***

Self experimentation

• Vitamin D – 6,000IU in the morning - this is still working well.  I am still wondering whether to put this up to 8,000IU to see what happens.  This is because I read Seth Roberts had tried this dosage with good results and I read something by Charles Poliquin that suggested that May was the point in the year that most people had very low Vitamin D levels.
• Epsom salts – I am currently taking three baths a week with about 350-400g of salts in.  I always sleep a lot better on those nights than other nights.  I also notice a deterioration in sleep if I miss a bath because I am away.  This is a significant supplement for me.
• No coffee – I haven’t been hitting the espresso much recently and I am tending towards just drinking coffee on a Saturday, when I carb-up.  I drink 6-8 cups of green tea most days instead.  This seems to work relatively well at keeping me going without putting me into a caffeine coma.
• Weight loss – I was just over 90kg at the end of March.  I am aiming to drop a few kilos very slowly down to around 84-85kg over about 12 weeks in total.  It’s not onerous but it does require me to remember not to eat between meals.  Week 1 – 89.4kg, week 2 – 88.4kg, week 3 – 88.4kg, week 4 – 87.9kg, week 5 – 87.0kg.

***

Workouts

• Bench – this is still fun and shoulders seem to still be quite happy with it.  I tried doing a back-off set of five with 90kg (about 80% of the work weight) this week and it seemed to work well to finish the session.  I may keep this in for a few sessions to see how it affects things.  If I really like it, I may try it with the back squat session too.
• Hepburn ’B’ routine - I am currently using the power part of Hepburn’s ‘B’ routine for my squat and bench.  I used the power part of his ‘A’ routine for my squat for the best part of 18 months and it was awesome.  I first tried using the ‘B’ routine briefly a while back for my press and it didn’t really take.  So I decided to give it another try on a different lift when I began to hit the wall at the end of March and needed to drop the volume for a bit.  Impressions so far could be summarised by saying that the reduction in volume is very noticable and it’s a lot easier to get in the gym and get it done even when there is a lot going on in your life.

***

Fri: Upper

• Overhead press – 4 sets of 4-6 reps – 60kg – (4 x 4)
• Chest supported row – 80kg – 8 sets 0f 11 reps
• Dips – 4 sets of 3-6 reps – 40kg – (1 x 6, 3 x 5)

Sat: Upper

• Bench – 5-8 sets of 1 rep – 118kg (5)
• Wide grip chins – 4 sets 0f 4-6 reps – 25kg (2 x 5, 2 x 4)
• Rack pull to shrug – 6 sets of 2-3 reps – 250kg
• Hammer curls – 20kg – 3 sets of 8-12 reps (10)

Sun: Lower

• Back squat – 5-8 sets of 1 rep – 166kg (5)
• RDL – 3 sets of 4-6 reps – 165kg (3 x 5)

Mon: Upper

• Overhead press – 4 sets of 4-6 reps – 60kg (1 x 5, 3 x 4)
• Chest supported row – 80kg – 8 sets 0f 11 reps
• Dips – 4 sets of 3-6 reps – 40kg (2 x 6, 2 x 5)

Tues: Upper

• Bench – 5-8 sets of 1 rep – 118kg (6)
• Wide grip chins – 4 sets 0f 4-6 reps – 25kg (3 x 5, 1 x 4)
• Rack pull to shrug – 6 sets of 2-3 reps – 250kg
• Hammer curls – 20kg – 3 sets of 8-12 reps (11)

Weds: REST

Thurs: Lower

• Back squat – 5-8 sets of 1 rep – 166kg (6)
• RDL – 3 sets of 4-6 reps – 165kg (3 x 6)

Good progress still being made, although nothing drastic is occurring.  Basically, bodyweight is still creeping down gently and lifts are all creeping up cautiously.

***

Self experimentation

• Vitamin D – 6,000IU in the morning - this is still working well.  However, after reading a post by Seth Roberts, I am starting to consider putting this up to 8,000IU.  I also read something by Charles Poliquin that suggested that May was the point in the year that most people had very low Vitamin D levels.
• Epsom salts – I just noticed that I have not been commenting on my use of epsom salts.  These are undoubtedly the most significant supplement I use.  I take three baths a week with about 350-400g of salts in.  I always sleep a lot better on those nights than other nights.  I also notice a deterioration in sleep if I miss a bath because I am away.
• No coffee – I haven’t been hitting the espresso much recently and I am tending towards just drinking coffee on a Saturday, when I carb-up.  I drink 6-8 cups of green tea most days instead.  This seems to work relatively well at keeping me going without putting me into a caffeine coma.
• Weight loss – I was just over 90kg at the end of March.  I am aiming to drop a few kilos very slowly down to around 84-85kg over about 12 weeks in total.  Week 1 – 89.4kg, week 2 – 88.4kg, week 3 – 88.4kg, week 4 – 87.9kg, week 5 – 87.0kg.

