFAs) have unique properties purported to influence several aspects of metabolism, including energy expenditure and protein function. Supplementing with n-3 PUFAs may increase whole-body resting metabolic rate (RMR), by enhancing Na+ /K+ ATPase (NKA) activity and reducing the efficiency of sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA) activity by inducing a Ca2+ leak-pump cycle. The purpose of this study was to examine the effects of fish oil (FO) on RMR, substrate oxidation, and skeletal muscle SERCA and NKA pump function in healthy older individuals. Subjects (n = 16 females; n = 8 males; 65 ± 1 years) were randomly assigned into groups supplemented with either olive oil (OO) (5 g/day) or FO (5 g/day) containing 2 g/day eicosapentaenoic acid and 1 g/day docosahexaenoic acid for 12 weeks. Participants visited the laboratory for RMR and substrate oxidation measurements after an overnight fast at weeks 0 and 12. Skeletal muscle biopsies were taken during weeks 0 and 12 for analysis of NKA and SERCA function and protein content. There was a main effect of time with decrease in RMR (5%) and fat oxidation (18%) in both the supplementation groups. The kinetic parameters of SERCA and NKA maximal activity, as well as the expression of SR and NKA proteins, were not affected after OO and FO supplementation. In conclusion, these results suggest that FO supplementation is not effective in altering RMR, substrate oxidation, and skeletal muscle SERCA and NKA protein levels and activities, in healthy older men and women.

No effect of beetroot juice supplementation on exercise economy and performance in recreationally active females despite increased torque production

This study investigated the effects of acute and chronic beetroot juice (BRJ) supplementation on submaximal exercise oxygen uptake (VO₂), time trial (TT) performance, and contractile properties of the plantar flexors in females. Study 1: Using a double blind, randomized, crossover design, 12 recreationally active females using hormonal contraceptives supplemented acutely (2.5 h) and chronically (8 days) with 280 mL BRJ/d (~26 mmoles nitrate [NO3−]) or a NO3−‐free placebo (PLA). On days 1 and 8, participants cycled for 10 min at 50% and 70% VO_2peak and completed a 4 kJ/kg body mass TT. Plasma [NO3−] and nitrite ([NO₂⁻]) increased significantly following BRJ supplementation versus PLA. There was no effect of BRJ supplementation on VO₂ at 50% or 70% VO_2peak, or TT performance. Study 2: 12 recreationally active females (n = 7 from Study 1) using hormonal contraceptives participated in a baseline visit and were supplemented acutely (2.5 h) and chronically (8 days) with 280 mL BRJ/d. Maximum voluntary strength (MVC) of the plantar flexors was assessed and a torque‐frequency curve performed. BRJ had no effect on MVC, voluntary activation, peak twitch torque, time to peak torque, or half relaxation time. Following both acute (46.6 ± 4.9% of 100 Hz torque) and chronic (47.2 ± 4.4%) supplementation, 10 Hz torque was significantly greater compared to baseline (32.9 ± 2.6%). In summary, BRJ may not be an effective ergogenic aid in recreationally active females as it did not reduce submaximal exercise VO₂ or improve aerobic TT performance despite increasing low frequency torque production.

DHA supplementation decreases resting metabolic rate in healthy young females

This study examined the independent effects of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid supplementation on resting metabolic rate (RMR) and substrate oxidation in young healthy females and males. EPA or DHA supplementation had no effect on RMR and substrate oxidation in males, while DHA reduced RMR by ∼7% (p < 0.01) in females. In conclusion, these data establish potential sex differences on RMR in response to DHA supplements.

Novelty Supplementing with DHA decreases resting energy expenditure in healthy young females but not males.

No longer beeting around the bush: a review of potential sex differences with dietary nitrate supplementation

Over the last decade there has been substantial interest in the health and athletic performance benefits associated with acute and chronic dietary nitrate (NO3–) supplementation. Dietary NO3–, commonly found in leafy green and root vegetables, undergoes sequential reduction to nitrite and nitric oxide (NO) via the enterosalivary circulation. Importantly, NO has been shown to elicit a number of biological effects ranging from blood pressure reduction to improved exercise economy and athletic performance. However, a common absence within biological research is the lack of female participants, which is often attributed to the added complexity of hormonal fluctuations throughout the menstrual cycle. Despite mounting evidence supporting significant anthropometric, metabolic, and physiological differences between the sexes, this problem extends to the field of dietary NO3– supplementation where women are underrepresented as research participants. This review examines the existing dietary NO3– supplementation research with regards to dietary NO3– pharmacokinetics, resting blood pressure, exercise economy and performance, and mechanisms of action. It also provides evidence and rationale for potential sex differences in response to dietary NO3– supplementation and future directions for this field of research.

