Posts in general physical therapy
Stretching Not Shown To Improve Muscle Length
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Static stretching, involving holding a muscle at end of its’ length for a sustained period of time, is a common component of most individual’s exercise programs but its’ useful compared to other forms of exercise including aerobic and strength training is questionable. Research is unclear on the benefits of static stretching for most individuals, as well as, the ideal parameters for the most effective stretch. Conversely, utilization of mobility or dynamic warm up activities has been shown to improve subsequent performance and reduce an individual’s injury risk.

Our understanding behind the benefits of static stretching has evolved over the years due to research indicating flexibility gains are more likely due to changes in stretch tolerance (neural adaptations) vs. changes in length (muscular adaptations). Thus, individuals who stretch reduce their sensitivity to the tensile load and in turn are able to stretch beyond previous sensory barriers. A recent review of the literature shines further light on this area of exercise and further questions previously held beliefs.

Freitas and colleagues reviewed the available evidence on the impact of stretching on muscle and tendon tissue (Scand J Med Sci Sports. 2018). Authors reviewed 26 studies for their review of the literature. They reported stretching programs ranged from 3 to 8 weeks with an average of 20 minutes of exercise per week. Consistent with our current understanding participants demonstrated improvements in tolerance to passive stretch after training, but no changes were noted in muscle or tendon mechanical properties. This indicates the flexibility gains which followed the exercise programs were primarily due to an improvement in the ability to tolerate a stretch (desensitization). Thus, the authors concluded benefits experienced under 8 weeks are most likely to occur at the sensory level. Those without a specific mobility need (ex. post operatively or post immobilization) are advised to strength train through a complete range of motion to maintain and improve their current flexibility.

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Should Women with Osteoporosis Engage in High Intensity Resistance and Impact Training?

Despite the fact that bones respond favorably to high impact exercise and high-intensity resistance training these types of exercise are typically avoided in women with osteoporosis due to concerns that heavy loading of ‘fragile’ bone may result in increased risk of fracture. The LIFTMOR trial (Watson et al 2017, J Bone Mineral Research) calls into question this traditional belief that osteoporotic females should not lift heavy weights.

 This high-quality trial investigated the effects of an 8-month, 2x/week high intensity, progressive resistance and impact weight-bearing training (>80-85% of 1 rep max) in women with osteoporosis compared to women participating in low-resistance (<60% 1 rep max) exercise targeting mobility and balance. The high-intensity exercisers gained bone mass where their low-intensity counterparts lost bone mass. The high intensity group also had significant improvements in measures linked to fall risk as well as height.

 Importantly, in the over 2600 high-intensity training sessions, only 1 mild adverse event was noted and that participant returned to high intensity training to complete the study without concerns.

 High-intensity exercises included (*all exercise sessions supervised by a physical therapist):

Dead lift

Overhead press

Back squat

Jumping chin-ups with drop landings

 

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Skipping Breakfast Impairs Subsequent Resistance Training Workouts
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The basics of sleep, hydration, and nutrition are the low hanging fruits of performance. Easy to access, albeit hard to change at times, but extremely impactful on our overall health and wellbeing. The cognitive and physical benefits of breakfast are well established and the timing and contents of the meal has been shown to influence future athletic performance. A previous blog discussed the importance of pre and post workout protein intake and a new article further supports the utilization of pre workout meal.

Authors in the Journal Of Strength And Conditioning Research studied the impact of a pre workout meal on resistance trained men (Naharudin et al. 2019). Participants were included if they performed strength training at least 3 days per week and ate routinely ate breakfast prior to their workouts. In the study, each participant’s 10 rep max was found during a back squat and bench press exercise. They were then randomized to either a breakfast containing 1.5 grams of carbohydrate per kg of body weight or water only. 2 hours post meal each participant performed 4 sets at 90% of their 10 rep max on each of the 2 exercises. As expected, total work performed and performance was significantly lower in the group who skipped breakfast.