***

Workouts

Some general observations and for those people who have asked questions:

• Bench – this is still fun and shoulders seem to still be quite happy with it.  It would be nice to get up to 130kg or so in the next couple of months but we shall see.
• Rack pull to shrugs – these are from above the knee and I don’t feel them in the legs at all.  They seem to have suddenly become a bit easier so I am thinking of pushing the weight up quickly and seeing what happens.
• Chest supported rows – I am doing high reps partly because of the postural benefits of getting more volume in (I still do a lot of work sitting down) and partly because my dumbbells don’t go any higher than 40kg (c. 85lbs).
• RDLs – these were a big shock to the system.  The sets of five reps felt like cardio when I first did them, although the 160kg weight feels like air after the 240kg rack pull on the previous day.  They do make my hamstrings sore the next day, though, so I have dropped the glute-ham raises for a bit until they calm down.
• Hammer curls – I do these mainly for a break between shrugs with the weight that is usually set up on the dumbbell handles, hence the higher reps.

***

Fri: Upper

• Overhead press – 4 sets of 4-6 reps – 58kg – (3 x 6, 1 x 5)
• Chest supported row – 80kg – 8 sets 0f 11 reps
• Dips – 4 sets of 3-6 reps – 40kg – (3 x 4, 1 x 3)

Sat: Upper

• Bench – 5-8 sets of 1 rep – 114kg (7)
• Wide grip chins – 4 sets 0f 4-6 reps – 20kg (2 x 6, 2 x 5)
• Rack pull to shrug – 6 sets of 2-3 reps – 250kg (6 x 2)
• Hammer curls – 18kg – 3 sets of 8-12 reps (12)

Sun: Lower

• Back squat – 5-8 sets of 1 rep – 164kg (7)
• RDL – 3 sets of 4-6 reps – 165kg (3 x 4)

Mon: Upper

• Overhead press – 4 sets of 4-6 reps – 60kg (4 x 4)
• Chest supported row – 80kg – 8 sets 0f 11 reps
• Dips – 4 sets of 3-6 reps – 40kg (4 x 4)

Tues: Upper

• Bench – 5-8 sets of 1 rep – 114kg (6)
• Wide grip chins – 4 sets 0f 4-6 reps – 25kg (3 x 6, 1 x 5)
• Rack pull to shrug – 6 sets of 2-3 reps – 250kg (1 x 3, 5 x 2)
• Hammer curls – 20kg – 3 sets of 8-12 reps (8)

Weds: REST

Thurs: Lower

• Back squat – 5-8 sets of 1 rep – 164kg (8)
• RDL – 3 sets of 4-6 reps – 165kg (3 x 5)

***

Science, scientific interest and news

• Boing Boing has a great logical fallacies poster, in case you missed it.  Put it in your forum signature line and save yourself a lot of time arguing.  (I save even more time by not frequenting forums).
• NPR reports on some recent research (you can get the full paper there) that criticises the notion of the normal distribution in human endeavours.
• Tony Ingram at BBOY Science has written a long discussion of placebo, which is well worth your time.  However, I do have a rhetorical question, because I am completely results-focused and dislike authority of any kind.  Is it “bogus” if it works?  If that’s too black-and-white, let me add another consideration into the equation: include patient care as an integral part of the treatment and ask the question again.  If you really don’t understand the point I am making, go watch Patch Adams again.

Sleep and stress

• Joel Smith talks about a subject close to my heart – the importance of reducing stress in order to maximise performance.
• Dr Briffa reports on a recent study that explains how sleep makes it easier to lose weight.

Personal training and coaching

• Charles Poliquin’s team have reviewed an article comparing sprints with long-distance running programmes for improving aerobic performance and body composition.  Interestingly, while both programmes were effective in improving 2km times, the sprint programme caused much greater fat loss.
• Weighty matters discusses some recent research that has been done into the metabolic effects of massive weight-loss plans as can be seen on television programmes like The Biggest Loser.  It’s provactive stuff that deserves looking into properly.
• And Jerry Brainium reports on some recent research that indicates it is possible to gain muscle while on a very slight calorie deficit.  The thing that excited me about this research was that it was done on athletes and not on overfat beginners.
• Mike Nelson explains why he doesn’t use foam rolling any more.  He also defends himself against a hostile attack with dignity.  As Mike explains, we should be working together to find ways to improve our clients progress and our own progress.  We shouldn’t be fighting over why people don’t agree with us.  After all, this is science and not politics, right?

Injury prevention

• Phil Page discusses a recent study performed with UK soccer players.  It found that the soccer players who had chronic groin strains also had decreased gluteus medius (hip abductor) muscle activation on the injured leg.
• Sports Medicine Research reviews a study about the injury incidence amongst ultra-marathon runners.

***

That’s all folks!

A Comparison of Strength and Power Characteristics Between Power Lifters, Olympic Lifters, and Sprinters – in this fascinating little study, the researchers found that the sprinters were able to perform higher jump squats at the same percentages of their 1RM squat than Olympic lifters.