Novelty Dietary NO3– supplementation has been shown to have positive impacts on health and athletic performance in generally male populations. However, women are underrepresented in dietary NO3– supplementation research. The present evidence suggests that sex differences exist in response to dietary NO3– supplementation and this review highlights avenues for future research.

Sweat Loss and Hydration Habits of Female Olympic, Varsity and Recreational Ice Hockey Players

This study measured sweat losses, voluntary fluid intake, sodium balance, and carbohydrate intake of female ice hockey players during on-ice practices at the Olympic, varsity, and recreational levels. Testing was conducted on 25 Canadian Olympic players, 21 varsity, and 21 recreational players. The average sweat rate for the Olympic players (0.99±0.08 L/h) was significantly greater than both the varsity (0.67±0.05 L/h, p=0.001) and the recreational players (0.42±0.03 L/h, p<0.001), and the varsity players also had a significantly greater sweat rate than the recreational athletes (p=0.016). Total fluid intake was significantly greater for both the Olympic (p=0.001) and varsity players (p=0.007) compared to the recreational group. Only 3 of 25 Olympic players lost>1.5% BM and 4 others lost>1% BM, with no players in both the varsity and recreational teams losing>1% BM. Half of the Olympic players consumed some carbohydrate during practice, but most of the varsity and recreational players did not. In conclusion, sweat rates in female ice hockey players during practices were proportional to competitive level. Fluid intake was similar between groups and resulted in only a few athletes at the Olympic level being at risk of excess body mass loss.

Incorporation of Omega-3 Fatty Acids Into Human Skeletal Muscle Sarcolemmal and Mitochondrial Membranes Following 12 Weeks of Fish Oil Supplementation

Fish oil (FO) supplementation in humans results in the incorporation of omega-3 fatty acids (FAs) eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C20:6) into skeletal muscle membranes. However, despite the importance of membrane composition in structure–function relationships, a paucity of information exists regarding how different muscle membranes/organelles respond to FO supplementation. Therefore, the purpose of the present study was to determine the effects 12 weeks of FO supplementation (3g EPA/2g DHA daily) on the phospholipid composition of sarcolemmal and mitochondrial fractions, as well as whole muscle responses, in healthy young males. FO supplementation increased the total phospholipid content in whole muscle (57%; p < 0.05) and the sarcolemma (38%; p = 0.05), but did not alter the content in mitochondria. The content of omega-3 FAs, EPA and DHA, were increased (+3-fold) in whole muscle, and mitochondrial membranes, and as a result the omega-6/omega-3 ratios were dramatically decreased (-3-fold), while conversely the unsaturation indexes were increased. Intriguingly, before supplementation the unsaturation index (UI) of sarcolemmal membranes was ∼3 times lower (p < 0.001) than either whole muscle or mitochondrial membranes. While supplementation also increased DHA within sarcolemmal membranes, EPA was not altered, and as a result the omega-6/omega-3 ratio and UI of these membranes were not altered. All together, these data revealed that mitochondrial and sarcolemmal membranes display unique phospholipid compositions and responses to FO supplementation.

Narrative Review of Hydration and Selected Health Outcomes in the General Population

Although adequate hydration is essential for health, little attention has been paid to the effects of hydration among the generally healthy population. This narrative review presents the state of the science on the role of hydration in health in the general population, specifically in skin health, neurological function (i.e., cognition, mood, and headache), gastrointestinal and renal functions, and body weight and composition. There is a growing body of evidence that supports the importance of adequate hydration in maintaining proper health, especially with regard to cognition, kidney stone risk, and weight management. However, the evidence is largely associative and lacks consistency, and the number of randomized trials is limited. Additionally, there are major gaps in knowledge related to health outcomes due to small variations in hydration status, the influence of sex and sex hormones, and age, especially in older adults and children.

Administration of Caffeine in Alternate Forms

There has been recent interest in the ergogenic effects of caffeine delivered in low doses (~ 200 mg or ~ 3 mg/kg body mass) and administered in forms other than capsules, coffee and sports drinks, including chewing gum, bars, gels, mouth rinses, energy drinks and aerosols. Caffeinated chewing gum is absorbed quicker through the buccal mucosa compared with capsule delivery and absorption in the gut, although total caffeine absorption over time is not different. Rapid absorption may be important in many sporting situations. Caffeinated chewing gum improved endurance cycling performance, and there is limited evidence that repeated sprint cycling and power production may also be improved. Mouth rinsing with caffeine may stimulate nerves with direct links to the brain, in addition to caffeine absorption in the mouth. However, caffeine mouth rinsing has not been shown to have significant effects on cognitive performance. Delivering caffeine with mouth rinsing improved short-duration, high-intensity, repeated sprinting in normal and depleted glycogen states, while the majority of the literature indicates no ergogenic effect on aerobic exercise performance, and resistance exercise has not been adequately studied. Studies with caffeinated energy drinks have generally not examined the individual effects of caffeine on performance, making conclusions about this form of caffeine delivery impossible. Caffeinated aerosol mouth and nasal sprays may stimulate nerves with direct brain connections and enter the blood via mucosal and pulmonary absorption, although little support exists for caffeine delivered in this manner. Overall, more research is needed examining alternate forms of caffeine delivery including direct measures of brain activation and entry of caffeine into the blood, as well as more studies examining trained athletes and female subjects.

