No clear benefit of muscle heating on hypertrophy and strength with resistance training.

Heat is a major stressor during exercise, though its value in driving adaptation is not well understood. Muscle heating can upregulate pathways facilitating protein synthesis and could thereby enhance effects of exercise training, however, few studies have investigated this possibility. We examined whether heating active muscle during resistance training differentially affected physical and functional adaptations. Within a randomised contralateral-limb control study, ten healthy, resistance-untrained individuals (21 ± 3 y; 5 female) completed 30 sessions of progressive resistance training (12 weeks), performing 4 × 8 unilateral knee extensions at 70% of 1RM. One randomly-allocated thigh was heated during, and for 20 min after, each session using an electric pad eliciting muscle temperatures of >38 °C (HOT); the contralateral limb remained unheated (CON). Training intensity was progressed using 4-weekly strength assessments. Quadricep lean mass (measured using DXA) increased by 15 ± 7% in HOT (p = 0.00) and 15 ± 6% in CON (p = 0.00); the difference being trivial (p = 0.94). Peak isokinetic torque at 90°.s-1 increased by 30 ± 25% (HOT; p = 0.00) and 34 ± 33% (CON; p = 0.01), with no difference (p = 0.84) between limbs. Rate of torque development increased ∼40%, with no difference between limbs (p = 0.73). The increase in 3-RM strength was also similar in HOT (75 ± 16%) and CON (71 ± 14%; p = 0.80 for difference). No differences in mass or strength changes were evident between sexes. In conclusion, supplemental heating of active muscle during and after each bout of resistance training showed no clear positive (or negative) effect on training-induced hypertrophy or function.

Can Neck Strength be Measured Using a Single Maximal Contraction in a Simulated Contact Position?

Salmon, DM, Handcock, PJ, Sullivan, SJ, Rehrer, NJ, and Niven, BE. Can neck strength be measured using a single maximal contraction in a simulated contact position? J Strength Cond Res 32(8): 2166-2173, 2018-Neck strengthening has been postulated to potentially reduce the incidence and severity of concussions and neck injuries in collision-based sports. A quick and reliable method to assess neck strength would permit identification of those at risk and tracking of progress after injury. The purpose of this study was to determine if neck strength could be reliably assessed in a simulated contact posture using a single maximal contraction. During a single session, 30 healthy male university students performed 3 maximal voluntary contractions of the neck musculature in each of the following directions: extension (Ext), flexion (Flx), left lateral flexion (LtFlx), and right lateral flexion (RtFlx). To evaluate the reliability of these measures, intraclass correlation coefficients (ICCs) were calculated. The findings revealed a significant effect for direction (p < 0.01), where Ext (234.8 N) tested stronger than Flx (141.0 N), LtFlx (134.5 N), and RtFlx (123.0 N). In addition, Flx tested stronger than RtFlx (p = 0.03). No other differences were observed between LtFlx and RtFlx. When the combined mean values of the trials (1: 151.6 N, 2: 160.0 N, 3: 163.5 N) and the interaction contrast were compared, these were not significant (p = 0.08-1.0), indicating no changes in peak force occurred over the 3 trials. The ICC values for Ext, RtFlx, and LtFlx were all "excellent" (0.91-0.94), whereas Flx demonstrated "good" reliability (0.86). In a simulated contact posture, a reliable measure of peak force was obtained using a single maximal contraction. This may have practical applications for the quick and reliable assessment of contact sport athletes in a position that has functional relevance to their sports.

Neck strength and self-reported neck dysfunction: what is the impact of a season of Rugby Union?

BACKGROUND: Neck strength has been reported to reduce the incidence of concussions and neck injuries. However, little is known about how neck strength changes over a playing season. The aim of this study was to understand the impact a 20-week rugby season has on neck strength, neck pain (NP) and neck stiffness (NS) in a cohort of rugby players, relative to a non-contact control group. METHODS: This prospective cohort study employed a fixed-frame dynamometer to measure neck strength in a simulated contact posture in rugby players (N.=32) and controls (N.=15). During each assessment, participants performed a single maximal voluntary contraction in extension, flexion, left (LtFlx) and right lateral flexion (RtFlx). To quantify neck dysfunction, "current," "average," and "worst" NP and NS were measured using visual analogue scales. RESULTS: Post-season improvements (35.3-59.1 N) in neck strength were observed for the forwards for all measured directions (P<0.01), and were significant when compared to controls. For the backs, improvements were seen in extension, flexion and LtFlx (P=0.01-0.05), with only extension (29.8 N) and flexion (35.14 N) remaining significant when contrasted against the controls. The controls' neck strength remained unchanged over the season. Despite improvements in peak force, NP increased (all three measures) for the forwards (P=0.01-0.04), while only current (P=0.03) and worst NP (P=0.04) increased for the backs. Unexpectedly, NS remained unchanged for the forwards, while backs reported increases for all three measures (P=0.01-0.02). CONCLUSIONS: A season of rugby resulted in neck strength adaptations in the rugby players. Despite these improvements, increased levels of NP and NS were reported.