Strength and power characteristics of sports speed - this study found strong correlations between jump squat performance as a proportion of body weight and sprint ability, as well as between jump squat performance and countermovement jump performance (i.e. vertical jump ability).  However, there were not good correlations between 3RM squat performance and sprint or countermovement jump performance, even when expressed relative to bodyweight.

These studies aren’t necessarily related to the study I am looking at today but if you are looking for studies that include jump squats, these are the only other ones I have reviewed to date.

***

So what’s the study?

Today’s study is called Peak power, force and velocity during jump squats in professional rugby players, by Turner, Unholz, Potts and Coleman, in Journal of Strength and Conditioning Research, 2011.

The researchers wanted to investigate the influence of load on peak power output, peak barbell velocity, and peak vertical ground reaction force during jump squats performed by professional athletes.

***

So what did the researchers do?

The researchers experimented using 11 professional rugby union players in a single session.  The rugby players comprised various positions (see this guide if you are unsure), including both forwards and backs, including 5 front-row players, 1 back-row player (sic), 3 half-backs and 2 wingers.

The subjects were asked to perform a range of jump squats between 20kg (the Olympic bar) up to and including their 1RM jump squat.  The 1RM jump squat was estimated in advanced as their 5RM back squat.  Each attempt was followed by a 3-minute rest period to allow adequate recovery.  Each subject was deemed to have reached their 1RM when their feet did not leave the ground, which was monitored and judged using the force plate data in real time.

***

What happened?

The researchers found that there was a significant correlation between the load used for the jump squats and power output.  They found that peak power output was highest at the lower end of the loads used, which corresponded to 20-30% of 1RM jump squat (which, you may recall, was estimated at 5RM back squat).

So if the 5RM back squat was 150kg then the starting point for estimating the optimum load for peak power output would be using a jump squat of just 30-45kg.  That’s not a lot of weight.

However, since lower loads than 20% were not used, the researcher speculate that jump squats with less weight than 20% of 1RM, or even no weight at all, would yield higher peak power outputs.  In other words, plyometrics would yield higher peak power outputs than jump squats.

***

Why is this interesting?

It’s interesting because right at the beginning of the study, the researchers discuss how the highest power output might be achieved for a given jump squat exercise and they discuss the importance of high power output for athletic performance.  But they don’t actually state that they are assuming that training at the highest possible power output will automatically create the best training effect for power output.  Nevertheless, this assumption is being made.  And while it sounds sensible (unless you are an Olympic lifter in which case it probably sounds crazy), it might not necessarily be true.

For example, look at a study I reviewed recently on accomodating resistance (Alterations of speed of squat movement and the use of accommodated resistance).  In this study, you can see that there was a very significant difference in the level of power developed between the different groups over the course of a 12-week training programme, as follows:

• The heavy resistance/slow movement group improved power 4.8%
• The lighter resistance/fast movement group improved power 11.0%
• The accomodated resistance group improved power 17.8%

So if you just looked at the first two groups, you might suppose that since the group that used the heavier weight ended up with a lower power output improvement, this supports the idea that training at higher power outputs means you end up improving power by a greater amount.

However, this seems to break down when you use accomodating resistance.  While it is not possible to see whether the power outputs of the accomodating resistance group were higher or lower during training in that study, we can look at another study and see that the addition of accomodating resistance does not acutely change the power output when compared to a light weight.

For reference, you can see this in Acute effects of elastic bands during the free-weight barbell back squat exercise, where the addition of bands did not cause any acute changes in power output compared with the lighter squat weight.

Of course, there are huge limitations with making inferences between studies like this but if you don’t speculate, you won’t accumulate…

And if you enjoyed reading this, there’s lots more reviews at Strength and Conditioning Research.

RFD is simply a measurement of how quickly you can get to a given level of force.  But what influences RFD?  How can we manipulate it?  So far, researchers have identified a number of factors, including:

• The level of neural activation
• Cross-sectional muscle area
• Fibre-type composition

Neural activation is typically measured by the EMG activity, which is a measure of the electrical activity within the muscle and therefore of the motor unit action potentials carried down the efferent nerves to the muscle fibres.

***

What’s the study?

The study is called Increased rate of force development and neural drive of human skeletal muscle following resistance training, by Aagaard, Simonsen, Andersen, Magnusson and Dyhre-Poulsen, in Journal of Applied Physiology, 2002.

The researchers wanted to investigate changes in RFD, impulse and neural drive as a result of by heavy resistance training.

***

What did they do?

The researchers took 15 male subjects and put them through a progressive heavy-resistance training programme for 14 weeks.  The training programme included a number of lower body exercises, including hack squats, leg press, knee extension, hamstring curls, and seated calf raises.  The training sessions comprised 4-5 sets of loads ranging from 3-10RM.

Maximum strength, maximal RFD and the impulse of the quadriceps muscle were calculated using a dynamometer that permitted both isokinetic and isometric operations.  EMG readings were taken simultaneously.

***

What happened?