No Strength Gain Differences Found Between Low and High Load Exercise IF Reps Are Taken To Failure
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In our previous blogs we have discussed the errors most exercise participants make when selecting intensity (amount of weight) while at the gym. Humans are often poor estimators and when it comes to strength training they often select weights below the intensity required to promote optimal strength and muscle gains. Trying to base a weight off a one repetitions maximum is time consuming, impractical, and possibly contraindicated for some weight training participants. Conversely, research articles continued to support using fatigue as an alternative to the 1 repetition maximum weight selections. Fatigue takes the guesstimation out of exercise weight selection and can be very effective at promoting optimal strength gains.

Dinyer and colleagues in The Journal Of Strength And Conditioning Research randomized untrained women to either a low or high intensity weight training program (2019). All of the women underwent clinical and body mass (% fat free mass) testing before and after the 12 week training program. Each group was assigned to a weight equaling a low (30% of 1 rep max) or high (80% of 1 rep max) intensity for 2-3 sets during 4 exercises (lat pulldown, military press, leg extension, and leg curl). Both groups took their workout sets to fatigue. Authors reported while both groups improved their maximum strength at the end of the 12 weeks there were no differences between the low or high intensity groups. In addition no changes in fat free mass were noted in the groups.

This study highlights the importance of working with a sub maximal weight and lifting it a maximum number of times for optimal strength gains. We recommend selecting a repetition range first (ex. 8-12 reps) then selecting a weight, but adjusting this weight higher if you can perform more repetitions than your established rep range.

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The Neck's Impact On Recovery From Concussion
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Concussions have received significant media and medical research attention over the last decade due to in part to the incidence of chronic traumatic encephalopathy (CTE) among former football athletes. This increase in attention to brain injuries has led to improved medical training and early recognition of concussion symptoms leading to improved care of athletes and patients suffering from post concussion symptoms. Authors estimate an incidence of 750 cases of mild traumatic brain injury per 100,000 person years and close to half of all of these individuals will experience post concussion symptoms including headaches, neck pain, dizziness, balance impairments, and fatigue. Experts in concussion report a large percentage of these symptoms may not be due to the brain but instead concurrent injury to the neck, specifically the upper neck bones.

Kennedy and colleagues examined a cohort of patients with persistent post concussion symptoms (median 5 weeks post concussion) to determine the coexistence of associated neck impairments (JOSPT. 2019). Authors examined patients both before and after treatment of their necks. Consistent with prior research impairments of the upper joints and musculature were found among this cohort including neck pain, limited range of motion, muscle and joint tenderness. These impairments are consistent with findings from patients with cervicogenic headaches and likely help explain the positive benefits of treating the neck in patients with concussion.

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Does Hamstring Stretching Improve Muscle Length?
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Stretching either dynamically or statically has long been shown to create both short and long term improvements in flexibility, but the mechanism of action behind this form of exercise continues to evolve. Changing human tissue takes considerable time and consistent forces. For example, consider muscle growth or bone density adaptions to exercise. Previous research on the benefits of stretching assumed a structural change in the muscle (sarcomeres in series) was responsible for improvements in muscle flexibility, but more recent research demonstrates improvements in stretch tolerance are more responsible for these positive changes. A recent article examined these mechanisms in a group of individuals with limited hamstring length.

Brusco and colleagues assessed the impact of static hamstring stretching in a group of individuals with limited hamstring flexibility (Eur J App Physiology. 2019). Participants performed a seated hamstring stretch on an isokinetic machine to their maximum tolerance. Hamstrings were stretched for 8 bouts of 60 seconds, twice a week for 6 weeks. Total duration under stretch equaled 96 minutes over the 6 weeks. Authored measured both flexibility and muscle characteristics before and after the study. Consistent with prior research each individual’s range of motion improved but no changes in muscle tendon mechanical properties were noted. This indicates improvements in flexibility were secondary to the improvements in an individual’s tolerance to stretch. Thus, trained individuals were conditioned to tolerate more stretch as they moved through the study.