The Beneficial Effect of Parasympathetic Reactivation on Sympathetic Drive During Simulated Rugby Sevens.

PURPOSE: To determine whether a facilitated recovery via cold-water immersion (CWI) after simulated rugby sevens would influence parasympathetic reactivation and repeated-sprint (RS) performance across 6 matches in a 2-d tournament. METHODS: Ten male team-sport athletes completed 6 rugby sevens match simulations over 2 d with either postmatch passive recovery (PAS) or CWI in a randomized crossover design. Parasympathetic reactivation was determined via the natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent R-R intervals (ln rMSSD). RS performance was calculated as time taken (s) to complete 6 × 30-m sprints within the first half of each match. RESULTS: There were large increases in postintervention ln rMSSD between CWI and PAS after all matches (ES 90% CL: +1.13; ±0.21). Average heart rate (HR) during the RS performance task (HRAverage RS) was impaired from baseline from match 3 onward for both conditions. However, HRAverage RS was higher with CWI than with PAS (ES 90% CL: 0.58; ±0.58). Peak HR during the RS performance task (HRPeak RS) was similarly impaired from baseline for match 3 onward during PAS and for match 4 onward with CWI. HRPeak RS was very likely higher with CWI than with PAS (ES 90% CL: +0.80; ±0.56). No effects of match or condition were observed for RS performance, although there were moderate correlations between the changes in HRAverage RS (r 90% CL: -0.33; ±0.14), HRPeak RS (r 90% CL: -0.38; ±0.13), and RS performance. CONCLUSION: CWI facilitated cardiac parasympathetic reactivation after a simulated rugby sevens match. The decline in average and peak HR across matches was partially attenuated by CWI. This decline was moderately correlated with a reduction in RS performance.

Reliability of repeated isometric neck strength and endurance testing in a simulated contact posture.

The purpose of this study was to examine the reliability of repeated isometric measurements of neck strength and endurance in a simulated rugby contact posture. Data were collected from healthy active university students (n = 20) over 3 sessions. Each session consisted of a single maximal voluntary contraction (MVC) and endurance trial for extension and flexion. The endurance trials were analyzed to determine the area under the force curve (%AUC) and the time to fatigue (TTF). Reliability was calculated using the SEM and minimal detectable change (MDC). The results revealed that the MVC values for extension were nonsignificant for session (p = 0.21), whereas some session differences were seen for flexion (p = 0.01), where session 1, 115.3 N was less than session 3, 126.4 N (p = 0.03). For %AUC, flexion values (%AUC 86.0) were greater than extension (%AUC 59.4) (p = 0.02). A similar effect was observed for TTF with flexion (125.0 seconds) having significantly greater TTF than extension (86.1 seconds). For peak force, the greatest SEM and MDC were achieved for extension (15.3 and 42.3 N), while flexion produced lower values (11.3 and 31.2 N). In contrast, for the endurance trials, SEM and MDC were greater in flexion than in extension. The findings from this study indicate that the neck musculature can be reliably assessed in a simulated contact posture. For peak force, extension provided more consistent measures across time as there seems to be a learning effect for flexion. Additionally, the SEM and MDC scores provide a useful tool for future assessment of neck strength and endurance.

Body armour: the effect of load, exercise and distraction on landing forces.

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 ± 9.2 years, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, maximal aerobic fitness (VO(2max)) 50 ± 8.5 ml (.) kg(-1 .) min(-1), BMI 27.6 ± 3.1, mean ± s) completed a VO(2max) test. Experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P < 0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P < 0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury.

Impact of police body armour and equipment on mobility.