The researchers found that following the 14-week heavy resistance training programme, the measurements changed as follows:

• Maximum strength, as measured by maximum isometric quadriceps contraction increased with training, from 291.1 ± 9.8 to 339.0 ± 10.2 Nm.
• RFD increased at various time points as follows:
• 30ms – from 1,601 ± 117 to 2,020 ± 19 Nm/s
• 50ms – from 1,802 ± 121 to 2,201 ± 106 Nm/s
• 100ms – from 1,543 ± 83 to 1,806 ± 69 Nm/s
• 200ms – from 1,141 ± 45 to 1,363 ± 44 Nm/s
• Contractile impulse increased at the same time points as follows:
• 0 – 30ms – from 0.73 ± 0.04 to 0.91 ± 0.05 N/m/s
• 0 – 50ms – from 2.12 ± 0.14 to 2.64 ± 0.14 N/m/s
• 0 – 100ms – from 8.48 ± 0.50 to 10.18 ± 0.45 N/m/s
• 0 – 200ms – from 27.97 ± 1.37 to 33.31 ± 1.25 N/m/s
• Normalised RFD to reach 1/6 of maximum strength increased 15%, while normalised RFD to reach 1/2 maximum strength and 2/3 maximum strength did not change significantly.
• Mean average EMG increased 77–143% in the vastus lateralis (0–30, 0–50, and 0–100 ms), 25% in vastus medialis (0–100 ms), and 22–44% in the rectus femoris (0–50 and 0–100 ms).  However, no changes in maximum EMG amplitude were observed as a result of training.
• Rate of EMG rise (change in EMG divided by change in time) increased 54–106% in vastus lateralis (0–30, 0–50, and 0–75 ms), 41–68% in vastus medialis, and 71–97% in rectus femoris (0–30 and 0–50 ms).

***

So what did they conclude?

The researchers conclude that the 14-week, heavy resistance training programme caused significant increases in RFD and impulse, as well as in the neural drive to the quadriceps muscles.

They note that the significant (15%) increase in RFD observed in the first 1/6 of the development of maximum force corresponds to the very onset of contraction.  They therefore suggest that qualitative changes might have occurred as a result of this training programme, such as:

• increased motoneuron recruitment
• changes in motoneuron firing frequency
• increased incidence of discharge doublets
• changes in fibre type
• changes in sarcoplasmic reticulum Ca2+ kinetics

The researchers also note that the increases in RFD noted above were in fact also accompanied by a rise in efferent neural drive, as measured by the increase in mean EMG activity.  However, it is also noted that the the rate of increase of the EMG signal also increased, which may have had an impact on the results.

The researchers also note that in a connected study using a sample of the same subjects following the same programme, it was found that type II muscle fibre hypertrophy was observed after the period of training (19% increase cross-sectional area of those fibres).  However, no change in fibre-type proportion was noted.  In addition, muscle fibre pennation angle also increased, which allowed for a significant increase in physiological muscle fibre area.

***

Practical implications

The important thing to note from this study is that heavy resistance training increases maximum strength, rate of force development (RFD), neural drive (as measured by EMG activity) and type II fibre hypertrophy.

This ties in with Bobbert’s support of Verkoshansky’s comments in the review article on depth jumps I read last week.  Bobbert and Verkoshansky believed that it is possible in improve jumping performance first by simply practicing the sport movement, secondly by using heavy resistance training and thirdly by using plyometrics in that order.

It may be the case that, until the appropriate level of strength is achieved, plyometrics are not necessary to improve rate of force development, as the weights will do that for you anyway.  Where the appropriate level of strength might be is another matter…

And if you enjoyed reading this, there’s lots more reviews at Strength and Conditioning Research.

***

Strength & Conditioning

1. Can maximal squat strength predict 5m sprint times in untrained people as well as athletes?
2. Are differences in muscular hypertrophy along the length of a muscle after long-term resistance training attributable to the regional differences in muscle activation during the exercise being performed?
3. Do hex-bar deadlift jumps allow higher rates of force development and peak power outputs than traditional jump squats?
4. Are ground contact times related to running economy?
5. Which commonly used rehabilitation exercise has the highest gluteus medius activation?
6. Does training with powerlifting gear lead to greater strength gains than without gear?
7. Is sprint performance affected by leg recovery in the flight phase?
8. Are total ground reaction forces during sprinting correlated with 100m performance?
9. Is fatigue different after strength and hypertrophy workouts?
10. Does muscle adapt uniformly along its length to exercise?
11. Is periodization any better than a random, varied program?
12. Do plyometrics lead to soccer-related performance improvements in adolescents?
13. What happens to gluteal activation in monster walks when resistance bands are moved distally from the knees to the ankles to the forefeet?
14. Does strength training really help sports performance?
15. What is the difference in muscle activation between bilateral and unilateral bridge and plank exercises?

