Enzo Palombo, Swinburne University of Technology

Recent outbreaks of bird flu – in US dairy herds, poultry farms in Australia and elsewhere, and isolated cases in humans – have raised the issue of food safety.

So can the virus transfer from infected farm animals to contaminate milk, meat or eggs? How likely is this?

And what do we need to think about to minimise our risk when shopping for or preparing food?

How safe is milk?

Bird flu (or avian influenza) is a bird disease caused by specific types of influenza virus. But the virus can also infect cows. In the US, for instance, to date more than 80 dairy herds in at least nine states have been infected with the H5N1 version of the virus.

Investigations are under way to confirm how this happened. But we do know infected birds can shed the virus in their saliva, nasal secretions and faeces. So bird flu can potentially contaminate animal-derived food products during processing and manufacturing.

Indeed, fragments of bird flu genetic material (RNA) were found in cow’s milk from the dairy herds associated with infected US farmers.

However, the spread of bird flu among cattle, and possibly to humans, is likely to have been caused through contact with contaminated milking equipment, not the milk itself.

The test used to detect the virus in milk – which uses similar PCR technology to lab-based COVID tests – is also highly sensitive. This means it can detect very low levels of the bird flu RNA. But the test does not distinguish between live or inactivated virus, just that the RNA is present. So from this test alone, we cannot tell if the virus found in milk is infectious (and capable of infecting humans).

Does that mean milk is safe to drink and won’t transmit bird flu? Yes and no.

In Australia, where bird flu has not been reported in dairy cattle, the answer is yes. It is safe to drink milk and milk products made from Australian milk.

In the US, the answer depends on whether the milk is pasteurised. We know pasteurisation is a common and reliable method of destroying concerning microbes, including influenza virus. Like most viruses, influenza virus (including bird flu virus) is inactivated by heat.

Although there is little direct research on whether pasteurisation inactivates H5N1 in milk, we can extrapolate from what we know about heat inactivation of H5N1 in chicken and eggs.

So we can be confident there is no risk of bird flu transmission via pasteurised milk or milk products.

However, it’s another matter for unpasteurised or “raw” US milk or milk products. A recent study showed mice fed raw milk contaminated with bird flu developed signs of illness. So to be on the safe side, it would be advisable to avoid raw milk products.

How about chicken?

Bird flu has caused sporadic outbreaks in wild birds and domestic poultry worldwide, including in Australia. In recent weeks, there have been three reported outbreaks in Victorian poultry farms (two with H7N3 bird flu, one with H7N9). There has been one reported outbreak in Western Australia (H9N2).

The strains of bird flu identified in the Victorian and Western Australia outbreaks can cause human infection, although these are rare and typically result from close contact with infected live birds or contaminated environments.

Therefore, the chance of bird flu transmission in chicken meat is remote.

Nonetheless, it is timely to remind people to handle chicken meat with caution as many dangerous pathogens, such as Salmonella and Campylobacter, can be found on chicken carcasses.

Always handle chicken meat carefully when shopping, transporting it home and storing it in the kitchen. For instance, make sure no meat juices cross-contaminate other items, consider using a cool bag when transporting meat, and refrigerate or freeze the meat within two hours.

Avoid washing your chicken before cooking to prevent the spread of disease-causing microbes around the kitchen.

Finally, cook chicken thoroughly as viruses (including bird flu) cannot survive cooking temperatures.

Are eggs safe?

The recent Australian outbreaks have occurred in egg-laying or mixed poultry flocks, so concerns have been raised about bird flu transmission via contaminated chicken eggs.

Can flu viruses contaminate chicken eggs and potentially spread bird flu? It appears so. A report from 2007 said it was feasible for influenza viruses to enter through the eggshell. This is because influenza virus particles are smaller (100 nanometres) than the pores in eggshells (at least 200 nm).

So viruses could enter eggs and be protected from cleaning procedures designed to remove microbes from the egg surface.

Therefore, like the advice about milk and meat, cooking eggs is best.

The US Food and Drug Administration recommends cooking poultry, eggs and other animal products to the proper temperature and preventing cross-contamination between raw and cooked food.

In a nutshell

If you consume pasteurised milk products and thoroughly cook your chicken and eggs, there is nothing to worry about as bird flu is inactivated by heat.

The real fear is that the virus will evolve into highly pathogenic versions that can be transmitted from human to human.