Body armour is used widely by law enforcement and other agencies but has received mixed reviews. This study examined the influence of stab resistant body armour (SRBA) and mandated accessories on physiological responses to, and the performance of, simulated mobility tasks. Fifty-two males (37 ± 9.2 yr, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, VO2max 50 ± 8.5 ml kg(-1) min(-1), BMI 27.6 ± 3.1, mean ± SD) completed a running VO2max test and task familiarisation. Two experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing SRBA and appointments (loaded) and one without additional load (unloaded). During each session participants performed five mobility tasks: a balance task, an acceleration task that simulated exiting a vehicle, chin-ups, a grappling task, and a manoeuvrability task. A 5-min treadmill run (zero-incline at 13 km·h(-1), running start) was then completed. One min after the run the five mobility tasks were repeated. There was a significant decrease in performance during all tasks with loading (p < 0.001). Participants were off-balance longer; slower to complete the acceleration, grapple and mobility tasks; completed fewer chin-ups; and had greater physiological cost (↑ %HRmax, ↑ %VO2max, ↑ RER) and perceptual effort (↑ RPE) during the 5-min run. Mean performance decreases ranged from 13 to 42% while loaded, with further decreases of 6-16% noted after the 5-min run. Unloaded task performance was no different between phases. Wearing SRBA and appointments significantly reduced mobility during key task elements and resulted in greater physiological effort. These findings could have consequences for optimal function in the working environment and therefore officer and public safety.

Changes in the timed finger-to-nose task performance following exercise of different intensities.

OBJECTIVE: The purpose of this study was to determine the effect of different levels of exercise intensity on the timed finger-to-nose (FTN) task, a measure of upper limb coordination included in the Sport Concussion Assessment Tool (SCAT2). METHODS: A three-group crossover randomised design was used to investigate changes in FTN times at three levels of exercise intensity; no exercise/rest (NE), moderate intensity exercise (ME) and high-intensity exercise (HE). Heart rates and a rating of perceived exertion (Borg Scale) were recorded to verify the level of exercise intensity. Participants performed three trials of the timed FTN task: pre-exercise, post-exercise and 15 min after the cessation of exercise. Linear mixed models were used to compare FTN change scores associated with exercise. RESULTS: Ninety asymptomatic participants (45♂:45♀) aged 18-32 years completed the study. Changes in FTN scores from pre-exercise showed that the HE condition was facilitated relative to NE at post-exercise (8% faster, 95% CI 5% to 10%, p<0.001) and at post-15 (3% faster, 95% CI 1% to 6%, p=0.005). ME did not show such a facilitation following exercise (2% faster, 95% CI 0% to 4%, p=0.081 and 1% faster, 95% CI 1% to 4%, p=0.225 respectively). CONCLUSIONS: Performance on the FTN task is enhanced by a short period of HE, and this effect persists for at least 15 min. There was no evidence of such an effect with ME.

Does exercise evoke neurological symptoms in healthy subjects?

Concussion is a common injury in collision sports and is evidenced by a variety of signs and symptoms. The recording of neurological symptoms is an important component of screening for a concussion and in return-to-play decisions. However similar symptoms are prevalent in the general population and are reported to be associated with participation in physical activities. The purpose of this study was to document the neurological symptoms reported by healthy individuals following controlled bouts of exercise. A crossover randomised design with 2 levels of exercise intensity, moderate intensity and high intensity, each of 15min duration was used. Participants completed a standardised postconcussion symptom checklist prior to exercise (pre), immediately following exercise (post-1) and again after 15 min of rest (post-2). 60 participants were recruited into the study. A summed symptom score was calculated and analysed with a 2-way repeated measures ANOVA procedure. The intensityxtime interaction (F(2,118)=23.94, p<0.001) demonstrated a significant increase in symptom scores for the high intensity condition immediately following exercise (p<0.001). Although the moderate intensity showed a similar trend this was not significant. These findings suggest that sports medicine professionals need to be aware of the effect of exercise on symptom reporting when assessing and in making return-to-play decisions.

The Green Prescription: a field of dreams?

Increasing the physical activity of New Zealanders has assumed a higher priority with new primary healthcare strategies. Physical Educators, the professionals who research, teach and practise in the domain of physical activity and exercise, have raised concerns regarding the strategies employed. This essay details several misgivings with public health initiatives designed to increase physical activity, and makes a case for recognising the expertise of graduates specifically trained in this specialist field. A system of referral to accredited exercise professionals is suggested to be a more efficacious means of changing physical activity behaviours.