***

Biomechanics

1. Does a wide-stance, powerlifting squat automatically lead to increased forces on the lower back?
2. Does a pelvic compression belt applied at a high position decrease laxity and increase stiffness of the sacroiliac joint?
3. Is there a clinical model for the human fascial system?
4. Are kinematic running patterns and spring mass behaviour affected by the fatigue caused by repeated sprints?
5. Is there a low-back cost to hip-centric exercise?
6. In female weightlifters, are lifts more dependent on technique or power output?
7. Which hamstring muscle is under the most stress during sprinting?
8. Is barefoot running more economical than shod running?
9. Do wide stance squats result in greater activation of adductors and gluteus maximus?
10. What causes the residual force enhancement after stretch?
11. Do barefoot runners tend to be mid-foot and forefoot strikers?
12. Does leg stiffness change in sprinters with fatigue caused by repeated sprints?
13. Does isometric rotational training improve baseball bat velocity?
14. Does trunk muscle activity differ when lifting objects of unexpected weight?
15. What is the current state of fascia research?

***

Physiology

1. Is there a dose response in respect to exercise performed and improvements in insulin sensitivity?
2. Does growth hormone supplementation have any effect on muscular strength and size?
3. Do cardiovascular or muscular fitness improve lipid profiles in overweight men?
4. Does lactic acid actually benefit muscles during anaerobic exercise?
5. Is the molecular signaling in muscle different after strength or hypertrophy workouts?
6. What is the role of myostatin in muscle homeostasis?
7. Is age-related muscle loss actually activity-related muscle loss?
8. What effect does strength training have on satellite cells?
9. Can skeletal bone gains achieved by strength training in youth be maintained into old age?

 ***

Physical Therapy

1. Does the relative activation of the hip muscles affect the degree of anterior pelvic tilt during prone hip extension?
2. Does vastus medialis muscle weakness lead to lateral movement of the patella?
3. Does a diaphragmatic breathing program improve abdominal motion during breathing?
4. Do tight hamstrings predict lower back pain during prolonged standing?
5. Are we currently underestimating the damage to health via inactivity?
6. Is general joint laxity a risk factor for knee injury in sport?
7. Is the current approach to the treatment of lower back pain unreasonably avoiding the use of manual therapy?
8. What proportion of sports injuries is caused by overuse?
9. Is massage an effective tool for reducing muscle soreness after exercise?
10. Is barefoot running biomechanically different from traditional shod running?
11. Is the lack of reliability in palpation for establishing the location of bodily discomfort caused by a lack of expertise?
12. Does increasing the strength of the quadriceps muscles reduce patellofemoral pain?
13. Do traditional markers of flexibility, strength and endurance correlate with the scores on a movement screen?
14. Does neural tension reduce hamstring flexibility?
15. Do subjects with lower back pain display less hip and pelvic ROM during rotation than subjects without?
16. Can we learn anything about running from barefoot running?

***

So don’t forget, you’ll need to subscribe today to make sure you receive the May edition when it comes out tomorrow.  Check out the subscribe page here.

I’m still having a lot of fun with the bench press and the shoulders feel OK so far.  I should note that it is probably equivalent to a one-board pin press, as I am working from the bottom up to avoid killing myself while training singles alone in my garage…

***

Self experimentation

• Vitamin D – 6,000IU in the morning - this is still working very well and I am going to carry on doing this for a while.
• No coffee – this has now stopped and I am back on to a single shot of espresso after lunch.  It’s nice without sending me into the caffeine-imposed daze that I used to get in the afternoons.
• Weight loss – I was just over 90kg at the end of March.  I am aiming to drop a few kilos very slowly down to around 84-85kg over about 12 weeks in total.  Week 1 – 89.4kg, week 2 – 88.4kg, week 3 – 88.4kg, week 4 – 87.9kg.

***

Workouts

Fri: Upper + hamstring assistance

• Overhead press – 4 sets of 4-6 reps – 58kg
• Chest supported row – 8 sets 0f 10 reps
• Chins – 4 sets of 2-3 reps – 40kg
• Dips – 4 sets of 3-4 reps – 40kg
• Glute-ham raise – blue and pink bands – 3 sets of 5 reps

Sat: Upper

• Bench – 5-8 sets of 1 rep – 114kg (5)
• Wide grip chins – 4 sets 0f 4-6 reps – 20kg (4 x 5)
• Rack pull to shrug – 6 sets of 2-3 reps – 240kg (4 x 3, 2 x 2)

Sun: Lower

• Back squat – 5-8 sets of 1 rep – 164kg (5)
• RDL – 3 sets of 4-6 reps – 160kg (3 x 4)

Mon: Upper + hamstring assistance

• Overhead press – 4 sets of 4-6 reps – 58kg
• Chest supported row – 8 sets 0f 10 reps
• Chins – 4 sets of 2-3 reps – 40kg
• Dips – 4 sets of 3-4 reps – 40kg
• Glute-ham raise – blue and pink bands – 3 sets of 5 reps

Tues: Upper

• Bench – 5-8 sets of 1 rep – 114kg (6)
• Wide grip chins – 4 sets 0f 4-6 reps – 22.5kg (4 x 4)
• Rack pull to shrug – 6 sets of 2-3 reps – 240kg (5 x 3, 1 x 2)

Weds: REST

Thurs: Lower

• Back squat – 5-8 sets of 1 rep – 164kg (6)
• RDL – 3 sets of 4-6 reps – 160kg (3 x 5)

***

Resistance training

• Conditioning Research draws our attention to some recent research about the potentially similar effects of load in hypertrophy, so long as the load is taken to failure.