That scenario is much more frightening than any potential spread though food.

Enzo Palombo, Professor of Microbiology, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

So you’ve got yourself a gym membership or bought a set of home weights. Now what? With the sheer amount of confusing exercise advice out there, it can be hard to decide what to include in a weights routine.

It can help to know there are broadly two types of movements in resistance training (lifting weights): compound exercises and isolation exercises.

So what’s the difference? And what’s all this got to do with strength, speed and healthy ageing?

What’s the difference?

Compound exercises involve multiple joints and muscle groups working together.

In a push up, for example, your shoulder and elbow joints are moving together. This targets the muscles in the chest, shoulder and triceps.

When you do a squat, you’re using your thigh and butt muscles, your back, and even the muscles in your core.

It can help to think about compound movements by grouping them by primary movement patterns.

For example, some lower body compound exercises follow a “squat pattern”. Examples include bodyweight squats, weighted squats, lunges and split squats.

We also have “hinge patterns”, where you hinge from a point on your body (such as the hips). Examples include deadlifts, hip thrusts and kettle bell swings.

Upper body compounded exercises can be grouped into “push patterns” (such as vertical barbell lifts) or “pull patterns” (such as weighted rows, chin ups or lat pull downs, which is where you use a pulley system machine to lift weights by pulling a bar downwards).

In contrast, isolation exercises are movements that occur at a single joint.

For instance, bicep curls only require movement at the elbow joint and work your bicep muscles. Tricep extensions and lateral raises are other examples of isolation exercises.

Compound exercises can make daily life easier

Many compound exercises mimic movements we do every day.

Hinge patterns mimic picking something off the floor. A vertical press mimics putting a heavy box on a high shelf. A squat mimics standing up from the couch or getting on and off the toilet.

That might sound ridiculous to a young, fit person (“why would I need to practise getting on and off a toilet?”).

Unfortunately, we lose strength and muscle mass as we age. Men lose about 5% of their muscle mass per decade, while for women the figure is about 4% per decade.

When this decline begins can vary widely. However, approximately 30% of an adult’s peak muscle mass is lost by the time they are 80.

The good news is resistance training can counteract these age-related changes in muscle size and strength.

So building strength through compound exercise movements may help make daily life feel a bit easier. In fact, our ability to perform compound movements are a good indicator how well we can function as we age.

What about strength and athletic ability?

Compound exercises use multiple joints, so you can generally lift heavier weights than you could with isolation exercises. Lifting a heavier weight means you can build muscle strength more efficiently.

One study divided a group of 36 people into two. Three times a week, one group performed isolation exercises, while the other group did compound exercises.

After eight weeks, both groups had lost fat. But the compound exercises group saw much better results on measures of cardiovascular fitness, bench press strength, knee extension strength, and squat strength.

If you play a sport, compound movements can also help boost athletic ability.

Squat patterns require your hip, knee, and ankle to extend at the same time (also known as triple extension).

Our bodies use this triple extension trick when we run, sprint, jump or change direction quickly. In fact, research has found squat strength is strongly linked to being able to sprint faster and jump higher.

Isolation exercises are still good

What if you’re unable to do compound movements, or you just don’t want to?

Don’t worry, you’ll still build strength and muscle with isolation exercises.

Isolation exercises are also typically easier to learn as there is no skill required. They are an easy and low risk way to add extra exercise at the end of the workout, where you might otherwise be too tired to do more compound exercises safely and with correct form.

In fact, both isolation and compound exercises seem to be equally effective in helping us lose body fat and increase fat-free muscle mass when total intensity and volume of exercises are otherwise equal.

Some people also do isolation exercises when they want to build up a particular muscle group for a certain sport or for a bodybuilding competition, for example.

I just want a time efficient workout

Considering the above factors, you could consider prioritising compound exercises if you’re:

• time poor
• keen to lift heavier weights
• looking for an efficient way to train many muscles in the one workout
• interested in healthy ageing.

That said, most well designed workout programs will include both compound and isolation movements.

Correction: This article has been amended to reflect the fact a weighted row is a pull pattern, not a push pattern.

Mandy Hagstrom, Senior Lecturer, Exercise Physiology. School of Health Sciences, UNSW Sydney and Anurag Pandit, PhD Candidate in Exercise Physiology, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.