Exercise Metabolism: Fuels for the Fire

During exercise, the supply of adenosine triphosphate (ATP) is essential for the energy-dependent processes that underpin ongoing contractile activity. These pathways involve both substrate-level phosphorylation, without any need for oxygen, and oxidative phosphorylation that is critically dependent on oxygen delivery to contracting skeletal muscle by the respiratory and cardiovascular systems and on the supply of reducing equivalents from the degradation of carbohydrate, fat, and, to a limited extent, protein fuel stores. The relative contribution of these pathways is primarily determined by exercise intensity, but also modulated by training status, preceding diet, age, gender, and environmental conditions. Optimal substrate availability and utilization before, during, and after exercise is critical for maintaining exercise performance. This review provides a brief overview of exercise metabolism, with expanded discussion of the regulation of muscle glucose uptake and fatty acid uptake and oxidation.

Guelph Family Health Study: pilot study of a home-based obesity prevention intervention

OBJECTIVE

To examine the feasibility and preliminary impact of a home-based obesity prevention intervention among Canadian families.

METHODS

Families with children 1.5-5 years of age were randomized to one of three groups: (1) four home visits (HV) with a health educator, emails, and mailed incentives (4HV; n = 17); (2) two HV, emails, and mailed incentives (2HV; n = 14); or (3) general health advice through emails (control; n = 13). Parents randomized to the 2HV and 4HV groups completed post-intervention satisfaction surveys. At baseline and post-intervention, parents reported frequency of family meals and their children's fruit, vegetable, and sugar-sweetened beverage (SSB) intake. We assessed the children's physical activity, sedentary behaviour, and sleep using accelerometers and their % fat mass using bioelectrical impedance analysis. Differences in outcomes at post-intervention, controlling for baseline, were examined using generalized estimating equations.

RESULTS

Of the 44 families enrolled, 42 (96%) had 6-month outcome data. Satisfaction with the intervention was high; 80% were "very satisfied" and 20% were "satisfied." At post-intervention, children randomized to the 4HV and 2HV groups had significantly higher fruit intake and children randomized to the 2HV group had significantly lower percentage of fat mass, as compared to the control. No significant intervention effect was found for frequency of family meals, the children's vegetable or SSB intake, physical activity, sedentary behaviour, or sleep.

CONCLUSIONS

Our results suggest that the delivery of a home-based intervention is feasible among Canadian families and may lead to improved diet and weight outcomes among children. A full-scale trial is needed to test the effectiveness of this home-based intervention.

CLINICAL TRIALS REGISTRATION NUMBER

NCT02223234.

IOC consensus statement: dietary supplements and the high-performance athlete

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete's health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.

Ablating the protein TBC1D1 impairs contraction-induced sarcolemmal glucose transporter 4 redistribution but not insulin-mediated responses in rats

TBC1 domain family member 1 (TBC1D1), a Rab GTPase-activating protein and paralogue of Akt substrate of 160 kDa (AS160), has been implicated in both insulin- and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase-mediated glucose transporter type 4 (GLUT4) translocation. However, the role of TBC1D1 in contracting muscle remains ambiguous. We therefore explored the metabolic consequence of ablating TBC1D1 in both resting and contracting skeletal muscles, utilizing a rat TBC1D1 KO model. Although insulin administration rapidly increased (p < 0.05) plasma membrane GLUT4 content in both red and white gastrocnemius muscles, the TBC1D1 ablation did not alter this response nor did it affect whole-body insulin tolerance, suggesting that TBC1D1 is not required for insulin-induced GLUT4 trafficking events. Consistent with findings in other models of altered TBC1D1 protein levels, whole-animal and ex vivo skeletal muscle fat oxidation was increased in the TBC1D1 KO rats. Although there was no change in mitochondrial content in the KO rats, maximal ADP-stimulated respiration was higher in permeabilized muscle fibers, which may contribute to the increased reliance on fatty acids in resting KO animals. Despite this increase in mitochondrial oxidative capacity, run time to exhaustion at various intensities was impaired in the KO rats. Moreover, contraction-induced increases in sarcolemmal GLUT4 content and glucose uptake were lower in the white gastrocnemius of the KO animals. Altogether, our results highlight a critical role for TBC1D1 in exercise tolerance and contraction-mediated translocation of GLUT4 to the plasma membrane in skeletal muscle.