Personal training and coaching

• I often read the EliteTrack blogs, although I don’t always find myself instinctively agreeing with everything that is said.  As always, this is a good sign when reading.  If you are always reading things you agree with, I always think that there is probably something wrong with your mindset.  This interesting speculation by Carl Valle wonders whether the reason for the decreased gluteal activation he is seeing in athletes is because they cycle less as kids, even though coaches often reduce cycling in their conditioning programmes to avoid reductions in gluteal activation.  A little could be better than nothing at all…
• Picking apart life’s mess has a great post on why it will appear to coaches that praise of good performances leads to worse performances and criticism of poor performances leads to better performances.  It’s all a matter of statistics.

Diet, paleo diet and evolutionary adaptations

• Healthy Diets and Science reports on some relatively old research showing that higher cholesterol levels are correlated with longer lifepans.  Given that this study was published nearly 20 years ago, I wonder whether those of us who have hope that the medical profession will come to its senses about cholesterol are whistling in the dark.
• Dr Briffa reports on a very recent research review on the effectiveness of high-protein diets for a range of health measures.

Stress, sleep and health

• Matt Metzgar has found another study indicating that lower levels of stress tolerance lead to increased calorie consumption.
• Fight Ageing reports that exercise reduces the risk of Alzheimer’s Disease.

Other interesting stuff

• Sign Of The Times reports on recent research suggesting that the memento mori, or the contemplation of death on a regular basis, is not a damaging psychological phenomenon but potentially a very helpful one.  It can certainly help people put minor problems into proper perspective and sometimes it can really motivate people to change things about their lives that they don’t like.
• And as the Scholarly Kitchen notes regarding researchers, most want less to read, rather than more.  This is why our Strength and Conditioning Research publication is so cool, because it means you only have one place to look each month for everything that’s new in the sector.

***

That’s all folks!

Today’s study is kind of a follow-up to that thought process, although, as always, the answers you go looking for are not the ones you find…

***

So what’s the study?

The study is called Dynamic control of muscle stiffness and h reflex modulation during jumping and hopping, by Dyhre-Poulsen, Simonsen and Voigt, in Journal of Physiology, 1990.

Now, let’s not get intimidated by the excessively complicated title.  The researchers are just investigating the size of the h reflex and the stiffness of the muscles.  If we just cover off the h reflex, everything else will fall into place…

***

So what is the h reflex?

The h reflex, or Hoffmann’s reflex, is a muscular reaction to an electrical stimulus.  It occurs when you electrically stimulate the nerves that innervate the Ia afferent neurons leading from the muscle spindles.  Again, relax, as we can easily explain the processes that are going on here.

You may recall that muscle spindles are found within muscles.  Muscle spindles are simply sensory receptors that monitor the length of the muscle at all times.  And when a muscle is stretched, the Ia afferent neurons are the ones coming out of the muscle spindle transmiting information about this stretching process to the spinal cord.  They do this in the form of changes in the rate of action potentials.  The spinal cord then transmits information back via efferent neurons, which then causes changes within the muscle.  This process is at the root of the stretch reflex.

The h reflex can be tested using a mild electrical stimulator to create the stimulus and an EMG set, to record the muscle activity response.  The muscle activity response usually takes the form of a clear wave, called an h wave, and it occurs around 0.03s after the stimulus.

The h reflex is very similar to to the knee-jerk reflex, where the physician taps you on the knee and your leg jerks.  However, if you note the definition above, you will see that the h reflex is initiated by the electrical impulse stimulating the Ia afferent neuron and therefore skips out the muscle spindle.  The knee-jerk test goes via the muscle spindle because it is mechanically induced, whereas the h reflex goes via the Ia afferent neuron because it is electrically induced.

***

So what did the researchers do?

The researchers wanted to see how the central nervous system, i.e. the spine, controlled the intrinsic properties of the muscles during hopping and jumping movements, including depth jumps.

They decided to use the h reflex as a proxy for the stretch reflex so as to avoid the complication of trying to adminster a controlled mechanical stimulus during movement.  They therefore set out to see what happened to the h reflex depending on what kind of movement was performed.

To achieve this, they had three experienced volleyball players carry out three different movements over a 5 hour period, racking up around 200 jumps each.

• Landing from a 60cm box
• Depth jumps from a 60cm box
• Hopping

During the movements, the researchers took measurements using a force plate, surface EMG electrodes and a camera that picked up the reflective markers on the subjects’ key anatomical markers.

Also during the movements, the researchers instigated an h reflex by way of a photocell positioned at 45cm above the ground.  As the subjects dropped or hopped past the photocell, the h reflex was initiated by way of an electrical stimulus to the subject’s calf muscle.  However, the stimulus was not delivered immediately upon the subject passing the photocell but was administered after a random time delay, ensuring that in each jump, the h reflex occured at a different time, enabling the researchers to build up a broad picture.

