Effects of Music and Vibration on Morning Muscle Strength and Cognitive Measures in Males

Fifteen male adults. Through interviews, it was established that the volunteers had minimal knowledge of the effects of time-of-day or time-since-sleep on human performance. Verbal explanation of the experimental procedure was provided to everyone; this included the aims of the study; the possible risks associated with participation and the experimental procedures to be utilized. Any questions were answered. Individuals then provided written, informed consent before participating in the study. The experimental procedures were approved by the Human Ethics Committee at Liverpool John Moores University (ETHICS CODE: 251108LJMUREC75). The study was conducted in accordance with the ethical standards of the journal and complied with the principles of the Declaration of Helsinki.

All participants were required to visit the biomechanics laboratory (Liverpool, UK) on eight occasions. Participants completed (i) one maximum repetition (1RM) for bench press and back squat, ii) three familiarization sessions of strength and cognitive performance tests one week prior to the experimental protocol. During familiarizations participants completed a 7-day food diary that was analyzed using Nutritics® analysis software (2026, Education Edition, version 6.20, Ireland) by a SENr registered Sports and Exercise Nutritionist. The remaining sessions consisted of iii) three experimental sessions, all at least 72-h apart as a standardized recovery period. The experimental part comprised three experimental trials a) preferred music at original tempo (MUS), b) preferred music accelerated 15% (MUS15) and c) No-Music (CON)] between 07:00 and 08:40 h. Participants retired the previous night around 22:30 h, woke up at 06:30 h and arrived at the laboratory at 07:00 h in a fasted state. Participants were instructed to avoid training or intense physical activity 48 h prior to any of the visits, otherwise, participants maintained their normal daily routines. Music was delivered during strength and power measures and whilst resting through participant's own headphones in both music conditions. Loudness was normalized for both track-set and played at ~75dB to avoid practical and auditory-health concerns. Researchers and participants were blinded to intervention and conditions, track-sets were labeled MUS1 and MUS 2 and duration were matched by adding and empty track at the end of MUS15 to match duration removing biases. The order of treatment was revealed at the end of the by a researcher responsible for anonymization and randomization (JA).

All trials were performed with only one participant at a time, but with a staggered start so one participant came in at 06:45, the next 07:00 h and the last for that morning's session at 07:15 h. This scheduling for participants was kept consistent for all sessions. All participants lived no more than 15 mins away from the University laboratories. Participants were equally allocated, based on their 1RM for bench press and back squat into three groups (A, B and C), by listing 1RMs from highest to lowest and assigning letters A, B and C in order. The incidence of the learning effect was minimized by assigning the experimental conditions in counterbalanced order. The present study was carried out between the months of November to February (UK Autumn to Winter), with morning sunlight exposure limited to <80 Lux before arriving at the laboratory. The sunrise range for the duration of the study was 07:12 to 07:03 h.

2.3. Music intervention The music intervention was designed using a structured protocol informed by findings from previous experimental studies. Existing research has examined music across multiple dimensions, including preferred versus non-preferred music, fast versus slow tempo, high versus low volume, self-selected versus researcher-selected tracks, explicit versus censored content and genre differences. Based on this literature, the present intervention was developed based on modes of music selection and levels of intensity previously associated with beneficial effects on strength-endurance, maximal strength, and affective responses.

2.3.1. Post-session - Brunel music rating inventory-2 (BMRI-2) To ensure MUS was highly motivational and to understand how time-stretching may affect MUS15, participants were required to complete the BMRI-2 (BMRI PAPER REFERENCE HERE) assessing each track-set's characteristic.

2.4. Protocol and measurements: familiarization sessions The participants completed three familiarization sessions of all the strength, cognitive and questionnaire measures, before being considered as ready to participate in the study. Familiarization sessions took place at 09:30 h over a three-week period and finished one week before the study commenced to minimize learning effects. Participants arrived 0.5 hours before the start of the test and rested in a seated position, to minimize the influence of prior muscle activity. Participants completed the familiarization in the following order: i) cognitive battery of tests, ii) isometric maximal voluntary contraction (MVC) with and without percutaneous electrical stimulation, iii) back squat and bench press.

1. Cognitive battery of tests Trail Making Test (TMT; parts A and B) Rey Auditory Verbal Learning Test Stroop word-colour interference test ii) Isometric maximal voluntary contraction Participants performed isometric MVCs of the quadriceps muscles (3 s duration), both with and without twitch interpolation percutaneous stimulation.

Twitch interpolation The quadriceps were electrically stimulated using two moistened surface electrodes which were positioned proximally over the vastus lateralis and distally over the vastus medialis. The skin was prepared prior to placement of each electrode by shaving and light abrasion of the skin, followed by cleaning with an isopropyl alcohol swab.

Voluntary Activation = = [1 - (Size of interpolated twitch / Size of resting twitch)] x 100

During familiarization sessions, participants alternated between performing MVCs with and without twitch interpolation, so that approximately three trials of each were performed within each session. Standardized strong verbal encouragement during each familiarization session/trial and real-time visual feedback of their performance was provided to the participants via the computer display onto a large screen placed in front of them.

iii) Back squat and bench press Participants were familiarized with back squat and bench press three times prior to commencement of the testing cycle. Each participant was asked to perform the back squat with incremental loads (40, 60, 80% 1RM) for one repetition at each load and 5-min rest was allowed between each effort. Likewise for bench press, each participant performed one repetition against each incremental load (40, 60 and 80 % 1RM) and again 5-min rest was given between each working effort. This was done so that the upper loads required for the experimental trials were known to be comfortably within each of the participants' physical capabilities and as such there was minimal likelihood of them failing to perform the required efforts for data collection.

2.4. Experimental Protocol and Measurements The experimental sessions took place a week after the last familiarization with 72 h recovery between the three experimental conditions. Upon arrival at the laboratory, they were asked to insert a soft flexible rectal probe, approximately 10 cm beyond the external anal sphincter. Participants then rested for 30 min in seated position to assess resting rectal temperature (Trec). Skin temperature (Tsk) was assessed simultaneously by skin thermistors, which were placed at four locations on the left side of the body. The average of the last 5 min of the 30 min resting period was recorded for resting Trec and Tsk temperatures.

Participants completed profile of mood states questionnaire, their subjective rating of sleep (using sleep questions from the Liverpool Jet lag Questionnaire; effort and rating of perceived exertion (RPE). After the initial rest measurements, participants warmed up on a cycle ergometer for 5 min at 150 W. Post warm-up, participants removed rectal probes in private and skin thermistors were taken off. After which, MVC and bench press and back squat exercises were then undertaken.