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 And what did they find?

The researchers observed that:

• In landing – the h reflex was very low upon landing but recovered afterwards.  The h reflex during movement was generally lower than the h reflex at rest.  EMG activity measurements recorded a preparatory co-contraction of the soleus and anterior tibialis prior to landing.
• In hopping – the h reflex was low during the flight phase but increased just before touchdown and remained high in the stance phase.  EMG activity measurements recorded a preparatory contraction of the anterior tibialis prior to touchdown but not of the soleus.  The EMG activity of the soleus peaked at 45ms after touchdown, probably on account of the stretch reflex, and remained high until take-off again.
• In drop jumps – the h reflex declined towards landing and was very low at landing.  As with the landing, EMG activity measurements recorded a preparatory co-contraction of the soleus and anterior tibialis prior to landing.

In general, the researchers found that the h reflex was lower during movement than at rest.  They also found that the size of the h reflex was independent of the EMG activity of the soleus and anterior tibialis muscles.

The researchers used their collected data to calculate the stiffness of the muscles at various points during the movements.  They found that the stiffness of the muscles peaked 10ms after impact and then decreased significantly, before becoming negative for the remainder of the landing.

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So what did the researchers conclude?

The researchers found that the h reflex is strongly inhibited during a downward jump.  They conclude that since this inhibition occurs significantly before touchdown, this must be part of the process of motor control over the landing.

The researchers also found that the EMG activity was very different between landing and hopping.  During hopping, there was no preparatory contraction of the soleus muscle.  Rather the EMG activity began just after touchdown, which was probably the stretch reflex.

The researchers also discovered that the stiffness of muscles peaked 10ms after impact, decreased and then became negative.  Negative stiffness implies that mechanical energy is being lost and that the muscles are no longer functioning as springs but as dampening agents.  Since the EMG activity does not correlate with this shift in stiffness, the researchers suggest that it is unlikely that this change is a result of antagonist muscle activity.

Ultimately, the researchers suggest that the property of muscle stiffness is controlled by the central nervous system.  They explain that the muscle is changed from a spring to a dampening agent.  They also note that afferent input (such as occurs during the stretch reflex and the stretch shortening cycle) cannot be that important, as the h reflex (a proxy for the stretch reflex) is overriden by the central nervous system during the movements in this experiment.

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Limitations

Obviously, this study had some big limitations, the biggest of which is probably the assumption that the h reflex can be used as a proxy for the stretch reflex.  However, there is also an assumption that it is valid to test the stretch reflex during another movement that has already been initiated.  Finally, there was some serious mathmatical manipulation involved in calculating the muscle stiffness, which involved some chunky assumptions.

• Short-term effects on lower-body functional power development: weightlifting vs. vertical jump training programs - this study investigated whether there is a difference in training effect depending on whether physical education students were trained using Olympic lifts or vertical jumps.
• Does performance of hang power clean differentiate performance of jumping, sprinting, and changing of direction? - this study found that the hang clean does correlate well with other athletic tasks.

This week, I’m going to continue in the same vein but focus a little more on jumping.  I did a brief two-part series on plyometrics a while back but I think there is still plenty more to go at in this field.  If you’d like to check out the older reviews, you can find them here:

• A comparison of plyometric techniques for improving vertical jump ability – the researchers studied a number of different plyometrics techniques and compared them over a period of time. Depth jumps were found to be most effective.  However, they also found that there were no increases in elastic energy storage as a result of jump training.
• Muscle fibre characteristics after a period of plyometric training – researchers were surprised to discover that an 8-week period of plyometrics improved vertical jump ability by causing hypertrophy.

OK, enough looking back through the archives.  Let’s get on and look at today’s study, as there is much to be learned.

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So what’s the study?

Today’s study is a review article called Drop jumping as a training method for jumping ability, by Bobbert, in Sports Medicine, 1990.

Bobbert wrote the review article to help strength coaches grasp the breadth of research into depth jumps and to help them to design jump programmes that would help their athletes.

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So what did he find?

It all started with Yuri Verkoshansky

Bobbert explains that drop jumping, or depth jumping, was popularised by Yuri Verkoshansky, who used it with Soviet track and field athletes to great effect during the 1950′s and later.  You can read more about Verkoshansky here and here.

However, as many people will be keen to tell you, because of the iron curtain and the language barrier, exactly how Verkoshansky used depth jumps in track and field training programmes remains poorly reported.  Bobbert explains that Verkoshanksy saw the training process as progressing from:

1. practicing the sport,
2. using weights to develop strength, and
3. using reactive exercises to develop rate of force development.

Bobbert notes that many researchers and coaches forget this progression and try to introduce plyometrics earlier in the process.

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So does the research support the use of depth jumps?

Bobbert reports that the research on depth jumps is overwhelmingly positive.  In a meta-analysis, he notes that in a collection of 12 studies on unskilled jumpers, only one study failed to show an improvement in vertical jumping ability as a result of the depth jumping intervention.

In one of those studies, The effects of a 6 week depth jumping programme on the jumping abilities of figure skaters, by Keohane, Unpublished Masters Thesis, 1977, it was found that the depth jumps not only improved standardised vertical jumping ability but also sports-specific jumping ability.

And the same pattern was found in a meta-analysis of three studies on skilled jumpers.  All of them found increases in vertical jump ability as a result of depth jumps.

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What factors influenced the size of the training adaptations?

In this review paper, no key factors were identified from the literature that could predict the effectiveness of the programme.  However, it does not appear from the review that extensive data analysis was performed.

The meta-analysis also suggests that the height of the box used for the depth jumps is not critical, as different heights were used in the various studies and yet no trend was observed when comparing them.

***

Comparing squat jumps, countermovement jumps and drop jumps

Bobbert explores the different types of jump used in research studies.  Squat jumps begin from a static, crouched position.  Countermovement jumps begin from an upright position and involve a quick knee-bend before take-off.  Depth jumps involve a drop from a box onto the jumping platform before rebounding into the jump.

Bobbert wisely points out at this point that most vertical jump tests are in fact countermovement jump tests.

Bobbert also notes that while the heights achieved in countermovement and depth jumps are similar, this does not mean that the muscular force output (or ground reaction forces, depending on which way you want to look at it) are the same in both cases.  Since in the depth jump the duration of pushing off is much shorter than in the countermovement jump, by definition, the forces must be greater in the depth jump.  And this is in fact what can be measured.

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What about elastic energy storage?

Bobbert notes that Cavagna was the first to propose the elastic energy theory of the stretch-shortening cycle.  Cavagna proposed that the tendons lengthen during the stretch phase and store potential energy.  This energy is then released during the shortening phase.

Cavagna proposed this theory after observing that during two immediately consecutive squat jumps, the second was higher than the first.  The energy stored was therefore deduced as follows:

Energy = Mass x Gravity x (Height of 2nd jump – Height of 1st jump)

However, Bobbert queries the ability of the elastic energy storage theory to explain the whole of the difference in jump heights for several reasons, as follows:

• The stretch preceding the jump in the countermovement jump, or the impact in the depth jump or the consecutive squat jumps, might cause both spinal and local reflexes and these could cause increases in force exerted by the muscle.
• The force exerted by muscle fibres can be increased by potentiation.  Potentiation can be caused by the muscle exerting force but it can also be caused by the muscle being stretched.  The interesting thing about potentiation is that it doesn’t need to involve the stretch shortening cycle, as it can still be observed several minutes after the potentiating exercise.

So it would be unfair to suggest that Energy as measured by the above formula is equal to elastic energy stored, as other factors are almost certainly contributing to the expression of force during the rebound jump or second jump.  The formula therefore needs additional terms to remove these effects before it can be considered accurate.

Readers who remember my previous writings on plyometrics will recall that I am not yet completely convinced by two popular ideas: (1) that tendons (N.B. I said “tendons”) store energy, and (2) that the muscle-tendon unit can be trained to store more elastic energy than it would naturally do (pace Zatsiorsky).

However, I am the first to note that there is quite a lot of research to suggest that muscles (N.B. I said “muscles”) store energy and the recent work on titin supports this idea.  This is a subtle difference but an important one.  Hopefully, soon someone will figure out some other ways (not just in vitro) to separate out the effects of elastic energy storage in muscles and tendons and we can what is going on.

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Does an optimum jump height exist?

Bobbert notes a number of studies that seem to demonstrate that as the height of the box used in depth jumps is increased, so does the height of the jump but only up to a point.  After a certain height box, the height of the jump starts to decrease again.

This is explained by the researchers as indicative of the Golgi tendon organ inhibiting the expression of force.  However, Bobbert suggests that it is more likely caused by a deterioration in jumping technique.

Bobbert notes that there are two types of technique observed during depth jumps.  One type is the rebound type, which is typically observed in most subjects using most sensible box heights.  This leads to greater ground reaction forces and a shorter impact time.  The other type is almost a mimic of the countermovement jump, in which the subject allows a greater length of time in contact with the ground and absorbs the force of landing before jumping again.  Bobbert suggests that this technique was likely adopted by the subjects who were depth jumping from very high boxes, hence the reduced performance.

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What did he conclude?

Bobbert concludes that the overarching approach of Verkoshansky is supportable from the research, that the training process should be approached as follows:

1. practicing the sport,
2. using weights to develop strength, and
3. using reactive exercises to develop rate of force development.

He also notes that depth jumps have a lot of evidence to support their use in training programmes.  However, with the studies at his disposal, he was unable to identify which variables led to the greatest increases in performance, although the height of the box did not appear to be a key variable.

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What were the limitations?

Obviously, the main limitation to this study is that it is a review article published in 1990 and there has been a lot of research since then in respect of how muscles work.